U.S. patent application number 12/415068 was filed with the patent office on 2010-09-30 for apparatus and method for oilfield material delivery.
Invention is credited to Philippe Gambier, Joe Hubenschmidt, Rajesh Luharuka, Jean-Louis Pessin, Rod Shampine.
Application Number | 20100243251 12/415068 |
Document ID | / |
Family ID | 42782703 |
Filed Date | 2010-09-30 |
United States Patent
Application |
20100243251 |
Kind Code |
A1 |
Luharuka; Rajesh ; et
al. |
September 30, 2010 |
Apparatus and Method for Oilfield Material Delivery
Abstract
An apparatus for mixing and delivering a material to a high
pressure flow of fluid, comprises a pressure vessel comprising: a
particulate solids inlet aperture located substantially in an upper
portion of the pressure vessel; a first liquid inlet in fluid
communication with a first high pressure line and the pressure
vessel and comprising a first valve; and a first outlet in fluid
communication with the pressure vessel and a second high pressure
line and comprising a third valve.
Inventors: |
Luharuka; Rajesh; (Stafford,
TX) ; Shampine; Rod; (Houston, TX) ; Pessin;
Jean-Louis; (Cailloux, FR) ; Gambier; Philippe;
(Houston, TX) ; Hubenschmidt; Joe; (Sugar Land,
TX) |
Correspondence
Address: |
SCHLUMBERGER TECHNOLOGY CORPORATION;David Cate
IP DEPT., WELL STIMULATION, 110 SCHLUMBERGER DRIVE, MD1
SUGAR LAND
TX
77478
US
|
Family ID: |
42782703 |
Appl. No.: |
12/415068 |
Filed: |
March 31, 2009 |
Current U.S.
Class: |
166/283 ;
166/75.15 |
Current CPC
Class: |
E21B 43/267
20130101 |
Class at
Publication: |
166/283 ;
166/75.15 |
International
Class: |
E21B 43/26 20060101
E21B043/26; E21B 43/267 20060101 E21B043/267 |
Claims
1. An apparatus for mixing and delivering a material to a high
pressure flow of fluid, comprising: a pressure vessel comprising: a
particulate solids inlet aperture located substantially in an upper
portion of the pressure vessel; a first liquid inlet in fluid
communication with a first high pressure line and the pressure
vessel and comprising a first valve; and a first outlet in fluid
communication with the pressure vessel and a second high pressure
line and comprising a third valve.
2. The apparatus of claim 1, further comprising a second liquid
inlet in fluid communication with at least one additive source and
the pressure vessel and comprising a second valve.
3. The apparatus of claim 1, further comprising a particulate
solids reservoir connected to the particulate solids inlet
aperture.
4. The apparatus of claim 3 wherein the particulate solids
reservoir is one of a funnel, a silo, and a hopper.
5. The apparatus of claim 3 further comprising a valve connected
between the pressure vessel and the particulate solids reservoir
and operable to control flow of particulate solids from the
particulate solids reservoir to the pressure vessel.
6. The apparatus of claim 1, further comprising a first pumping
equipment connected to the first liquid inlet and capable of
inducing a pressure exceeding the pressure of the high-pressure
line.
7. The apparatus of claim 1, wherein the first high-pressure line
is connected to the second-high-pressure line upstream of a choke,
the choke disposed between the first high pressure line and the
first outlet, wherein the choke is operable to reduce the pressure
of the second high-pressure line below the pressure of the first
high-pressure line.
8. The apparatus of claim 1, further comprising an additive
carrying line connected to at least one additive source and to the
second liquid inlet.
9. The apparatus of claim 8, wherein the additive source is a
source containing an additive selected from the group including
proppant coating, viscosity breakers, friction reducing agents,
cross-link delaying agents, lubricants, fiber, explosive chemicals,
bonding agents, adhesives, clean frac fluid, a scale inhibitor, and
combinations thereof.
10. The apparatus of claim 1, wherein the third valve is a one-way
valve operable to isolate the pressure vessel from the second
high-pressure line and to selectively enable flow from the pressure
vessel to the second high-pressure line.
11. The apparatus of claim 1, further comprising a pumping
apparatus connected to the second high-pressure line upstream of
the first liquid inlet.
12. The apparatus of claim 1, wherein the pressure vessel is a
tubular vessel.
13. The apparatus of claim 1, further comprising a second outlet
having a fourth valve and in fluid communication with the pressure
vessel in the upper portion of the pressure vessel.
14. The apparatus of claim 13 wherein the second outlet is
connected to an overflow destination.
15. The apparatus of claim 1 wherein the pressure vessel is a
horizontally oriented tubular vessel.
16. The apparatus of claim 15 further comprising an internal feed
screw operable to transport the particulate solids from a location
near the particulate solids inlet to a location near the first
outlet.
17. The apparatus of claim 1 wherein the pressure vessel comprises
at least two pressure vessels connected to the main high-pressure
line down-stream from the high-pressure pumping mechanism.
18. The apparatus of claim 17, further comprising pumping equipment
connected to the at least two pressure vessels and capable of
selectively inducing a pressure exceeding the pressure of the
high-pressure line into the at least two pressure vessels.
19. The apparatus of claim 17, wherein the pressure vessels are
connected to separate additive sources.
20. A method for mixing and delivering a material to a high
pressure flow of fluid, comprising: introducing a particulate solid
into a mixing apparatus; introducing a liquid additive into the
mixing apparatus and thereby mix the solid and liquid additive;
increasing the pressure of the mixing apparatus to a pressure
exceeding the pressure of a high-pressure line; and opening a valve
between the mixing apparatus and the high-pressure line to release
the particulate solid and the liquid additive into the
high-pressure line.
21. The method of claim 20, wherein increasing comprises: closing
valves on lines for introducing the particulate solid and for
introducing the liquid additive; and introducing a fluid, that is
substantially the same as fluid present in the high-pressure line,
into the mixing apparatus.
22. The method of claim 20, wherein increasing further comprises:
diverting flow from the high-pressure line to a pressure increasing
device; operating the pressure decreasing device to decrease the
pressure of the high-pressure line such that at a point downstream
from the diversion the pressure in the high-pressure line is lower
than the pressure in the diverted flow; and directing the diverted
flow into the mixing apparatus.
23. The method of claim 20, wherein introducing comprises
increasing the pressure in a line carrying the liquid additive to
the mixing apparatus to a pressure exceeding the pressure of the
high-pressure line.
24. The method of claim 20, wherein the liquid additive is an
additive selected from the group including proppant coating,
viscosity breakers, friction reducing agents, cross-link delaying
agents, lubricants, fiber, explosive chemicals, bonding agents,
adhesives, clean frac fluid, and combinations thereof.
25. The method of claim 20, further comprising opening a valve to
divert overflow created by the introduction of particulate solid or
liquid additive into an overflow destination.
26. A method of adding an additive to a proppant flow on the
high-pressure side of a stimulation treatment apparatus,
comprising: operating pumping equipment to pump a clean frac fluid
at a desired high pressure into a high-pressure line; isolating a
pressure vessel connected to the high-pressure line from the
high-pressure line; introducing a proppant into the pressure
vessel; introducing an additive into the pressure vessel thereby
mixing the proppant and the additive into a proppant-additive
slurry; increasing the pressure in the pressure vessel to exceed
the clean frac fluid pressure; and opening a valve from the
pressure vessel into the high-pressure line thereby introducing the
proppant-additive slurry into the high-pressure line downstream of
the pumping equipment.
Description
FIELD
[0001] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art. Embodiments of the disclosed apparatus and
method relate generally to systems and methods for delivering an
oilfield material to a well at an oilfield.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0003] Production of oil and gas from subterranean formations
presents a myriad of challenges. One such challenge is the lack of
permeability in certain formations. Often oil or gas bearing
formations, that may contain large quantities of oil or gas, do not
produce at a desirable production rate due to low permeability; the
low permeability causing a poor flow rate of the sought-after
hydrocarbons. To increase the flow rate, a stimulation treatment
can be performed. Once such stimulation treatment is hydraulic
fracturing. Hydraulic fracturing is a process whereby a
subterranean hydrocarbon reservoir is stimulated to increase the
permeability of the formation, increasing the flow of hydrocarbons
from the reservoir. A fracturing fluid is pumped at very high
pressure, e.g., in excess of 10,000 psi, to crack the formation
thereby creating larger passageways for hydrocarbon flow.
[0004] While the high pressure introduced may produce cracks in a
formation, the removal of the pressure back to normal borehole
pressures, often cause the closing of the cracks much in the manner
that a crack wedged open in a piece of wood may close when the
wedge used to produce the crack is removed. Such closing of the
reservoir cracks produced by the hydraulic fracturing operating is
very undesirable.
[0005] To avoid the closing of reservoir cracks when the hydraulic
pressure is lowered, the fracturing fluid may have proppants added
thereto, such as sand or other solids that fill the cracks in the
formation, so that, at the conclusion of the fracturing treatment,
when the high pressure is released, the cracks remain propped open,
thereby permitting the increased hydrocarbon flow possible through
the produced cracks to continue into the wellbore.
[0006] In order to pump the fracturing fluid into the well, large
oilfield operations generally employ any variety of positive
displacement or other fluid delivering pumps.
[0007] A positive displacement pump may be a fairly large piece of
equipment with associated engine, transmission, crankshaft and
other parts, operating at between 200 Hp and about 4,000 Hp. A
large plunger is driven by the crankshaft toward and away from a
chamber in the pump to dramatically affect a high or low pressure
thereat. This makes a positive displacement pump a good choice for
high pressure applications. Hydraulic fracturing of underground
rock, for example, often occurs at pressures between 10,000 to
20,000 PSI or more.
[0008] When employing oilfield pumps, regular pump monitoring and
maintenance may be sought to help ensure uptime and increase
efficiency of operations. A pump, as with any form of industrial
equipment, is susceptible to natural wear that could affect uptime
or efficiency. This may be of considerable significance in the case
of pumps for large-scale oilfield operations as they are often
employed at the production site and operated at a near round the
clock basis and may operate under considerably harsh protocols. For
instance, in the case of hydraulic fracturing applications, a
positive displacement pump may be employed at the production site
and intended to operate for six to twelve hours per day for more
than a week generating extremely high pressures. Thus, wear on pump
components during such operation may present in a variety of
forms.
[0009] Abrasive wear occurs when the particles within the fluid
impact on the exposed surfaces of the machinery and impart some of
their kinetic energy into the exposed surface. If sufficiently
high, the kinetic energy of the impacting particles creates
significant tensile residual stress in the exposed surface, below
the area of impact. Repeated impacts cause the accumulation of
tensile stress in the bulk material that can leave the exposed
surface brittle and lead to cracking, crack linkage and gross
material loss.
[0010] In particular, internal valve seals of the pump are prone to
failure, especially where abrasive oilfield material is directed
through the pump during a fracturing application. These internal
valve seals may be of a conformable material in order to allow
proper sealing. However, the conformable nature of the seal may
leave it susceptible to deterioration by abrasive oilfield
materials that are pumped through the valves. Additionally, other
components of the pump may be susceptible to wear by abrasives that
are pumped through the pump. Such deterioration of pump components
may considerably compromise control over the output of the pump and
ultimately even render the pump ineffective.
[0011] Efforts have been made to actually prevent pump damage by
pumped abrasives. These efforts include introducing abrasives, such
as proppants, at locations subsequent to the pressure producing
valves and other particularly susceptible oilfield pump components.
For example, as detailed in U.S. Pat. No. 3,560,053 to Ortloff, a
pressurized abrasive slurry may be introduced to an oilfield fluid
after the fluid has been directed from an oilfield pump. In this
manner, the oilfield pump may be spared exposure to the potentially
damaging abrasive slurry.
[0012] Unfortunately, the method described above, is achieved by
the addition of a significant amount of equipment at the oilfield.
Often this equipment may require its own monitoring and maintenance
due to exposure to the abrasive slurry. For example, mixing and
blending equipment along with pressurization equipment, including
susceptible valving, may be required apart from the primary
oilfield pumps described above. Thus, while the original pumps may
be spared exposure to abrasives, another set of sophisticated
equipment remains exposed.
[0013] Because the fracturing fluid is pumped at extremely high
pressure, the proppants included in the fracturing fluid can be
coated in order to increase their durability and use under
high-pressure conditions and to minimize proppant flow back from
propped hydraulic fractured oil and gas wells. The coating of
proppants is well known in the state of the art. In U.S. Pat. No.
5,597,784 to Sinclair et al, a method is disclosed for coating the
proppant in a resin. Proppants are typically coated in a factory or
at a location remote to the well site and transported to the well
site after coating has been applied.
[0014] Transporting the coated proppant to the well site means that
the choices for materials with which the proppant can be coated are
limited to those types of coatings that will not sustain damaged in
the shipping process. Also, when the proppant is received at the
well site and pumped through the high-pressure pumps, the proppant
is at risk to become damaged within the processing equipment.
[0015] In addition to coatings, stimulation fluid is often
augmented with other additives to aid in the stimulation or
propping operations. Such additives include lubricants, viscosity
breakers, friction reducing agents, cross-link delaying agents,
fiber, explosive chemicals, bonding agents, and adhesives. It is
desirable that these additives are mixed with the proppant prior to
introduction into the high-pressure flow of a hydraulic stimulation
treatment.
[0016] From the foregoing it will be apparent that there remains a
need for a system of pumping abrasive slurry that does not impact
the wear and tear of an oilfield pump or pump components.
[0017] From the foregoing it will be apparent that there remains a
need for a proppant coating mechanism that offers improved process
control over the proppant coating process. Furthermore, from the
foregoing it will be apparent that it would be desirable to provide
a mechanism for introducing proppant and related additives as a
mixture without requiring pumping of such a mixture through the
high-pressure pumps used to produce the hydraulic pressure used to
stimulate hydrocarbon reservoirs.
SUMMARY
[0018] An oilfield material delivery mechanism and method of
operation thereof is disclosed. The mechanism provides a highly
efficient approach for introducing harsh materials into a
high-pressure fluid flow while avoiding pumping the oilfield
material through pumping equipment that is susceptible to abrasive
wear from such materials. The mechanism includes a particulate
solids reservoir and a pressure vessel. The pressure vessel
includes a first liquid inlet in fluid communication with a first
high-pressure line and comprising a first valve, a particulate
solids inlet aperture connected to the particulate solids reservoir
and located substantially in an upper portion of the pressure
vessel and comprising a second valve operable to selectively
isolate the pressure vessel from the particulate solids reservoir,
and a first outlet in fluid communication with a second
high-pressure line and comprising a third valve.
[0019] The oilfield material delivery mechanism may be operated to
introduce a particulate slurry into a high-pressure line by
isolating the pressure vessel from the high-pressure line,
introducing, under low-pressure conditions, particulate solids into
the pressure vessel through a particulate solids inlet aperture,
providing high-pressure clean-fluid flow into the pressure vessel,
and discharging high-pressure slurry flow from the pressure vessel
into the high-pressure line.
[0020] In an embodiment, an apparatus for mixing and delivering a
material to a high pressure flow of fluid, comprises a pressure
vessel comprising: a particulate solids inlet aperture located
substantially in an upper portion of the pressure vessel; a first
liquid inlet in fluid communication with a first high pressure line
and the pressure vessel and comprising a first valve; and a first
outlet in fluid communication with the pressure vessel and a second
high pressure line and comprising a third valve. Alternatively, the
apparatus further comprises a second liquid inlet in fluid
communication with at least one additive source and the pressure
vessel and comprising a second valve. Alternatively, the apparatus
further comprises a particulate solids reservoir connected to the
particulate solids inlet aperture. The particulate solids reservoir
may be one of a funnel, a silo, and a hopper. The apparatus may
further comprise a valve connected between the pressure vessel and
the particulate solids reservoir and operable to control flow of
particulate solids from the particulate solids reservoir to the
pressure vessel. Alternatively, the apparatus further comprising a
first pumping equipment connected to the first liquid inlet and
capable of inducing a pressure exceeding the pressure of the
high-pressure line. Alternatively, the first high-pressure line is
connected to the second-high-pressure line upstream of a choke, the
choke disposed between the first high pressure line and the first
outlet, wherein the choke is operable to reduce the pressure of the
second high-pressure line below the pressure of the first
high-pressure line.
[0021] Alternatively, the apparatus further comprises an additive
carrying line connected to at least one additive source and to the
second liquid inlet. The additive source may be a source containing
an additive selected from the group including proppant coating,
viscosity breakers, friction reducing agents, cross-link delaying
agents, lubricants, fiber, explosive chemicals, bonding agents,
adhesives, clean frac fluid, a scale inhibitor, and combinations
thereof. Alternatively, the third valve is a one-way valve operable
to isolate the pressure vessel from the second high-pressure line
and to selectively enable flow from the pressure vessel to the
second high-pressure line. Alternatively, the apparatus further
comprises a pumping apparatus connected to the second high-pressure
line upstream of the first liquid inlet. Alternatively, the
pressure vessel is a tubular vessel. Alternatively, the apparatus
further comprises a second outlet having a fourth valve and in
fluid communication with the pressure vessel in the upper portion
of the pressure vessel. The second outlet may be connected to an
overflow destination. Alternatively, the pressure vessel is a
horizontally oriented tubular vessel and may further comprise an
internal feed screw operable to transport the particulate solids
from a location near the particulate solids inlet to a location
near the first outlet. Alternatively, the pressure vessel comprises
at least two pressure vessels connected to the main high-pressure
line down-stream from the high-pressure pumping mechanism. The
apparatus may further comprise pumping equipment connected to the
at least two pressure vessels and capable of selectively inducing a
pressure exceeding the pressure of the high-pressure line into the
at least two pressure vessels. The pressure vessels may be
connected to separate additive sources.
[0022] In an embodiment, a method for mixing and delivering a
material to a high pressure flow of fluid comprises introducing a
particulate solid into a mixing apparatus; introducing a liquid
additive into the mixing apparatus and thereby mix the solid and
liquid additive; increasing the pressure of the mixing apparatus to
a pressure exceeding the pressure of a high-pressure line; and
opening a valve between the mixing apparatus and the high-pressure
line to release the particulate solid and the liquid additive into
the high-pressure line. Alternatively, increasing comprises closing
valves on lines for introducing the particulate solid and for
introducing the liquid additive and introducing a fluid, that is
substantially the same as fluid present in the high-pressure line,
into the mixing apparatus. Alternatively, increasing further
comprises diverting flow from the high-pressure line to a pressure
increasing device; operating the pressure decreasing device to
decrease the pressure of the high-pressure line such that at a
point downstream from the diversion the pressure in the
high-pressure line is lower than the pressure in the diverted flow;
and directing the diverted flow into the mixing apparatus.
Alternatively, introducing comprises increasing the pressure in a
line carrying the liquid additive to the mixing apparatus to a
pressure exceeding the pressure of the high-pressure line.
Alternatively, the liquid additive is an additive selected from the
group including proppant coating, viscosity breakers, friction
reducing agents, cross-link delaying agents, lubricants, fiber,
explosive chemicals, bonding agents, adhesives, clean frac fluid,
and combinations thereof. Alternatively, the method further
comprises opening a valve to divert overflow created by the
introduction of particulate solid or liquid additive into an
overflow destination.
[0023] In an embodiment, a method of adding an additive to a
proppant flow on the high-pressure side of a stimulation treatment
apparatus comprises operating pumping equipment to pump a clean
frac fluid at a desired high pressure into a high-pressure line;
isolating a pressure vessel connected to the high-pressure line
from the high-pressure line; introducing a proppant into the
pressure vessel; introducing an additive into the pressure vessel
thereby mixing the proppant and the additive into a
proppant-additive slurry; increasing the pressure in the pressure
vessel to exceed the clean frac fluid pressure; and opening a valve
from the pressure vessel into the high-pressure line thereby
introducing the proppant-additive slurry into the high-pressure
line downstream of the pumping equipment.
[0024] In an embodiment, a method of operating at least two
pressure vessels to inject a particulate slurry into a
high-pressure line, comprises a first operating cycle comprising:
isolating a pressure vessel from the high-pressure line,
introducing, under low-pressure conditions, particulate solids into
the pressure vessel through a particulate solids inlet aperture, a
second operating cycle comprising: providing high-pressure flow
into the pressure vessel, and providing a high-pressure slurry flow
from the pressure vessel into the high-pressure line. The method
further comprises causing the at least one pressure vessel to
operate in the first operating cycle while operating at least one
pressure vessel in the second operating cycle, and synchronizing
switching a first pressure vessel from the first operating to a
second operating cycle and switching a second pressure vessel from
the second operating cycle to the first operating cycle in a manner
such that at least one of the at least two pressure vessels is
operating in the second operating cycle at any one time.
Alternatively, the method further comprises switching a first
pressure vessel from the first operating cycle to the second
operating cycle and switching a second pressure vessel from the
second operating cycle to the first operating cycle, and
synchronizing the switching in a manner such the at least two
pressure vessels are operating in the second operating cycle
simultaneously. Alternatively, the at least two pressure vessels is
at least four pressure vessels organized as independent pairs. The
at least two pressure vessels may be at least four pressure vessels
organized in at least two phased pairs wherein at least one pair of
pressure vessels switch between first and second operating cycles
at a time that is different from when at least one other pair
switch between first and second operating cycles. Alternatively,
the at least two pressure vessels is at least three pressure
vessels (sequentially numbered 1 through n wherein n is the total
number of pressure vessels) and wherein synchronizing comprises
cycling the pressure vessels such that when pressure vessel.sub.i
modn+2 transitions from the second operating cycle to the first
operating cycle and pressure vessel.sub.i modn+1 transitions from
the first operating cycle to the second operating cycle.
Alternatively, the first operating cycle further comprises
returning overflow of fluid created by introduction of particulate
solids from the pressure vessel to a clean fluids reservoir.
[0025] Alternatively, providing comprises diverting clean fluid
from the high-pressure line upstream from a location at which the
high-pressure slurry flow from the pressure vessel is introduced
into the high-pressure line. Alternatively, the second operating
cycle further comprises: equalizing the pressure of the pressure
vessel and the high-pressure line by increasing the pressure in the
pressure vessel prior to providing high-pressure clean-fluid flow
into the pressure vessel. Equalizing may comprise operating a
pressure multiplier device connected to the pressure vessel.
Alternatively, introducing comprises allowing the particulate
solids to fall under gravity from a particulate solids reservoir
into the pressure vessel. Introducing may further comprise metering
the particulate solids introduced into the pressure vessel through
a feeder valve. Alternatively, the first operating cycle further
comprises feeding the particulate solids into the pressure vessel
by rotating a feed screw located inside the pressure vessel.
Alternatively, the first operating cycle further comprises: mixing
the particulate solids with clean fluid prior to introducing the
particulate solids into the pressure vessel and introducing
comprises pumping the mixture of particulate solids and clean fluid
into the pressure vessel using a low-pressure pump. Alternatively,
the second operating cycle comprises: causing the pressure of the
pressure vessel to slightly exceed the pressure of the
high-pressure line thereby producing the high-pressure slurry flow
from the pressure vessel into the high-pressure line.
[0026] Alternatively, the high-pressure clean-fluid flow is
introduced into the pressure vessel in a location substantially
near the top of the pressure vessel. Alternatively, the method
further comprises depressurizing the pressure vessel and a line
carrying overflow from the pressure vessel to the clean fluids
reservoir by decreasing the pressure in the pressure vessel prior
to opening a valve permitting overflow clean-fluid flow out of the
pressure vessel. Depressurizing may comprise operating a pressure
reducing device connected to the pressure vessel to decrease the
pressure in the pressure vessel. Alternatively, the method further
comprises suctioning out fluid from the pressure vessel to a clean
fluids reservoir prior to introducing particulate solids into the
pressure vessel. Alternatively, introducing further comprises
isolating the pressure vessel from a particulate solids reservoir
located above the pressure vessel using a check valve.
Alternatively, the pressure vessel comprises at least one tubular
pipe oriented in a manner not allowing gravity transfer of solids
from the inlet aperture to an outlet aperture connected to the
high-pressure line. Alternatively, the method further comprises
causing the pressure of the pressure vessel to exceed the pressure
of the high-pressure line sufficiently to divert a substantial
portion of the flow of the high-pressure line flow through the
pressure vessel thereby producing the high-pressure slurry flow
from the pressure vessel into the high-pressure line.
[0027] In an embodiment, an apparatus for mixing and delivering a
material to a high pressure flow of fluid, comprises a particulate
solids reservoir; and a pressure vessel comprising: a first liquid
inlet in fluid communication with a first high-pressure line and
comprising a first valve; a particulate solids inlet aperture
connected to the particulate solids reservoir and located
substantially in an upper portion of the pressure vessel and
comprising a second valve operable to selectively isolate the
pressure vessel from the particulate solids reservoir; and a first
outlet in fluid communication with a second high-pressure line and
comprising a third valve. Alternatively, the particulate solids
reservoir is one of a funnel, a silo, and a hopper. Alternatively,
the second valve located between the pressure vessel and the
particulate solids reservoir is a high-pressure valve operable to
selectively provide a path through which particulate solids may
enter into the pressure vessel.
[0028] Alternatively, the apparatus further comprises a feeder
valve located below an exit aperture at the bottom of the
particulate solids reservoir by which the particulate solids may be
metered when introduced into the pressure vessel. The second valve
may be connected between the pressure vessel and the particulate
solids reservoir is a check valve and wherein the pressure vessel
comprises a valve seat on the interior surface of the pressure
vessel and located at the particulate solids inlet aperture whereby
a positive pressure differential between the interior of the
pressure vessel and the particulate solids reservoir causes a valve
disk of the valve to seat against the valve seat. The second valve
may be connected between the pressure vessel and the particulate
solids reservoir comprises a linear actuator connected to the valve
disk whereby a displacement of the linear actuator opens the valve
to permit flow of particulate solids for the particulate solids
reservoir into the pressure vessel. Alternatively, the third valve
connected between the pressure vessel and second high-pressure line
comprises a spring loaded check valve and where the exterior of the
pressure vessel comprises a valve seat located at the first outlet
whereby a positive pressure differential between the interior of
the pressure vessel and the second high-pressure line causes the
third valve to open and wherein the spring causes a valve disk of
the third valve to seat against the valve seat when the pressure in
the pressure vessel is substantially equal or less than the
pressure of the second high-pressure line. Alternatively, the third
valve connected between the pressure vessel and second
high-pressure line comprises a linear actuator operable to
selectively open and close the valve; and where the exterior of the
pressure vessel comprises a valve seat located at the first outlet
whereby a negative pressure differential between the interior of
the pressure vessel and the second high-pressure line causes a
valve disk of the third valve to seat against the valve seat and
wherein the linear actuator may cause the valve disk of the third
valve to move away from the valve seat thereby opening the third
valve.
[0029] Alternatively, the first high-pressure line is connected to
the second-high pressure line upstream of a choke, the choke
disposed between the first high-pressure line and the first outlet,
wherein the choke is operable to reduce the pressure of the second
high-pressure line above the pressure of the first high-pressure
line. Alternatively, the apparatus further comprises an overflow
outlet located in an upper portion of the pressure vessel thereby
providing a mechanism for removing fluid within the pressure vessel
displaced by particulate solids introduced into the pressure
vessel. Alternatively, the apparatus further comprises an overflow
line connected between the first outlet and the third valve, and
via a side connection on the connection between the first outlet
and third valve, to a suction pump connected to a clean fluids
reservoir whereby a portion of the fluid in the pressure vessel may
be suctioned out of the pressure vessel by the suction pump into
the clean fluids reservoir prior to introduction of particular
solids into the pressure vessel thereby avoiding an overflow
condition. Alternatively, the pressure vessel further comprises a
cylindrical wall comprising the first liquid inlet and the overflow
outlet integrated into the cylindrical wall. Alternatively, the
pressure vessel is a long horizontally oriented tubular vessel. The
apparatus may further comprise an internal feed screw operable to
transport the particulate solids from a location near the
particulate solids inlet to a location near the first outlet.
Alternatively, the pressure vessel is a long horizontally oriented
pressure pipe wherein the particulate solids reservoir further
comprises a clean fluid inlet and wherein the apparatus further
comprises a low-pressure slurry pump connected between the
particulate solids reservoir and the pressure vessel and operable
to pump a slurry produced in the particulate solids reservoir into
the pressure vessel.
[0030] In an embodiment, a method of operating at least one
pressure vessel to inject a particulate slurry into a high-pressure
line, comprises a first operating cycle comprising: isolating the
at least one pressure vessel from the high-pressure line;
introducing particulate solids into the pressure vessel through a
particulate solids inlet aperture; a second operating cycle
comprising: providing high-pressure flow into the pressure vessel;
and providing a high-pressure slurry flow from the pressure vessel
into the high-pressure line. The method further comprises operating
the at least one pressure vessel in the second operating cycle to
create a heterogeneous flow of slurry into the high-pressure line.
Alternatively, operating comprises alternately operating the at
least one pressure vessel in the first operating cycle and the
second operating cycle. Alternatively, the fluid in the high
pressure line and the high pressure slurry flow comprise
contrasting properties. Alternatively, the particulate slurry
comprises at least one of a proppant, a proppant coating, and fill
material. Alternatively, the high pressure line comprises
substantially clean treatment fluid. Alternatively, the at least
one pressure vessel comprises at least two pressure vessels. The
method may further comprise causing one pressure vessel to operate
in the first operating cycle while operating the other pressure
vessel in the second operating cycle. The method may further
comprise switching a first pressure vessel from the first operating
cycle to the second operating cycle and switching a second pressure
vessel from the second operating cycle to the first operating
cycle, and synchronizing the switching in a manner such the at
least two pressure vessels are operating in the second operating
cycle simultaneously. The at least two pressure vessels may be at
least four pressure vessels organized in at least two phased pairs
wherein at least one pair of pressure vessels switch between first
and second operating cycles at a time that is different from when
at least one other pair switch between first and second operating
cycles. Alternatively, the second operating cycle further comprises
equalizing the pressure of the pressure vessel and the
high-pressure line by increasing the pressure in the pressure
vessel prior to providing high-pressure clean-fluid flow into the
pressure vessel.
[0031] In an embodiment, a method of operating at least one
pressure vessel to inject a particulate slurry into a high-pressure
line, the high pressure line comprising substantially clean
treatment fluid, comprises a first operating cycle comprising:
isolating the at least one pressure vessel from the high-pressure
line; introducing, under low-pressure conditions, particulate
solids into the pressure vessel through a particulate solids inlet
aperture; a second operating cycle comprising: providing
high-pressure flow into the pressure vessel; and providing a
high-pressure slurry flow from the pressure vessel into the
high-pressure line. The method further comprises operating the at
least one pressure vessel in the second operating cycle for a
predetermined time interval to create heterogeneous flow of slurry
into the high-pressure line.
[0032] Alternatively, the predetermined time interval comprises
operating the at least one pressure vessel in the second operating
cycle for a predetermined duration of time. The predetermined
duration may comprise from about one second to about two minutes.
Alternatively, the method further comprises stopping the second
operating cycle for a second predetermined duration of time. The
second predetermined duration of time may comprises from about one
second to about two minutes. The first predetermined time interval
may comprise from about one second to about two minutes and the
second predetermined time interval may comprise from about one
second to about two minutes. The high pressure line may supply
treatment fluid to the wellbore during the second predetermined
time interval.
[0033] Alternatively, the predetermined time interval comprises
operating the at least one pressure vessel in the second operating
cycle for a first predetermined duration of time and operating the
at least one pressure vessel in the first operating cycle for a
second predetermined duration of time. Alternatively, operating
comprises operating the at least one pressure vessel to produce
slurry at the predetermined time intervals of a predetermined
density in the high pressure line. The predetermined density may be
about 0.1 pounds of proppant per gallon to about 16.0 pounds of
proppant per gallon. Alternatively, the second operating cycle
comprises causing the pressure of the pressure vessel to slightly
exceed the pressure of the high-pressure line thereby producing the
high-pressure slurry flow from the pressure vessel into the
high-pressure line.
[0034] In an embodiment, a method of fracturing a subterreanean
formation penetrated by a wellbore utilizing at least one pressure
vessel to inject a particulate slurry into a high-pressure line,
the high pressure line comprising substantially clean treatment
fluid, comprises isolating the at least one pressure vessel from
the high-pressure line; introducing, under low-pressure conditions,
particulate solids into the pressure vessel through a particulate
solids inlet aperture to form the slurry, the slurry having a
predetermined property different than a property of the treatment
fluid; providing high-pressure flow into the pressure vessel;
providing a high-pressure slurry flow from the pressure vessel into
the high-pressure line to inject the slurry into the high pressure
line at a predetermined time interval to create heterogeneous flow
of slurry into the high-pressure line; and routing the high
pressure line to the wellbore to perform a fracturing job in the
wellbore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a high-level schematic illustration of an oilfield
material delivery mechanism used to introduce an oilfield material
into a high-pressure fluid flow to a well bore.
[0036] FIG. 2 is a cross-section schematic of one of the oilfield
material delivery subassemblies of FIG. 1 and related
equipment.
[0037] FIG. 3 is a detailed cross-section providing structural
details of one embodiment of the pressure vessel illustrated in
FIG. 2.
[0038] FIG. 4 illustrates an embodiment for connecting the pressure
vessel of FIG. 2 and 3 to a high-pressure fluid line.
[0039] FIGS. 5a and 5b are schematic illustrations of two
approaches for dealing with overflow of fluid resulting from the
introduction of oilfield material into the pressure vessel of FIGS.
2 through 4.
[0040] FIG. 6 illustrates a pair of subassemblies for delivery of
oilfield material and that are synchronized
[0041] FIG. 7 is a flow chart illustrating the coordination of
stages of two pressure vessels of FIG. 6.
[0042] FIG. 8 is a perspective view of trailer mounted oilfield
material delivery mechanism constructed as an array of pressure
vessels, oilfield material reservoirs, related valves, and
connecting pipes.
[0043] FIG. 9 is a schematic illustration of an embodiment similar
to the illustration of FIG. 7 in which the pressure vessel may be
pre-pressurized and pre-depressurized prior to opening valves.
[0044] FIG. 10 is a cross-section of an oilfield material delivery
mechanism having a horizontally oriented pressure vessel.
[0045] FIG. 11, which is composed of FIGS. 11a and 11b, is a
schematic diagram of an embodiment of an oilfield delivery
mechanism having a horizontally oriented pressure vessel.
[0046] FIG. 12 is schematic diagram of an oilfield delivery
mechanism subassembly used in an oilfield delivery mechanism as
described in FIGS. 1 through 12 with the addition of a port
allowing introduction of an additive to the flow in a high-pressure
fluid line.
[0047] FIG. 13 is a schematic diagram of an aggregation of oilfield
delivery mechanisms in the manner of FIG. 12 wherein the
aggregation allows for introduction of combinations of additives
into the high-pressure fluid line.
[0048] FIG. 14 is a perspective overview of the oilfield material
delivery mechanisms of FIGS. 1 through 13 employed in an
oilfield.
DETAILED DESCRIPTION
[0049] In the following detailed description, reference is made to
the accompanying drawings that show, by way of illustration,
specific embodiments in which the invention may be practiced. These
embodiments are described in sufficient detail to enable those
skilled in the art to practice the invention. It is to be
understood that the various embodiments of the invention, although
different, are not necessarily mutually exclusive. For example, a
particular feature, structure, or characteristic described herein
in connection with one embodiment may be implemented within other
embodiments without departing from the spirit and scope of the
invention. In addition, it is to be understood that the location or
arrangement of individual elements within each disclosed embodiment
may be modified without departing from the spirit and scope of the
invention. The following detailed description is, therefore, not to
be taken in a limiting sense, and the scope of the present
invention is defined only by the appended claims, appropriately
interpreted, along with the full range of equivalents to which the
claims are entitled. In the drawings, like numerals refer to the
same or similar functionality throughout the several views.
[0050] It should also be noted that in the development of any such
actual embodiment, numerous decisions specific to circumstance must
be made to achieve the developer's specific goals, such as
compliance with system-related and business-related constraints,
which will vary from one implementation to another. Moreover, it
will be appreciated that such a development effort might be complex
and time-consuming but would nevertheless be a routine undertaking
for those of ordinary skill in the art having the benefit of this
disclosure.
[0051] Disclosed herein is an apparatus and method for introducing
an oilfield material, such as proppant, proppant coating, and
proppant additives on the high-pressure side of a hydraulic well
stimulation system. Proppants and any additives are introduced into
one or more pressure vessels at low pressure. After proppants and
any additives have been introduced into the pressure vessel, the
pressure vessel inlets used to add proppant and/or additives to the
pressure vessel are closed, and a diversion of high-pressure fluid
from the high-pressure line is used to pressurize the pressure
vessel to a pressure slightly above the pressure of the
high-pressure line. When the pressure has increased sufficiently to
cause a flow from the pressure vessel into the high-pressure line,
a fluid pathway from the pressure vessel to the high-pressure line
is opened causing the majority of fluid flow to pass through the
pressure vessel thereby carrying proppant and any additives into
the high-pressure line and subsequently into the wellbore and the
formation.
[0052] The apparatus and method described herein provides for an
economical, reliable, and scalable mechanism for introducing
proppant, coated proppants, and proppant additives into a the
high-pressure fluid used to treat or crack formations in hydraulic
stimulation treatments without pumping the proppant and additives
through the high-pressure pumps and without resorting to complex
machinery.
[0053] FIG. 1 is a high-level schematic illustration of an oilfield
material delivery mechanism 100 used to introduce an oilfield
material, such as proppant and proppant additives into a
high-pressure fluid flow used in the stimulation of subsurface
formations through an wellbore. The oilfield material delivery
mechanism 100 is made up primarily of pressure inducing equipment
150, such as the triplex pump shown, and material supply equipment
175. As detailed below, the material supply equipment 175 is linked
to the pressure inducing equipment 150 for delivery of oilfield
material including proppants and, possibly, proppant additives into
a wellbore, borehole, or well 320 at an oil field 301 (See FIG.
14).
[0054] As shown in FIG. 1, the pressure inducing equipment 150
includes a positive displacement triplex pump atop a skid 159. The
pump includes a conventional crankshaft 155 that is powered by a
driveline 157 to generate pumping of an oilfield fluid from a fluid
end 156 of the pump and through a fluid line 170 toward the
material supply equipment 175 and ultimately to the noted well 320
(FIG. 14). More specifically, the pressurization of the oilfield
fluid may be a result of coordinated reciprocation of plungers and
striking of sealing valves of the fluid end 156 to generate
pressures of up to about 20,000 PSI, for employment in a fracturing
application.
[0055] Continuing with reference to FIG. 1, the material supply
equipment 175 of the oilfield material delivery mechanism 100 is
shown linked to the pressure inducing equipment 150 through a fluid
line 170 as indicated above. Material supply equipment 175 is
connected to the fluid line 170 such that oilfield material 275
(See FIG. 5 et. seq below) may be supplied from one or more
oilfield material delivery subassemblies 185 into the fluid line
170 in one of the many embodiments described herein below and
alternatives thereto. For a fracturing operating, the oilfield
material 275 may include at least one proppant such as, but not
limited to, sand, ceramic material or a bauxite mixture. The oil
field material 275 disposed in the supply reservoir 201 may
comprise more than one material such as, but not limited to, sand,
ceramic material, fiber, a bauxite material, and combinations
thereof, as will be appreciated by those skilled in the art.
Additionally, other abrasives or potentially caustic materials may
be employed for a variety of other applications such as a cement
slurry for cementing. With this in mind, the material supply
equipment 175 is configured to deliver the oilfield material 275 to
the oilfield fluid flow within the fluid line 170 in a synchronized
and isolated manner. Thus, the pressure inducing equipment 150,
including for example, pump components of the fluid end 156 that
might be susceptible to damage upon exposure to the oilfield
material, may substantially avoid such exposure. Conversely, some
oilfield material, for example coatings applied to proppants, which
might be damaged if exposed to pressure inducing equipment, may
similarly avoid such exposure.
[0056] FIG. 2 is a cross-section schematic of one of the oilfield
material delivery subassemblies 185 and related equipment. It
should be noted, and as discussed in greater detail below, that in
embodiments multiple subassemblies 185 may be deployed and
synchronized to cooperate to provide a controlled flow of oilfield
material into the fluid line 170. FIG. 2 illustrates just one such
subassembly 185. In brief, an oilfield material delivery
subassembly 185 includes a reservoir and a pressure vessel. These
are connected to one another using a combination of valves to allow
metering of material delivered from the reservoir into the pressure
vessel and for isolating the two from one another. The pressure
vessel is further connected to a high-pressure line that may be
used to deliver clean fracturing fluid into the pressure vessel and
for pressurizing the pressure vessel. The pressure vessel is
further connected to the fluid line 170 through a discharge port
such that when pressurized fluid flow may occur from the pressure
vessel into the fluid line 170. The pressure vessel also may
include an overflow outlet to allow displaced fracturing fluid to
exit the pressure vessel as oilfield material is introduced into
the pressure vessel. The inlet for clean fracturing fluid, the
discharge port, and the overflow outlet all contain high-pressure
valves that may be used to selectively isolate the pressure vessel
from the respective lines to which these inlets, ports, and outlets
are connected to allow for introduction of oilfield material from
the oilfield material reservoir into the pressure vessel with
corresponding exit of overflow of fracturing fluid, pressurization
of the pressure vessel and, subsequently, release of slurry from
the pressure vessel into the fluid line 170.
[0057] Continuing now with FIG. 2, an oilfield material supply
reservoir 201 is connected to a pressure vessel 203 via an oilfield
material supply inlet aperture 205 preferably located at the top of
the pressure vessel 203. The oilfield material supply reservoir 201
may be, for example, a funnel, a silo, a hopper, or an equivalent
piece of equipment suitable for delivering a solid material by
gravity from one vessel into another through an aperture.
[0058] A metering gate valve 207, e.g., a feeder valve, is
connected between the pressure vessel 203 and the oilfield material
supply reservoir 201 so that the quantity of the oilfield material
275 (See FIG. 5 et. seq below) delivered into the pressure vessel
203 may be controlled.
[0059] The interior of the pressure vessel 203 may be isolated from
the oilfield material supply reservoir 201 using refill valve 217.
The refill valve 217 may be a check valve that only allows flow
from the reservoir 201 into the pressure vessel 203, but not in the
opposite direction.
[0060] The pressure vessel 203 further contains a first liquid
inlet 209 in fluid communication with a high-pressure line 211 and
the pressure vessel 203. The inlet 209 comprises a high-pressure
valve 210 that may be operated to isolate the interior of the
pressure vessel 203 from the high-pressure line 211.
[0061] When the refill valve 217 is open and the metering gate
valve 207 is open oilfield material 275 flows by gravity from the
reservoir 201 into the pressure vessel 203. The introduction of
oilfield material 275 into the pressure vessel causes displacement
of any fluid already in the pressure vessel 203. As will be
appreciated from the discussion herein below, during normal
operations of the subassembly 185, fracturing fluid continuously
flows through the pressure vessel 203 during a slurry release phase
until the inlet high-pressure valve 210 is closed. At that point,
pressure equalizes between the pressure vessel 203 and the fluid
line 170 causing the discharge valve 215 to close. At that point
the pressure vessel 203 will have fluid up to about the level of
the inlet port 209. Therefore, during the recharge phase, as
oilfield material 275 is introduced, there will be a displacement
of fluid by the introduced oilfield material 275. That overflow may
leave the pressure vessel 203 through an overflow outlet 218. The
overflow outlet 218 may further include an overflow valve, such as
a high pressure valve 219 to isolate the interior of the pressure
vessel 203 from an overflow return pipe 221. The return pipe 221
may be connected to a clean fluid reservoir.
[0062] The pressure vessel 203 further has an oilfield material
discharge outlet 213 in fluid communication with the pressure
vessel 203 and the fluid line 170 and comprising a discharge valve,
such as a check valve 215. The discharge check valve 215 may be
designed to block flow from the fluid line 170 into the pressure
vessel 203 while allowing, when opened, flow from the pressure
vessel 203 into the fluid line 170.
[0063] In one embodiment, the high-pressure line 211 feeding into
the pressure vessel 203 is connected as a diversion to the main
fluid line 170. A choke 223 located on the high pressure fluid line
170 between the connection 225 of the high-pressure diversion line
211 to the high pressure fluid line 170 and the connection 227 of
the pressure vessel discharge line 229 to the high pressure fluid
line 170, reduces the pressure in the fluid line 170 below the
pressure introduced into the pressure vessel 203 through the
diversion line 211. The produced pressure differential causes the
opening of the discharge check valve 215 and the main fluid flow to
pass through the pressure vessel 203 thereby discharging the
contents thereof into the fluid line 170.
[0064] FIG. 3 is a detailed cross-section providing structural
details of one embodiment of the pressure vessel 203. The pressure
vessel 203 may be constructed to have a cylindrical wall that
includes the first liquid inlet 209 and the overflow outlet 218
integrated into the cylindrical wall.
[0065] A top head 305 having a flange 307 may be secured to a
recess 309 of the steel pipe 300 using a retainer nut 311.
Similarly, a bottom cap 313 having a flange 315 may be secured to a
recess 317 of the steel pipe 300 using a retainer nut 319. An
interference fitted steel lining 321 may be used to line the
interior wall of the steel pipe 300. The steel lining 321 may be
advantageously replaced when worn from abrasion or corrosion.
[0066] In one embodiment, the discharge valve 215 is a standard
discharge valve used in high pressure positive displacement pumps
to passively close through action of a spring 325 and accessible
through a discharge valve cover 323. In an embodiment, the
discharge valve 215 is a valve that may be opened and closed using
a linear actuator 216 or similar suitable actuator. The refill
high-pressure valve 217 may be composed of a valve disk 327 with
mating surfaces that seat on a valve seat 329 of the top cap 305.
The valve disk 327 may be caused to move, thereby selectively
opening or closing the valve 217 using a linear actuator or similar
suitable actuator located inside the reservoir 201 connected to the
valve disk 327.
[0067] In the embodiment of pressure vessel 203 illustrated in FIG.
3, the discharge valve 215 is connected to the fluid line 170 using
a discharge line 331 connected in a bend through the discharge
valve 215. The discharge line 331 is then connected to the fluid
line 170 using a T-junction (not shown) or similar suitable
connection on the fluid line 170.
[0068] FIG. 4 illustrates an embodiment for connecting the pressure
vessel 203 to the fluid line 170. A pass-through valve assembly 401
allows in-line connection of the pressure vessel 203 to the fluid
line 170.
[0069] FIGS. 5a and 5b are schematic illustrations of two
alternative approaches for dealing with overflow of fracturing
fluid resulting from the introduction of oilfield material into the
pressure vessel 203. FIG. 5a is a cross-section of an embodiment of
the oilfield material delivery subassembly during a recharging
operation. In the embodiment of FIG. 5a the subassembly 185'
contains a perforated pipe 501 connecting the pressure vessel 203
to the reservoir 201.
[0070] As discussed herein above, the pressure vessel 203 goes
through two major operational stages, referred to herein is as
Stage 1: refill and Stage 2: release. In Stage 1: a low-pressure
recharging phase in which oilfield material 275 is introduced into
the pressure vessel 203 via gravity from the reservoir 201. In
Stage2: after the pressure vessel 203 has been charged with
oilfield material 275, the pressure vessel 203 is, by operation of
the valves on inlets and outlets thereto, transitioned into a
high-pressure phase in which the contents of the pressure vessel
203 is released into the fluid line 170.
[0071] FIG. 5a illustrates the recharging phase. During the
recharging phase, the oilfield material 275 enters the pressure
vessel 203 from the reservoir 201 and flows to the lower portion of
the pressure vessel 203 by operation of gravity and mixes with
fracturing fluid 503 to form a slurry 277. This oilfield material
275 displaces some of the fluid present in the pressure vessel 203.
The overflow caused by the displaced fluid exits the pressure
vessel 203 through the overflow outlet 218. In the embodiment 185',
the overflow fluid also exits the pressure vessel 203 through the
oilfield material inlet aperture 205 into the perforated pipe 501.
The overflow fluid may then exit the pipe through the
perforations.
[0072] FIG. 5b is a cross-section of an embodiment for dealing with
the excess of fracturing fluid produced by the introduction oil
field material into the pressure vessel. A pressure vessel 203'''
only has the high pressure clean fluid inlet 209, the oil field
material inlet aperture 205 and slurry discharge port 213 (as well
as associated valves 210, 217, and 215, respectively). The overflow
outlet 221''' is located at T-junctions 163 on the discharge pipe
167, respectively. As the start of refilling operations, a fixed
amount of the displaced clean fluid (equal to the volume of the oil
field material 275 that will be introduced) is first pumped out of
the pressure vessel 203''', before the introduction of oil field
material 275, by a low-pressure pump 169 through an overflow pipe
221''' connected to the T-Junction 163 on the discharge pipe 167
through a filter 171 into the fracturing fluid tank 173. The
overflow pipe 221''' is selectively isolated from the discharge
pipe 167 by a high-pressure valve 168.
[0073] The operation of filling and discharging the pressure vessel
203''' is analogous to that of pressure vessels 203 and 203'
described hereinabove; analogous equipment is indicated using the
same reference numeral with the superfix ''' (triple prime).
[0074] The subassemblies 185 may be combined into arrays of
subassemblies that when synchronized appropriately may produce a
near-continuous flow of slurry having the oilfield material 275
mixed with fracturing fluid. FIG. 6 illustrates a pair of
subassemblies 185a and 185b that are synchronized. The subassembly
185b on the right of FIG. 6 is operating in Stage 1: recharge. The
high-pressure line 211b is shut-off by high-pressure valve 210b;
the gate valve 207b and refiner valve 217b (not shown) are open,
allowing oilfield material 275 to drop by gravity into the pressure
vessel 203b. In the pressure vessel 203b the oilfield material 275
mixes with clean fluid 601, such as fracturing fluid. The overflow
high-pressure valve 219b is open allowing overflow to exit the
pressure vessel 203b. Because the pressure vessel 203b is not
pressurized, the discharge check valve 215b is closed.
[0075] The subassembly 185a on the left of FIG. 6 is operating in
Stage 2: discharge. The high-pressure line 211a is flowing through
the open high-pressure valve 210a; the gate valve 207a and refiner
valve 217a (not shown) are closed, preventing oilfield material 275
from dropping into the pressure vessel 203a. In the pressure vessel
203a the oilfield material 275 has previously mixed with clean
fracturing fluid 601 producing a slurry 603. The overflow
high-pressure valve 219a is closed. Because the pressure vessel
203a is pressurized by the high-pressure flow through high-pressure
line 211a and the pressure in the fluid line 170 has been reduced
by the choke 223, the discharge check valve 215a is open permitting
the slurry 603 to flow into the fluid line 170.
[0076] The operations of the pressure vessels 203a and 203b may be
coordinated such that when one pressure vessel goes offline for
charging, the other pressure vessel begins releasing slurry thereby
producing a near-continuous flow of slurry into the fluid line
170.
[0077] FIG. 7 is a flow chart illustrating the coordination of the
stages of two pressure vessels 203a and 203b, respectively. Each
fill stage 801 consists of filling the pressure vessel 203 with
oilfield material 275 such as proppant or the like, steps 803a and
803b, respectively; closing the refilling aperture and the overflow
outlet, steps 805a and 805b, respectively; and opening the
high-pressure flow into the pressure vessel, step 807a and 807b,
respectively. Conversely, each discharge stage 809 consists of
opening the high-pressure inlet valve, steps 811a and 811b,
respectively; allowing the content, i.e., the slurry, to exit the
pressure vessel, steps 813a and 813b, respectively; and closing the
high-pressure inlet flow and depressurizing the pressure vessel,
step 815a and 815b, respectively. It should be noted that the steps
of pressurizing 807a and b, and depressurizing 815a and b, are
optional steps used to protect valves and other equipment from the
pressure driven blast of fluid that result form opening a valve
when there is a large pressure differential between the two sides
of the valve (See FIG. 9 and accompanying discussion below).
[0078] The fill stage 801a of the pressure vessel 203a may be
coordinated to coincide with the slurry release stage 809b of the
pressure vessel 203b, and the fill stage 801b of the pressure
vessel 203b may be coordinated to coincide with the discharge stage
809a of the pressure vessel 203a.
[0079] Refilling a pressure vessel 203 with oilfield material 275
may take longer than discharging the pressure vessel 203. Thus, if
the pressure vessel 203 in stage 1 has not finished charging when
the other pressure vessel 203 has finished releasing the slurry
flow in fluid line 170 would be interrupted and an interval of
clean fluid would pass through the fluid line 170. While that may
at times be a desirable operational technique used by an operator
of the oilfield delivery mechanism 175, it is desirable to be able
to control that behavior. To allow for longer refill times than
discharge times as well as increase the injection rate of the
oilfield materials, more than two subassemblies 185 may be combined
into a larger mechanism 100.
[0080] FIG. 8 is a perspective view of trailer mounted oilfield
material delivery mechanism 175' consisting of an array of eight
subassemblies for oilfield material delivery 185 each containing a
pressure vessel 203 and an oilfield material reservoir 201.
[0081] The coordination of the filling and slurry release of
multiple pressure vessels is timed such that at least one pressure
vessel is releasing slurry when the other pressure vessels are
charging. Consider n pressure vessels that are indexed 1 through n.
When a pressure vessel numbered i mod n+2 transitions from stage
two to stage one, i.e., going from slurry release to filling,
pressure vessel number i mod n+1 is made to transition from stage
one to stage two, i.e., going from filling to discharging.
[0082] The amount of slurry to be delivered into the wellbore or
borehole 320 (See FIG. 14) may also need to be increased beyond the
capacity of a single pressure vessel 203. Therefore, subassemblies
185 may be combined in parallel and work together in the same
stage. Such pairs (or triples, quadruples, etc.) are then made to
transition between stage one and stage two in unison or out-of-sync
to produce a higher injection rate with a higher degree of
near-continuousness. For example, in the illustration of FIG. 8,
four pairs of subassemblies 185 are shown. Each pair is a
coordinated unit in which the members of the pair are coordinated
to alternate between recharging and slurry release. The four pairs
are made to operate out of sync with one another such that the
pairs switch between Stage 1 and Stage 2 at different times. This
mode of operation increases the continuousness of the slurry
flow.
[0083] Tremendous pressure differential may exist between the
high-pressure side and the low-pressure side of the valves used in
the oilfield material delivery mechanism 175. The high-pressure
side is typically in excess of 10,000 PSI, sometimes as high as
20,000 PSI. The low-pressure side, on the other hand, is normally
one atmosphere, i.e., 0 PSI (gauge). Opening valves to such
pressure differential causes a tremendous blast of fluid through
the valve and very rapid deterioration of the valve and nearby
surfaces. To avoid that problem, in one embodiment, pressure
multipliers and reducers are employed.
[0084] FIG. 9 is a schematic illustration of an embodiment similar
to the illustration of FIG. 7. In this embodiment, the
high-pressure inlet line 211 is augmented with a pressure
multiplying hydraulic cylinder 901. The hydraulic cylinder 901a on
the left-hand side of the figure has been compressed, thereby
increasing the pressure inside the pressure vessel 203a.
Conversely, in the illustration of pressure vessel 203b, the
hydraulic cylinder 901b has been released, thereby decreasing the
pressure inside the pressure vessel 203b. These operations are
performed prior to opening the high-pressure inlet valves 210a and
210b, respectively, the refill valves 217a and 217b, respectively,
and the overflow valves 219a and 219b, respectively, thereby
equalizing the pressure prior to opening valves and thereby
avoiding wear associated with the blast of fluid caused by a large
pressure differential over a valve as it opens.
[0085] Hereinabove, a gravity fed oilfield delivery mechanism 175
has been described in which gravity operates to transport oilfield
material through a vertically oriented pressure vessel 203 from an
oilfield material supply inlet aperture 205 to a discharge outlet
213 located at the bottom of the pressure vessel 203. Such an
arrangement presupposes two things: the vertical arrangement of the
pressure vessel 203 and that the specific gravity of the oilfield
material 275 is heavier than the fluid in the pressure vessel 203.
In an embodiment, the pressure vessel is horizontally oriented.
Thus, in that embodiment, gravity will not suffice to move the
oilfield material 275 through the pressure vessel rather an
internally located screw is used to move material through the
pressure vessel from the inlet aperture to the discharge
outlet.
[0086] FIG. 10 is a cross-section of a horizontally oriented
pressure vessel 203' suitable for introducing an oilfield material
275 into a fluid line 170 according to the general principles
described hereinabove and related equipment. The pressure vessel
203' may be a tubular vessel--preferably constructed from steel or
another suitable material for containing a contents at
high-pressure.
[0087] As described hereinabove, an oilfield material supply
reservoir 201' is connected to the pressure vessel 203' via an
oilfield material supply aperture 205'. The flow of oilfield
material 275 into the pressure vessel 203' may be controlled
through a feeder valve (not shown) and the pressure vessel 203' may
be isolated from the reservoir 201' using a high-pressure valve
217'.
[0088] During Stage 1: refill operations, oilfield material 275
drops through gravity into the pressure vessel 203'. Inside the
pressure vessel 203' the oilfield material is advanced from the
feeding end of the pressure vessel 203' using an internally located
screw 181. The screw is connected to a centrally located driveshaft
183 and driven by an external drive 185.
[0089] As in the gravity feed examples, overflow created by the
introduced oilfield material 275 may exit through an overflow
outlet 218' controlled by a high-pressure valve 219'. During Stage
2: discharge operations, high-pressure clean fluid enters from the
high-pressure line 211' and the slurry of fracturing fluid mixed
with oilfield material 275 exits through a discharge outlet 213'
into the fluid line 170'.
[0090] As with the vertically oriented pressure vessel 203
described hereinabove, horizontally oriented pressure vessels 203'
may be combined into larger systems in which multiple units are
coordinated to alternate between Stage 1: refill operation and
Stage 2: discharge operation to provide a near-continuous flow of
slurry into the fluid line 170' in the manner described
hereinabove, for example, in conjunction with FIGS. 7 through
9.
[0091] FIG. 11 (which is divided into FIGS. 11a and 11b)
illustrates an embodiment of a horizontally oriented pressure
vessel 203'' used for introducing oilfield material on the
high-pressure side of a hydraulic fracturing operation. FIG. 11a is
a side view of an oilfield material delivery mechanism 185''. FIG.
11b is a cross-section top view of the oilfield material delivery
mechanism 185'' illustrated in FIG. 11a along the line a-a. The
oilfield material delivery mechanism 185'' consists of one or more
reservoirs 191. Each of the reservoirs 191 in connected to a clean
fluid pipe (not shown) via a clean fluid inlet 193. By introducing
clean fluid into the reservoirs 191 together with oilfield material
275, a slurry is produced inside the reservoirs 191. The slurry
drops through gravity into a low-pressure slurry pump 195 powered
by a power source 197. During Stage 1 :refill operations the
low-pressure pump 195 pumps the slurry into one or more
horizontally oriented pressure pipes 199. The pressure pipes 199
take the role of the pressure vessels 203 and 203' described
hereinabove. However, pressure pipes 199 typically would be
standard high-pressure pipes normally used for high-pressure fluid
conveyance, e.g., in hydraulic fracturing operations. Such pipes
having an inner diameter of less than 6 inches may not be suitable
for implementations using an internal screw drive as discussed
hereinabove in conjunction with FIG. 10.
[0092] Except for aforementioned differences, the operation and
structure of the oilfield material delivery mechanism 185'' is
analogous to that of oilfield delivery mechanisms 185 and 185'
described hereinabove; similar components have been designated with
like reference numerals given the superfix '' (double-prime).
[0093] FIG. 12 is a schematic illustration in which the oilfield
material delivery mechanism 175 has been extended to provide
additives to the fluid mixture in the pressure vessel 203. There
are many types of additives that may be added to treatment fluids.
These include coating materials for coating the oilfield material
275 delivered from the reservoir 201, viscosity breakers (e.g.,
oxidizers and enzymes, common oxidative breakers are the ammonium,
potassium and sodium salts of peroxydisulfate), friction reducing
agents (e.g., hydrolyzed acrylamide, grease and lubricating oil),
cross-linkers (e.g., Titanium, Zirconium, Aluminum, Antimony,
inorganic species such as borate salts and trasition-metal
complexes, Boric acid), cross-link delaying agents (e.g.,
Ligands--triethanolamine, acetylacetone, ammonium lactate),
lubricants (e.g., grease, and gelled fluid), fiber (e.g., silica),
explosive chemicals (e.g., hydrogen peroxide, RDX, HMX, PETN, PBX),
bonding agents and adhesives (e.g., resin, curable epoxies), and/or
combinations thereof, as will be appreciated by those skilled in
the art. Some of the additive materials listed hereinabove act as
coating materials for the oilfield material with excess of the
additive suspended in the fracturing fluid.
[0094] While the additives may not necessarily be directly related
to enhance the properties of the oilfield material 275, e.g., where
the oilfield material 275 is a proppant, the oilfield material 275
may act as a carrier of the additive and retain the additive in the
fractures 210. Specially such would be the case when the oilfield
material grain surface has an affinity to bond with the additives
that are to be transported to the reservoir. In this case the
additive also behaves as a coating to the oilfield material
275.
[0095] Continuing now with FIG. 12, in addition to the inlets,
outlets, and apertures and ancillary valves described hereinabove
in conjunction with pressure vessels 203, 203', 203'', and 203''',
the pressure vessel 203'''' includes an additive inlet port 231
with an accompanying high-pressure valve (additive inlet valve) 233
connected to an additive source 235 via an additive carrying line
234. During slurry release operations the additive inlet valve 233
is closed.
[0096] With the subassembly for introducing an oilfield chemical
185'''', the Stage 1 :refill operation may include the substeps of
introducing oilfield chemical 275 from the reservoir 201 and the
substep of introducing additive from the additive source 235. These
substeps may be combined in any combination, e.g., in one operating
cycle the substep of introducing oilfield material 275 may be
omitted and in the Stage 2:release phase only additive is
discharged into the fluid line 170. In another operation cycle only
oilfield material 275 may be introduced into the pressure vessel
203'''' thereby providing a slug of oilfield material without the
additive.
[0097] Alternatively, the additive is added during the release
Stage 2. In that alternative the additive inlet valve 233 is closed
during the refill stage and opened in conjunction with the
high-pressure inlet valve 210. In some manner, for example with a
triplex pump, the additive stream is pressurized to a level
equivalent to the pressure in the pressure vessel 203 to allow flow
of additive into the pressurized pressure vessel 203.
[0098] The subassemblies 185'''' are preferably aggregated into
assemblies of multiple subassemblies as discussed hereinabove in
conjunction with FIGS. 1 through 11. The subassemblies 185'''' are
then cycled in a coordinated fashion to introduce a near-continuous
flow of oilfield material combined with the additive.
[0099] In an embodiment, illustrated in a simplified form in FIG.
13, several subassemblies 185'''' for introducing additive combined
with an oilfield material into a high-pressure stream may be
connected in sequence to introduce multiple additives to the
stream. As in the previous examples the high-pressure flow from the
fluid line 170 is diverted into the pressure vessel 203''''a. In
pressure vessel 203''''a a first additive is added to the stream in
the manner explained hereinabove from the first additive source
235a. The output released from the first pressure vessel 203''''a
is then routed into the second pressure vessel 203''''b where it is
combined with a second additive from the second additive source
235b and the output from the second pressure vessel 203''''b is fed
into the third pressure vessel 203''''c. A third additive is added
to the stream from the third additive source 235c. Finally, the
output released from the third pressure vessel 203''''c is
introduced into the fluid line 170 in the manner described
hereinabove.
[0100] In an embodiment each output stream is added directly to the
fluid line 170 without being pumped through other pressure vessels
203''''.
[0101] By combining an additive, e.g., a coating, to the fluid flow
on the high-pressure side the coating is not subjected to the wear
produced by the pressure inducing equipment. This process thus
allows for additives that would not fare well when exposed to the
harsh handling that high-pressure pumps impose on the fluid pumped
there through. Conversely, to the extent that the additives are
harmful to the pumps, the pumps are not thus exposed and that wear
is avoided.
[0102] Turning now to FIG. 14, with added reference to FIG. 1, an
overview of the above-described oilfield material delivery
mechanism 100 in operation at an oilfield 301 is shown. In the
embodiment shown, the oilfield material delivery mechanism 100 is
employed in a fracturing operation at the oilfield 301. The
pressure inducing equipment 150 of FIG. 1 is a part of a larger
pressure inducing assembly 375 including a host of pumps atop the
skid 159 (See FIG. 1). A high-pressure fluid flow 210 as detailed
above with reference to FIGS. 1 through 12, may thereby be
generated and directed toward the material supply equipment 175.
Pumps may be located downstream of the pressure inducing assembly
375 and/or adjacent the material supply equipment 175 for providing
flow to the material supply equipment 175 and/or the choke 223, as
will be appreciated by those skilled in the art.
[0103] Material supply equipment 175 may operate to introduce
oilfield material 275 such as proppant into the fluid flow 210 on
the high-pressure side of the pressure inducing assembly 375. The
fluid flow 210 is directed past a well head 310 into a well 320
drilled into the oilfield 301. The well 320 may traverse a
fracturable production region 330 of the oilfield 301. The delivery
of high-pressure fluid flow may thereby be employed to promote the
production of hydrocarbons from the production region 330. That is,
as detailed above, the fluid flow 210 may include oilfield material
275 in the form of an abrasive proppant to encourage the fracturing
of geologic formations below the oilfield 301 to enhance the noted
hydrocarbon production.
[0104] The oilfield material delivery mechanism 100, the
subassembly 185 or group of subassemblies 185, 185', 185'',
185'''', 185'''', and the fill stages 801a, 801b, the discharge
stages 809a, 809b, described hereinabove may be operated to create
a heterogeneous (i.e. non-homogenous or non-continuous) slurry flow
operation, wherein alternating flow of slurry and clean fluid (such
as the slurry 603 and the fluid 601) is supplied to the wellbore
320, thereby enabling heterogeneous placement of the slurry 603 and
the oilfield material 275 in the wellbore 320, as will be
appreciated by those skilled in the art. Heterogeneous placement of
oilfield material 275, such as proppant and the like, may be
advantageous for the creation of highly conductive fractures in the
formation 303 and/or the production region 330, as recited in U.S.
Pat. Nos. 6,776,235 and 7,451,812, and commonly assigned and
co-pending application Ser. No. 11/608,686, the disclosures of each
of which are incorporated by reference herein in their
entireties.
[0105] The operation of the oilfield material delivery mechanism
100, the subassemblies 185, 185', 185'', 185'''', 185'''', and the
fill stages 801a, 801b, the discharge stages 809a, 809b may be
varied to produce heterogeneous flow of slurry 603 having a desired
density concentration in the wellbore 320, to produce a flow of
slurry 603 entering the wellhead 310 at predetermined intervals
and/or for a predetermined duration. In a non-limiting example, a
flow of slurry 603 at the wellhead 310 may range from a density of
about 0.1 to about 16.0 ppg (pounds of proppant per gallon)and may
flow at a predetermined time for about one second to about two
minutes in duration and at intervals from about one second to about
two minutes. In the intervals between the flow of slurry 603 at the
wellhead 310, clean liquid or fluid 601 flows to the wellhead 310
or slurry 603 having a density of less than 0.1 ppg flows to the
wellhead 310. Heterogeneous proppant placement may be advantageous
for a fracturing method such as, but not limited to, introducing a
one of a slurry and proppant-laden slurry into a wellbore 320 for a
predetermined period of time.
[0106] In a non-limiting example, a method of operating for
heterogeneous placement of oilfield material may comprise
alternating fluid flows having a contrast in their respective
properties in order to stimulate the subterranean formation
penetrated by a wellbore. The contrast in properties may include,
but is not limited to, fluids having different densities, fluids
having a difference in the size of proppant utilized, and/or fluids
having a difference in the concentration of the fluids, such as the
concentration of the oilfield material in the treatment fluids.
[0107] In a non-limiting example, a method of operating for
heterogeneous placement of oilfield material may comprise designing
an initial model such as a fracturing model, operating the
equipment (such as the oilfield material delivery mechanism 100,
the subassemblies 185, 185', 185'', 185'''', 185'''') to effect the
model, and altering the operation of the equipment based on
operating data acquired from the equipment and/or from the wellbore
320.
[0108] In a non-limiting example, a method of operating for
heterogeneous placement of oilfield material may comprise the
oilfield material of the treatment fluid may comprise a proppant
and channel-forming fill material including, but not limited to,
fibers or particles, dissolvable, or degradable, or combinations
thereof, that act as a fill during the creation of fractures in the
formation but may be subsequently removed to create channels in the
formation to promote production of the fluid of interest from the
wellbore 320.
[0109] In a non-limiting example, rather than alternating flows of
slurry and clean fluid, the heterogeneous flow operation may be
operated to create alternating flows of high density (i.e. proppant
rich) slurry and low density (i.e. proppant lean) slurry, depending
on the requirements of the operation, as will be appreciated by
those skilled in the art.
[0110] As opposed to merely monitoring some degree of damage to
pressure inducing equipment, the herein described oilfield material
delivery mechanism and method of operation thereof avoids of the
harmful effects that result from pumping abrasive slurries through
the pressure inducing equipment. The reduced wear on the pressure
inducing equipment prolongs the life of these components, minimizes
maintenance costs and down-time. Furthermore, the herein described
embodiments are fully scalable and provide an elegant solution that
require only relatively simple equipment, and yet provide a great
deal of flexibility in the introduction of oilfield material and
additives to a high-pressure fluid flow.
[0111] The particular embodiments disclosed above are illustrative
only, as the invention may be modified and practiced in different
but equivalent manners apparent to those skilled in the art having
the benefit of the teachings herein. Furthermore, no limitations
are intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore
evident that the particular embodiments disclosed above may be
altered or modified and all such variations are considered within
the scope and spirit of the invention. In particular, every range
of values (of the form, "from about A to about B," or,
equivalently, "from approximately A to B," or, equivalently, "from
approximately A-B") disclosed herein is to be understood as
referring to the power set (the set of all subsets) of the
respective range of values. Accordingly, the protection sought
herein is as set forth in the claims below.
* * * * *