U.S. patent application number 13/457362 was filed with the patent office on 2012-12-20 for subsea pressure control system.
This patent application is currently assigned to BP CORPORATION NORTH AMERICA INC.. Invention is credited to Matthew Herrold, Adam Dudley Lawrence Hudson, Stephen Geoffrey Raymer, George Austin Zener.
Application Number | 20120318529 13/457362 |
Document ID | / |
Family ID | 46026989 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120318529 |
Kind Code |
A1 |
Herrold; Matthew ; et
al. |
December 20, 2012 |
SUBSEA PRESSURE CONTROL SYSTEM
Abstract
A subsea pressure control system includes an inlet flowline, a
pressure sensing device coupled into the inlet flowline and in
fluid communication with the inlet flowline, a controller coupled
to the pressure sensing device, an actuator coupled to the
controller, and a valve coupled to the actuator and a fluid outlet.
The controller may be responsive to the pressure sensing device,
the actuator may be responsive to the controller, and the valve may
be responsive to the actuator to regulate a measured pressure of
the pressure sensing device at or below a setpoint pressure.
Another subsea pressure control system includes a controller
responsive to a setpoint pressure in a flowline, and a valve
responsive to a signal from the controller, wherein the signal is
based on the setpoint pressure and actuates the valve from a closed
position to an open position.
Inventors: |
Herrold; Matthew; (Surrey,
GB) ; Hudson; Adam Dudley Lawrence; (Houston, TX)
; Raymer; Stephen Geoffrey; (Houston, TX) ; Zener;
George Austin; (Houston, TX) |
Assignee: |
BP CORPORATION NORTH AMERICA
INC.
Houston
TX
|
Family ID: |
46026989 |
Appl. No.: |
13/457362 |
Filed: |
April 26, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61481976 |
May 3, 2011 |
|
|
|
Current U.S.
Class: |
166/375 ;
166/321 |
Current CPC
Class: |
E21B 43/01 20130101 |
Class at
Publication: |
166/375 ;
166/321 |
International
Class: |
E21B 34/08 20060101
E21B034/08 |
Claims
1. A subsea pressure control system comprising: an inlet and an
inlet flowline; a pressure sensing device coupled into the inlet
flowline and in fluid communication with the inlet flowline; a
controller coupled to the pressure sensing device; an actuator
coupled to the controller; and a valve coupled to the actuator and
a fluid outlet.
2. The system of claim 1 wherein the controller is responsive to
the pressure sensing device.
3. The system of claim 2 wherein the controller comprises a
setpoint pressure and is configured to compare the setpoint
pressure to a measured pressure of the pressure sensing device.
4. The system of claim 1 wherein the actuator is responsive to the
controller.
5. The system of claim 4 wherein the valve is responsive to the
actuator.
6. The system of claim 5 wherein the actuator is responsive to the
controller based on a setpoint pressure to move the valve between a
closed position isolating the inlet flowline from the fluid outlet
and an open position exposing the inlet flowline to the fluid
outlet.
7. The system of claim 6 wherein the valve is moved to the open
position if a measured pressure of the pressure sensing device
exceeds the setpoint pressure, and the valve is moved to the closed
position if the measured pressure is at or below the setpoint
pressure.
8. The system of claim 1 wherein the actuator is operably coupled
to the valve to selectively expose the inlet flowline to the fluid
outlet.
9. The system of claim 1 wherein the pressure sensing device
measures a fluid pressure in the inlet flowline.
10. The system of claim 1 wherein the pressure sensing device
comprises a pressure transducer.
11. The system of claim 1 wherein the controller comprises an
electronic control module and the actuator comprises an electric
actuator.
12. The system of claim 1 wherein the pressure sensing device and
the controller comprise a master hydraulic cylinder and a slave
hydraulic cylinder.
13. The system of claim 1 wherein the actuator comprises a
hydraulic actuator.
14. The system of claim 1 wherein the valve comprises a choke.
15. The system of claim 1 further comprising a flowline coupled
between the inlet and a subsea wellhead manifold.
16. The system of claim 1 further comprising at least one backup
pressure control subsystem coupled to the inlet.
17. A subsea pressure control system comprising: a flowline
configured for connection into a subsea fluid containment system; a
controller configured to be responsive to a setpoint pressure in
the flowline; and a valve configured to be responsive to a signal
from the controller, wherein the signal is based on the setpoint
pressure and actuates the valve from a closed position to an open
position to expose the flowline to the sea or a container.
18. The system of claim 17 further comprising a pressure sensing
device configured to be responsive to a measured pressure in the
flowline, wherein the signal is based on the measured pressure
exceeding the setpoint pressure.
19. The system of claim 18 wherein the valve is responsive to a
second signal from the controller, wherein the second signal is
based on the measured pressure equaling or falling below the
setpoint pressure, and the second signal actuates the valve from
the open position to the closed position to isolate the flowline
from the sea or the container.
20. The system of claim 17 further comprising at least one backup
pressure control subsystem coupled to the flowline, wherein the
backup pressure control subsystem is operable if the valve fails to
actuate from the closed position to the open position.
21. A method of controlling a pressure in a subsea fluid
containment system, comprising: determining a setpoint pressure for
a subsea pressure control system; coupling the subsea pressure
control system into the subsea fluid containment system; measuring
a pressure of the subsea fluid containment system; comparing the
measured pressure to the setpoint pressure; and exposing the subsea
fluid containment system to the sea or a container using the subsea
pressure control system if the measured pressure exceeds the
setpoint pressure.
22. The method of claim 21 further comprising isolating the subsea
fluid containment system from the sea using the subsea pressure
control system if the measured pressure falls below the setpoint
pressure.
23. The method of claim 21 further comprising adjusting the
setpoint pressure while subsea.
24. The method of claim 21 further comprising modulating the
measured pressure.
25. The method of claim 21 further comprising opening a backup
subsystem to expose the subsea fluid containment system to the sea.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 61/481,976 filed May 3, 2011, and
entitled "Subsea Pressure Control System."
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
[0003] In producing oil and gas from offshore wells, a wellhead is
employed at the seafloor and the hydrocarbons flow from the
wellhead through tubular risers to the surface where the fluids are
collected in a receiving facility located on a platform or other
vessel. Normally, the flow of hydrocarbons is controlled via a
series of valves installed on the wellhead, the risers, and in the
receiving facility at the surface. At times, temporary flow lines
from the wellhead to a receiving facility or other containment
target, such as an existing reservoir, may be installed. The
transfer of fluids from the wellhead to a receiving facility or
other containment target often times involves communication from a
high pressure system to a lower pressure system. In all such
instances, it is important to prevent excessive pressure from
building up in the interconnecting flow lines. Such excessive
pressures could build up due to hydrate formation, sudden changes
in pressure in the well bore, slugging flow, or excessive back
pressure from valve closings or from other processes.
[0004] Water pressures could cause equipment failures at the sea
floor, which may be 5,000-7,000 feet or more below the surface. At
those depths, the water pressure exceeds 2,000 p.s.i. Because of
the depth and pressures, effectuating repairs at such depths
requires that equipment and tools be handled by deep diving,
remotely operated vehicles (ROV's), which are essentially robots
controlled by an operator in a surface vessel. Controlling the
vehicles from such distances and using the ROV's to repair and/or
replace equipment and components is a difficult and time consuming
task. Consequently, a device is required to limit pressures in the
subsea flow lines and other hydrocarbon-containing equipment to
non-destructive levels, and to relieve excess pressure when
required.
SUMMARY
[0005] Accordingly, there remains a need in the art for regulating
fluid pressures between high pressure subsea systems and lower
pressure subsea systems while in the subsea environment. Any
pressure relief device installed at the sea bed must be capable of
reliable operation at the pressures that are encountered, and must
withstand the corrosive environment of the sea. Further, it would
be advantageous if the pressure setting at which the pressure
relief device operates can be adjusted while the device is
installed and in position subsea, rather than having to disconnect
the device from a piping and/or containment system and then make
the lengthy trip to the surface for adjustment. Still further, it
would be advantageous if the pressure relief device operates only
so long as to relieve enough pressure to bring the piping and/or
containment system back to below the predetermined pressure
setting, such that only the minimal amount of system fluids are
released.
[0006] An embodiment of a subsea pressure control system includes
an inlet and an inlet flowline, a pressure sensing device coupled
into the inlet flowline and in fluid communication with the inlet
flowline, a controller coupled to the pressure sensing device, an
actuator coupled to the controller, and a valve coupled to the
actuator and a fluid outlet. The controller may be responsive to
the pressure sensing device. The controller may include a setpoint
pressure and may be configured to compare the setpoint pressure to
a measured pressure of the pressure sensing device. The actuator
may be responsive to the controller. The valve may be responsive to
the actuator. The actuator may be responsive to the controller
based on a setpoint pressure to move the valve between a closed
position isolating the inlet flowline from the fluid outlet and an
open position exposing the inlet flowline to the fluid outlet. The
valve may be movable to the open position if a measured pressure of
the pressure sensing device exceeds the setpoint pressure, and to
the closed position if the measured pressure is at or below the
setpoint pressure. The actuator may be operably coupled to the
valve to selectively expose the inlet flowline to the fluid
outlet.
[0007] In some embodiments, the controller includes an electronic
control module and the actuator comprises an electric actuator. The
pressure sensing device and the controller may include a master
hydraulic cylinder and a slave hydraulic cylinder. The actuator may
include a hydraulic actuator. The valve may include a choke. The
system may include a flowline coupled between the inlet and a
subsea wellhead manifold. The system may include at least one
backup pressure control subsystem coupled to the inlet.
[0008] In further embodiments, a subsea pressure control system
includes a flowline configured for connection into a subsea fluid
containment system, a controller configured to be responsive to a
setpoint pressure in the flowline, and a valve configured to be
responsive to a signal from the controller, wherein the signal is
based on the setpoint pressure and actuates the valve from a closed
position to an open position to expose the flowline to the sea or a
container. The system may further include a pressure sensing device
configured to be responsive to a measured pressure in the flowline,
wherein the signal is based on the measured pressure exceeding the
setpoint pressure. The valve may be responsive to a second signal
from the controller, wherein the second signal is based on the
measured pressure equaling or falling below the setpoint pressure,
and the second signal actuates the valve from the open position to
the closed position to isolate the flowline from the sea. In some
embodiments, the system includes at least one backup pressure
control subsystem coupled to the flowline, wherein the backup
pressure control subsystem is operable if the valve fails to
actuate from the closed position to the open position.
[0009] In some embodiments, a method of controlling a pressure in a
subsea fluid containment system includes determining a setpoint
pressure for a subsea pressure control system, coupling the subsea
pressure control system into the subsea fluid containment system,
measuring a pressure of the subsea fluid containment system,
comparing the measured pressure to the setpoint pressure, and
exposing the subsea fluid containment system to the sea using the
subsea pressure control system if the measured pressure exceeds the
setpoint pressure. The method may further include isolating the
subsea fluid containment system from the sea using the subsea
pressure control system if the measured pressure falls below the
setpoint pressure. The method may further include adjusting the
setpoint pressure while subsea, modulating the measured pressure,
and opening a backup subsystem to expose the subsea fluid
containment system to the sea.
[0010] Thus, embodiments described herein comprise a combination of
features and advantages intended to address various shortcomings
associated with certain prior devices, systems, and methods. The
various characteristics described above, as well as other features,
will be readily apparent to those skilled in the art upon reading
the following detailed description, and by referring to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] For a detailed description of exemplary embodiments of the
invention, reference will now be made to the accompanying drawings
in which:
[0012] FIG. 1 is a schematic view of an exemplary subsea
hydrocarbon recovery system employing a subsea manifold coupled to
multiple hydrocarbon flow lines and containers;
[0013] FIG. 2 is an elevation view of a subsea manifold coupled to
a subsea pressure control system in accordance with embodiments and
principles disclosed herein;
[0014] FIG. 3 is a enlarged view of the subsea pressure control
system of FIG. 2;
[0015] FIG. 4 is a perspective view of the primary pressure control
subsystem of the subsea pressure control system of FIGS. 2 and
3;
[0016] FIG. 5 is an elevation view of the subsea manifold coupled
to an alternative pilot operated hydraulic embodiment of a subsea
pressure control system in accordance with embodiments and
principles disclosed herein;
[0017] FIG. 6 is a schematic of the hydraulic sensor and controller
for a pilot operated primary pressure control subsystem of the
subsea pressure control system of FIG. 6; and
[0018] FIG. 7 is a flowchart illustrating an exemplary embodiment
of a method for controlling a pressure in a subsea fluid
containment system.
DETAILED DESCRIPTION
[0019] In the drawings and description that follow, like parts are
typically marked throughout the specification and drawings with the
same reference numerals, respectively. Certain terms are used
throughout the description and claims to refer to particular
features or components. As one skilled in the art will appreciate,
different persons may refer to the same feature or component by
different names. This document does not intend to distinguish
between components or features that differ in name but not
function. The drawing figures are not necessarily to scale. Certain
features and components may be shown exaggerated in scale or in
somewhat schematic form and some details of conventional elements
may not be shown in the interest of clarity and conciseness. The
present invention is susceptible to embodiments of different forms.
Specific embodiments are described in detail and are shown in the
drawings, with the understanding that the present disclosure is to
be considered an exemplification of the principles of the
invention, and is not intended to limit the invention to that
illustrated and described herein. It is to be fully recognized that
the different teachings of the embodiments discussed below may be
employed separately or in any suitable combination to produce
desired results.
[0020] The terms "including" and "comprising" are used in an
open-ended fashion, and thus should be interpreted to mean
"including, but not limited to . . . ." Unless otherwise specified,
any use of any form of the terms "couple", "attach", "connect" or
any other term describing an interaction between elements is not
meant to limit the interaction to direct interaction between the
elements and may also include indirect interaction between the
elements described. Thus, if a first device couples to a second
device, that connection may be through a direct connection, or
through an indirect connection via other devices, components, and
connections.
[0021] A subsea pressure relief or control system for underwater
applications is disclosed herein. The system may be employed in
many underwater applications; however, it has particular
application as a device to relieve overpressures that may develop
in subsea flowlines, manifolds, tanks, vessels and reservoirs
containing and/or transporting hydrocarbons from the sea floor or
between subsea containment systems. For convenience, the word
"container" may be used herein to refer to all such
hydrocarbon-containing lines, manifolds, tanks, vessels and
reservoirs.
[0022] Referring to FIG. 1, an exemplary embodiment of an offshore
or subsea well control system 200 for recovering hydrocarbons from
a subsea wellbore 201 is shown. In this embodiment, the system 200
includes a blowout preventer (BOP) 202 mounted to a wellhead 203 at
the sea floor 204, and a capping stack 205 mounted atop the BOP
202. In certain embodiments of a well control system for producing
from the well 201, hydrocarbons are allowed to flow through the BOP
202, through a lower marine riser package (not shown), and through
risers 213 to a hydrocarbon-receiving vessel at the surface, such
as a platform 211 floating on sea water 215. In this example,
however, the capping stack 205 has been substituted for a lower
marine riser package in a situation, for example, where hydrocarbon
flow is not controlled via the normal path and is instead diverted
and collected via an alternate collection system.
[0023] In other embodiments, the subsea system 200 includes, and
the pressure control embodiments described below are compatible
with, wellheads, BOP's, capping stacks, Christmas trees, flowlines,
jumpers, manifolds, processing units, risers, pipeline end
terminals (PLETs), flowline end terminations (FLETs), pipeline end
manifolds (PLEMs), in-line tees (ILTs), and other subsea
transportation systems.
[0024] The capping stack 205 includes at least one fluid outlet 206
controlled by a valve 207 for controlling the flow of hydrocarbons
from the well to various destinations, including into a
distribution manifold 208. In turn, one or more flowlines 209 are
connected to valved outlets 210 in the manifold 208 and are
employed to transport the hydrocarbons from the well to one or more
hydrocarbon storage vessels at the surface, such as platform 211,
or containers or reservoirs located subsea. For example, one or
more of the flowlines 209 may coupled to a well and reservoir near
the well 201. Furthermore, another source of hydrocarbons may be
coupled into the network of flowlines 209 at another location. If
such additional source of hydrocarbons provides a higher fluid
pressure than the flowline network is generally capable of
handling, the integrity of the flowline network can be jeopardized.
A pressure relief device 10 may be coupled to the subsea manifold
208 such that it is in fluid communication with hydrocarbons
contained in the manifold 208. When the valved outlet 210
interconnecting the flowline 209 and the manifold 208 is open, the
pressure relief device 10 is likewise in fluid communication with
the flowline 209. Exemplary embodiments of a pressure relief
device, or pressure control system, in accordance with principles
disclosed herein are described in detail below.
[0025] Referring now to FIG. 2, a subsea distribution manifold 308,
similar to the distribution manifold 208 of FIG. 1, includes
outlets 310. It should be noted that the manifold 308 may be
coupled between a well and a surface container, between two wells
or reservoirs, between two subsea containers, or other combinations
thereof in which two fluid systems are connected and there is the
potential for communication of a higher pressure to a lower
pressure fluid between the two fluid systems. The distribution
manifold 308 also includes a fluid connection 320 to a base member
322. The base member 322 includes a fluid coupling 324 to an inlet
flowline 352 of an embodiment of a subsea pressure control system
350. The inlet flowline 352 separates into two portions, a first
portion flowline portion 352a leading to a primary pressure control
subsystem 380, and a second flowline portion 352b leading to one or
more backup pressure relief subsystems 360, 370 as described more
fully below.
[0026] Additional reference can now be made to FIG. 3 for an
enlarged view of the subsea pressure control system 350 and the
primary pressure control subsystem 380. The second flowline portion
352b includes the backup pressure relief subsystems 360 including
one or more outlet tubes 361 each supporting a burst disc 362, or
other rupturable or one way member for releasing fluid or exposing
the second flowline portion 352b to the sea water 215. An upper end
portion of the second flowline 352b includes a pressure relief
valve 370 having an outlet 372 to the surrounding sea water 215 or
another high pressure containment vessel. In some embodiments, the
pressure relief valve 370 is a flow control valve adapted for
subsea use. In certain embodiments, the pressure relief valve 370
includes a valve for onshore use modified for subsea use. For
example, the valve outlet 372 may include a U-tube piping
arrangement to prevent formation of hydrates when the hydrocarbons
come into contact with seawater. In certain embodiments, the
pressure relief valve 370 and the pressure relief subsystem 360
with burst disc 362 are backup subsystems to the primary pressure
control subsystem 380. In some embodiments, the pressure relief
valve 370 is a secondary pressure control subsystem that operates
before the tertiary pressure control subsystem 360 including the
burst disc 362. In other embodiments, the operation of the pressure
relief valve 370 and the pressure relief subsystem 360 with burst
disc 362 are switched in time to backup the primary pressure
control subsystem 380; that is, the pressure relief subsystem 360
with burst disc 362 is the secondary pressure control subsystem and
the pressure relief valve 370 is the tertiary pressure control
subsystem.
[0027] Still referring to FIG. 3, an inlet coupling 354 couples the
first flowline portion 352a and the rest of the primary pressure
control subsystem 380 to the initial flowline 352. A sensor 382 is
coupled into the first flowline portion 352a. In some embodiments,
the sensor 382 is a pressure sensor or transducer. In other
embodiments as described elsewhere herein, the sensor 382 can be
another type of pressure sensing device. For ease of description,
the following discussion will refer to the sensor 382 as the
pressure sensor 382. The pressure sensor 382 is coupled into the
first flowline portion 352a to communicate with fluid pressure
therein, and then is also electrically coupled to an electronic
control module 388, or controller, by electrical line 384. The
controller 388 is electrically coupled to an actuator 390 by
electrical line 386. The actuator 390 is coupled to a valve 392,
which in some embodiments is a choke valve. The valve 392 includes
a coupling 394 coupled to an outlet or exhaust pipe 396 (FIG. 2),
396a (FIG. 3) that communicates with the surrounding sea water 215
or another high pressure containment vessel. In some embodiments,
the coupling 394 is a choke coupling.
[0028] Referring now to FIG. 4, additional details of one
embodiment of the primary pressure control subsystem 380 are shown.
In the embodiment shown in FIG. 4, the inlet coupling 354 is an
inlet for coupling to the flowline 352 (not shown in FIG. 4). The
inlet 354 is mounted to a manifold 355 to which the pressure sensor
382 may also be coupled. The manifold 355 receives fluid flow from
the inlet flowline 352 which is fluidly coupled to the manifold 308
and the hydrocarbon fluid flow network and container systems as
described with respect to FIG. 1. The controller 388 may be secured
to a mount 389 adjacent the manifold 355 and the pressure sensor
382 or may be remote or set apart from the subsystem 380. The
controller 388 may include a housing, a processor, a memory, a
power source, and other features common to electronic controllers.
As will be described more fully below, the processor and memory of
the controller 388 may be configured for certain functions and
processes.
[0029] The controller 388 is electrically coupled to the pressure
sensor 382 via line 384, electrically coupled to the actuator 390
via the electrical line 386, and in some embodiments, includes an
electrical line 385 to a power source. In some embodiments, the
electrical line 385 is a flying lead to a battery box with subsea
batteries on a mud mat or other nearby subsea equipment. In some
embodiments, the actuator 390 is an electric choke actuator such as
those manufactured by FMC Technologies. In other embodiments, as
will be described more fully below, the actuator can take other
forms. In certain embodiments, the valve 392 may be an FMC
Technologies electric choke, a Master Flo Valve Inc. adjustable
subsea choke, or a Cameron CC Series subsea choke. Other choke
valves are also possible and known to one having skill in the art.
The choke coupling 394 leads into an outlet pipe 395 and the outlet
396 to the surrounding sea water 215.
[0030] Finally, the primary pressure control subsystem 380 may
include lift eyes 398 for lifting and transporting the subsystem
380, and also an ROV panel 330 for operably coupling to and
interacting with an ROV. The ROV panel 330 includes handles 334, a
plug-in connection 336 and an operating connection 332.
[0031] Referring now to FIGS. 5 and 6, an alternative embodiment of
a primary pressure control subsystem is shown, including hydraulic
pressure sensing, control, and actuation of the choke actuator. The
manifold 308 as previously described is coupled into a subsea
pressure control system 550 in the same manner as already
described, including inlet flowlines 552, 552a, 552b, and backup
subsystems 560, 570, with subsystem 570 including an outlet 572.
However, instead of an electronically based primary pressure
control subsystem, a primary pressure control subsystem 580 is
hydraulically based. A pressure sensing piston 582 and cylinder 583
arrangement is fluidly coupled into the first flowline portion 552a
by tubing 585 and tubing 584. The cylinder 583 arrangement may also
be referred to as a slave cylinder. The slave cylinder 583 includes
an outlet tubing 586 ultimately coupled to an upper portion of an
actuator 590, which in this embodiment is a hydraulic actuator.
Tubing 585 also fluidly couples to a first cylinder 587 retaining a
first end of a hydraulic piston 588. A second end of the hydraulic
piston 588 is retained in a second cylinder 589. The hydraulic
piston 588 and cylinders 587, 589 arrangement may also be referred
to as a master cylinder 599. A tubing 591 fluidly couples the
second cylinder 589 to a lower portion of the actuator 590. Also
coupled between the tubings 586, 591 is a tubing 593, or flying
lead, that fluidly couples to a hydraulic fluid supply or bladder
595 (FIG. 6). As will be described in more detail below, the master
cylinder 599 and slave cylinder 583 arrangement is a pressure
sensing and control device wherein non-hydraulic pressure is
converted to hydraulic pressure via the master cylinder-slave
cylinder relationship.
[0032] Referring more specifically to FIG. 6, the master cylinder
599 is a control device that converts the non-hydraulic pressure in
the flowline 552a into hydraulic pressure in order to actuate the
slave cylinder 583. As the pressure in the flowline 552a increases,
the piston 588 moves in the cylinders 587, 589, and this movement
is transferred through the hydraulic fluid to result in movement of
the piston 582 in the slave cylinder 583 which actuates the
actuator 590. By varying the comparative surface-area of the
cylinders 587, 589 in the master cylinder 599 and the slave
cylinder 583, the amount of force and displacement applied to the
slave cylinder 583 is varied relative to the amount of force and
displacement that is applied to the master cylinder 599 and its
components 587, 588, 589. The resulting hydraulic force is applied
to the actuator 590 via the slave cylinder 583. Thus, the master
cylinder 599, slave cylinder 583 arrangement is a pressure sensing
and/or measuring device that is responsive to the pressure in the
flowline 552a and reacts to the pressure to control the actuator
590. The actuator 590 is responsive to the master-slave cylinder
599, 583 to actuate a valve 592 (FIG. 5), such as a hydraulic choke
valve. The valve 592 is responsive to the actuator to selectively
expose or isolate the flowline 552a relative to an outlet 596 and
the surrounding sea 215. The outlet 596 is coupled to the valve 592
via the coupling 594 (FIG. 5).
[0033] In certain embodiments, and with continued reference to
FIGS. 5 and 6, the piston/cylinder 588, 587 is a pilot operated
piston on the OPEN side of the circuit as shown in FIG. 6. The
assembly 582, 583, 585 is a pilot operated system which functions
to apply pressure to one side of the cylinder 587, while the other
side of the piston 588 is exposed to seawater hydrostatic pressure
as shown in FIG. 6. A control fluid is located in the volume on one
side of the piston 588 in the cylinder 589 that is coupled to the
line 591, which is coupled to the CLOSE side of the circuit and the
actuator 590. As pressure builds in the high pressure source line
552a, the pilot lines 584, 585 pressure up the cylinder 582 and the
OPEN side of the actuator 590 while simultaneously pressuring up
the cylinder 587 to cause the cylinder 589 to pull fluid from the
CLOSE side of the actuator 590. This creates a differential
pressure that moves the actuator 590 in the open direction, thus
evacuating the high pressure source line 552a through the valve 592
and the outlet 596. Conversely, as the pilot pressure drops in
lines 552a, 584, 585, the seawater pushes back on the cylinder 589,
increasing the control pressure in line 591 as well as to the CLOSE
side of the actuator 590 while the cylinder 583 pulls fluid from
the line 586 as well as on the OPEN side of the actuator 590. In
some embodiments, pressure relief check valves are needed on both
the OPEN and CLOSE control lines 586, 591 in order to keep the
actuator 590 from being overpressurized during operation. The
subsea bladder 595 of control fluid may replace any vented control
fluid, and associated check valves may prevent the bladder 595 from
being overpressurized during normal operation.
[0034] In some embodiments, the hydraulic primary pressure control
subsystem 580 may require less to no power compared to that of the
electrical primary pressure control subsystem 380. In the hydraulic
primary pressure control subsystem 580, a fixed volume of hydraulic
fluid is moved in the subsystem. Hydraulic power may be provided by
the high pressure source from the reservoir in some embodiments. In
other embodiments, hydraulic power can be stored in a hydraulic
accumulator. Such a hydraulic system reduces or minimizes the need
to draw on subsea batteries or other electrical power sources.
[0035] In operation, the primary pressure control subsystems 380,
580 are autonomous pressure controllers that maintain pressure
below an adjustable setpoint pressure or predetermined pressure by
venting the minimum amount of fluid into the sea. At the surface,
and before the deployment of the subsystems 380, 580 in the subsea
pressure control systems 350, 550, the setpoint pressure is
determined and implemented. For the electrical subsystem 380, the
controller 388 is configured or programmed with the desired
setpoint pressure. The setpoint pressure is the pressure below
which the subsea well, flowline, manifold, container or similar
system is in a normal range, and above which creates an
overpressure situation. For the hydraulic subsystem 580, the master
and slave cylinder arrangement 599, 583 is designed and dimensioned
to react to the desired setpoint pressure.
[0036] Next, the subsea pressure control systems 350, 550 are
deployed subsea including the primary pressure control subsystems
380, 580, respectively. The systems 350, 550 may be coupled into or
between any of the various containers and systems already described
herein, including any number of different subsea connectors such as
a CVC hub, and can be serviced by ROV's. Consequently, the systems
350, 550 can connect anywhere in the flowline and containment
system network as shown and described with reference to FIG. 1.
[0037] Then, the pressure sensor 382 and the hydraulic master and
slave cylinder arrangement 599, 583 of subsystem 550 are allowed to
sense, measure, and monitor the pressure in the flowlines 352a,
552a and ultimately the subsea fluid containment system, while also
comparing the measured pressure to the setpoint pressure. When the
setpoint pressure is exceeded in the subsea fluid containment
system, the controller 388 and the hydraulic master and slave
cylinder arrangement 599, 583 respond and direct the actuators 390,
590 to actuate the valves 392, 592 to open and expose the
subsystems 380, 580 and the subsea fluid containment system to the
surrounding sea. Because of the dynamic and responsive nature of
the controller 388 and hydraulic 599, 583 controllers of the
subsystems 380, 580, the valves 392, 592 can be actuated closed
when the measured pressure is detected to be at or below the
setpoint pressure, thereby isolating the fluid containment system
from the sea and releasing only the quantity of fluids necessary to
bring the pressure below the setpoint pressure.
[0038] In some embodiments, the primary pressure control subsystems
380, 580 are designed to release the minimum amount of hydrocarbons
possible into the sea, while protecting the subsea fluid
containment system from an overpressure situation. The subsystems
380, 580 ensure minimal release of fluids to the sea by closing the
valves 392, 592 immediately upon or soon after bringing the system
pressure back below the setpoint pressure. Such controllability,
sensitivity, and reaction time to the setpoint pressure is enabled
by direct communication among and between the valve actuator 390,
the controller 388, and the pressure sensor 382 for the electronic
subsystem 380, and the similarly-functioning components of the
hydraulic subsystem 580.
[0039] Furthermore, in at least the electronic subsystem 380, the
setpoint pressure can be easily adjusted subsea by changing the
program settings in the controller 388. A ROV may interact with the
ROV panel 330 to re-program or re-configure the controller 388 to
respond to a new setpoint pressure.
[0040] The controllability of the subsystems 380, 580 provides a
gradual modulation of the system pressure, to avoid pressure spikes
which could lead to an overpressure situation. As the valves 392,
592 are being operated in response to the comparison between the
measured pressure and the setpoint pressure, the controllers 388,
599 and actuators 390, 590 are also operable to vary the positions
of the valves 392, 592 between fully open and fully closed to
modulate the flow rate therein.
[0041] Thus, the subsea pressure control systems 350, 550 can
closely regulate the pressure of a subsea well, flowline, manifold,
containment or similar subsea fluid system below a given setpoint
using the primary pressure control subsystems 380, 580. The
pressure sensors, controllers, actuators, and valves, or chokes,
may work together to release fluid and relieve pressure from the
subsea fluid containment system only until the pressure is reduced
below the setpoint. In additional embodiments, the backup pressure
relief subsystems 360, 370, 560, 570 as previously described may
also be provided, in various combinations, to relieve pressure from
the subsea fluid containment system in the event that the primary
pressure control subsystems 380, 580 do not bring the measured
pressure back below the setpoint pressure.
[0042] As previously described, the subsea pressure control systems
350, 550 and/or the primary pressure control subsystems 380, 580
may be coupled to and between various fluid containment or flowline
systems. In addition, the subsea pressure control systems 350, 550
and/or the primary pressure control subsystems 380, 580, in various
combinations, may be implemented in a device disposed as a
transition point between a higher rated pressure system and the
lower rated pressure system and including a series of valves and
sensors that will close and isolate the higher pressure system from
the lower pressure system.
[0043] In an embodiment of a method 600 of controlling a pressure
in a subsea fluid containment system, and with reference to the
flowchart of FIG. 7, the method starts at box 602 and includes
determining a setpoint pressure for a subsea pressure control
system at box 604. The method further includes deploying the subsea
pressure control system at box 606, coupling the subsea pressure
control system into a subsea fluid containment system at box 608,
and measuring a pressure of the subsea fluid containment system at
box 610. Then, the measured pressure is compared to the setpoint
pressure to determine whether the measured pressure exceeds the
setpoint pressure at box 612. If "No", then the measured pressure
continues to be monitored at box 610. If "Yes", then the method
includes opening a valve in the subsea pressure control system to
expose the subsea fluid containment system to the sea at box 614,
and closing the valve to isolate the subsea fluid containment
system from the sea when the measured pressure falls below the
setpoint pressure at box 616. As detailed herein, the
responsiveness of the valve to the actuators described herein,
which are responsive to the controllers described herein, which are
responsive to the measured pressure, allows the closing of the
valve and re-isolation of the subsea fluid containment system to be
achieved while releasing only those fluids necessary to bring the
measured pressure back below the setpoint pressure.
[0044] In alternative embodiments, and in various combinations, the
method may include adjusting the setpoint pressure for the subsea
pressure control system while subsea at box 618. The method may
further include modulating the measured pressure of the subsea
fluid containment system at box 620. The method may further include
opening a backup subsystem to expose the subsea fluid containment
system to the sea, at box 622, in the event the valve opening at
box 614 is insufficient to lower the measured pressure to the
setpoint pressure.
[0045] While specific embodiments have been shown and described,
modifications can be made by one skilled in the art without
departing from the scope or teachings herein. The embodiments as
described are exemplary only and are not limiting. Many variations
and modifications of the systems, apparatus, and processes
described herein are possible and are within the scope of the
disclosure. For example, the relative dimensions of various parts,
the materials from which the various parts are made, and other
parameters can be varied. Accordingly, the scope of protection is
not limited to the embodiments described, but is only limited by
the claims that follow, the scope of which shall include all
equivalents of the subject matter of the claims.
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