A modular, distributed, rov retrievable subsea control system, associated deepwater subsea blowout preventer stack configuration, and methods of use

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Title of Invention: A Modular, Distributed, ROV Retrievable Subsea Control System,

Associated Deepwater Subsea Blowout Preventer Stack Configuration, and Methods of Use

Inventors: Graeme Reynolds

FIELD OF THE INVENTION

[0001] The inventions relate to offshore drilling operations and more specifically to a deepwater subsea blowout preventer stack configuration and its control system architecture, system interface, and operational parameters.

BACKGROUND OF THE INVENTION

[0002] When drilling in deepwater from a floating drilling vessel, a blowout preventer stack (BOP Stack) is typically connected to a wellhead, at the sea floor, and a diverter system, which is mounted under the rig sub-structure at the surface via a marine riser system. Although pressure containing components, connectors, structural members, reentry guidance systems, load bearing components, and control systems have been upgraded for the operational requirement, the overall system architecture has remained common for more than two decades.

[0003] The BOP Stack is employed to provide a means to control the well during drilling operations and provide a means to both secure and disconnect from the well in the advent of the vessel losing position due to automatic station keeping failure, weather, sea state, or mooring failure.

[0004] A conventionally configured BOP Stack is typically arranged in two sections, including an upper section (Lower Marine Riser Package) which provides an interface to a marine riser via a riser adapter located at the top of the package. The riser adapter is secured to a flex-joint which provides angular movement, e.g. of up to ten degrees (10°), to compensate for vessel offset. The flex-joint assembly, in turn, interfaces with a single or dual element hydraulically operated annular type blowout preventer (BOP), which, by means of

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WO 2006/023690 PCT/US2005/029487 the radial element design, allows for the stripping of drill pipe or tubulars which are run in and out of the well. Also located in the Lower Marine Riser Package (or upper section) is a hydraulically actuated connector which interfaces with a mandrel, typically located on the top of the BOP Stack lower section. The BOP Stack lower section typically comprises a series of hydraulically operated ram type BOPs connected together via bolted flanges in a vertical plane creating a ram stack section. In turn, the ram stack section interfaces to a hydraulically latched wellhead connector via a bolted flange. The wellhead connector interfaces to the wellhead, which is a mandrel profile integral to the wellhead housing, which is the conduit to the wellbore.

[0005] Conduit lines integral to the marine riser provide for hydraulic fluid supply to the BOP Stack Control System and communication with the wellbore annulus via stack mounted gate valves. The stack mounted gate valves are arranged in the ram stack column at various positions allowing circulation through the BOP Stack column depending on which individual ram is closed.

[0006] The unitized BOP Stack is controlled by means of a control system containing pilot and directional control valves which are typically arranged in a control module or pod. Pressure regulators are typically included in the control pod to allow for operating pressure increase/decrease for the hydraulic circuits which control the functions on the unitized BOP Stack. These valves, when commanded from the surface, either hydraulically or electrohydraulically direct pressurized hydraulic fluid to the function selected. Hydraulic fluid is supplied to the BOP Stack via a specific hydraulic conduit line. In turn, the fluid is stored at pressure in stack-mounted accumulators, which supply the function directional control valves contained in redundant (two (2)) control pods mounted on the lower marine riser package or upper section of the BOP Stack.

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[0007] Currently, most subsea blowout preventer control systems are arranged with “open” circuitry whereby spent fluid from the particular function is vented to the ocean and not returned to the surface.

[0008] A hydraulic power unit and accumulator banks installed within the vessel provide a continuous source of replenishment fluid that is delivered to the subsea BOP Stack mounted accumulators via a hydraulic rigid conduit line and stored at pressure. The development and configuration of BOP Stacks and the control interface for ultra deep water applications has in effect remained conventional as to general arrangement and operating parameters.

[0009] Recent deepwater development commitments have placed increased demands for well control systems, requiring dramatic increases in the functional capability of subsea BOP Stacks and, in turn, the control system operating methodologies and complexity. These additional operational requirements and complexities have had a serious effect on system reliability, particularly in the control system components and interface.

[0010] Although redundancy provisions are provided by the use of two control pods, a single point failure in either control pod or function interface is considered system failure necessitating securing the well and retrieving the lower marine riser package, containing the control pods, or the complete BOP Stack for repair.

[0011] Retrieving any portion of the BOP Stack is time consuming creating “lost revenue” and rig “down time” considering the complete marine riser must be pulled and laid down.

[0012] Running and retrieving a subsea BOP Stack in deepwater is a significant event with potential for catastrophic failure and injury risk for personnel involved in the operation.

[0013] In addition, vessel configuration, size, capacity, and handling equipment has been dramatically increased to handle, store, and maintain the larger more complex subsea

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BOP Stacks and equipment. The configuration and pressure rating of the overall BOP Stack requires substantial structural members be incorporated into the assembly design to alleviate bending moment potential, particularly in the choke and kill stab interface area between the Lower Marine Riser Package and BOP Stack interface. These stab interfaces may see in excess of two hundred and seventy five thousand (275,000’) ft/lbs. separating forces, again requiring substantial section modulus in the structural assemblies, which support these components.

[0014] Further, a lower marine riser package apron or support assembly size has increased to accommodate the contemporary electro-hydraulic control pods and electronic modules necessary to control and acquire data from an overall Unitized BOP Stack assembly.

[0015] Substantial increases in the overall weight and size of high pressure BOP Stacks has created problems for drilling contractors who have a high percentage of existing vessels, which will not accommodate these larger stacks without substantial modifications and considerable expense. In most cases, the larger, heavier and more complex units are requiring by operators for “deep water” applications and reduce the potential for negotiating a contract for the particular rig without this equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0001] The various drawings supplied herein are representative of one or more embodiments of the present inventions.

[0002] Fig. 1 is a view in partial perspective of a subsea BOP Stack comprising a riser connector, a BOP assembly, and a modular retrievable element control system;

[0003] Fig. 2 is a view in partial perspective of a riser connector;

[0004] Fig. 3 is a view in partial perspective of a riser connector;

[0005] Fig. 4 is a view in partial perspective of a control module;

[0006] Fig. 5 is a view in partial perspective of a control module mated to a receiver;

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[0007] Fig. 6 is a view in partial perspective cutaway of a control module;

[0008] Fig. 7 is a view in partial perspective of an interface between a stab of control module and receiver on a BOP assembly; and

[0009] Fig. 8 is a flowchart of an exemplary method of use.

DETAILED DESCRIPTION OF

EXEMPLARY EMBODIMENTS OF THE INVENTIONS

An aspect of the invention relates to a distributed function control module adapted for use in a modular blowout preventer (BOP) stack for use subsea, comprising: a. a housing, adapted to be manipulated by a remotely operated vehicle (ROV), further comprising a stab portion adapted to be received into a BOP stack control module receiver; b. a pressure compensator disposed within the housing, the pressure compensator further comprising a bladder;

c. control electronics disposed within the housing, the control electronics adapted to control a predetermined function with respect to the BOP stack; and d. a wet mateable connector interface disposed proximate the stab portion, the wet mateable connector interface adapted to operatively connect the control electronics to a controllable device associated with the BOP stack that performs the predetermined function.

[0016] Referring now to Fig. 1, the present inventions comprise elements that, when assembled and unitized, form a reconfigured subsea Blowout Preventer Stack (BOP Stack) 1 including modular retrievable element control system 200. Variations of the architecture and components of modular retrievable element control system 200 may be utilized subsea, e.g. in production tree, production riser, and subsea manifold control interface applications.

[0017] In a preferred embodiment, BOP Stack 1 comprises riser connector 10, BOP assembly 100, and wellhead connector 50.

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[0018] BOP assembly 100 includes control modules 200 that, in a preferred embodiment, are arranged in a vertical array and positioned adjacent to the particular function each control module 200 controls, such as hydraulic functions. Composition of control module 200 sections preferably include materials that are compatible on both the galvanic and galling scales and be suitable for long term immersion in salt water.

[0019] BOP assembly 100 is configured to accept and allow the use of distributed functional control modules 200 which are remotely operated vehicle (ROV) retrievable (the ROV is not shown in the figures). The use of this modular distributed control system architecture in subsea BOP Stack applications allows for the re-configuration of existing BOP stack arrangement designs to reduce weight and complexity in the integration and unitization of the elements required to form the overall BOP Stack 1.

[0020] BOP assembly 100 may be unitized and may comprise elements such as a hydraulic connector to interface to the subsea wellhead, one or more blowout preventers 115

5a

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WO 2006/023690 PCT/US2005/029487 (e.g. ram type blowout preventers), annular 110 or spherical type blowout preventers, a plurality of hydraulic connectors to interface to a marine riser (not shown in the figures) and hydraulically operated gate type valves for isolation and access for choke and kill functions.

[0021] Riser connector 10 comprises riser adapter 11, guideline-less reentry assembly 14, and multi-bore connector 15. Flex joint 13 is disposed intermediate riser adapter 11 and multi-bore connector 15. One or more flex loops 12 may be present and in fluid communication with ports on riser adapter 11. Multi-bore connector 15 provides an interface to BOP assembly 100.

[0022] BOP assembly 100 may be further adapted to receive one or more control modules 200 into docking stations 202 as well as other modules, e.g. annular preventer 110, RAM preventer 115, blowout preventers (not specifically shown), connectors (not specifically shown), “Fail Safe” gate valves (not specifically shown), sub system interface values (not specifically shown), or the like, or combinations thereof. One or more lines 120,

e.g. kill and/or choke lines, may be present as well as various control pathways such as hydraulic conduit 101 and/or MUX cables (e.g. cables 26 in Fig 2).

[0023] Hang-off beams 102 may be provided to allow for support of BOP assembly 100 during certain operations, e.g. in a moon pool area such as for staging and/or testing prior to running.

[0024] Referring now to Fig. 2, riser connector 10 is typically adapted to provide a connector, such as riser adapter 11, to interface with a marine riser (not shown in the figures). In a preferred embodiment, riser connector 10 comprises one or more MUX cables 26 and hydraulic conduit hoses 25. Riser connector 10 may also incorporate integral connection receptacles for choke/kill, hydraulic, electric, and boost line conduit interfaces. In a preferred embodiment, riser connector 10 is configured with connector 15 as a multi-bore connector rather than single bore connector, although either configuration may be used. This allows for

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WO 2006/023690 PCT/US2005/029487 riser connector 10 to absorb loading and separating forces as well as bending moments within its body where substantial section modulus exists. Further, it decreases the need for a substantial fabricated structure to alleviate the potential for separation of a line holding a high pressure, e.g. line 120 (Fig. 1).

[0025] In a preferred embodiment, one or more subsea wet mateable connectors 21 are also integrated into riser connector 10 for interfacing with BOP assembly 100 (Fig. 1). This interface may be used to supply power and/or communications to control modules 200 (Fig. 1) located on BOP assembly 100. In a preferred embodiment, the marine riser and its interfaces, such as choke/kill, hydraulic, electric, and boost, may be disconnected or reconnected in one operation from riser connector 10.

[0026] In certain embodiments, riser connector 10 may also include riser connector control module 28 which comprises one or more junction boxes and subsea electronics module which may be integral with junction box 27. Using riser connector control module 28 may allow control of riser connector 10 and lower marine riser package functions independent of the BOP stack in the event the marine riser must be disconnected from BOP stack 100 (Fig. 1) and pulled back to the surface.

[0027] In a preferred embodiment, subsea electronics module 27 may provide for connections such as electrical connections and may be equipped with connector receptacles for interfacing to ROV devices, e.g. ROV retrievable control modules 200 (Fig. 1) such as to facilitate control of riser connector functions.

[0028] In a preferred embodiment, subsea electronics module 27 provides one or more interfaces from main multiplex cables 26 to a lower marine riser package which contains multibore riser connector 15. Wet make/break electrical connectors which may be present, e.g. 21, may be integral to riser connector 15, e.g. via pressure balanced, oil-filled cables.

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[0029] Apron plate 30, which is of sufficient area to provide for mounting of junction boxes 27, may be present to provide a transition from main multiplex control cable connectors to the wet mateable assemblies located in multi-bore connector 15. Power and other signals to riser connector control module 28 may be effected via an oil filled pressure compensated cable assembly (not shown) that is connected to electrical junction boxes 27 mounted on apron plate 30. In a preferred embodiment, two junction boxes 27 are provided for redundancy and each may be distinguished from the other, e.g. labeled or provided with different colors. Apron plate 30 may be attached to guideline-less reentry funnel 16 (Fig. 3).

[0030] In a .preferred embodiment, riser connector 10 includes flex joint 13 and one or more flex loops 12, e.g. to allow for angular movement to compensate for vessel offset. The upper flange adapter or flex-joint top connection typically interfaces to a flange of riser adapter 11 containing kick-out flanged assemblies for connection of lines 120 (Fig. 1) interfacing with the marine riser, e.g. formed hard pipe flow-loops that interface choke and kill line 120 to the main marine riser.

[0031] Referring now to Fig. 3, riser connector 10 interfaces with BOP assembly 100 (Fig. 1) using guideline-less receiver assembly 24 and connector mandrel 19. Connector mandrel 19 is typically connected to BOP assembly 100 through riser connector mandrel flange 23 which may be further adapted to provide mounting for choke/kill, hydraulic, MUX cable, boost, electric connectors and stabs, and the like, or a combination thereof.

[0032] In a preferred embodiment, riser connector mandrel flange 23 is of the API ring-groove type and interfaces with a matching flange which forms the lower connection of flex-joint assembly 13 or additional elements, e.g. annular blowout preventers which may be mounted on lower marine riser package .

[0033] Guideline-less receiver assembly 24 comprises guideline-less reentry funnel 16 and guideline-less reentry receiver 17. Multi-bore connector 15 may be arranged to reside

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WO 2006/023690 PCT/US2005/029487 in guideline-less reentry funnel 16 and guideline-less reentry receiver 17 may be attached to the top of BOP assembly 100 (Fig. 1). In a preferred embodiment, guideline-less reentry funnel 16 is configured with a funnel portion that interfaces with a corresponding funnel portion of guideline-less reentry receiver 17.

[0034] In further configurations, orientation dogs 20 and corresponding orientation slots 29 may be used to align riser connector 10 with respect to BOP assembly 100 (Fig. 1). This alignment system provides correct orientation of multi-bore connector 15 and its integral peripheral receptacles with corresponding receptacles of BOP assembly 100, e.g. hydraulic stab 18 and/or choke stab 22, during reentry operations.

[0035] The connector upper flange of multi-bore connector 15 may be of an API ring groove type and interface with a matching flange which forms a lower connection of flex joint 13.

[0036] In a preferred embodiment, the bottom or lower flex loop connection 12 interfaces to multi-bore connector 15, e.g. a studded ring groove connection, via an API flange.

[0037] Referring to Fig. 4, control module 200 includes electronics housing 220 connected to compensator housing 222 which is in communication with or otherwise connected to pressure compensated solenoid housing 218. Pilot valve 216 is located between pressure compensated housing 218 and sub plate mounted (SPM) valve 224. In certain embodiments, pilot valve 216 is adapted to interface with and actuate a predetermined function of SPM valve 224, e.g. via hydraulic activation.

[0038] Hydraulic fluid is typically supplied to control module 200 via supply manifold 226. Control module 200 communicates with BOP assembly 100 (Fig. 1) through electrical cable 232 (Fig. 5) in communication with wet mateable connector 228.

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[0039] Control module 200 is connected to BOP assembly 100 (Fig. 1) via stab 212 that includes a hydraulic seal 210. In a preferred embodiment, hydraulic seal 210 comprises a molded elastomer with an integral reinforcing ring element. Hydraulic seal 210 may be retained in stab 212 via tapered seal retainers which are screw cut to match a female thread profile machined into the stab port interface.

[0040] In an embodiment, hydraulic seals 210, also called packer seals, mount into stab 212 and are positioned and retained in a machined counterbore which is common to the hydraulic porting through the body of stab 212. When mated, the stab internal ports containing packer seals 210 align and interface with the matching ports contained in female receptacle 270 (Fig. 7) that are machined on the outside to accept flanged subsea connections. These flanged subsea connections may be retained by SAE split flanges and fasteners and may be provided with weld sockets for pipe, screw cut for tubing connectors, or various hose connectors (i.e., JIC, SAE, or NPT) terminating methods.

[0041] In preferred embodiments, wet mateable connector 228 comprises conductors or pins to supply power, signals, or both to electronics (not shown) within control module 200. In addition, a fiber optic conductor connection interface (not shown) may be included for signal command or data acquisition requirements depending on the functional application of the particular module assignment.

[0042] SPM valve 224 may further include vent port 214. SPM valve 224 (Fig. 4) typically includes a flanged, ported body cap or top member which contains an actuating piston and one or more integral pilot valves 216. Pilot valve 216 may be solenoid actuated and may be a pressure compensated, linear shear-seal type arranged as a three-way, two position, normally closed, spring return pressure compensated with a five thousand p.s.i. working pressure (WP).

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[0043] Supply manifold 226 porting and arrangement may vary for valve operation in normally open or normally closed modes. Hydraulic fluid is supplied to pilot valves 216 through a dedicated port through the stab 212. Pressure regulators integral to the supply manifold 226 are provided for supply to function circuits requiring reduced or regulated pressures.

[0044] Pilot valves 216 interface with solenoid actuators that are contained in pressure compensated solenoid housing 218. Pressure compensated solenoid housing 218 is preferably filled with di-electric fluid providing a secondary environmental protection barrier.

[0045] Referring to Fig. 5, control module 200 is typically inserted into receiver 238 and may be released by actuating a hydraulic lock dog release 230. Receiver 238 is part of BOP assembly 100 and may be integral to a mounting plate which is permanently mounted to a BOP assembly frame.

[0046] SPM valve 224 (Fig. 4) on control module 200 may comprise one or more SPM directional control valves 240 whose manifold pockets may be investment cast from stainless steel with the porting arranged for supply, outlet, and vent functions of three-way, two position, piloted SPM directional control valves 240.

[0047] Modem manufacturing techniques, such as investment casting, may be employed for components such as the SPM valve 240, SPM valve 224, and supply manifold 226 providing substantial weight reduction and machining operations.

[0048] Referring to Fig. 6, retrievable control modules 200 include atmosphere chamber 260 containing electronics control input/output (I/O) modules, such as an electronic board 256, and one or more power supplies. In a preferred embodiment, atmosphere chamber 260 is maintained at one atmosphere. In currently preferred embodiments, control module 200 further includes one or more pressure compensating bladders 262, pilot valve actuating

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WO 2006/023690 PCT/US2005/029487 solenoids 266, pilot valves 216 (Fig. 4), and poppet valve type SPM valves 240 (Fig. 5) which are piloted from solenoid operated pilot valves 216.

[0049] Pressure compensating bladder 262 is contained within pressure compensated solenoid housing 218 to aid in equalizing the housing internal pressure, e.g. with seawater head pressure. An open seawater port 254 may be provided and a relief valve (not shown), e.g. a ten p.s.i. relief valve, may be contained within pressure compensated solenoid housing 218 to limit pressure build up inside pressure compensated solenoid housing 218, allowing equalization of the compensator bladder 262 volume against pressure compensated solenoid housing 218 volume, including a pressure compensated chamber 250. Pressure compensated chamber 250 may be accessed through an oil fill port 252.

[0050] A mandrel, e.g. conduit 268, may be disposed more or less centrally through pressure compensated solenoid housing 218 to provide a conduit, at preferably one atmosphere, for electrical/fiber optic conductors from a wet make/break connector half located in stab 212 (Fig. 4). In addition, the internal profile of mandrel 268 may be machined with a counterbore shoulder that is drilled with preparations to accept molded epoxy filled, male connectors for an electrical wiring attachment. In turn, the wiring attachment may terminate at corresponding male connectors at solenoids 266, e.g. via boot seals and/or locking sleeves 264.

[0051] Pressure compensated solenoid housing 218 interfaces with atmosphere chamber 260 containing the electronics module. In an embodiment, atmosphere chamber 260 mates to pressure compensated solenoid housing 218 via a bolted flange, which is machined with an upset mandrel containing redundant radial seals. In addition, the internal wire/fiber optic conduit, e.g. conduit 268, mates to an internal counterbore profile via a matching male mandrel also containing redundant radial a-ring seals. Atmosphere chamber 260 may further be equipped with flanged top providing access to the electronics chassis, wiring harness, and

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WO 2006/023690 PCT/US2005/029487 pigtail wiring connection. In embodiments, the flanged top is also provided with an upset mandrel containing redundant O-ring seals which interface to the top of atmosphere chamber 260.

[0052] In a preferred embodiment, all seal interfaces are machined with test ports to provide a means to test the internal and external O-ring seals to ensure integrity prior to module installation. In addition, housing 260 is typically equipped with “charge” and “vent” ports 258 for purging housing 260, such as with dry nitrogen, providing further environmental protection for the electronics components. Each port 258 may further be equipped with a shut-off valve and secondary seal plug.

[0053] In deep subsea use, electrical/electronic interface integrity may be assured by the environmental protection of electrical or fiber optic conductors using a stainless steel conduit spool equipped with redundant seal sub type interface, or the like.

[0054] Fig. 7 illustrates a preferred embodiment of the interface between stab 212 (Fig. 4) of control module 200 (Fig. 4) and receiver 238 (Fig. 5) on BOP assembly 100 (Fig.

1). Stab 212 includes male stab 272 that correspond to female receptacle 270 on receiver 238. Female receptacles 270 may contain ports for hydraulic supply 234, 236, 242, 244 (Fig.

5), which provide input and outlets to an assigned blowout preventer stack. Connector body through-bores for female receptacle 270 are machined with preparations to accept poly-pack type radial seal assemblies to seal on male stabs 272.

[0055] In a preferred embodiment, the base of male stab 272 is machined with a counterbore profile to accept the male half of the connector insert containing male pins. The counterbore is recessed deep enough to allow the insert to be set back in the stab body providing protection for the individual pins and alleviating the potential for damage during handling.

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[0056] A corresponding male mandrel profile is machined into the female receptacle base to accept the female half of a connector pair. Both the male mandrel in female receptacle 270 and female counterbore in the male stab 272 are machined with matching tapers, which provide a centering function and positive alignment for the male/female connector halves when stab 272 enters female receptacle 270. In addition, this centering/alignment method further assures correct hydraulic port, equal packer seal alignment, squeeze and loading when male stab 272 is mated in female receptacle 270.

[0057] The connection between male stab 272 and female receptacle 270 is maintained by a hydraulic latch 278, and communication is achieved through a wet mateable connector assembly 284, which is preferably of the wet make/break type. Hydraulic communication between male stab 272 and female receptacle 270 is maintained through packer seal assemblies 282.

[0058] Male stab 272 interfaces with SPM valve 240 (Fig. 5) through supply channel 274 or function channel 276 which contain redundant O-ring seals with back-up rings. The seal subs locate the manifold element to the stab body via counterbores in each member. Conduit 268 may interface with receiver 238 through conduit mandrel 286.

[0059] Additionally, fitting 280 may be present to terminate a cable at receptacle 270. For example, fitting 280 may be an SAE.-to-J.I.C. adapter fitting to terminate a pressure balanced, oil filled cable at receptacle 270.

[0060] In the operation of a preferred embodiment, distributed function control module 200 (Fig. 1) may be installed subsea by using an ROV to position distributed function control module 200 proximate control module receiver 238 (Fig. 5) in BOP stack 100 (Fig. 1) installed subsea. Once positioned, the ROV inserts stab end 272 (Fig. 7) of distributed function control module 200 into distributed function control module receiver 238 which is adapted to receive stab end 272. At a predetermined time, as the insertion occurs, first wet

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WO 2006/023690 PCT/US2005/029487 mateable electncal connector 228 (Fig. 5) disposed proximate stab end 272 is mated to second wet mateable electrical connector 228 (Fig. 5) disposed proximate receiver 270 (Fig. 7). Once mated, electrical connectivity between control electronics 256 (Fig. 7) disposed within distributed function control module 200 is enabled between control electronics 256 and an electronic device disposed outside distributed function control module 200.

[0061] As the need arises, e.g. for maintenance or repair, an ROV may be positioned proximate end 220 (Fig. 5) of the inserted distributed function control module 200 (Fig. 1) distal from stab end 272 (Fig. 7) and distributed function control module 200 disengaged from receiver 270 (Fig. 7), i.e. by withdrawing distributed function control module 200 from receiver 270.

[0062] The foregoing disclosure and description of the inventions are illustrative and explanatory. Various changes in the size, shape, and materials, as well as in the details of the illustrative construction and/or a illustrative method may be made without departing from the spirit of the invention.