U.S. patent number 3,780,809 [Application Number 05/243,360] was granted by the patent office on 1973-12-25 for method and apparatus for controlling wells.
This patent grant is currently assigned to Esso Production Research Company. Invention is credited to Robert C. Ayers, Jr., Jack H. Bayless, John W. Graham, James R. Lloyd, William D. Loth, Robert E. Williams.
United States Patent |
3,780,809 |
Ayers, Jr. , et al. |
December 25, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
METHOD AND APPARATUS FOR CONTROLLING WELLS
Abstract
An improved method and apparatus are disclosed for controlling
flow of fluid through a conduit disposed within a well extending
beneath the surface of the earth. The apparatus includes a
subsurface valve situated on the conduit and provided with means
for actuating the valve between an open and closed position to
control the flow of fluid through the conduit. The valve
automatically closes at the end of a preset flow period unless
reset in response to an external signal to reinitiate the
predetermined period to closure. Normally a surface generated
signal, as for example a pressure pulse, is periodically directed
to the actuating means to reinitiate the flow period. The frequency
of the pulses is adjusted as required to assure that the actuating
means will receive a pulse prior to the end of the flow period so
flow will not be interrupted. If the pulses are interrupted, as for
example by a rupture in the well conduit, the valve will close
automatically at the end of the flow period.
Inventors: |
Ayers, Jr.; Robert C. (Houston,
TX), Bayless; Jack H. (Houston, TX), Graham; John W.
(Alvin, TX), Lloyd; James R. (Houston, TX), Loth; William
D. (Houston, TX), Williams; Robert E. (Houston, TX) |
Assignee: |
Esso Production Research
Company (Houston, TX)
|
Family
ID: |
22918446 |
Appl.
No.: |
05/243,360 |
Filed: |
April 12, 1972 |
Current U.S.
Class: |
166/374; 166/53;
137/624.11; 166/316 |
Current CPC
Class: |
E21B
34/108 (20130101); E21B 34/16 (20130101); E21B
2200/04 (20200501); Y10T 137/86389 (20150401) |
Current International
Class: |
E21B
34/00 (20060101); E21B 34/10 (20060101); E21B
34/16 (20060101); E21b 043/00 () |
Field of
Search: |
;166/64,53,65,314,224 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Novosad; Stephen J.
Assistant Examiner: Staab; Lawrence J.
Claims
What is claimed is:
1. In a subsurface valve for controlling the flow of fluid through
a well conduit, the improvement comprising means for actuating the
valve between open and closed positions at the end of a preset flow
period and means responsive to an external signal received prior to
the end of said flow period for resetting said actuating means to
reinitiate said preset flow period prior to actuation.
2. The apparatus of claim 1 wherein said actuating means includes a
timer for determining the span of said flow period.
3. The apparatus of claim 1 wherein said actuating means includes a
differential pressure actuated means for determining the span of
said flow period prior to actuation.
4. The apparatus of claim 1 wherein the span of said flow period is
determined from the cumulative volume of fluid flowing through said
conduit.
5. The apparatus of claim 1 wherein said actuating means includes a
means responsive to pressure within said well conduit for resetting
same.
6. A safety device for controlling flow of a well fluid through a
vertical conduit within a well extending beneath the surface of the
earth which comprises a subsurface valve adapted to be disposed
within said conduit and provided with means for urging the valve
towards a closed position, means for holding said valve open until
the end of a preselected flow period, and means responsive to an
external signal received prior to the end of said flow period for
reinitiating said preset flow period prior to valve closure.
7. The apparatus of claim 6 wherein said means urging said valve
towards said closed position includes a spring.
8. The apparatus of claim 6 including a timer for determining the
span of said flow period.
9. The apparatus of claim 6 including a differential
pressure-actuated means for determining the span of said flow
period.
10. The apparatus of claim 6 wherein said means is responsive to
pressure within said well conduit.
11. A safety device for controlling flow of a well fluid being
produced through a conduit within a well extending beneath the
surface of the earth which comprises:
a. a subsurface valve configured to be disposed within said conduit
and adapted in a closed position to stop said flow of well
fluid;
b. means for urging said valve towards the closed position; and
c. means for holding said valve in the open position against the
urging of said means throughout the duration of a preselected flow
period, said means permitting said valve to close at the end of
said flow period; and
d. means responsive to an external signal received prior to the end
of said flow period for reinitiating said preset flow period prior
to valve closure.
12. The apparatus of claim 11 wherein said actuator means includes
a timer for determining the span of said flow period prior to
actuation.
13. The apparatus of claim 11 wherein said actuator means includes
a differential pressure actuated means for determining the span of
said flow period prior to actuation.
14. The apparatus of claim 11 wherein said actuator means inlcudes
a means responsive to pressure within said well conduit for
resetting same.
15. A safety device for controlling flow of a well fluid being
produced through a conduit within a well extending beneath the
surface of the earth which comprises:
a. a subsurface valve adapted to be disposed within said conduit
and provided with biasing means for urging said valve towards the
closed position;
b. means for holding said valve in the open position against said
biasing means;
c. means associated with said valve for indicating the termination
of a predetermined flow period;
d. means associated with said holding means and responsive to said
indicating means for releasing said holding means to close said
valve upon termination of said flow period; and
e. means associated with said indicating means and responsive to a
signal generated at the earth's surface for resetting said
indicating means and reinitiating said flow period to permit
deferral of termination of said flow period.
16. A method for regulating the flow of fluid within a well conduit
extending beneath the earth's surface comprising:
a. controlling the flow of fluid within said conduit at a
subsurface control point so as to terminate flow of fluid thereby
at the end of a predetermined flow period in the absence of a
control signal during said flow period, and
b. transmitting a signal from the earth's surface at a frequency
such that said signal arrives at said control point prior to the
end of each said flow period whereby flow continues
uninterrupted.
17. The method of claim 16 wherein said signal is a pressure pulse
and is transmitted through fluid in said conduit.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved downhole valve particularly
useful as a safety valve in wells drilled for the production of
crude oil and natural gas.
2. Description of the Prior Art
Wells drilled offshore for the production of crude oil and natural
gas are subject to a number of hazards which may lead to their
casings being accidentally ruptured. Among these are platform
failures due to severe storms or collisions, equipment failures
caused by erosive well fluids, and explosions or fires stemming
from accidents during workovers or other surface operations. The
provision of well safety equipment to close in the well in the
event of an emergency is therefore an important aspect in designing
such wells.
In the past, the primary approach to well protection has been the
provision of a fluid-velocity actuated valve in the producing
string. These safety valves have a number of inherent drawbacks.
For instance, since they are actuated only by an abnormal flow
velocity, it is necessary to produce the wells at reduced rates to
maintain sufficient reserve producing capacity to assure emergency
valve actuation. In addition, there is a lack of any positive means
of controlling the valve from the surface. Finally, testing a
velocity actuated valve requres a rapid change in producing rate to
a level substantially abve normal, which may in turn damage the
producing formation.
The problems with velocity-actuated safety valves can in many cases
be mitigated by using surface-controlled, hydraulically actuated
subsurface valves. In these installations a valve together with a
hydraulic actuator is installed downhole in the well conduit. A
hydraulic control conduit extends from the valve actuator to the
surface along the exterior of the well conduit so that it will not
impair movement of tools through the inner bore. These valves are
generally maintained open hydraulically and close in response to a
drop in hydraulic pressure in a control line or similar conduit.
This type system has the advantage that the valve can be positively
controlled from the surface, may be tested safely, and requires no
reserve producing capacity. Because of the external hydraulic fluid
line, however, it has the disadvantage of requiring more space than
a velocity-actuated valve. By advance planning space can be
provided for these systems in new wells, but in many existing wells
there is insufficient room. In the latter situation the only way to
install such a system is in an internal concentric string of pipe.
This in turn reduces the diameter of the flow path and frequently
creates an undesirably high flow restriction, rendering deployment
of the system impractical.
There therefore exists a need for an improved subsurface safety
valve which can be positively controlled from the surface, can
safely be tested, requires no mechanical connection with the
surface, and does not require reserve producing capability. Such an
improved valve would not have the space limitations attendant with
surface controlled, hydraulically actuated subsurface valves.
SUMMARY OF THE INVENTION
The present invention provides a subsurface safety valve which
requires no mechanical connection to the surface and alleviates the
problems outlined above. The improved subsurface safety valve of
the invention is useful primarily in controlling the flow of fluid
through a conduit within a well for the production of crude oil or
natural gas. The improvement comprises a means for actuating the
valve which maintains the valve open throughout the duration of a
preset flow period and automatically closes the valve at the end
thereof unless the actuating means is set by an intervening
external signal to reinitiate the preset flow period prior to
closure. The span of the predetermined flow period may, for
example, be defined by a specific time interval or by a particular
volume of fluid. The external signal used to reset the device is
preferably a surface generated pressure pulse which is transmitted
through a well fluid.
The present method involves producing a well through a conduit
including a safety valve constructed in accordance with the
invention and periodically generating a signal at the earth's
surface which is detectable at the valve and serves to reinitiate
the flow period of the valve acutator. The frequency of the pulses
is adjusted as required to pulse the valve prior to termination of
the flow interval, and thereby prevent the valve from closing. To
test the valve or close it from the surface, the periodic signals
are interrupted so that the valve closes at the end of the flow
period. Preferably the valve is reopened by increasing the pressure
within the conduit above the valve to a level in excess of that
below it.
The method and apparatus of the invention require no mechanical
linkage between the valve and the surface, can be run and removed
with wireline tools, can be tested on a rountine basis, and can
automatically shut in wells in the absence of intermittent signals
from the surface. It will therefore be apparent that the present
invention offers significant advantages over systems available
heretofore.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic of the subsurface safety valve system of the
invention.
FIG. 2 is a cross-sectional elevation view of a valve assembly
constructed in accordance with the present invention in its open
position.
FIG. 3 shows the apparatus of FIG. 2 with the valve in its closed
position.
FIG. 4 is a schematic of electric componentry which can be used
with the valve assembly shown in FIGS. 2 and 3.
FIG. 5 is a schematic of another embodiment of a safety valve
constructed in accordance with the present invention in its open
position.
FIG. 6 is a schematic of the system of FIG. 5 showing the flow
interval timer being reset to its initial position.
FIG. 7 schematically depicts the system of FIG. 5 with the valve in
the closed position.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a schematic elevation of the subsurface safety valve
system of the present invention. The system shown includes a well
conduit 11 extending from the top of offshore platform 12 into a
borehole in the floor 13 of the body of water 14. Although not
shown in the drawing, the lower end of the conduit is in
communication with a producing formation. Surface equipment for
controlling flow of produced fluid includes a manually controlled
master valve 15 and a flow control device 16, as for example a
pressure actuated motor valve, situated on the well conduit. A
controller 17 for regulating the position of the flow control
device is also shown. This may comprise a source of high pressure
gas together with a timing device. Downhole equipment includes
safety valve 18 coupled with an actuator 19. The actuator and valve
are normally enclosed within an outer housing provided with
external seals and adapted for installation and removal with
wireline operated tools.
The actuator maintains the downhole valve in the open position
throughout the span of a flow period having a preset duration and
closes the valve without intervention from the surface at the
termination of the flow period. The actuator is resettable in
response to an external signal to reinitiate the preset flow period
prior to valve closure. In the system shown in FIG. 1, controller
17 can be set to periodically actuate a valve or other flow control
device to restrict flow and thus create a pressure pulse in the
well conduit. A pressure responsive means situated downhole on the
valve actuator will respond to this pulse by resetting the flow
interval to zero and restarting the flow period to closure so that
flow continues uninterrupted.
If positive downhole closure is required, or if it is desired to
test the downhole valve, the controller at the surface is adjusted
to omit the periodic pressure pulse. This results in the downhole
actuator receiving no signal and closing the valve after the
duration of the predetermined flow interval. Similarly, in the
event the well casing is severed or severely damaged, the actuator
will receive no reset signal and the valve will automatically
close, shutting in the well.
The safety valve is preferably a normally closed device. A full
opening ball valve is preferred, but numerous other closure devices
would be satisfactory for use with the system. It will generally be
most convenient to employ surface generated pressure fluctuations
in the flow stream to signal the downhole actuator; however, other
systems, as for example, acousitc, electrical or radio signal could
be used.
The longevity of the flow period prior to closure is variable
within wide limits consistent with the present invention. It is
preferred, however, that a relatively short flow interval be
employed. When the flow period is defined in terms of time or fluid
volume, this has the advantage of reducing substantially the volume
of flow through the conduit between loss of well control due to
damage and subsequent closure of the valve. A number of devices for
controlling the duration of the flow interval will be readily
apparent. The preferred systems are, however, responsive to either
elapsed time or to the cumulative volume of fluid flowing through
the safety valve.
FIG. 2 and 3 are cross-sectional elevation views of one
configuration of safety valve exemplary of the apparatus of the
present invention. The apparatus shown includes an outer housing 21
having seals 10 and expansible dogs 20 situated on the upper
exterior to permit it to be anchored within the well conduit
against vertical movement and sealed against circumferential flow.
A slidable cylindrical mandrel 22 is disposed within the outer
housing. A ball 23 having an aperture 23A therethrough is rotatably
mounted within the lower interior of the mandrel. The ball engages
the outer housing by means not shown so that as the mandrel slides
from the lower position, FIG. 2, to the upper, FIG. 3, the ball
rotates from the open to the closed position. The mandrel is biased
toward the upper position by compressed spring 24 situated between
the outer flange 25 of the mandrel and the inner shoulder 26 of the
outer housing. Spring-biased latch 27 extends inwardly whenever its
compressed spring is permitted to expand, FIG. 2, and is locked in
place above the mandrel by solenoid actuated locking member 29 to
block it against movement so that the valve remains open. When the
locking member is withdrawn to free the latch, the spring-loaded
mandrel slides upwardly forcing the latch into its receptacle
within the outer housing and closing the valve, as shown in FIG. 3.
Valve closure is assisted by differential pressure exerted by the
flowing well stream. Spring-biased ball detent 28 engages a recess
28A in the outer housing when the mandrel is fully extended. To
reopen the valve, pressure within the well conduit above the closed
valve is increased to a level in excess of pressure below it. The
differential pressure required to generate a force sufficient to
overcome the ball detent should also be sufficient to overcome the
force of the spring 24 so that the mandrel will snap back to its
original position, opening the ball valve.
The actuator is adpated to close the valve at the end of a preset
flow period unless an intervening external signal is received which
resets the actuator and causes it to reinitiate the flow period,
thereby deferring closure for the span of an additional flow
interval. In the embodiment shown in FIGS. 2 and 3, the actuator
closes the subsurface valve by unlocking latch 27 which when
extended and locked into place restrains spring-biased mandrel 22
in its lower position to keep the valve open. Position of the lock
on latch 27 may for example be controlled by a solenoid designed to
fail safe. Solenoid 20 when energized, forces locking member 29
downward, overcoming spring 29B to hold latch 27 in place. Whenever
the solenoid is deenergized, spring 29B forces the locking member
upward, causing the valve to close.
Electrical or electronic componentry associated with the valve may
be mounted within the wall of outer housing 21, as for example
within the circumferential housing designated by numeral 30 in the
drawings. This will normally include a source of electric power, as
for example, a battery or turbine generator, to provide energy for
the solenoid and associated control circuitry. The latter includes
a pressure sensitive device in communication with the inner bore of
the valve housing. This device, which may for example be a pressure
transducer or pressure switch, is actuated in response to a
pressure condition within the section of the well conduit above the
valve, as might be created by restricting flow or by shutting the
well in at the surface for a brief interval. The pressure-sensitive
device acts in combination with a timer or similar device for
indicating the termination of the predetermined flow period. The
signal from the pressure sensitive device serves to reset the timer
and reinitiate the timed interval, permitting deferral of
termination of the flow period and thereby maintaining the valve
open for an additional flow period.
FIG. 4 is a schematic diagram of componentry which can be used for
this purpose. Shown is a battery 31 which provides a source of
power for a circuit including resistor 32, solenoid 29A, and
capacitor 42. As capacitor 42 charges, the voltage across resistor
32 and solenoid 29A decreases until a point is eventually reached
at which the voltage drop across the solenoid is insufficient to
hold locking pin 29 against spring 29B. This permits the spring to
lift the locking pin which in turn results in closure of the valve.
The flow period to closure is governed by the time period required
to charge the capacitor to the critical level and can be varied by
changing the resistance of resistor 32. A normally open pressure
switch 43, which closes in response to a pressure increase, is
situated in a second circuit which also includes capacitor 42. In
response to a pressure signal the switch closes, discharging the
capacitor through the pressure switch circuit. When the pressure
switch reopens, its circuit is again broken, permitting the
capacitor to begin charging. The flow period is thus reinitiated,
deferring closure of the valve for the duration of another flow
period.
As pointed out above, after closure, the valve is normally reopened
by increasing pressure within the well conduit to a level above
that which exists within the portion of the conduit situated
beneath the valve. This increase actuates the pressure sensor which
closes the pressure switch discharging the capacitor and
re-initiating the timed flow cycle. Discharging the capacitor
permits sufficient current to again flow through the solenoid to
cause it to force locking pin 29 downward. The locking member will,
however, be temporarily restrained from movement by spring-biased
latch 27, which is temporarily blocked against movement by the
exterior of the mandrel until such time as the differential
pressure across the valve depresses the mandrel to its open
position. With the mandrel depressed the latch extends inwardly and
is locked in place to hold the valve open.
FIGS. 5, 6 and 7 depict schematically another embodiment of the
apparatus of the present invention. It will be understood that the
arrangement of the structural elements shown in the drawing is for
convenience of illustration only and that the entire system shown
would normally be arranged such that it could be conveniently
enclosed within a wireline retrievable outer housing. The apparatus
includes a valve body 33 having an inner extending cylindrical bore
34. A conduit 35 with an external circumferential shoulder 36 is
slidably disposed within the bore of the valve body, dividing it
into an upper chamber 37 and lower chamber 38 separated by the
slidable piston formed by shoulder 36. The lower end of the conduit
is closed, as by means of a cap 39, but the conduit has two lateral
ports designated by numeral 40 for admitting fluid. The upper end
of the conduit is open, completing the flow path through the valve
body. When the piston is in its uppermost position within the valve
body, as shown in FIG. 7, the two lateral ports in the lower end of
the conduit are flush with inner shoulder 41 at the lower end of
the bore through the valve body and thereby seal the conduit
against flow. Thus, with the piston in its upper position the valve
is closed, whereas in the lower position the valve is open to
flow.
The position occupied by the piston, and thus the operating
position of the valve, is controlled by the pressure differential
between the upper and lower chambers positioned above and below the
piston, respectively. It will normally be desired to include a
biasing means, for example compressed spring 36A on the underside
of the piston, to assure that the valve will close in the event of
failure of hydraulic circuitry. Well pressures routed by a pilot
valve designated generally by numeral 50 provide the pressure
differentials required to operate the valve. In this connection it
will be noted that during normal producing operations, fluid flows
upwardly through the valve creating a pressure differential across
the valve, the pressure below being higher than that above.
The pilot valve typically includes a cylindrical housing 51 within
which a pilot piston 52 is slidably disposed. The pilot piston has
two pairs of unconnected flow paths extending therethrough. The
lower pair, numbered 53 and 54, are arranged horizontally for
straight-through flow. The upper pair, numbered 55 and 56, have
crossed paths of flow which are independent of one another. The
cylindrical housing enclosing the pilot valve includes two
corresponding pairs of ports extending therethrough. One pair is
situated on each side and they are arranged for alignment with the
ends of either the crossed or the horizontal pair of flow paths,
depending on the position of the pilot piston within the cylinder.
A high pressure fluid conduit, designated by numeral 57, leads form
a well conduit port situated below the valve to high pressure
source port 58 of the pilot valve cylinder. Low pressure conduit 59
extends from a well conduit port positioned above the valve to low
pressure source port 60 on the pilot cylinder. Upper chamber
conduit 61 and lower chamber conduit 62 connect the chambers above
and below the valve piston to upper and lower chamber ports on the
pilot cylinder designated by numerals 63 and 64 respectively.
With the upper end of the pilot piston containing the crossed flow
paths aligned with the ports through the pilot valve cylinder,
FIGS. 4 and 5, the low pressure conduit is in communication with
the lower chamber and the high pressure conduit with the upper
chamber. In this pilot position the differential pressure across
the valve piston forces it downward, maintaining the valve in the
open position. When the pilot piston is in its upper position, FIG.
6, the horizontal, straight-through flow paths are aligned with the
ports through the pilot cylinder housing. Thus, in this pilot
position the low pressure conduit is in communication with the
upper chamber whereas the high pressure conduit is in communication
with the lower chamber. The resultant differential pressure in
combination with spring 36A forces the valve piston upwardly,
closing the valve to flow.
A spring 65 or other biasing means acts to bias the pilot piston
downwardly so that it tends to stay in the crossed configuration.
The position of the pilot piston (and the valve) is governed by
displacement of a spring-biased actuator piston. This pilot
actuating piston is designated by numeral 70 in the drawing and is
shown slidably disposed within a cylinder 71. A spring 72 is
disposed within the actuator cylinder above the piston and
compresses to bias it against upward movement. The actuator piston
is otherwise free to travel up or down within its cylinder,
depending on the differential pressure acting across it. A rod 73
attached to the lower end of pilot piston 52 extends from thee
pilot cylinder through openings provided with suitable seals into
the upper end of the actuator cylinder. As the spring-biased
actuator piston approaches the upper extremity of its cylinder, it
drives the piston rod upwardly, shifting the pilot piston into the
horizontal straight-through flow configuration and causing the
valve to close.
As pointed out above, the position occupied by the actuator piston
is governed by the disposition of a control fluid. This control
fluid, which may for example, be a hydraulic fluid, is disposed
within the chamber situated above and below the actuator piston.
The chamber beneath the piston is in communication with a lower
chamber having a distensible member 75 therein, separating the
control fluid from the fluid contained within high pressure fluid
conduit 61. The chamber above the actuator piston is in
communication with a similar upper chamber also having a
distensible member therein, designated by numeral 76, but
separating the control fluid therein from the fluid within the low
pressure fluid conduit 62. Thus the differential pressure between
the high pressure fluid conduit and the low pressure fluid conduit
is exerted through the control fluid. A directional flow
restriction 77 is included in the flow path between the two
distensible members and is arranged to severely restrict flow from
the chamber in pressure communication with the high pressure
conduit to the chamber in pressure communication with the low
pressure conduit. Thus, in the normal flow situation in which the
valve is open (FIGS. 5 and 5) and pressure below it exceeds that
above it, the flow of control fluid is impeded, retarding
substantially the rate of ascent of the actuator piston. The
directional flow restriction permits unimpeded flow in the opposite
direction. As a result, when the flow of the well is restricted at
the earth's surface and the differential pressure across the valve
is reduced to the point that the force generated by the spring
biasing the actuator piston is greater than the force on the piston
resulting from differential pressure, the control fluid flows
freely, permitting rapid return of the actuator piston to its
initial position. This directional flow restriction acts as a dash
pot type timer, permitting the actuator piston to be displaced
upwardly through a preset flow interval, which can be varied by
adjusting the resistance to flow and yet be rapidly returned by
means of a surface generated pressure signal to reinitiate the
cycle. If the pressure transient reducing the differential pressure
across the valve is not received prior to termination of the preset
flow interval, the actuator piston will reach the upper end of its
cylinder and drive the pilot piston upwardly resulting in closure
of the valve. It will be noted that this flow interval timer is
responsive to the product of pressure differential and elapsed time
which is in turn proportional to cumulative fluid flow through the
valve. The closed valve may subsequently be reopened by increasing
the pressure within the well conduit above the valve. Once the
pressure above approaches that below the valve, the springs biasing
the actuator piston and the pilot piston will force them downward,
depressing the pilot piston to the crossed flow path configuration.
Thereafter, reduction of the pressure above the valve to a level
below that existing under the valve will then cause the
differential pressure across the valve piston to open the
valve.
* * * * *