U.S. patent application number 14/426893 was filed with the patent office on 2015-08-27 for injection device.
The applicant listed for this patent is TCO AS. Invention is credited to Keith Donald Woodford.
Application Number | 20150240601 14/426893 |
Document ID | / |
Family ID | 47137156 |
Filed Date | 2015-08-27 |
United States Patent
Application |
20150240601 |
Kind Code |
A1 |
Woodford; Keith Donald |
August 27, 2015 |
INJECTION DEVICE
Abstract
An injection device for use in injecting a fluid into a target
location includes a housing defining an inlet for communicating
with a source of injection fluid, an outlet for communicating with
a target injection location, and a separate reference port for
communicating with a reference pressure source. The device also
includes first and second valve members mounted within the housing,
wherein the second valve member defines a flow path therethrough to
facilitate fluid communication between the inlet and outlet of the
housing. A sealing arrangement is provided between the second valve
member and the housing such that fluid pressure at the housing
inlet and housing reference port apply a force on the second valve
member to cause said second valve member to move relative to the
first valve member and vary flow between the inlet and the
outlet.
Inventors: |
Woodford; Keith Donald;
(Blackburn, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TCO AS |
Bergen |
|
NO |
|
|
Family ID: |
47137156 |
Appl. No.: |
14/426893 |
Filed: |
September 10, 2013 |
PCT Filed: |
September 10, 2013 |
PCT NO: |
PCT/EP2013/068736 |
371 Date: |
March 9, 2015 |
Current U.S.
Class: |
166/305.1 ;
166/222; 166/381; 166/67 |
Current CPC
Class: |
E21B 34/10 20130101;
E21B 34/08 20130101; E21B 41/00 20130101 |
International
Class: |
E21B 41/00 20060101
E21B041/00; E21B 34/10 20060101 E21B034/10; E21B 34/08 20060101
E21B034/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2012 |
GB |
1216064.4 |
Claims
1. An injection device for use in injecting a fluid into a target
location, comprising: a housing defining an inlet for communicating
with a source of injection fluid, an outlet for communicating with
a target injection location, and a separate reference port for
communicating with a reference pressure source; a first valve
member mounted within the housing; a second valve member mounted
within the housing and defining a flow path therethrough to
facilitate fluid communication between the inlet and outlet of the
housing; a sealing arrangement provided between the second valve
member and the housing such that fluid pressure at the housing
inlet and housing reference port apply a force on the second valve
member to cause said second valve member to move relative to the
first valve member and vary flow between the inlet and the
outlet.
2. The injection device according to claim 1, wherein a portion of
the sealing arrangement is in communication with the inlet of the
housing such that inlet pressure can establish a force on the
second valve member in a first direction, and a portion of the
sealing arrangement is in communication with the reference pressure
port of the housing such that reference pressure can establish a
force on the second valve member in a second direction which is
opposite to the first direction.
3. The injection device according to claim 1, wherein the sealing
arrangement is configured such that movement of the second valve
member is achieved in accordance with a pressure differential
between inlet and reference pressures.
4. The injection device according to claim 1 wherein the sealing
arrangement defines an inlet sealing area to be exposed to inlet
pressure, and a reference sealing area to be exposed to reference
pressure.
5. The injection device according to claim 4, wherein the inlet and
reference sealing areas are substantially equal.
6. The injection device according to claim 4, wherein the inlet and
reference sealing areas are different to establish a force bias on
the second valve member by action of the inlet and reference
pressures.
7. The injection device according to claim 1, wherein inlet
pressure establishes a force on the valve member to cause said
valve member to move in a direction to increase flow and the
reference pressure establishes a force on the valve member to cause
said valve member to move in a direction to decrease flow.
8. The injection device according to claim 1, wherein a portion of
the sealing arrangement is in communication with the outlet of the
housing.
9. The injection device according to claim 8, wherein the sealing
arrangement substantially eliminates the effect of outlet pressure
on the valve member.
10. The injection device according to claim 8, wherein the sealing
arrangement is configured such that outlet pressure establishes
first and second substantially equal and opposite forces on the
second valve member, such that any net force is substantially
minimised.
11. The injection device according to claim 8, wherein the sealing
arrangement is configured to permit the outlet pressure to provide
a desired bias force on the second valve member.
12. The injection device according to claim 1, wherein the sealing
arrangement defines first and second outlet sealing areas between
the second valve member and the housing, and each of the first and
second outlet sealing areas is configured to be exposed to outlet
pressure.
13. The injection device according to claim 12, wherein the first
and second sealing areas permit outlet pressure to generate a force
on the second valve member in opposite directions.
14. The injection device according to claim 12, wherein the first
and second outlet sealing areas are substantially equal.
15. The injection device according to claim 12, wherein the first
and second outlet sealing areas are different.
16. The injection device according to claim 1, wherein the sealing
arrangement comprises one or more seal members.
17. The injection apparatus according to claim 1, wherein the
sealing arrangement includes first and second seal assemblies which
extend between the second valve member and the housing.
18. The injection apparatus according to claim 17, wherein each of
the first and second seal assemblies comprise one or more seal
members.
19. The injection apparatus according to claim 17, wherein the
first seal assembly isolates the housing inlet from the housing
outlet, such that fluid communication between the inlet and the
outlet is directed through the flow path in the second valve
member.
20. The injection apparatus according to claim 17, wherein the
second seal assembly isolates the housing outlet from the housing
reference port.
21. The injection device according to claim 17, wherein the first
seal assembly defines an inlet sealing area arranged in the device
to be exposed to inlet pressure.
22. The injection device according to claim 17, wherein the first
seal assembly defines a first outlet sealing area arranged in the
device to be exposed to outlet pressure.
23. The injection device according to claim 17, wherein the second
seal assembly defines a reference sealing area arranged in the
device to be exposed to reference pressure.
24. The injection device according to claim 17, wherein the second
seal assembly defines a second outlet sealing area arranged in the
device to be exposed to outlet pressure.
25. The injection device according to claim 1, comprising a biasing
arrangement operable to bias the second valve member in a desired
direction.
26. The injection device according to claim 25, wherein the biasing
arrangement is operable to bias the second valve member to move in
a direction to decrease flow between the inlet and the outlet.
27. The injection device according to claim 25, wherein the second
valve is arranged in the device to be actuated to move in a
direction to decrease flow by a combination of biasing force from
the biasing arrangement and the action of reference pressure, and
to be actuated to move in a direction to increase flow by the
action of inlet pressure.
28. The injection device according to claim 25, wherein, in use,
the biasing arrangement establishes a force on the second valve
member to permit a desired pressure differential within the
injection device to be achieved.
29. The injection device according to claim 1, for use in injecting
a fluid into a wellbore target location.
30. The injection device according to claim 1, wherein, in use, the
inlet fluid pressure at the inlet of the housing is at least
partially defined by fluid pressure within at least one of an
associated injection line and/or an associated source of injection
fluid, and the outlet fluid pressure is at least partially defined
by fluid pressure at an associated target location.
31. The injection device according to claim 1, wherein the
reference pressure is atmospheric or less than atmospheric.
32. The injection device according to claim 1, wherein, in use, the
reference pressure port is in communication with a source of
reference pressure, excluding reference pressure from the target
location.
33. The injection device according to claim 1, wherein, in use, the
reference pressure port is in communication with a local source of
reference pressure.
34. The injection device according to claim 1, comprising a source
of reference pressure.
35. The injection device according to claim 34, wherein the source
of reference pressure is located within the housing.
36. The injection device according to claim 1, wherein, in use, the
reference pressure port is in communication with a source of
reference pressure at a remote location.
37. The injection device according to claim 1, where, in use, the
outlet of the housing is in communication with a target location
which is positioned on one side of a pressure varying device, and
the reference pressure port is in communication with a location
which is positioned on an opposite side of the pressure varying
device.
38. The injection device according to claim 37, wherein the
pressure varying device may comprise a pump.
39. The injection device according to claim 1, wherein, in use, the
outlet of the housing is in communication with an inlet of a pump
assembly, and the reference pressure port is in communication with
an outlet of the same pump assembly.
40. The injection device according to claim 1, wherein reference
pressure applied at the reference pressure port is user
variable.
41. The injection device according to claim 1, wherein the first
and second valve members cooperate to define a restriction to flow
to establish a back pressure in the inlet side assisting to
maintain the inlet pressure above the outlet pressure.
42. The injection device according to claim 1, wherein the first
and second valve members are selectively engeagable to permit the
first valve member to selectively seal the flow path in the second
valve member.
43. The injection device according to claim 42, wherein the second
valve member is moveable within the housing to become separated
form the first valve member, to thus permit flow through the flow
path.
44. The injection device according to claim 1, wherein the first
valve member is fixed relative to the housing, such that movement
of the second valve member is required to vary flow.
45. The injection device according to claim 1, wherein the first
valve member is defined by a component which is separate from the
housing, and said first valve member is permitted to move within
the housing.
46. The injection device according to claim 1, wherein the first
valve member is located on the inlet side of the second valve
member.
47. The injection device according to claim 1, comprising a
limiting arrangement for limiting or restricting movement of the
first valve member, wherein the limiting arrangement functions to
limit movement of the first valve member at a point of limitation
and permit the second valve member to move beyond the point of
limitation and to become disengaged from the first valve
member.
48. The injection device according to claim 1, comprising at least
one check valve for preventing flow through the injection device in
a direction from the outlet to the inlet.
49. A method for injecting a fluid into a target location,
comprising: communicating an injection fluid to an inlet of a
housing of an injection device; communicating an outlet of the
housing to a target location; communicating a reference port of the
housing to a source of reference pressure; causing a second valve
member to move relative to a first valve member by exposure to
pressure at the inlet of the housing and pressure at the reference
pressure port of the housing, wherein such movement permits flow
through a flow path of the valve member to be adjusted.
50. A pumping system comprising: a flow line; a pump associated
with the flow line and defining an inlet side and an outlet side;
an injection device according to claims 1, wherein the outlet of
the injection device housing is in communication with the flow line
on an inlet side of the pump.
51. The pumping system according to claim 50, wherein the reference
pressure port of the injection device housing is in communication
with the flow line on an outlet side of the pump.
52. An injection system for injecting a fluid into a target
location, comprising: an injection line in communication with a
source of injection fluid; an injection device coupled to the
injection line and comprising: a housing defining an inlet coupled
to the injection line, an outlet for communicating with a target
injection location, and a separate reference port for communicating
with a reference pressure source; a first valve member mounted
within the housing; a second valve member mounted within the
housing and defining a flow path therethrough to facilitate fluid
communication between the inlet and outlet of the housing; and a
sealing arrangement provided between the second valve member and
the housing and configured such that fluid pressure at the housing
inlet and housing reference port apply a force on the second valve
member to cause said second valve member to move relative to the
first valve member and vary flow between the inlet and the
outlet.
53. The injection system according to claim 52, wherein the
injection device defines a first injection device and the injection
system comprises a second injection device located upstream of the
first injection device.
54. The injection device according to claim 53, wherein the second
injection device comprises an outlet in communication with the
inlet of the first injection device.
55. A method for creating an injection system, comprising:
determining a required pressure differential between an injection
line and a target injection location which maintains the injection
line at a positive pressure; determining an operational threshold
pressure differential of an injection fluid; determining a required
number of discrete pressure reduction stages within the injection
line to provide the required pressure differential between the
injection line and target location while maintaining each pressure
reduction stage below the operational threshold pressure
differential of the injection fluid; and installing a number of
injection devices within an injection line to correspond to the
determined number of discrete pressure reduction stages.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an injection device for
injecting a fluid to a target location, such as into a downhole
location.
BACKGROUND TO THE INVENTION
[0002] Many industries require fluids to be delivered, or injected,
from a source to a target location. For example, in the oil and gas
industry many well completions include a means of injecting
chemicals into the wellbore at a point in the completion for the
purposes of corrosion reduction, scale reduction, hydrate
reduction, well stimulation, a variety of optimisation strategies
or the like. It is highly desirable to be able to control the rate
of injection, and in typical applications the preference is to
permit a relatively constant rate of injection to be achieved,
irrespective of and pressure fluctuations within the system.
Injection may also be required at other locations, such as into the
wellbore, associated formation, annulus and the like. Injection
could also be required at a subsea location, such as at a Christmas
tree, flow line, jumper, manifold, wing line or the like. Some
other examples of injection in the oil and gas industry include
downhole injection of a fluid to assist production.
[0003] A typical wellbore completion installation with injection
capabilities is diagrammatically illustrated in FIG. 1. The
wellbore, generally identified by reference numeral 10, comprises a
casing string 12 located within a drilled bore 14 which extends
from surface 16 to intercept a hydrocarbon bearing formation 18. A
lower annulus area 20 defined between the casing 12 and bore 14 may
be filled with cement 22 for purposes of support and sealing. A
production tubing string 24 extends into the casing 12 from a
wellhead 26 and production tree 28. A lower end of the production
tubing string 24 is sealed against the casing 12 with a production
packer 30 to isolate a producing zone 32. A number of perforations
34 are established through the casing 12 and cement 22 to establish
fluid communication between the casing 12 and the formation 18.
Hydrocarbons may then be permitted to flow into the casing 12 at
the producing zone 32 and then into the production tubing 24 via
inlet 36 to be produced to surface. Artificial lift equipment, such
as an electric submersible pump (ESP) 37 may optionally be
installed inline with the production tubing 24 as part of the
completion to assist production to surface. The production tree 28
may provide the necessary pressure barriers and provides a
production outlet 38 from which produced hydrocarbons may be
delivered to a production facility (not shown), for example.
[0004] A small bore injection line or conduit 40, which is often
referred to as a capillary line, runs alongside the production
tubing 24 from a surface located injection fluid source 42 to a
downhole target location, which in the illustrated example is a
lower end of the production tubing 24, below the ESP 37. The
production tubing 24 may include an optional injection mandrel 44.
An injection pump 46 is located at a topside location to facilitate
injection of the injection fluid 42.
[0005] An injection valve 48 is located in a lower region of the
injection line 40 and functions to permit fluid injection into the
production tubing 24, in some cases preferentially at a constant
injection rate, while preventing reverse flow back into the
injection line 40. Known valves for such purposes include an
injection check valve, such as illustrated in FIG. 2. In this
example the check valve 48 includes a housing 50 with an inlet 52
for communicating with the injection line 40 and an outlet 54 for
communicating with the production tubing 24. A poppet member 56
(other similar members such as pistons and balls are also known) is
mounted in the housing 50 and is biased by a spring 58 towards a
closed position in which the poppet 56 sealingly engages a seat 60
to prevent flow through the housing 50. To permit injection the
fluid pressure at the inlet 52 must establish a downward force on
the poppet 56 which exceeds the combined force of the spring 58 and
the pressure at the outlet 54, which act in the opposing direction.
Accordingly, in normal flow conditions the inlet pressure will be a
fixed differential above the outlet pressure by a magnitude
dictated primarily by the force of the spring 58, and also by any
back-pressure created at the inlet by the effect of the poppet 56
and seat defining a flow restriction. An exemplary graphical
representation of the effects of varying the inlet or outlet
pressures is provided in FIG. 3. As shown, irrespective of pressure
fluctuations at the outlet 54, the inlet pressure 62 will always be
a fixed value above the outlet pressure 64 by a differential 66
which is defined primarily by the spring 58.
[0006] In chemical injection there is always a hydrostatic pressure
gradient present in the injection line 40. This pressure gradient
is a function of the density of the fluid and the true vertical
height of the well known as the TVD (True Vertical Depth). As depth
increases, the hydrostatic pressure will linearly increase, such
that the maximum hydrostatic pressure will act at the inlet 52 of
the injection valve 48. This hydrostatic pressure will act in a
direction to open the valve poppet member 56 against the combined
resistance of the spring 58 and the pressure at the valve outlet
54, which will be largely equal to the pressure within the
production tubing 24 at the point of injection. There may be
circumstances where the hydrostatic pressure force acting at the
valve inlet 52 exceeds the resistance provided by the valve outlet
pressure and the spring 58, for example where large hydrostatic
pressures exist in deeper wells, and/or where relatively low
wellbore pressures exist, for example due to operation of the ESP
37. In such circumstances the result can be the undesirable flow or
cascading of injection fluid into the target location. This effect
may be termed "hydrostatic fall-through".
[0007] If unchecked such hydrostatic fall-through will occur until
the hydrostatic pressure within the injection line 40 is in
equilibrium with the target location pressure and the resistance
provided by the valve spring 58. If the injection fluid is not
continuously replenished, or not replenished as quickly as the
injection fluid cascades through the valve 48, then the result will
be the creation of low, vacuum or near vacuum pressures in the
upper region of the injection line 40. Such a vacuum may present
the injection line 40 to adverse mechanical forces and stresses,
such as radial collapse forces. Furthermore, the established vacuum
may be defined by a pressure which is lower than the vapour
pressure of the injection fluid, thus causing the injection fluid
to boil. This may be compounded by the effect of the increased
temperatures associated with wellbore environments. The consequence
of vacuum occurrence in chemical injection lines is that the
original fluid may not be able to retain its intended state and the
fluid carrier will boil off. This has the potential of many adverse
effects, such as solid depositing, viscosity change, crystal
formation, waxing, partial or full solidification, and generally
changes within the fluid causing loss of effectiveness of the
injection chemical, and the like.
[0008] To provide a numerical example, for an injection line which
has a TVD of 1420 meters with an injection fluid having a density
of 1050 kg/m.sup.3, the hydrostatic pressure (calculated by the
product of fluid density, gravity and TVD) acting at the inlet 52
of the valve 48 will be in the region of 146 bar. If the pressure
in the production tubing 24 at the point of injection is 95 bar,
and assuming that the valve spring 58 and other flow resistance is
equivalent to providing 2 bar of pressure resistance, then this
creates a pressure differential across the valve of 49 bar.
Accordingly, due to the tendency for the system to seek equilibrium
the injection fluid within the injection line 40 will cascade
through the valve 48 until the height of injection fluid
establishes a hydrostatic pressure at the valve inlet 52 which is
in equilibrium with the pressure in the production tubing plus
other resistance, which in the present example will be 97 bar.
Thus, a hydrostatic pressure of 97 bar at the valve inlet 52 will
require the injection fluid to cascade to define a height of around
942 metres. This will therefore leave the upper 478 meters of the
injection line 40 under vacuum conditions, which is graphically
illustrated in FIG. 4.
[0009] Such hydrostatic fall-through may be addressed by increasing
the spring force rating of the spring 58. This will function to
increase the resistance to flow through the valve 48, such that a
greater pressure differential between valve inlet 52 and outlet 54
can be accommodated before the onset of hydrostatic fall-through. A
graphical example of the use of a more powerful valve spring is
illustrated in FIG. 5. As in the previous graphical example of FIG.
3, the effect of the spring is such that irrespective of pressure
fluctuations at the valve outlet 54, the inlet pressure 70 will
always be a fixed value above the outlet pressure 72 by the
differential 68. In this exemplary case a differential of around 80
bar is established by a more powerful spring, and such a spring
would prevent the occurrence of hydrostatic fall-through in the
specific numerical example provided above.
[0010] However, the size of a valve spring may be limited by the
size of the injection valve and available space to accommodate
deployment and installation of such a valve. Further, in
circumstances where very large pressure differentials exist, the
required size of a valve spring may be impossible to accommodate
within the valve.
[0011] In addition to establishing a desired pressure differential
across a valve using a spring, it is also known in the art to
utilise the effect of a flow restriction within a valve to
establish a desired backpressure within the injection line 40.
Also, such a flow restriction may be variable to ensure a
consistent injection flow rate can be achieved irrespective of the
pressure differential.
[0012] As described above, in known injection valves a fixed
differential between valve inlet and outlet is provided. Thus, the
expectation and desire is that the valve inlet pressure will track
any variations in the outlet pressure by the fixed differential.
The intention of this is to prevent hydrostatic fall-through, and
to facilitate a relatively constant injection rate. However, in
certain circumstances, for example where the outlet pressure should
drop, for example due to activation of an ESP, it has been observed
that there is an unexpected sudden rush of injection fluid through
the valve. This is contrary to expectation, which is that a
substantially continuous injection rate should be achieved by
self-adjustment of the valve to maintain the fixed pressure
differential between inlet and outlet. Further, such a sudden rush
of injection fluid through the valve may cause damage to the
valve.
[0013] Furthermore, in the exemplary completion system shown in
FIG. 1 an optional ESP 37 is provided, wherein the injection fluid
is injected upstream, or on the inlet side of the ESP 37. The
injection fluid may function to inhibit scale and the like within
the ESP 37, to condition the production fluids to permit more
efficient pumping, for example by reducing the viscosity of the
production fluids, and the like. In this respect, when the ESP 37
is activated the pressure at the pump inlet, and thus at the
injection location will fall. As described above, the injection
valve 48 should permit this fall in pressure to be accommodated and
ensure that the injection line pressure is maintained at a fixed
differential above the target location pressure, and self-adjusts
to ensure a consistent flow rate of injection fluid.
[0014] Expected, and indeed desired pressure profiles at the inlet
and outlet of the ESP 37, and at the inlet 52 of the valve 48 is
graphically illustrated in FIG. 6. In this respect, as the ESP 37
is activated the pump inlet pressure 74 should fall, and the pump
outlet pressure 76 should rise, until a steady state running
condition is preferably achieved. In view of the fixed pressure
differential provided by the valve 48, illustrated by line 78 in
FIG. 6, the inlet pressure 80 of the valve 48 will be maintained at
a fixed value above the inlet pressure 74 of the pump 37, and will
thus define a substantially equivalent pressure profile, albeit at
a fixed differential higher.
[0015] However, despite the expectation and desire for the pump
inlet and outlet pressures to reach a steady state shortly after
activation of the ESP 37, the present inventor has observed that in
practice this may not be the case. For example, during fluid
injection, such as injection of a diluent to modify the viscosity
of the production fluids, the pressure profiles observed may be
more accurately depicted in FIG. 7--it should be noted that FIG. 7
represents a generalisation of the observations made by the
applicant. In this respect, when the ESP 37 is activated the pump
inlet pressure 82 falls, and the pump outlet pressure 84 rises,
with the inlet pressure 86 tracking above the pump inlet pressure
82 by the magnitude of the fixed differential 88, as expected.
However, it has been observed that the pump inlet and outlet
pressures 82, 84 may not achieve the expected and desired steady
state, and as illustrated in FIG. 7 these pressures may fluctuate
for an extended period following activation of the ESP 37. In this
respect the observation is that pump inlet pressure 82 may fall
while outlet pressure 84 rises, followed by an increase in inlet
pressure 82 and corresponding fall in outlet pressure 84, with the
cycle repeating. Further, as the valve inlet pressure 86 tracks
above the pump inlet pressure 82 by the fixed differential 88 then
this also fluctuates, and as a consequence so, too, does the
injection fluid pressure 90 at the surface. Such pressure
fluctuations can cyclically load the completion equipment, such as
the ESP 37, surface pump 46, injection line 40 and the like, which
may have a detrimental effect, for example by fatiguing the
equipment, by establishing greatly interrupted and irregular
production, reducing the lifetime of the completion equipment
requiring more frequent workover and servicing, requiring a greater
monitoring and reducing the understanding about the effectiveness
of the fluid being injected, perhaps leading to increased fluid
injection in attempts to counter the effects of this observation of
pressure fluctuations.
[0016] A greater understanding of the causes of such observations,
and any solutions to address such causes, is desired.
SUMMARY OF THE INVENTION
[0017] Aspects of the present invention relate to an injection
device for use in injecting a fluid into a target location. Such an
injection device may include a housing having an inlet for
communication with an injection line or source of injection fluid,
an outlet for communication with a target injection location, and a
reference pressure port for communicating with a source of
reference pressure, wherein the reference pressure port is isolated
from the outlet. A valve member may be mounted within the housing.
The injection device may be configured such that fluid pressures at
the inlet and reference pressure port act to cause said valve
member to move within the housing to vary flow between the inlet
and the outlet. In some embodiments the injection device may
include a sealing arrangement which permits pressures at the inlet
and reference pressure port to move the valve member. Such a
sealing arrangement may optionally function to control the effect
of fluid pressure at the outlet acting on the valve member. In some
embodiments the sealing arrangement may optionally function to
substantially eliminate the effect of fluid pressure at the outlet
acting on the valve member.
[0018] Aspects of the present invention also relate to a method for
injecting a fluid into a target location. Such a method may
comprise communicating an inlet of an injection device to a source
of injection fluid, and communicating an outlet of the injection
device to a target location. The method may further comprise
permitting a valve member mounted within the injection device to be
moved by action of pressure at the inlet of the device and by
pressure acting at a reference port of the device which is isolated
form the outlet. Such movement of the valve member may function to
vary flow between the inlet and the outlet.
[0019] Such an injection device and method seeks to address certain
unforeseen problems and observations which are contrary to
expectation in injection processes. In this respect, through
diligent investigations and research the present inventor has
discovered certain reasons for such observations and problems. For
example, in some cases problems in known injection valves may be
attributed to the fact that such valves function to modify valve
inlet pressure based almost exclusively on the valve outlet
pressure, which is understood to be largely equal to the pressure
at the injection location, which in certain cases may be subject to
large variations. Such problems may be mitigated in the present
invention by permitting the valve member of the injection device to
be moved by action of a fluid pressure provided at a reference
pressure port which is isolated from the outlet of the housing. In
certain embodiments the effect of outlet pressure may be
substantially eliminated in the present invention.
[0020] As noted above, previously known injection valves
principally operate by modifying valve inlet pressure based on
valve outlet pressure. As such, in the event of a variation in
outlet pressure, inlet pressure should be varied accordingly.
However, in some instances an unexpected surge of flow through the
valve occurs when the outlet pressure varies. The present inventor
has attributed this observation to the compressibility of the fluid
being injected, and in particular to the requirement for a
volumetric change in a fluid to occur in the event of a pressure
change.
[0021] More specifically, fluids are often considered to be
incompressible. This, however, is only true to a limited extent and
when high pressures are applied to fluids they do compress.
Therefore if the pressure of an injection fluid at the inlet of a
valve is required to fall, for example, a volume of fluid must be
dissipated in order for this to occur. The valve inlet will be
coupled to a source of injection fluid, and in some cases extremely
long injection conduits will be utilised for this purpose, for
example in downhole applications. As such, the volume of the
injection fluid within an injection conduit may be significant,
such that the volume of fluid to be dissipated in order to permit
the pressure fall may also be significant. This fluid can only be
dissipated through the injection valve. No matter how efficient the
injection valve is at maintaining a differential pressure and
tracking a change in outlet pressures, the valve will have to
dissipate this volume of fluid to accommodate the fall in inlet
pressure. It has been found the volumes of fluid that require
dissipation due to pressure fall, for example, as may be found as a
pump, such as an electric submersible pump (ESP), is activated to
reduce pressure presented to an injection valve or device outlet,
are more than is often thought.
[0022] Conversely, it has been observed that following the
dissipation of fluid in the injection line, as ESP inlet pressure
falls, the ESP inlet pressure may then be seen to rise. In order to
facilitate a continuing delivery of chemical through the injection
valve, its inlet pressure must be increased. As fluid is delivered
to increase inject line pressure flow is consumed by the fluid
compressibility and enlargement of the injection line, thus causing
a cessation or reduction of fluid flow through the injection valve.
Thus creating a fall in flow following a surge of flow. This can
lead to a cyclic repetition of a rise and surge of flow followed by
a fall and loss of flow.
[0023] Although a general situation has been suggested above in
which pressure variations occur at a target location by use of an
ESP, this may not always be the case, and such pressure variations
may occur due to many reasons.
[0024] In addition to the compressibility of the fluid, any
associated injection conduit may enlarge under internal pressure.
This means its internal volume will increase thus requiring more
fluid to be introduced in order to reach a required pressure.
Therefore in order for the injection conduit to fall in pressure
the volume of fluid entrained at its starting pressure must be
fully dissipated in order to reach a lower pressure. This fluid
volume dissipation therefore results in a significant rise, or
surge of flow through the injection valve as the inlet pressure
falls.
[0025] According to a first aspect of the present invention there
is provided an injection device for use in injecting a fluid into a
target location, comprising:
[0026] a housing defining an inlet for communicating with a source
of injection fluid, an outlet for communicating with a target
injection location, and a separate reference port for communicating
with a reference pressure source;
[0027] a first valve member mounted within the housing;
[0028] a second valve member mounted within the housing and
defining a flow path therethrough to facilitate fluid communication
between the inlet and outlet of the housing; and
[0029] a sealing arrangement provided between the second valve
member and the housing and configured such that fluid pressure at
the housing inlet and housing reference port apply a force on the
second valve member to cause said second valve member to move
relative to the first valve member and vary flow between the inlet
and the outlet.
[0030] In use, the effect of the reference pressure acting on the
sealing arrangement may contribute to movement of the second valve
member. As such, the effect of the reference pressure may function
to control movement of the second valve member and thus control
flow through the valve. Such an arrangement may permit the second
valve member to be controlled without reliance, or with a reduced
reliance, on pressure at the housing outlet, which may be
substantially equivalent to pressure at the target injection
location, as is the case in prior art devices.
[0031] The sealing arrangement may be configured to substantially
confine any flow between the inlet and the outlet to the flow path
of the second valve member. That is, the sealing arrangement may be
such that flow between the inlet and outlet of the housing may only
be achieved through the flow path of the second valve member.
[0032] For the purposes of clarity, pressure acting at the inlet of
the housing may be defined as inlet pressure, pressure acting at
the outlet of the housing may be defined as outlet pressure, and
pressure acting at the reference pressure port may be defined as
reference pressure.
[0033] The sealing arrangement may be directly mounted between the
second valve member and the housing. For example, the sealing
arrangement may directly engage the second valve member and the
housing.
[0034] The sealing arrangement may be indirectly mounted between
the second valve member and the housing. For example, the sealing
arrangement may indirectly engage at least one of the second valve
member and the housing. In one embodiment an intermediate component
may be provided between the sealing arrangement and at least one of
the second valve member and the housing.
[0035] A portion of the sealing arrangement may be in communication
with the inlet of the housing such that inlet pressure may
establish a force on the second valve member in a first direction.
A portion of the sealing arrangement may be in communication with
the reference pressure port of the housing such that reference
pressure may establish a force on the second valve member in a
second direction. The second direction may be opposite to the first
direction. In such an arrangement the forces generated by the
effect of pressures at the inlet and reference pressure port may
result in a net movement of the second valve member to thus vary
flow between the inlet and the outlet.
[0036] The sealing arrangement may be configured such that movement
of the second valve member is achieved in accordance with a
pressure differential between inlet and reference pressures. The
sealing arrangement may be configured to establish a preferential
bias of forces applied by action of inlet and reference
pressures.
[0037] The sealing arrangement may define a sealing area between
the second valve member and the housing. The sealing area may
determine the magnitude of a force applied on the second valve
member upon exposure to various pressures.
[0038] In one embodiment the sealing arrangement may define an
inlet sealing area configured to be exposed to inlet pressure, and
a reference sealing area configured to be exposed to reference
pressure. A ratio of the inlet and reference sealing areas may
affect a net force generated on the second valve member by the
inlet and reference pressures.
[0039] The inlet and reference sealing areas may be substantially
equal. In such an arrangement a net force applied on the second
valve member may be a function of a pressure differential between
the inlet and reference pressures.
[0040] The inlet and reference sealing areas may by different. In
such an arrangement a force bias on the second valve member may be
applied by the sealing arrangement by action of the inlet and
reference pressures. That is, a net force applied on the second
valve member may be a function of both a differential of inlet and
reference sealing areas and a differential between the inlet and
reference pressures.
[0041] The injection device may be configured such that inlet
pressure establishes a force on the valve member to cause said
valve member to move in a direction to increase flow, for example
initiate flow, between the inlet and the outlet of the housing. The
injection device may be configured such that reference pressure
establishes a force on the valve member to cause said valve member
to move in a direction to decrease flow, for example to prevent
flow, between the inlet and the outlet of the housing.
[0042] A portion of the sealing arrangement may be in communication
with the outlet of the housing. The sealing arrangement may be
configured to control the effect of the outlet pressure on the
second valve member.
[0043] In one embodiment the sealing arrangement may be configured
to substantially eliminate the effect of outlet pressure on the
valve member. In such an embodiment the sealing arrangement may be
configured such that the effect of outlet pressure does not
establish or significantly minimises any net force on the second
valve member. Such an arrangement may remove or eliminate any
reliance on outlet pressure to control movement of the second valve
member. This may contribute to addressing problems associated with
prior art devices where variations in outlet pressure may have a
detrimental effect on operation of the injection device.
[0044] The sealing arrangement may be configured such that outlet
pressure may establish first and second substantially equal and
opposite forces on the second valve member, such that any net force
is substantially minimised.
[0045] The sealing arrangement may be configured such to permit the
outlet pressure to provide a desired bias force on the second valve
member. In such an arrangement any effect of outlet pressure may be
utilised in a desired way, for example to bias the second valve
member to move in a desired direction.
[0046] The sealing arrangement may define first and second outlet
sealing areas between the second valve member and the housing,
wherein each of the first and second outlet sealing areas is
configured to be exposed to outlet pressure. The first and second
sealing areas may be configured to permit outlet pressure to
generate a force on the second valve member in opposite
directions.
[0047] In one embodiment the first and second outlet sealing areas
may be substantially equal. In such an arrangement the effect of
outlet pressure acting on the first and second outlet areas may be
cancelled out, such that no or minimal net force is applied on the
second valve member by outlet pressure.
[0048] In one embodiment the first and second outlet sealing areas
may be different. In such an arrangement the effect of the same
outlet pressure acting on the first and second outlet areas may
present a net force acting in one direction, and thus the outlet
pressure may act to apply this bias force on the second valve
member in this one direction.
[0049] The sealing arrangement may comprise one or more seal
members. The sealing arrangement may comprise one or more of
sliding seal members, o-rings, bellows seals, diaphragm seals
piston rings or the like.
[0050] The sealing arrangement may include first and second seal
assemblies which extend between the second valve member and the
housing.
[0051] The first seal assembly may comprise one or more seal
members.
[0052] The second seal assembly may comprise one or more seal
members.
[0053] The first seal assembly may be configured to isolate the
housing inlet from the housing outlet, such that fluid
communication between the inlet and the outlet is permitted only
through the flow path in the second valve member.
[0054] The second seal assembly may be configured to isolate the
housing outlet from the housing reference port.
[0055] The first seal assembly may define an inlet sealing area
configured to be exposed to inlet pressure.
[0056] The first seal assembly may define a first outlet sealing
area configured to be exposed to outlet pressure.
[0057] The second seal assembly may define a reference sealing area
configured to be exposed to reference pressure.
[0058] The second seal assembly may define a second outlet sealing
area configured to be exposed to outlet pressure.
[0059] The inlet, reference and first and second outlet sealing
areas may be as defined above.
[0060] The device may comprise a biasing arrangement configured to
bias the second valve member in a desired direction. The biasing
arrangement may be configured to bias the second valve member to
move in a direction to decrease flow between the inlet and the
outlet, for example to close the injection device. The biasing
arrangement may be selected to provide a desired biasing force.
[0061] The second valve member may be configured to be actuated to
move in a direction to decrease flow by a combination of biasing
force from a biasing arrangement and the action of reference
pressure. The second valve member may be configured to be actuated
to move in a direction to increase flow by the action of inlet
pressure.
[0062] The biasing arrangement may be configured to establish a
force on the second valve member to permit a desired pressure
differential within the injection device to be achieved. For
example, the biasing arrangement may permit or require the
injection pressure to be maintained at a fixed pressure
differential above the reference pressure, by a magnitude
associated with the force applied by the biasing arrangement.
[0063] The biasing arrangement may comprise one or more springs,
such as a coil spring, wave spring, flat spring, disk spring,
Belleville spring or the like. The biasing arrangement may comprise
a deformable member capable of elastic recovery, such as an elastic
body subject to deformation, for example compression.
[0064] The biasing arrangement may be adjustable.
[0065] The second valve member may comprise a profile to permit
engagement with the biasing arrangement, such as an annular rib,
one or more pins, or the like. The biasing arrangement may directly
engage the second valve member. The biasing arrangement may
indirectly engage the second valve member, for example via an
intermediate component such as a plate member or the like.
[0066] The injection device may be configured for use in any
application, such as in any application where a fluid is required
to be injected into a target location, such as in the oil and gas
industry, chemical processing industry, manufacturing industry or
the like.
[0067] The injection device may be configured for use in injection
into a wellbore target location. The target location may be
associated with wellbore equipment or infrastructure. The target
location may be associated with downhole tubing or equipment, such
as production tubing, casing or liner tubing, drill pipe, coiled
tubing or the like.
[0068] The injection device may be configured for use in injection
into a separate flow line. Such a separate flowline may include a
pressure varying device, such as a pump assembly, for example an
electric submersible pump (ESP) assembly. In one embodiment the
injection device may be configured for use in injection of a fluid
into a flow line at a location which is upstream of a pressure
varying device. In such an arrangement the target injection
location may be located on an inlet side of such a pressure varying
device, and as such the target location may be subject to pressure
variations established by operation of the pressure varying device.
Thus, the injection device of the present invention may assist to
minimise any detrimental effect by virtue of the variations at the
target injection location.
[0069] The inlet fluid pressure at the inlet of the housing may be
at least partially defined by fluid pressure within an associated
injection line and/or an associated source of injection fluid. The
outlet fluid pressure may be at least partially defined by fluid
pressure at an associated target location.
[0070] The reference pressure may be selected to be any desired
pressure. In some embodiments the reference pressure may be
selected to be lower than the inlet pressure.
[0071] The reference pressure may be configured to define a minimal
pressure, such as atmospheric or less than atmospheric. Such an
arrangement may minimise the effect of the reference pressure of
applying a force on the second valve member. This arrangement may
be selected when, for example, the effect of the outlet pressure is
minimised or negated by the form of the sealing arrangement, such
that variation in flow through the injection device is controlled
largely by inlet pressure, and the presence of any associated
biasing arrangement acting on the second valve member.
[0072] The reference pressure port may be configured for
communication with any desired source of reference pressure. The
source of reference pressure may exclude the target location. Such
exclusion of the target location may minimise reliance on the
outlet pressure or target location pressure on operation of the
device. This may assist to minimise any effects of volumetric
expansion, or even contraction, of fluid positioned on the inlet
side of the housing, for example within an associated injection
line.
[0073] The reference pressure port may be configured for
communication with a local source of reference pressure. In one
embodiment the reference pressure port may be configured for
communication with a source of reference pressure which is
incorporated within the injection device, for example formed within
the housing of the injection device. Such a local source of
reference pressure may be configured to provide a fixed reference
pressure. In some embodiments a local source of reference pressure
may be variable.
[0074] The reference pressure port may be configured for
communication with a source of reference pressure at a remote
location. In some embodiments where the injection device is
utilised for injection into a downhole target location, the source
of reference pressure may be provided at surface level and/or at a
separate downhole location.
[0075] In one embodiment the outlet of the housing is configured to
communicate with a target location which is positioned on one side
of a pressure varying device, and the reference pressure port is
configured to communicate with a location which is positioned on an
opposite side of the pressure varying device. The pressure varying
device may comprise a pump, such as an ESP. The pressure varying
device may comprise a choke.
[0076] In one embodiment the outlet of the housing is configured to
communicate with an inlet of a pump assembly, and the reference
pressure port is configured to communicate with an outlet of the
same pump assembly. Such an arrangement may be utilised where the
pump assembly is used within a wellbore, such as to provide
artificial lift to produced fluid, to pressurise fluids for
injection into a surrounding formation or the like. In such an
arrangement, the effect of any significant pressure variation, in
particular a significant pressure decrease, experienced at the
reference pressure port (i.e., the pump outlet) is minimised, and
as such the effect of possible volumetric expansion or the like
within fluid located on the inlet side of the injection device is
also minimised.
[0077] The reference pressure applied at the reference pressure
port may be user variable. Such an arrangement may permit a user to
tune or vary the use of the injection device to accommodate
particular operation conditions, such as the density of the fluid
being injected and the like.
[0078] The first and second valve members may cooperate to define a
restriction to flow. This may establish a back pressure in the
inlet side assisting to maintain the inlet pressure above the
outlet pressure. This arrangement may assist to prevent hydrostatic
fall-through of an injection fluid. The degree of separation
between the first and second valve members may be adjustable to
adjust the restriction to flow. The degree of separation may be
adjusted automatically to maintain the inlet pressure above outlet
pressure. Such automatic adjustment may be achieved by the desire
for the injection device to continuously satisfy force equilibrium.
In such a case force equilibrium may permit the desired pressure
differential to be maintained.
[0079] The first and second valve members may be engageable. Such
engagement may permit the first valve member to seal the flow path
in the second valve member. The second valve member may be moveable
within the housing to become separated form the first valve member,
to thus permit flow through the flow path. The degree of separation
between the first and second valve members may define a restriction
to flow through the injection device, which may function to define
a back-pressure within the inlet side of the injection device.
[0080] The first valve member may be fixed relative to the housing,
such that movement of the second valve member is required to vary
flow.
[0081] The first valve member may be defined by an integral part of
the housing.
[0082] The first valve member may be defined by a component which
is separate from the housing. The first valve member may be
permitted to move within the housing. Permitting both the first and
second valve members to move within the housing may provide
advantages in terms of improving sealing between the first and
second valve members when engaged. For example, when engaged the
first valve member may be biased against the second member by inlet
fluid pressure to assist sealing therebetween.
[0083] The use of inlet pressure to assist sealing may permit
improved sealing to be achieved upon engagement of the first and
second valve members minimising the risk of leakage therebetween.
This in turn may, in some applications, minimise the possibility of
an associated injection line in communication with the housing
inlet being exposed to vacuum or negative pressure conditions, for
example due to hydrostatic fall-through.
[0084] The second valve member may be configured to support the
first valve member when engaged therewith. In such an arrangement
movement of the second valve member when engaged with the first
valve member will result in movement of both members. This
arrangement may permit the valve members to retain the flow path in
the second valve member closed in the event of such collective
movement of the valve members. This may assist to regulate or
minimise the effects of spurious or undesired pressure fluctuations
which may otherwise cause inadvertent disengagement of the members.
Such undesired pressure fluctuations may be transitory or fleeting
and not intended to represent operational pressure fluctuations.
For example, transitory pressure fluctuations may be created by
flow surges.
[0085] The first valve member may be located on the inlet side of
the second valve member.
[0086] Each valve member may define an engagement surface
configured to be mutually engaged to prevent flow through the
injection device. Each engagement surface may define a sealing
surface.
[0087] The first and second valve members may define a seal area at
the region of engagement. When the first and second valve members
are engaged inlet fluid pressure may act on one side, which may be
defined as an upstream side of the seal area. The bias force acting
on the first valve member may therefore be a function of the seal
area and the inlet pressure. Outlet fluid pressure may act on an
opposite side of the seal area, which may be defined as a
downstream side. The outlet pressure may define a force acting on
the first valve member which is a function of the seal area and the
outlet pressure. In this arrangement the first valve assembly may
be biased by the effect of a pressure differential between inlet
and outlet pressures.
[0088] The apparatus may comprise a limiting arrangement configured
to limit or restrict movement of the first valve member. The
limiting arrangement may be configured to limit movement of the
first valve member during opening of the valve assembly. The
limiting arrangement may be arranged to limit movement of the first
valve member at a point of limitation and permit the second valve
member to move beyond the point of limitation and to become
disengaged from the first valve member. The limiting arrangement
may be fixed relative to the housing.
[0089] The limiting arrangement may comprise a tether.
[0090] The limiting arrangement may comprise a land region
configured to be engaged by the first valve member when at a point
of limitation.
[0091] The limiting arrangement may comprise a no-go. The limiting
arrangement may comprise a shoulder arrangement. The limiting
arrangement may comprise an elongate member. The elongate member
may extend through the second valve member.
[0092] The first valve member may be biased by a biasing
arrangement in a desired direction. The biasing arrangement
associated with the first valve member may be configured to bias
said member in a direction towards engagement with the second valve
member. Such a biasing arrangement may assist sealing between the
valve members when engaged. The biasing arrangement associated with
the first valve member may comprise one or more springs, such as a
coil spring, wave spring, flat spring or the like. The biasing
arrangement may comprise a deformable member capable of elastic
recovery, such as an elastic body subject to deformation, for
example compression.
[0093] One of the first and second valve members may define a valve
seat member and the other of the first and second members may
define a valve body member. The valve seat member may define a
valve seat which is engaged by the valve body member.
[0094] The valve body member may comprise a pin. The valve body
member may comprise a ball. The valve body member may comprise a
disk, plug, plunger or the like.
[0095] The injection device may comprise a pressure rated frangible
arrangement configured to rupture upon exposure to a predetermined
pressure. The frangible arrangement may be located within the
housing. The frangible arrangement may be located on the inlet or
upstream side of the second valve member. The frangible arrangement
may be configured to isolate at least the second valve member from
inlet pressure until required. The frangible arrangement may
comprise a burst disk arrangement, rupture cartridge or the
like.
[0096] The injection device may comprise a surge protection
arrangement configured to provide protection against surging flow
within or through the housing. Such surging flow may be caused by a
particular pump duty cycle, rupturing of a frangible arrangement or
the like. The surge protection arrangement may be configured to
provide protection to the valve assembly. The surge protection
arrangement may be located within the housing. The surge protection
arrangement may be located on the inlet or upstream side of the
second valve member.
[0097] The surge protection arrangement may comprise a component
defining a flow path, wherein the flow path is restricted in the
event of surging flow. The flow path may be restricted by being
partially or fully closed. The surge protection arrangement may be
biased towards a condition in which the flow path is open, and
moved against said bias during surging flow. The magnitude of the
bias may define the surge rating of the surge protection
arrangement. The surge protection arrangement may comprise a spring
configured to bias the surge protection arrangement towards a
condition in which the flow path is open.
[0098] The injection device may comprise a filter arrangement
configured to filter injection fluid. The filter arrangement may be
mounted within the housing. The filter arrangement may be located
on the inlet or upstream side of the second valve member.
[0099] The injection device may comprise at least one check valve
configured to prevent flow through the injection device in a
direction from the outlet to the inlet. Such an arrangement may
eliminate the risk of flow reversal, for example in the event of
outlet pressure exceeding inlet pressure. At least one check valve
may be located on an outlet or downstream side of the second valve
member. At least one check valve may be located on an inlet or
upstream side of the second valve member. At least one check valve
may be located within the second valve member, for example within
the flow path of the second valve member. At least one check valve
may be mounted within the housing of the injection device. At least
one check valve may be provided separately and secured to the
housing of the injection device, for example via a suitable conduit
or the like.
[0100] The housing may be defined by a unitary component. The
housing may be defined by multiple components coupled together.
[0101] The inlet and outlets of the housing may be arranged in-line
with each other.
[0102] The inlet may be arranged on one end location of the housing
and the outlet may be arranged on one side of the housing.
[0103] The injection device may form part of an injection system.
The injection system may comprise multiple injection devices. At
least one of the multiple injection devices may be provided in
accordance with any aspect of the present invention. An injection
device according to any aspect of the present invention may be used
in combination with any other injection device. In one embodiment
the injection device may be used in series with a further injection
device. For example, two or more injection devices may be arranged
in series within a common injection line.
[0104] At least an injection device which is arranged to
communicate directly with a target location may be provided in
accordance with the present invention. Such an injection device may
be considered to be a final stage injection device. Other
associated injection devices which are located upstream of a final
stage injection device may or may not be provided in accordance
with the present invention. For example, an injection device
located upstream of a final stage injection device may modify inlet
pressure to said upstream injection device based on outlet pressure
of said injection device.
[0105] Where multiple injection devices are arranged in series
within an injection line, the devices may operate to divide any
required pressure differential between the injection line and
ultimate injection location into stages. This may reduce the
required pressure drop across an individual injection device, which
may provide advantages. For example, in some cases an injection
fluid may have behavioural problems when passed over an injection
device at a high differential pressure. Such problems may include
cavitation, depositing of solids or a change in the state of the
injection fluid, which may lead to reduced effectiveness, such as
chemical effectiveness, of the injection fluid. Accordingly, by use
of multiple injection devices arranged in series, the differential
pressure presented across each device may be restricted or reduced,
and in particular to levels which are advantageously lower than any
threshold where problems may occur within the injection fluid. Such
an advantageous use of more than one injection valve in series may
also be achieved while still providing the effect of avoiding low,
vacuum or near vacuum pressures within the injection line.
[0106] The injection device may be configured for use in
combination with one or more other injection devices arranged in
parallel. In such an arrangement multiple injection devices may be
arranged for injection of a fluid from a common injection fluid
source into multiple different locations.
[0107] The injection device may be configured to be coupled within
fluid tubing. The injection device may be configured to be located
at a downhole location. The injection device may be configured to
be located within downhole tubing. The injection device may be
configured to be located in an annulus surrounding downhole tubing.
The injection device may be configured to be located within a
pocket formed in downhole tubing. The injection device may be
configured to be located at a subsea location. The injection device
may be configured to be located at a surface location.
[0108] The injection device may be configured to be permanently
installed within an injection system. The injection device may be
configured to be temporarily installed within an injection system.
In one embodiment the injection device may be configured to be
deployed and/or retrieved by an elongate member, such as by
wireline, coiled tubing or the like.
[0109] The injection device may be for use with any suitable
injection fluid. Such an injection fluid may comprise a chemical.
Such an injection fluid may comprise any one of, for example, a
scale inhibitor, corrosion inhibitor, pH modified, viscosity
modified, diluent, water, oil, acid or the like. It will be
appreciated by those of skill in the art that any injection fluid
may be utilised with the injection device of the present
invention.
[0110] The injection device may be configured to inject a fluid
into a subterranean formation, for example for sequestration of a
fluid, to assist with production of fluids from the formation, to
support the surrounding subterranean geology, or the like.
[0111] The injection device may be configured for use in injecting
a fluid into any location of any flow line or flow process, such as
at any location of a flow line extending from a subterranean
formation to a surface location.
[0112] According to a second aspect of the present invention there
is provided a method for injecting a fluid into a target location,
comprising:
[0113] communicating an injection fluid to an inlet of a housing of
an injection device;
[0114] communicating an outlet of the housing to a target
location;
[0115] communicating a reference port of the housing to a source of
reference pressure;
[0116] causing a second valve member to move relative to a first
valve member by exposure to pressure at the inlet of the housing
and pressure at the reference pressure port of the housing, wherein
such movement permits flow through a flow path of the valve member
to be adjusted.
[0117] According to a third aspect of the present invention there
is provided a pumping system comprising:
[0118] a flow line;
[0119] a pump associated with the flow line and defining an inlet
side and an outlet side;
[0120] an injection device according to the first aspect, wherein
the outlet of the injection device housing is in communication with
the flow line on an inlet side of the pump.
[0121] In one embodiment the reference pressure port of the
injection device housing may be in communication with the flow line
on an outlet side of the pump.
[0122] The reference pressure port may be in communication with a
remote source of reference pressure.
[0123] The reference pressure port may be in communication with a
local source of reference pressure, for example provided by a
pressure reservoir within the housing of the injection device.
[0124] According to a fourth aspect of the present invention there
is provided an injection device for injecting a fluid into a target
location, comprising:
[0125] a housing defining an inlet for communicating with a source
of injection fluid, an outlet for communicating with a target
injection location, and a separate reference port for communicating
with a reference pressure source which excludes the target
injection location;
[0126] a valve member mounted within the housing and defining a
flow path therethrough to facilitate fluid communication between
the inlet and outlet of the housing, wherein the valve member is
moveable within the housing by exposure to fluid pressure at the
housing inlet and fluid pressure at the housing reference pressure
port to vary flow between the inlet and the outlet.
[0127] According to a fifth aspect of the present invention there
is provided an injection device for use in injecting a fluid into a
target location, comprising:
[0128] a housing including an inlet chamber for communicating with
an injection line, an outlet chamber for communicating with a
target location, and a reference chamber for communicating with a
reference pressure source;
[0129] a valve member mounted within the housing and defining a
valve flow path to facilitate fluid communication between the inlet
and outlet chambers;
[0130] a first seal assembly provided between the valve member and
the housing and isolating the inlet chamber from the outlet chamber
such that a pressure differential between the inlet and outlet
chambers acting over the first seal assembly will establish a force
on the valve member; and
[0131] a second seal assembly provided between the valve member and
the housing and isolating the reference chamber from the outlet
chamber such that a pressure differential between the reference
chamber and the outlet chamber acting over the second seal assembly
will establish a force on the valve member,
[0132] wherein the valve member is permitted to move within the
housing in accordance with the pressure forces applied via the
first and second seal assemblies to vary flow through the valve
flow path between the inlet and the outlet chambers.
[0133] According to a sixth aspect of the present invention there
is provided an injection system for injecting a fluid into a target
location, comprising:
[0134] an injection line in communication with a source of
injection fluid;
[0135] an injection device coupled to the injection line and
comprising: [0136] a housing defining an inlet coupled to the
injection line, an outlet for communicating with a target injection
location, and a separate reference port for communicating with a
reference pressure source; [0137] a first valve member mounted
within the housing; [0138] a second valve member mounted within the
housing and defining a flow path therethrough to facilitate fluid
communication between the inlet and outlet of the housing; and
[0139] a sealing arrangement provided between the second valve
member and the housing and configured such that fluid pressure at
the housing inlet and housing reference port apply a force on the
second valve member to cause said second valve member to move
relative to the first valve member and vary flow between the inlet
and the outlet.
[0140] The injection device may define a first injection device and
the injection system may comprise a second injection device located
upstream of the first injection device. In such an arrangement the
second injection device may comprise an outlet in communication
with the inlet of the first injection device.
[0141] The provision of a second injection device within the
injection system may permit a pressure differential between an
injection line and a target location to be divided into stages,
which may be advantageous in certain circumstances.
[0142] The second injection device may be configured similarly to
the first injection device. For example, the second injection
device may permit movement of an associated valve member by
exposure to a reference pressure which is isolated from an outlet
pressure.
[0143] The second injection device may be configured differently
from the first injection device.
[0144] The second injection device may comprise a housing defining
an inlet coupled to the injection line and an outlet for
communicating with the inlet of the first injection device. The
second injection device may comprise a first valve member mounted
within the housing. The second injection device may comprise a
second valve member mounted within the housing and defining a flow
path therethrough to facilitate fluid communication between the
inlet and outlet of the housing. The first and second valve members
may move relative to each other to vary flow through the flow path
of the second valve member, and thus also through the second
injection device.
[0145] The second injection device may comprise a sealing
arrangement provided between the second valve member and the
housing and configured such that fluid pressure at the housing
inlet and housing outlet may apply a force on the second valve
member to cause said second valve member to move relative to the
first valve member and vary flow between the inlet and the
outlet.
[0146] According to a seventh aspect of the present invention there
is provided a method for creating an injection system,
comprising:
[0147] determining a required pressure differential between an
injection line and a target injection location which maintains the
injection line at a positive pressure;
[0148] determining an operational threshold pressure differential
of an injection fluid;
[0149] determining a required number of discrete pressure reduction
stages within the injection line to provide the required pressure
differential between the injection line and target location while
maintaining each pressure reduction stage below the operational
threshold pressure differential of the injection fluid; and
[0150] installing a number of injection devices within an injection
line to correspond to the determined number of discrete pressure
reduction stages.
[0151] In such an arrangement an injection line may be created
which includes a number of injection devices to provide a required
number of discrete pressure differentials each below the
operational threshold pressure differential of an associated
injection fluid, yet which collectively maintain the injection line
in a positive pressure.
[0152] The injection devices may be located at any location along
the length of the injection line.
[0153] The pressure within the injection line may be associated, at
least partly, with hydrostatic pressure.
[0154] At least one injection device may be provided in accordance
with any other aspect.
[0155] Other aspects of the present invention may relate to the use
of the injection device according to any previous aspect, for
example in a wellbore injection system, in a downhole pumping
system, or the like.
[0156] Other aspects of the present invention may relate to a
completion system for a wellbore, such as a wellbore associated
with the exploration and production of hydrocarbons.
[0157] It should be understood that the features defined in
relation to one aspect may be applied to any other aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
[0158] These and other aspects of the present invention will now be
described, by way of example only, with reference to the
accompanying drawings, in which:
[0159] FIG. 1 is a diagrammatic illustration of a typical wellbore
system which includes injection capabilities;
[0160] FIG. 2 is a diagrammatic representation of a known injection
valve arrangement;
[0161] FIG. 3 is a diagrammatic illustration of inlet and outlet
pressure profiles of the injection valve of FIG. 2;
[0162] FIG. 4 graphically represents the effects of hydrostatic
fall-through within a capillary or injection line;
[0163] FIG. 5 provides an illustration of inlet and outlet pressure
profiles of the injection device of FIG. 2, with the use of a more
powerful spring;
[0164] FIGS. 6 and 7 illustrate, respectively, expected and actual
pressure profiles of the inlet and outlet pressures of a downhole
pump, and of the inlet pressure of an associate injection
valve;
[0165] FIG. 8 is a cross-sectional view of an injection device in
accordance with one embodiment of the present invention;
[0166] FIG. 9 is a cross-sectional view of an injection device in
accordance with an alternative embodiment of the present
invention;
[0167] FIG. 10 provides an exemplary pressure plot of the use of an
injection device according to the present invention, in which a
reference pressure from an outlet of a downhole pump is
utilised;
[0168] FIG. 11 provides an exemplary pressure plot of the use of an
injection device according to the present invention, in which a
reference pressure from a remote location, such as a surface
location, is utilised;
[0169] FIG. 12 is a cross-sectional view of an injection device
according to an alternative embodiment of the present
invention;
[0170] FIG. 13 is an exemplary pressure plot of the use of the
injection device of FIG. 12;
[0171] FIGS. 14 to 18 are cross-sectional views of an injection
device in accordance with respective alternative embodiments of the
present invention;
[0172] FIG. 19 is a diagrammatic representation of a downhole
injection system in accordance with an embodiment of the present
invention; and
[0173] FIG. 20 is an exemplary pressure plot of the injection
system of FIG. 19.
DETAILED DESCRIPTION OF THE DRAWINGS
[0174] The present invention relates to an injection device which
may be used in multiple applications. However, for exemplary
purposes some specific embodiments of an injection device have been
illustrated in the drawings, and described below, with a potential
application within a wellbore system, such as a wellbore system for
the extraction of oil and/or gas form a subterranean reservoir.
[0175] FIG. 1, which has also been described above, provides an
illustration of a wellbore completion installation, generally
identified by reference numeral 10, with injection capabilities via
injection valve 48. A known injection valve 48 is illustrated in
FIG. 2, which has already been described above. Furthermore, it has
been explained above that although with the use of such a known
injection valve 48 the expected pressure behaviour within an
injection system, which is reflected in FIG. 6, may not actually be
achieved, and in fact a more accurate representation of reality is
provided in FIG. 7. In this particular example, which involves the
use of a downhole pump, such as an ESP 37 (FIG. 7), upon activation
the pump 37, inlet and outlet pressures might continue to fluctuate
for extended periods, and may not reach a desired steady state
condition. It is believed by the present inventor that such
extended periods of fluctuation is caused by unsteady rates of
injection via the injection valve 48 which is initiated by a sudden
rush of injection fluid through the valve shortly after initial
activation of the pump 37. Through diligent investigation and
research performed by the present inventor it is considered that
such a rush of fluid through the valve is caused by the
compressibility of the injection fluid, as described below in
detail. However, in general terms, the present inventor believes
that as known injection valves require the valve inlet pressure to
track above valve outlet pressure, then in the event of a
relatively quick pressure change at the valve outlet, for example
by activation of a pump, then the fluid in the injection line
acting at the valve inlet will require to undergo a volumetric
change to accommodate the required change in pressure. This
volumetric change will cause the rush through the valve, and
destabilise the system.
[0176] A common injection or capillary control line size currently
used for chemical injection is 9.5 mm (3/8'') OD tube. Also, many
wells are completed with "deviation" where the well may be drilled
off at progressive angles to increase its reach from a central
commencement location. Therefore a well may possess a true vertical
depth of, for example, 2000 metres but in fact be far more in its
true deviated or Measured Depth (Md).
[0177] The normal internal volume of such a control line can be
summarised at varying measured depths as follows:
TABLE-US-00001 Capillary Line Length - metre Length - m 1000 2000
3000 4000 Volume - L 39.4 78.9 118.3 157.8
[0178] Fluids are often considered to be incompressible. This is
only true to a limited extent and when high pressures are applied
to fluids they do compress. This is a fluid property that is a
function of the compressibility of the fluid which may also change
with temperature and pressure.
[0179] Therefore if the capillary line 40 (FIG. 1) is at a given
pressure which then is required to fall, a volume of fluid must be
dissipated in order for this to occur. This fluid can only be
dissipated through the injection valve 48. No matter how efficient
the injection valve 48 is at maintaining a differential pressure
and tracks a change in outlet pressures, the valve will have to
dissipate this volume of fluid to accommodate a change in capillary
line pressure. It has been found the volumes of fluid that require
dissipation are more than is often thought.
[0180] In addition to the compressibility of the fluid, the
capillary line 40 itself will enlarge under internal pressure. This
means its internal volume will increase thus requiring more fluid
to be introduced in order to reach a required pressure. Therefore,
in order for the capillary line 40 to fall in pressure the volume
of fluid entrained at its starting pressure must be fully
dissipated in order to reach a lower pressure. This fluid volume
dissipation therefore results in a significant rise, or surge of
flow through the injection valve 48 as the capillary line pressure
falls.
[0181] This may occur as the ESP 37 is brought online causing the
ESP inlet pressure and therefore the valve outlet pressure to fall.
As the injection valve 48 attempts to maintain a fixed differential
from its inlet to outlet it allows the increased flow to occur
through itself. This rise in flow may be very significant and
constitute a flow surge through the injection valve 48. This has
another detrimental effect where the injection valve 48 can be
overwhelmed and once the flow surge has passed the valve may fall
in its resistance pressure and struggle to retrieve a fixed value
above its outlet pressure. In doing this the capillary line 40 must
gain in pressure before it can reach a value to overcome the valve
resistance pressure and continue to flow again.
[0182] The flow may therefore fluctuate, starting with a flow spike
followed by a fall in flow, a stop in flow and then a slow recovery
of flow until flow is normalised again.
[0183] A significant consequence of this is that flow of chemical
to the ESP 37 is not of a fixed value and is inconsistent. In this
respect certain chemicals are used, called diluents, to reduce
heavy oil viscosity or density to aid in production. A surge of
chemical or diluent flow may overdose the chemical or diluent
resulting in a lighter fluid for the ESP 37 to pump followed by a
fall in chemical flow which increases fluid weight causing a
reduction in ESP 37 pumping efficiency.
[0184] The ESP 37 therefore is seen to increase flow then suffer a
reduction in efficiency. This is generally illustrated in FIG. 7 in
which the ESP outlet pressure 84 is seen to rise as its inlet 82
falls but then suffers a decrease in efficiency where its outlet 84
falls again as the inlet 82 rises while the injection valve
pressure 86 is seen to track the ESP inlet pressure 82. This is due
to firstly the surge of chemical or diluent and then the fall in
chemical or diluent flow.
[0185] Another effect of this variation in pressures due to the
rise and fall of valve outlet pressure is that the surface
injection pressure 90 (a fixed value above the valve outlet
pressure by the valve resistance pressure minus the capillary line
hydrostatic pressure) will also vary which could create loading on
surface injection pump equipment 42.
[0186] The consequences of this cycling of load on the ESP 37 is
considered to be, as a minimum, greatly interrupted and inconstant
production, greater cycle load on the ESP 37 leading to reduced
lifetime requiring the well be worked over to service the ESP 37,
greater monitoring and a lack of understanding about the
effectiveness of the chemical or diluent input leading to increased
chemical or diluent input in attempts to counter the problem.
[0187] It is also possible that the surge effect through the
injection valve 48 could cause damage to its ability to provide a
back pressure. This could lead to a fall in resistance ultimately
allowing a vacuum to occur in the control line 40 which itself
creates risk of blockage, corrosion etc.
[0188] In view of such issues identified by, the inventor as
developed an injection device which seeks to address these
problems. An embodiment of such an injection device will now be
described with reference to FIG. 8.
[0189] The injection device, which is generally identified by
reference numeral 100 includes a housing 102 defining an inlet 104,
outlet 106 and a reference pressure port 108. The inlet 104 is
configured to be in communication with a source of injection fluid
110, for example via an injection line (not shown). The outlet 106
is configured to be in communication with a target location 112,
such as a downhole location. The reference pressure port 108 is
configured to be in communication with a source of reference
pressure 114.
[0190] The device 100 further includes a first valve member 116
which in the present embodiment is rigidly secured to the housing
102. A second valve member 118 is moveably mounted within the
housing 102 and defines a flow path 120 extending therethrough to
facilitate fluid communication between the inlet 104 and outlet
106. As will be described in further detail below, the second valve
member 118 is permitted to move in accordance with inlet and
reference pressures to vary flow between the inlet 104 and outlet
106.
[0191] The first and second valve members 116, 118 are configured
to be engaged and define a sealed area 122 therebetween, such that
when the first and second valve members 116, 118 are engaged flow
through the flow path 120 is prevented. However, when the second
valve member 118 is moved the valve members 116, 118 become
disengaged such that flow is permitted. Also, when the first and
second valve members 116, 118 are disengaged the gap defined
therebetween may create a flow restriction and movement of the
second valve member 118 may vary this flow restriction to assist to
vary flow of injection fluid through the device 100.
[0192] The device 100 further comprises a biasing spring 101, in
this case a coil spring, which acts on the second valve member 118
to bias this in an upward direction (relative to the orientation of
FIG. 8), towards engagement with the first valve member 116. Thus,
spring 101 effectively operates to bias the second valve member 118
towards a closed position.
[0193] The device 100 further comprises a sealing arrangement 122
which includes first and second sealing assemblies 124, 126
extending between the second valve member 116 and the housing 102.
The first sealing assembly 124 provides isolation between the inlet
104 and the outlet 106, such that flow between the inlet and outlet
must be achieved via the flow path 120 in the second valve member
118. Further, the second sealing assembly 126 isolates the outlet
106 from the reference pressure port 108.
[0194] The first sealing assembly 124 is exposed to inlet fluid
pressure, such that said inlet fluid pressure will establish a
force on the second valve member 118 in a downward direction
(relative to the orientation of FIG. 8). Further, the second
sealing assembly 126 is exposed to reference pressure such that
said reference pressure will establish a force on the second valve
member 118 in an upward direction (again, relative to the
orientation of FIG. 8). Accordingly, a net force will be applied on
the second valve member 118 by the action of the inlet and
reference pressures, and in particular in accordance with a
pressure differential between the inlet and outlet pressures.
[0195] In the present embodiment the first and second sealing
assemblies 124, 126 define equivalent seal areas, and as such there
is no effect on any seal area differential, although in other
embodiments such a seal area differential may be provided.
[0196] Furthermore, both the first and second sealing assemblies
124, 126 are exposed to outlet fluid pressure. Also, as the first
and second sealing assemblies 124, 126 define equivalent seal areas
then the effect of the outlet pressure will be cancelled, and no
net force will be created by outlet pressure. It should be noted,
however, that in other alternative embodiments a seal area
differential may be provided to establish a bias force generated by
outlet pressure.
[0197] Accordingly, in the present embodiment the outlet pressure,
which will largely be defined by pressure at the target location
112, will not have any effect on the operation of the device 100.
This may therefore avoid those problems identified above which stem
from possible variations in outlet pressure resulting in a sudden
surge through an injection device.
[0198] In use, for flow through the device 100 to be established,
the force applied on the second valve member 118 by the inlet
pressure must exceed to combined force applied by the reference
pressure and the spring 101. In this way, the inlet pressure may be
presented at a pressure which is greater than the reference
pressure by the appropriate equivalent pressure generated by the
spring 101, in addition to any backpressure created by the
restriction to flow between the first and second valve members 116,
118.
[0199] The device 100 may be used in conjunction with any desired
source of reference pressure 114. In particular, the effects and
advantages of the present invention may be achieved where the
source of reference pressure 114 excludes the target location
112.
[0200] An alternative embodiment of an injection device, in this
case generally identified by reference numeral 200, is shown in
FIG. 9, reference to which is now made. Device 200 is similar to
device 100 of FIG. 8, and as such like features share like
reference numerals, incremented by 100. Further, the operation of
the device 200 is largely similar to device 100, and as such only
the difference in structure and operation will be described with
reference to device 200.
[0201] In this respect device 200 also includes a housing 202
defining an inlet 204, outlet 206 and reference pressure port 208,
with first and second valve members 216, 218 mounted within the
housing 202. A sealing arrangement 222 comprising first and second
sealing assemblies 224, 226 is positioned between the second valve
member 218 and the housing, and functions, as before, to provide a
desired force bias on the second valve member 218 by action of
inlet and reference pressures.
[0202] In the present embodiment, however, the first valve member
216 is not rigidly secured to the housing 202, but is instead also
permitted to move within the housing 202. In particular, the first
valve member 216 is provided in the form of a pin which is mounted
on a spring 130 which acts to bias said valve member 216 into
engagement with the second valve member 218 to close the flow path
220 in said second valve member 218. Accordingly, when the first
and second valve members 216, 218 are engaged, movement of the
second valve member 218, for example by action of the various
pressures and the second valve member bias spring 201, will also
cause movement of the first valve member 216.
[0203] The housing 201 further comprises a limit arrangement in the
form of an annular lip 132, and the second valve member 216
includes a corresponding circumferential rib 134. When the first
and second valve members 216, are engaged, with the annular lip 132
and circumferential rib 134 disengaged, inlet fluid pressure will
act over the seal area 222 between the engaged valve members 216,
218, which will have the effect of pressing said members together.
This arrangement therefore permits inlet pressure to be utilised to
improve the seal between the valve members when engaged.
[0204] However, when the appropriate pressure forces applied at the
inlet is sufficient to move the second valve member downwardly, the
circumferential rib 134 of the first valve member 216 will
eventually engage the annular lip 132, such that continued downward
movement of the second valve member 218 will cause disengagement of
the valve members, thus establishing flow between the inlet 204 and
outlet 206.
[0205] Also shown in the present embodiment is a check valve
assembly 136 located at the outlet 206 of the housing, and which
functions to prevent backflow from the target location 212 into the
device. Although the check valve assembly 136 is shown mounted in
an integrated part of the housing 202, a separate check valve
assembly may instead be provided and secured relative to the outlet
206 of the housing 202.
[0206] As defined above, it is possible to use any desired source
of reference pressure, perhaps with the exception of pressure at
the target location. For example, in one exemplary use, the
injection device may be used in the wellbore completion arrangement
10 first shown in FIG. 1, reference to which is again made, wherein
the injection valve 48 in FIG. 1 may be replaced with the device
according to any embodiment of the invention. In such an exemplary
use the target location is on the inlet or suction side of an ESP
37. As noted above, problems have been discovered in prior art
systems which also use this target location to vary the pressure
within the associated injection line 40. However, in the present
exemplary use the reference pressure may be provided from the
outlet or delivery side of the ESP. A graphical representation of
the various pressure profiles associated with such an exemplary use
of the present invention is illustrated in FIG. 10.
[0207] As illustrated, when a pump (where use) such as an ESP is
activated the inlet pressure 140 will fall, and the outlet pressure
141 will rise. As the device utilises this outlet pressure 141 as a
reference pressure, this results in the inlet pressure 143 of the
device defines the same pressure profile, albeit at a differential
higher provided by the effect of the spring acting against the
second valve member in addition to the effect of any back pressure
created by flow through the device. As illustrated also in FIG. 10,
the pressure differential 146 between the inlet and outlet of the
device is no longer fixed, which differs from the prior art. Also,
the surface pressure 146 defines a similar profile to that of the
pump outlet pressure 142. As is clear from FIG. 10, the pump is
considered to reach a desired steady state condition, without any
problems occurring due to cascading of fluid through the
device.
[0208] In an alternative exemplary use, the device may be arranged
such that the reference pressure is provided from a source, for
example at surface level, which permits the reference pressure to
be varied. The associated pressure profiles of an associated ESP
and of the device is illustrated in FIG. 11. In this respect, when
the pump is activated the inlet pressure 150 falls. At this stage
the reference pressure 151 is fixed at a first value, and as such
the inlet pressure 152 of the device is initially constant at a
first value, which will be a fixed differential above reference
pressure 151. If at some point a change in reference pressure is
required, for example due to a change in density of injection
fluid, then this may be readily achieved, irrespective of the pump
inlet pressure. In the exemplary embodiment the change involves an
increase in reference pressure 151 (initiated around time interval
6), such that the inlet pressure 152 is seen to increase to a
second, higher level.
[0209] A further alternative embodiment of an injection device, in
this case generally identified by reference numeral 300, is shown
in FIG. 12. Device 300 is similar to device 200 shown in FIG. 9,
and as such like features share like reference numerals,
incremented by 100. For brevity, only differences between the
embodiments in FIGS. 9 and 12 will be highlighted. In this respect,
device 300 includes bellows type first and second sealing
assemblies 324, 326 which form the sealing arrangement. Further,
the device 300 comprises an integrated reference pressure reservoir
160 which contains an internal reference pressure which acts at the
reference port 308. Thus, the second valve member 318 is affected
by the pressure within this reservoir 160.
[0210] Further, the second valve member 318 includes a lower pin
142 which engages a plate 144, which in turn is acted on by the
bias spring 301, which in this case is a disk spring, mounted
within the reservoir 160.
[0211] In this present embodiment the device 300 does not
necessarily require the presence of any external source of
reference pressure, which may provide significant advantages in
terms of permitting a simplified system to be utilised.
Furthermore, in certain cases the pressure within the reservoir may
define a minimal pressure, such that the effect of any active
pressure is essentially negligible, such that any force applied to
move the second valve member 318 upwardly is achieve primarily by
the spring 301.
[0212] A pressure plot associated with the device 300 of FIG. 12 is
shown in FIG. 13, in this case again assuming that the device is
arranged to inject a fluid into the inlet side of an ESP, such as
ESP 37 of FIG. 1. Referring to FIG. 13, as a pump (where used) such
as an ESP is activated pump inlet pressure 162 falls. However, as
the reference pressure within reservoir 160 is constant, a constant
valve inlet pressure 164 and surface pressure 166 will be achieved,
with the pressure differential 168 between the device inlet 304 and
outlet 306 varying.
[0213] An injection device according to the present invention may
be embodied in a number of ways, and a selection of further example
embodiments are presented in FIGS. 14 to 18, reference to which
will now be made. For brevity only particular differences between
the embodiments will be identified.
[0214] Injection device 400 of FIG. 14 is generally similar to
device 200 of FIG. 9, and as such like features share like
reference numerals, incremented by 200. Device 400 includes bellows
type sealing assemblies 424, 426 which form the sealing arrangement
422.
[0215] Injection device 500 of FIG. 15 is generally similar to
device 200 of FIG. 9, and as such like features share like
reference numerals, incremented by 300. Device 500 includes bellows
sealing assemblies 524, 526 which form the sealing arrangement 522.
Further, the second valve member 516 includes an extension pin 170
which is engaged by a plate 172 which in turn is engaged by bias
spring 501.
[0216] Injection device 600 of FIG. 16 is generally similar to
device 200 of FIG. 9, and as such like features share like
reference numerals, incremented by 400. Device 600 includes bellows
sealing assemblies 624, 626 which form the sealing arrangement 622.
Further, the second valve member 616 includes an extension pin 174
which is engaged by a plate 176 which in turn is engaged by bias
spring 601.
[0217] Furthermore, the second valve member 616 includes a ball
member which cooperates with the second valve member 618. A support
stalk 178 extends through the flow path 620 of the second valve
member 618 and functions to limit movement of the ball of the first
valve member 616.
[0218] Injection device 700 of FIG. 17 is generally similar to
device 300 of FIG. 12, and as such like features share like
reference numerals, incremented by 400. In this embodiment the
first valve member 716 includes a profiled pin 180 which extends
upwardly therefrom and is received within an annular chamber 182.
the pin 180 and chamber 182 cooperate to limit movement of the
second valve member 716 to permit disengagement from the second
valve member 718.
[0219] Injection device 800 of FIG. 18 is generally similar to
device 300 of FIG. 12, and as such like features share like
reference numerals, incremented by 500. In device 800 the outlet
806 is provided inline with the inlet 804. This is achieved by
providing a flow path 186 around the reservoir chamber 660.
Further, device 800 includes a check valve assembly 190 in
communication with the outlet 806.
[0220] In some cases the required differential resistance pressure
required where an ESP is set to a very high Total Vertical Depth
(TVD) and the ESP will draw to extremely low pressures may be very
high. This is by way of a capillary line hydrostatic being large
due to the great depth (TVD) and the ESP drawing to an
exceptionally low pressure for the purposes of enhanced production,
for example. In such cases the fluid being injected may have
behavioural problems when passed over the injection device at a
high differential pressure. Such problems may include cavitation,
depositing of solids or a change in the state of the injection
fluid which may lead to reduced effectiveness, such as chemical
effectiveness.
[0221] The present inventor therefore considers it to be desirable
that in some situations a differential pressure be reduced to
levels that are under the thresholds where such issues may occur
with the injection fluid. This reduction in differential pressure,
however, may not be readily achieved in conventional prior art
systems as the requirement still exists that the overall resistance
within the injection device must be large enough to ensure there is
no vacuum in the capillary injection line.
[0222] To address this, an injection device according to the
present invention (such as in any embodiment described above) may
be installed at a lower point of injection but in addition to this
a second (or third etc.) injection valve may be installed at a
higher point in the injection line, for example at any higher point
in the injection line. Such an arrangement is illustrated in FIG.
19, reference to which is now made. In this respect, FIG. 19
provides a diagrammatic illustration of a wellbore system,
generally identified by reference numeral 910, which includes
injection capabilities and is largely similar to the system 10 of
FIG. 1. As such, like features share like reference numerals
incremented by 900. Thus, wellbore system 910 includes a casing
string 912 located within a drilled bore 914 which extends from
surface 916 to intercept a hydrocarbon bearing formation 918. A
lower annulus area 920 may be filled with cement 922 for purposes
of support and sealing. A production tubing string 924 extends from
a wellhead 926 and production tree 928. A lower end of the
production tubing string 924 is sealed against the casing 912 with
a production packer 930 to isolate a producing zone 932. A number
of perforations 934 are established through the casing 912 and
cement 922 to establish fluid communication between the casing 912
and the formation 918. Hydrocarbons may then be permitted to flow
into the casing 912 at the producing zone 932 and then into the
production tubing 924 via inlet 936 to be produced to surface.
Artificial lift equipment, such as an ESP 937 may optionally be
installed inline with the production tubing 924 as part of the
completion to assist production to surface. The production tree 928
may provide the necessary pressure barriers and provides a
production outlet 938 from which produced hydrocarbons may be
delivered to a production facility (not shown), for example.
[0223] A small bore injection line or conduit 940, which is often
referred to as a capillary line, runs alongside the production
tubing 924 from a surface located injection fluid source 942 to a
downhole target location, which in the illustrated example is a
lower end of the production tubing 924, below the ESP 937. The
production tubing 924 may include an optional injection mandrel
944. An injection pump 946 is located at a topside location to
facilitate injection of the injection fluid 942.
[0224] A first injection valve 948 is located at the lower end of
the injection line 940 in proximity to the location of injection.
This injection valve 948 may be provided in accordance with any
embodiment of the present invention. A second injection valve 949
is coupled to the injection line 940 at a location which is
upstream of the first injection valve 948. The second injection
valve 949 may be provided in accordance with any embodiment of the
present invention. The second injection valve 949 may be provided
in accordance with any known or conventional injection valve, such
as a conventional backpressure injection valve which may modify its
inlet pressure based on its outlet pressure.
[0225] With the example arrangement shown in FIG. 19, the overall
required differential pressure may be broken into two stages, thus
ensuring that the differential pressure occurring at any one of the
injection valves 948, 949 is reduced ensuring the injection fluid
is not subjected to high shear rates through the device under high
differential pressures.
[0226] This installation mode may be generally illustrated in the
below example where a very high setting depth (TVD) is required for
the ESP 937 which is intended to run at a very low intake pressure.
The injection line 940 is installed with a conventional back
pressure injection device (the second injection device 949) at
approximately 50% of its TVD and an injection device (the first
injection device 948) at the ESP intake depth (full TVD). If a
single back pressure device is used it would be required to have a
minimum back pressure resistance of 314 bar. However, if we assume
in the present illustration that the injection fluid has been found
to suffer degradation of properties if passed through a
differential of more than 180 bar, then this required pressure
differential of 314 bar will have an adverse effect on the
injection fluid. Therefore two stages are employed with an upper
device 949 and a lower device 948.
[0227] A process of designing or selecting the from of an
appropriate injection system in the present illustration is set out
in the table below:
TABLE-US-00002 Total Vertical Capillary Line Height (TVD) - metres
3050 Determine Capillary Hydrostatic Pressure Specific Gravity of
Injected Fluid 1.050 Density of Fluid - kg/m3 1050.00 TOTAL
Capillary Line Hydrostatic pressure - bar 314.2 Identify Chemical
Differential Limitations Maximum Allowable Differential - bar 180.0
Is Allowable Dp greater than required Dp? NO Required Stages of
Resistance 2 Determine Upper and Lower Stage Conditions Minimum ESP
Inlet Pressure - bar 86.0 Lower Device Resistance Pressure - bar
150.0 Lower Device Inlet Pressure - bar 236.0 Installation Depth of
Upper Stage (TVD) - metre 1480.0 % of Overall TVD for Installation
of Upper Stage - % 49% Capillary line height from lower to upper
stage (TVD) - m 1570.0 Hydrostatic Pressure in line from lower to
upper Stage - bar 161.8 Upper Stage Device outlet Pressure - bar
74.2 Upper Device Resistance Pressure - bar 100.0 Upper Device
Inlet Pressure - bar 174.2 Hydrostatic Pressure in line from upper
Stage to Surface - bar 152.5 Surface Injection Pressure - bar
21.8
[0228] Although in the example above the upper device is located at
approximately 50% of the TVD, this is only exemplary, and any
suitable depth may be utilised. This is illustrated in the further
example below, in which the upper device is located at an further
example depth of 71% of TVD.
TABLE-US-00003 Determine Upper and Lower Stage Conditions Minimum
ESP Inlet Pressure - bar 86.0 Lower Device Resistance Pressure -
bar 150.0 Lower Device Inlet Pressure - bar 236.0 Installation
Depth of Upper Stage (TVD) - metre 2180.0 % of Overall TVD for
Installation of Upper Stage - % 71% Capillary line height from
lower to upper stage (TVD) - m 870.0 Hydrostatic Pressure in line
from lower to upper Stage - bar 89.6 Upper Stage Device outlet
Pressure - bar 146.4 Upper Device Resistance Pressure - bar 100.0
Upper Device Inlet Pressure - bar 246.4 Hydrostatic Pressure in
line from upper Stage to Surface - bar 224.6 Surface Injection
Pressure - bar 21.8
[0229] Therefore by using two stages (upper and lower) each with
appropriate differential settings of 100 and 150 bar respectively,
the overall resistance is provided and the full injection line is
maintained in a positive pressure thus avoiding vacuum fall out
conditions and ensuring the injection fluid is passed through
differential pressures beneath its property change threshold of 180
bar.
[0230] The first example provided above may be further illustrated
in FIG. 20, which is a pressure plot along the length of the
injection line showing the individual pressure drop effect of the
first and second injection devices 948, 949.
[0231] It should be understood that the embodiments described
herein are merely exemplary and that various modifications may be
made thereto without departing from the scope of the invention. For
example, various embodiments have been described above, and it
should be recognised that further embodiments are possible in which
the features of some of the illustrated embodiments may be applied
to others. Thus, any combination of the illustrated features may be
possible.
[0232] Further, in the example of FIG. 19, any number of injection
devices may be utilised to provide the desired stages of pressure
drop along the length of the injection line.
* * * * *