System for operating hydraulic apparatus
United States Patent 3921500

This invention is directed to a system for operating apparatus which includes submerged hydraulically actuated devices and has provision for cycling the hydraulic fluid continuously in a closed loop from a high pressure side from which the actuated device is energized to a low pressure side which receives hydraulic fluid discharged from the device, and includes a system for repressuring the discharged hydraulic fluid with a gas which may also be recycled in an independent closed loop, the repressured hydraulic fluid then being continually recycled to function as the energy-transmitting medium in the system. The repressuring portion of the system is arranged for automatic operation. The system is adaptable to the operation of subsea well control apparatus.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
60/325, 60/416, 166/338, 166/368
International Classes:
F15B1/00; E21B33/035; E21B33/064; F15B1/02; F15B11/072; F15B21/04; (IPC1-7): F15B1/02; F15B21/04
Field of Search:
91/4,5 60
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US Patent References:

Primary Examiner:
Geoghegan, Edgar W.
Attorney, Agent or Firm:
Freeland Jr., Gibeau R. L. C. J.
What is claimed is

1. Means for operating an assembly of apparatus containing hydraulically actuated devices comprising:

2. Means in accordance with claim 1,

3. Means in accordance with claim 2 including:

4. Means in accordance with claim 3 wherein:

5. Means for operating apparatus in accordance with claim 1 wherein said means operable subsequently to increase the pressure in said second chamber while simultaneously reducing the pressure in said first chamber comprises

6. Means for operating apparatus in accordance with claim 1 including

7. Means for operating apparatus in accordance with claim 6 including,

8. Means in accordance with claim 7 wherein

9. Apparatus in accordance with claim 2 wherein

10. A control system for a device submerged in a body of water comprising:

11. A control system in accordance with claim 10 including means responsive to a predetermined increase in pressure in said low pressure conduit for automatically initiating operation of said first and said second valve means.

12. A control system in accordance with claim 10 wherein said control system is a system for controlling the operation of apparatus on a submerged well and said device is positioned at the submerged wellhead including

13. A control system for a subsea well including submerged hydraulically operated well control devices comprising

14. A control system in accordance with claim 13 including

15. A control system in accordance with claim 13 including


This invention relates to a system for operating, and controlling the operation of, apparatus which uses a hydraulic fluid under pressure as a motive fluid for energizing various devices. The invention comprises means for retaining all of the hydraulic fluid within the apparatus in an arrangement which permits the fluid to be cycled continuously as the energy-transmitting medium for the selective operation of hydraulically actuated devices in the apparatus. Of particular interest for applications of the present invention are installations where the apparatus is submerged in a body of water and is not readily available for adjustment or repair, and where it is undesirable to permit any of the hydraulic fluid either to be purposely discharged from or to inadvertently escape from the apparatus into the surrounding water.

The arrangement of the apparatus which embodies the invention and the system of its use and control makes it especially suitable for installation as a control means for wellhead apparatus, particularly for well control apparatus which is submerged in a body of water and affixed to subsea oil wells.

As the oil resources in the deeper waters of the oceans are being developed more consideration is being given to procedures for producing wells without the necessity of erecting fixed platforms at the wellsite. The expense of fixed platforms increases rapidly as the water depth increases, and unless a sufficient number of very productive wells can be drilled and produced from a single platform installation, it becomes economically unfeasible to recover the oil at that location. Various proposals have been made heretofore to treat subsea wells individually, that is, to drill them at their respective dispersed locations, to equip each with its own wellhead apparatus, and then by pipelines to bring the production from the individual wells together at a central, fixed offshore platform or to an on-land location. Some such individual subsea wells have successfully been drilled, equipped and produced, and the art in this area is continuously developing. It is within this environment that the present invention has important significance although it will be appreciated, as the description proceeds hereinafter, that the invention has useful application apart from the field of offshore oil recovery.

Subsea systems for controlling the operation of wellhead apparatus, of which I am aware, now in use in field operations employ hydraulic fluid pumps, located either above the surface of the water or incorporated in the submerged apparatus, to provide a supply of power fluid to operate subsea devices. Accumulators for the hydraulic fluid are mounted on the subsea equipment to provide an adjacent reservoir for the pressurized power fluid. When the hydraulic pump is above the surface of the water, these submerged accumulators necessarily are charged through long hydraulic lines, which are exposed to damage and the possible leakage of hydraulic fluid into the ambient water. Additionally, the inherent pressure drop in the long hydraulic lines limits the response of the submerged apparatus when it places a heavy demand on the pressurized fluid supply. Conversely, in those systems where the hydraulic pump is mounted directly on the submerged equipment, there is a practical limitation on the size of the pump which can be used, since the weight, conformation, compactness, and the area exposed to wave forces are important considerations both from the standpoint of handling and installing the equipment from a floating vessel and because of the water forces it must resist when it is installed in place. These restrictions on the size of the submerged pump may be such that it is not practical to incorporate in the submerged equipment a pump of adequate size to keep the accumulators continuously charged to working pressure during normal operations.

In either of the foregoing cases, if the demand of the system for power fluid exceeds the rate at which the submerged accumulators can be recharged either through the long hydraulic lines from the surface or by the pump incorporated in the submerged equipment, service will be interrupted until the accumulators can be charged to working pressure. Obviously, this is an undesirable circumstance.


The system of the present invention is designed to provide uninterrupted operation at rapid response rates, and when applied to submerged wells with the required operating hydraulic pressures at the submerged wellhead being unaffected by changes in water depth. To accomplish this, a plurality of hydraulic fluid accumulators are used and are separated into two functional portions of the system, one to provide a reservoir of fluid under pressure to energize the hydraulically actuated devices and the other to act as a low-pressure receiver for the hydraulic fluid discharged from the operating devices. The hydraulic portion of the system is a completely self-contained closed loop through which the hydraulic fluid content of the system is continuously recycled and which does not require replenishment during normal operation. When the system is applied to submerged wells, the hydraulic fluid discharged from the exhaust side of the hydraulically operated devices is discharged against substantially atmospheric pressure, regardless of the water depth. This latter feature circumvents the necessity for increasing the pressure in the energizing side of the hydraulic system as the depth of the water increases, as would be necessary if the hydraulic fluid were discharged against ambient hydrostatic pressure. Thus, the operational parameters of the system are not substantially changed by changes in the depths of water in which the apparatus may be installed.

In the present system, the accumulator which is functioning as a pressurized chamber for the hydraulic fluid is charged by a pressurized gas, and the accumulator which is functioning as a receiving chamber for the discharged hydraulic fluid is vented by a gas line at substantially atmospheric pressure. The system is arranged so that the pressurizing gas line and the venting line can be connected alternately to each of the pressure and receiving accumulators so that when the receiving accumulator becomes filled with discharged hydraulic fluid the pressurized gas line can be connected to it to cause it to function as the pressure chamber while at the same time the venting gas line is connected to what formerly was the pressure accumulator, so that the latter now becomes the receiving chamber. Means are provided in the system to make this switchover of accumulators automatic when the receiving accumulator reaches its filled capacity of hydraulic fluid, so that continuous operation of the system is accomplished without the necessary attention of the human operator. However, considering the problems incident to the environment of an offshore oil well in deep ocean waters, it is advisable for such use to build into the system some degree of redundancy such as an alternate provision for manually controlled operation in the event the automatic operating features malfunction.

Sufficient chamber capacity is built into the apparatus to provide a reasonable amount of continuous operation from the same pressure chamber before the switchover of accumulators, as described above, is necessary. This chamber capacity may be provided in single pressure and receiving accumulators, as will be illustrated schematically hereinafter, or the desired chamber capacity may be provided by a plurality of accumulators connected together in groups to function substantially as the single accumulators illustrated.

It is a desirable feature of this invention in offshore installations that the medium for providing pressure for pressurizing the hydraulic fluid in the pressure chamber on the energizing side of the hydraulic system is through a pressure gas line and also that substantially atmospheric pressure is maintained in the receiving chamber through means of a venting gas line. In submerged systems the gas lines can be projected from compressors and gas receivers at the water surface downwardly through the water and connected to the submerged apparatus. Since all of the hydraulic components of the system then are submerged within and usually well below the surface of the water, the chance of hydraulic fluid escaping into the ambient water is considerably reduced. The gas lines to the surface pass through the near-surface area, where the water forces are the greatest, and thus are more exposed to damage than are the deeper hydraulic lines. Damage to the gas lines is, of course, undesirable, but does not create the condition of water contamination, as would occur with a break in a hydraulic line.

Operation of individual valves and devices in the apparatus is controlled remotely from an appropriate console. It is understood in the art that a valve may be actuated from a remote location through electrical, hydraulic or pneumatic transmission conduits, or through acoustic or electro-magnetic radiation signals to initiate actuation of the valve, or by combinations of the foregoing. To simplify the description of the system, it will be described hereinafter as including gas transmission conduits for controlling the pressures in the hydraulic fluid accumulators and with electrically operated valves connected to electrical conductors for controlling the valves remotely. It will be understood, however, that the use of these specific elements in the description of the apparatus is by way of example and it is not intended to limit embodiments of the invention thereto. As noted previously, the automatic operation, which is a component feature of a portion of the system, is supplemented by means for manual remote operation as a precaution against compulsory shutdown.


FIG. 1 is a schematic representation of the system of this invention and illustrates the disposition of the various valves when a particular accumulator is being used as a pressure chamber for pressurized hydraulic fluid and an alternate accumulator is used as a receiving chamber for discharged hydraulic fluid.

FIG. 2 is a schematic representation showing the disposition of the valves in the system when an alternate accumulator is being used as the pressure chamber for pressurized hydraulic fluid and the first accumulator is being used as a receiving chamber to receive the discharged hydraulic fluid.

FIG. 3 is a schematic representation of the system of this invention as applied to well control apparatus which contains a plurality of hydraulically operated devices.

FIG. 4 is a representation in side elevation of a portion of control apparatus for a submerged wellhead and illustrates a manner of connecting the submerged apparatus to supply lines extending from the water surface.


Although this invention can be employed beneficially in a variety of installations, it will be described hereinafter principally as applied to an offshore well wherein the well control apparatus is secured to a well opening submerged below the surface of a body of water.

The control system illustrated in FIGS. 1 and 2 can conveniently be divided into three principal subassemblies, as indicated by the dashed line enclosures numbered respectively 10, 12 and 14. The subassembly 10 includes a portion of the apparatus which may be established at a location spaced apart from the other portions of the system to which it may be operatively connected by appropriate detachable connectors in the gas and electrical lines which are common to the subassemblies. For example, subassembly 10 may be located above the surface of a body of water in which the remainder of the system is submerged as in being connected to a submerged well opening.

Subassembly 12 includes the principal assembly of the valves through which the system is operated. This subassembly may, for example, be encapsulated in a pod which can be lowered through the body of water and connected automatically in operative relationship to the submerged control devices.

Subassembly 14 includes the devices which ultimately are operated by the system and related apparatus such as may be affixed at the submerged location. For example, subassembly 14 may include the well control devices such as blowout preventers, which are a component part of the well control apparatus.

In accordance with this invention the well control devices, as represented schematically by the cylinder and piston arrangement 20 are energized by a pressurized hydraulic fluid. In the posture of the system illustrated in FIG. 1, the accumulator 22 functions as a chamber for the hydraulic fluid under pressure. In the embodiment of the invention as applied to a submerged well, the receiver 22 preferably is installed as a part of the submerged wellhead apparatus, as illustrated in FIG. 4. In this location, the pressure chamber is placed immediately adjacent the well control devices operated by hydraulic fluid to eliminate the requirement of running hydraulic lines from the submerged apparatus to the surface of the water. Also, in this posture of the system, the accumulator 24 is connected as the chamber to receive the exhaust hydraulic fluid discharged from the operating well control device. The accumulator 24 also preferably is located in the submerged wellhead apparatus, as indicated in FIG. 4. As will be explained hereinafter, the accumulators 22 and 24 are alternately switched in function to operate at one time as a pressure chamber and at another time as a receiving chamber.

The accumulator 22 is partitioned by a flexible diagram 26 which separates the chamber 28 for hydraulic fluid from a pressurizing gas chamber 30. The gas chamber is in communication with a conduit 32, which is detachably connected through a connector 34, FIG. 1, in communication with a conduit 36 in the subassembly 12. The conduit 36 communicates through the valve 38 with a third conduit section 40, which in turn is in communication with a high-pressure gas receiver 42. Thus the high-pressure gas is conducted through the conduit arrangement described into the gas chamber 30 of accumulator 22 to apply gas pressure to the diaphragm 26 and to place the hydraulic content of the chamber 28 under pressure. Gas receiver 42 has sufficient capacity to exert a substantially constant pressure on the hydraulic fluid in chamber 28 as the fluid volume in the chamber decreases during operation of the apparatus.

The second accumulator 24 also is constructed with a flexible diaphragm 44 to separate the hydraulic fluid chamber 46 from the gas chamber 48 in a manner similar to that described for the accumulator 22. The gas content of accumulator 24 is in communication with the conduit 50 in subassembly 14. This conduit is placed in communication, through a detachable connector 52, with the conduit 54 in subassembly 12. The latter conduit communicates through valve 38 with conduit 56, which in turn communicates with a gas receiver 58. Receiver 58 is constructed with sufficient gas capacity to maintain the gas pressure in the accumulator 24 substantially constant as the volume of gas in this accumulator changes while the accumulator is receiving hydraulic fluid. Preferably, in this posture of the system the receiver 58 and the gas chamber 48 of the accumulator 24 are maintained at atmospheric pressure.

When accumulator 24 becomes filled with the hydraulic fluid discharged from device 20, valve 38 is operated to place gas chamber 48 of this accumulator in communication with the pressurized gas receiver 42 and simultaneously to place gas chamber 30 of accumulator 22 in communication with the low-pressure gas receiver 58 in a manner to be described more fully hereinafter. When this switchover occurs, chamber 46 of accumulator 24 becomes the reservoir of pressurized hydraulic fluid for operating the system and chamber 28 of accumulator 22 becomes the reservoir to receive the discharged hydraulic fluid.

Referring still to FIG. 1, conduit 60 for hydraulic fluid communicates with chamber 28 and is detachably connected through a connector 62 with a conduit 64 in subassembly 12. Conduit 64 is connected to a valve 66.

A similar hydraulic conduit 68 is in communication with chamber 46 and is connected through detachable connector 70 with a complementary conduit 72 is subassembly 12. Conduit 72 also is connected to valve 66.

In the posture of the system illustrated in FIG. 1, the pressurized hydraulic fluid from chamber 28 passes through valve 66 into conduit 74, which latter leads to a third valve 76 and to a fourth valve 78. The hydraulic fluid discharged from the operating device 20 subsequently passes through conduit 80 and through valve 66 and thence to receiving chamber 46 in a manner to be described in more detail hereinafter.

Valve 76 is subassembly 12 directly controls the operation of the hydraulically operated device 20. Thus, in the position of this valve indicated in FIG. 1, the pressurized hydraulic fluid passes from conduit 74 through valve 76 and into conduit 82 in communication with the valve. Conduit 82 is detachably connected through connector 84 to complementary conduit 86 in subassembly 14.

Hydraulically operated device 20 is indicated as a cylinder-and-piston arrangement, although obviously other forms of hydraulically operated devices may be employed in this system. The aforementioned conduit 86, which in the present instance carries pressurized hydraulic fluid to energize the hydraulically operated device, communicates with one end of cylinder 20. Second conduit 88 communicates with the other end of the cylinder. As will be understood in the art, the pressurized hydraulic fluid enters one end of the cylinder and pushes the piston toward the other end. As the piston moves it displaces hydraulic fluid which is exhausted or discharged from the cylinder through conduit 88. This conduit is connected through detachable connector 90 with conduit 92 in subassembly 12, which latter conduit is in communication with valve 76. The discharged hydraulic fluid flows through valve 76 into conduit 80 and thence through valve 66 into the connected conduits 72 and 68 and into the hydraulic fluid chamber of accumulator 24.

The arrangement and integrated operation of the valves in the subassembly 12 is such that conduit 80 will always be connected in the hydraulic fluid circuit to carry discharged hydraulic fluid away from the hydraulically operated devices toward the appropriate receiving accumulator. Pressure-sensitive device 94 is in communication with conduit 80 and is connected in the system to operate simultaneously valves 38 and 66. For example, if valves 38 and 66 are operated by electrically energized solenoids, a pressure-activated electrical switch may be used in the device 94 to direct an electrical current to each of the valves simultaneously to cause each valve to be changed to an alternate position.

As explained heretofore, the conduit 80 is arranged in respect to the valves in communication with it to conduct discharged hydraulic fluid to the selected receiving chamber. When the hydraulic fluid receiving chamber is filled to capacity, as illustrated by chamber 46 in accumulator 24 when progressing from FIG. 1 to FIG. 2, the hydraulic pressure in the interconnected conduits 68, 72 and 80 will increase as more discharged fluid is directed toward the receiving accumulator. The pressure-sensitive device 94 is arranged to be activated by a predetermined increase in pressure in conduit 80 to energize the valves 38 and 66 to cause them to change position. The system then assumes the posture illustrated in FIG. 2.

Referring to FIG. 2, the hydraulic fluid chamber 46 in accumulator 24 is represented as being filled to capacity. The resulting increase in pressure in conduit 80 has caused the pressure-sensitive device 94 to actuate valve 38 to place the pressurized gas receiver 42 in communication with the gas chamber 48 through the interconnected conduits 40, 54 and 50. As the same time, and through the same valve, the gas chamber 30 in accumulator 22 has been placed in communication with the atmospheric pressure gas receiver 58 through the intercommunicating conduits 56, 36 and 32. Simultaneously, the pressure-sensitive device 94 has activated valve 66 to place the conduit 74 in communication with the interconnected conduits 68 and 72, which latter now contain pressurized hydraulic fluid from chamber 46, and to place the conduit 80 in communication with the interconnected conduits 60 and 64 which lead to the hydraulic fluid chamber of accumulator 22. Thus, the functions of the two accumulators are switched and the first accumulator, which formerly contained the reservoir for pressurized hydraulic fluid, now becomes the receiving chamber, while the second accumulator, which formerly contained the receiving chamber, now becomes the reservoir for pressurized hydraulic fluid.

It will be noted that the switchover of functions of the accumulators through the automatic operation of the pressure-sensitive device 94 maintains the conduit 74 as a pressure-fluid carrying conduit and, as noted previously, conduit 80 is maintained as the discharged-fluid-carrying conduit. Thus, when the functions of accumulators 22 and 24 are exchanged valve 76 remains in its original position to direct the energizing, pressurized hydraulic fluid through the interconnected conduits 82 and 86 to consistently power the device 20 in the chosen direction. By this invention the functions of the accumulators 22 and 24 are switched automatically to provide a continuous supply of energizing hydraulic fluid to the operating device 20 without adversely affecting the operation of the latter.

Various valves in the wellhead apparatus are arranged to be activated by an appropriate signal sent from a remote location. By way of example, the valve 76 is connected to a console 96 in subassembly 10 through a signal-transmitting line 98. The console contains a plurality of separate stations, as represented schematically by the buttons 100, each of which can control the operation of a particular device in the submerged apparatus. The signal-transmitting line 98 may be a multiplexed system using a single pair of conductors to transmit the signals or a cable containing separate lines to each device, as will be understood in the art. A signal-generating means, such as a source of electrical power, is provided in subassembly 10, to provide a signal which is transmitted through line 98 to energize a selected unit in the assembly, such as the valve 76, and position it in a manner to cause the desired operation of he apparatus. For example, if device 20 is a piston-actuated blowout preventer and valve 76 is positioned as illustrated in FIGS. 1 and 2, the blowout preventer will be powered to a closed condition. To open the blowout preventer, valve 76 is operated to place the pressurized fluid conduit 74 in communication with conduit 92 and the discharged fluid conduit 80 in communication with the conduit 82. Thus, the energizing pressurized hydraulic fluid will enter cylinder 20 at the appropriate end to power the piston in the direction to open the blowout preventer and the hydraulic fluid in the other end of the cylinder will be discharged through conduits 86 and 82 through valve 76 into conduit 80.

The portion of the hydraulic circuit in subassembly 12 has included in it a valve 78 which also is connected through a signal-transmitting means to console 96. In the position of the valve illustrated in FIG. 1, the conduit 102, which is an extension of the pressurized hydraulic fluid conduit 74 is dead-ended in the valve. However, this valve may be operated upon a signal from console 96 to place the discharged hydraulic fluid conduit 80 in communication with the pressure hydraulic fluid conduit 102, as indicated by the dotted line 104a in FIG. 1. This position of valve 78 provides a bypass for the hydraulic fluid and permits the fluid to flow from the pressurized chamber, which would be the hydraulic fluid chamber in accumulator 22 in the instance of FIG. 1 through valve 66 and valve 78 into conduit 80 and again through valve 66 and into interconnected conduits 72 and 68 and thence into hydraulic fluid receiving chamber of accumulator 24. Valve 78 is provided primarily to permit one of the accumulators to be filled with hydraulic fluid and the other to be emptied at the start of operations of the entire system, or to permit the system to be placed in this desired condition of operation after a shutdown or other delay which occurred when both chambers were partly filled with hydraulic fluid.

Desirably an auxiliary chamber, preferably in the form of an accumulator 106 which has a flexible diaphragm 108 dividing it into a hydraulic fluid-containing chamber 104 and a gas-containing chamber 110 is provided in the system. Hydraulic fluid chamber 104 is placed in communication with the discharge fluid conduit 80 and gas chamber 110 is placed in communication through conduit 112 with the vent line 56 to the atmospheric pressure gas receiver 58. The auxiliary chamber is placed in the system to function as an expansion chamber for the hydraulic fluid and to assist in maintaining the pressure in the discharge fluid conduit 80 substantially at atmospheric pressure, and also to provide some make-up fluid if the hydraulic system requires it.

In the system illustrated in FIGS. 1 and 2, the pressurized gas receiver 42 is connected to a compressor 114 which draws the gas from the low-pressure receiver 58. Thus, the pressurizing gas portion of the assembly also may be a closed system. Preferably, the compressor 114 is selected with a capacity to maintain the receiver 58 at substantially atmospheric pressure. However, if desired, the low-pressure side of the system can be operated at a pressure other than atmospheric, either at a greater or lesser pressure. The relative difference in pressure of the two receivers determines the pressure differential imposed by the hydraulic fluid across the operating device, as 20, and offers further control of the system.

As described heretofore, desirably, each of the valves and the pressure sensitive device 94 in subassembly 12 is connected to the control console in subassembly 10 by complementary signal-transmitting means, such as by electrical conductors. This permits the system to be operated manually as well as automatically and provides a means for continuing the operating of the system if the automatic features of it, such as the pressure sensitive device 94, should malfunction. In some installations, as in the offshore environment, it may be desirable to gather the gas lines and the electrical lines extending between subassemblies 10 and 12 into a single bundle to assist in handling these lines and preventing their becoming entangled with each other or the submerged apparatus. This bundle is indicated by the dotted circle 116 in FIGS. 1 and 2 and by the same numeral in FIG. 4.

Referring now to FIG. 3, the system of this invention is illustrated diagramatically as applied to a particular arrangement of well control apparatus. Similar apparatus as applied to a submerged well is schematically illustrated in FIG. 4 which further illustrates a feature to which this invention can be adapted for offshore operations. To illustrate this environment the numeral 117, FIG. 3, indicates the surface of a body of water 119 in which the wellhead is submerged.

The arrangement of devices indicated in subassembly 14 of FIG. 3 and by FIG. 4 is commonly known as a blowout preventer (BOP) stack and is secured to the well opening during the time the well is being drilled and through some stages of its completion. When the well is completed a different arrangement of devices, called a "Christmas tree", is secured to the opening of the well casing, as is known in the art. The system of the present invention can be applied to operate the control devices of a Christmas tree and other assemblages of apparatus, and the application of the invention to the installation represented in FIGS. 3 and 4 is merely illustrative, and it is not intended to limit the application of this invention to such an arrangement.

A BOP stack normally comprises a series of vertically interconnected BOP's of different types, which can be operated independently of each other to control the well opening as circumstances require. In the apparatus illustrated in the drawings, the numeral 118 represents a bag-type BOP and the numerals 120, 122, 124 and 126 represent respective ram-type BOP's. The numerals 128 and 130 indicate elements of an assemblage made principally for offshore operations and represent hydraulically powered connectors, the connector 130 being used to detachably connect the BOP stack to the well casing and the connector 128 being used to detachably connect a marine riser 132 to the top of the BOP stack in a manner known to the art. It will be appreciated that not all of the devices indicated in the drawings need necessarily be included in the assemblage as represented to be within the purview of this invention and more or less, or different, forms of operating units may be assembled as the situation requires without departing from the inventive concept.

As stated heretofore, it is desirable that each of the hydraulically operated devices in the well head assemblage is selectively operable independently of the others. To this end, each device has associated with it a respective valve by which to control the hydraulic fluid circuit to it. Thus, for each of the operating units included in the assembly of apparatus indicated in subassembly 14 of FIG. 3, there is a control valve in subassembly 12. The valves which control the connectors and the BOP's of the wellhead apparatus, such as valves 134 and 136, may be similar in form and function to the previously described valve 76.

In FIG. 3, the accumulator 24 is functioning as the pressure chamber and accumulator 22 is the receiving chamber. The conduit 74 carrying pressurized hydraulic fluid to the various control valves takes the form of a manifold 138 from which individual branch conduits, as 140 and 142, lead to the respective control valves, as 134 and 136. The conduit 80, which carries the discharge hydraulic fluid away from the operating devices, also takes the form of a manifold 144, which is connected by individual branch conduits to respective valves as indicated by conduits 146 adn 148 connected to respective valves 134 and 136. The individual control valves are, of course, connected to the respective hydraulically actuated devices through corresponding interconnected conduits, such as conduits 150 and 152 for the pressure line of the hydraulic actuator 153 of connector device 130 and interconnected conduits 154 and 156 for the return line for discharged hydraulic fluid.

The well control system illustrated in FIG. 3 includes kill valve 158 and bleed valve 160, the use of which is well known in the art. Each of these valves has a respective control valve in subassembly 12, as 162 and 164, which is connected to the pressure fluid and discharge fluid manifolds 130 and 144. The kill and bleed valves illustrated are spring-biased to a closed position. Hence, only a single hydraulic fluid conduit is required for each, as represented by the interconnected conduits 166 and 168 for valve 158. The corresponding control valves 162 and 164 are arranged to be positioned to introduce a pressurized hydraulic fluid into the corresponding conduits to open the kill or bleed valve or alternatively to be positioned to connect the same corresponding conduit with the discharge manifold to release pressure from the kill or bleed valve to cause it to close as valve operation requires. The unit 170 in subassembly 12 of FIG. 3 represents a pressure reducing valve for controlling the pressure in the bag-type BOP 118.

As described in relation to FIG. 1, all of the conduits interconnecting subassembly 12 and subassembly 14 may be connected together by detachable connectors, which permit the subassemblies to be connected to and disconnected from each other in operating relationship. For working in submerged wells the detachable connectors may be operated from a remote location as from the surface of the water, without requiring diver assistance. By this arrangement, all of the control valves and the component portions of the hydraulic and electrical circuits, and including pressure-responsive device 94, may be incorporated in a pod 172 as illustrated in FIG. 4. The pod is arranged to be lowered from the surface of the water into engagement with a pod receiver 174. Each of the appropriate hydraulic lines in the pod is in communcation with a corresponding connector portion as 176 which mates with a complementary connector portion 178 on the pod receiver, which latter portion is in communication with the appropriate hydraulic conduit as, for example, conduit 50 on the wellhead control apparatus, which latter corresponds to subassembly 14. Where required, electrical connection can be made between the two subassemblies in a similar manner. It will be appreciated also that a system of detachable connectors may be used to interconnect the conduits and signal lines between subassemblies 10 and 12.

Various conduits connected to the pod receiver 174 are schematically indicated in FIG. 4. The conduits are gathered together in a bundle 180 or otherwise neatly arranged on the wellhead apparatus and the individual conduits are directed to the hydraulically operated devices to which they pertain as schematically illustrated by the lines 50 and 68 to accumulator 24, all of which is known to the art. The cable bundle 116 contains the gas lines and electrical lines, where applicable, connecting the pod with the surface console 96 and gas receivers 42 and 58, as has been mentioned heretofore. The cable bundle also contains the stress cable 182 by which the pod is raised and lowered through the water.

Because of the particular problems inherent in the offshore environment, it is advisable to provide duplicate pods 172, duplicate pod holders 174, and duplicate hydraulic circuitry 180 to afford a better chance for continued operation should a malfunction occur in one of the pod assemblies. This redundancy of equipment is familiar to the art, and hence it is not necessary for the present teaching to describe it in more detail.

As described with relation to valve 76 of FIG. 1, each of the control valves, as represented by way of example by valves 134 and 136 and 170 of FIG. 3, is controllable by an actuating signal from a remote location. Thus, the valves may be connected through individual electrical conductors with the control console 96 at the surface of the water so that, in addition to the automatic operation built into the system as described heretofore, each of the hydraulically operated devices in the wellhead equipment can be controlled manually independently of the other devices.

It is apparent that equivalents may be substituted for the particular elements described heretofore, and other modifications may be made to the system illustrated as a preferred embodiment without departing from the inventive concept, and it is intended that the invention encompass such equivalents and modifications within the scope of the appended claims.