RETRIEVABLE HYDRAULIC SUBSEA BOP CONTROL POD

Abstract

Systems and methods for improved hydraulic control systems for actuation of subsea equipment in deep water are disclosed. The hydraulic control system relies on smaller fluid flow associated with a hydraulic pressure pulse to actuate the small volume actuation control valve. In one embodiment, the system includes small diameter control umbilical hoses and pilot-operated valves with low actuation volumes. Particularly, a hydraulic control system for reducing the signal time to a subsea blowout preventer in water depth up to and greater than about 5000 feet. Some embodiments comprise a valve arrangement which hydraulically actuate one side of a hydraulic control function, while simultaneously evacuating the opposing circuit both at the seabed and at the surface. Some embodiments comprise an umbilical hose located proximate the center of an umbilical bundle. Preferably, the umbilical hose has a plurality of layers of reinforcing fibers which increase with the diameter of the reinforcement layer.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

REFERENCE TO A MICROFICHE APPENDIX

None.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to hydraulic control systems for actuation of subsea equipment, particularly to a hydraulic control system and method for use in deep water with a subsea Blowout Preventer (BOP) stack, more particularly for a hydraulic control system and method utilizing a retrievable control pod for the actuation of subsea Blowout Preventer (BOP) stacks.

2. Description of the Related Art

Offshore drilling for oil and natural gas from floating vessels is conventionally done through a drilling riser between the floating drilling vessel and a BOP stack located at the seabed.

The hydraulic functions of the BOP stack may be controlled by a hydraulic control system or an electro-hydraulic control system.

The first shallow-water subsea BOP control systems were discrete direct hydraulic control systems, in which hydraulic pressure is conveyed from the surface directly to a particular hydraulic actuator on the subsea BOP stack by way of a discrete hydraulic conduit.

Later subsea control systems were “piloted” discrete hydraulic control systems, in which hydraulic pilot signals are conveyed down a dedicated hydraulic conduit to a pilot valve, which directs hydraulic pressure from a subsea hydraulic manifold to a particular hydraulic actuator on the subsea BOP stack.

Other subsea control systems of this era included multifunction hydraulic systems which used various techniques to deliver more than one signal per hydraulic conduit; for example, coded hydraulic pulses, or a matrix of hydraulic signals, or sequenced signals at increasing pressures.

Still later control systems were “discrete” electro-hydraulic systems, with one electrical conductor per hydraulic function, or “multiplexed” (or “MUX”) systems, in which coded signals are transmitted via a small number of conductors.

Modern subsea control systems are almost exclusively MUX systems, which offer the advantages of ease of automation, rapid signal times between the surface and the seabed, and relatively easy retrievability of the control “pod”.

However, there are still scores of older hydraulic systems extant, particularly piloted hydraulic control systems which were originally designed to be used in conjunction with guideline-deployed subsea BOP stacks.

Referring now to FIG. 1, which is a perspective view of a typical subsea BOP stack, Lower Marine Riser Package (LMRP) and associated hydraulic control system of the prior art. For clarity, the LMRP is shown unlatched from the BOP stack, as if it were, for example, being tripped back to the surface.

The Subsea BOP stack 100 has stack framework 101 which supports the subsea BOP stack and also serves to guide the stack from the surface to the seabed along guidelines 102. Subsea BOP stack 100 also has lower female hydraulic receptacles 103A and 103B with fluid passages 104 which are hydraulically connected to BOP control lines 105.

Lower Marine Riser Package (LMRP) 106 forms an upper, separable part of the Subsea BOP stack, and generally comprises at least one annular BOP 106A, drilling riser 106B with attached choke & kill lines 106C, a flexible riser joint 106D, an LMRP latch 107 between the LMRP 106 and the subsea BOP stack 100, control pods 108A and 108B and a plurality of guideline funnels 109 guiding the LMRP along guidelines 102. LMRP 106 also comprises upper female hydraulic receptacles 110A and 110B.

Generally, guideline funnels 109 are diametrically opposed on opposite sides of the LMRP. (Note that the opposing guideline funnel is not shown in FIG. 1.) Control pods 108A and 108B may also fitted with their own, similar guideline funnels so that they may be retrieved separately from the LMRP.

Conventionally, control pods 108A and 108B are painted yellow and blue respectively, as those colors can be easily distinguished subsea by a closed-circuit television camera on a subsea remotely-operated vehicle (ROV).

Control pods 108A and 108B have control pod deployment cables 111A and 111B, and control pod umbilical 112A and 112B. Conventionally, control pod umbilicals 112A and 112B are clamped (not shown) to control pod deployment cables 111A and 111B with, for example, clamps of the types taught in U.S. Pat. Nos. 4,445,255 to Olejak, and 4,437,791 to Reynolds.

Control pods 108A and 108B also have latching mechanism 113A and 113B (latching mechanism 113B is not visible) on male members 114A and 114B male member 114B is not visible) which latch the control pods into upper female control receptacles 110A and 110B. Control pods 108A and 108B also have male hydraulic connectors 115A and 115B (not visible) which mate with upper female control receptacles 110A and 110B.

Referring now to FIG. 2, which is a perspective view of a control pod and its associated female hydraulic receptacles. Control pod 200 has control pod deployment cable 201, control pod umbilical 202, male member 203 with latching mechanism 204, and male hydraulic connector 205 with frustoconical surface 205A and a plurality of hydraulic ports 206.

Control pod 200 also has junction plate 202A (commonly called a “kidney plate”) deposed between control umbilical 202 and control pod 200 which provides hydraulic connections between the umbilical and the hydraulic piping and vavling within the pod.

LMRP 207 has upper female hydraulic receptacle 210, which has a plurality of inner hydraulic ports 209, inner frustoconical surface 209A, a plurality of outer hydraulic ports 210, and outer frustoconical surface 210A.

Subsea stack 211 has lower female hydraulic receptacle 212 with a plurality of inner hydraulic ports 214, inner frustoconical surface 214A, and spring mounts 213.\

When control pod 200 is latched into LMRP 207 by latching mechanism 204, frustoconical surface 205A on male hydraulic connector 205 mates with frustoconical surface 209A on upper female hydraulic receptacle 208.

When LMRP is latched to subsea stack 211 by LMRP latch 107 (in FIG. 1), frustoconical surface 210A on upper female hydraulic receptacle 208 mates with frustoconical surface 214A on lower female hydraulic receptacle 212.

For LMRP hydraulic control functions such as annular BOP 106A or LMRP latch 107 (both in FIG. 1), hydraulic pressure is supplied by control pod 200 to a hydraulic port 206 on the male hydraulic connector 205, which is hydraulically mated to an inner hydraulic port 209 on the upper female hydraulic receptacle 208, and routed to a control hose (not shown) leading to the particular LMRP control function.

For hydraulic functions in the BOP stack 211, such as opening or closing of a ram-type BOP, hydraulic pressure is supplied by control pod 200 to a hydraulic port 206 on male hydraulic connector 205, which is hydraulically mated to an inner hydraulic port 209 on the upper female hydraulic receptacle 208, which in turn is hydraulically connected to an outer hydraulic port 210 which mates hydraulically with inner hydraulic port 214 on lower female hydraulic receptacle 212. Inner hydraulic port 214 is in turn connected hydraulically to a BOP control hose 105 (shown in FIG. 1) leading to a particular BOP stack control function.

Subsea control well systems for hydraulically controlling subsea well equipment are generally shown in U.S. Pat. Nos. 3,460,614 and 3,701,549, which are incorporated by reference in their entirety.

As drilling water depths got much deeper throughout the 1990's, offshore drillers initially abandoned the use of guidelines to deploy and retrieve BOP stacks, and instead tripped the BOP stack “guidelineless,” often with the aid of ROVs. They also discovered that the currents in deep water could cause severe and deleterious “vortex-induced vibration” (“VIV”) in the control pod deployment cable 201 and the control pod umbilical 202 clamped to it, often severely damaging the expensive umbilical. Consequently, most drillers have abandoned the control pod deployment cable 201 on subsea BOP stacks run in deep water, and today run the control pod umbilical 202 attached the drilling riser 106B (in FIG. 1), usually clamped to the choke & kill lines 106C.

However, with the control pod umbilical attached to the riser, a control pod may be retrieved for inspection and repair only by tripping the entire LMRP with both pods attached, which is extremely expensive and time consuming. It would be advantageous to be able to retrieve one control pod at a time, without tripping the entire riser and LMRP, but to continue to run the umbilical attached to the riser to avoid deleterious VIV.

Some prior art systems sought to address this issue. One prior art system, for example, taught in U.S. Pat. No. 4,328,826 to Baugh, et al, features flat, vertically stacked flat connector plates which allow the control pod to connect to the control umbilical through a connector plate, which in turn allows the control pod to be fully retrievable. However, this and other prior art systems all require that the existing control pods with frustoconical hydraulic receptacles be replaced, at very high cost. It would therefore be advantageous to be able to inexpensively modify an existing hydraulic control system comprising a riser-mounted umbilical such that the existing hydraulic control pod is retrievable independent of the LMRP, the riser, and the other control pod.

Further, it would be advantageous if such a modification for an existing hydraulic control system could be easily retrofitted to the LMRP structure, and if it were sufficiently compact to fit within the confines of the existing equipment in the LMRP, which may, in some cases, require the modification to “wrap around” the other equipment.

Still further, the junction plate 202A is a complicated, heavy, and expensive machined part in which multiple hydraulic seals reside; although these seals are usually robust, the junction plate arrangement has the potential for multiple leak-paths between the umbilical and the control pod. It would therefore be advantageous to eliminate the junction plate 202A as an interface between the pod and the umbilical.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to hydraulic subsea control system for a subsea BOP stack comprising a retrievable hydraulic control pod with hydraulic receptacles, and an umbilical attached to the drilling riser. The hydraulic control system of the present invention comprising a subsea hydraulic umbilical line, a lower marine riser package having a hydraulic receptacle, a hydraulic control pod having a hydraulic connector for hydraulically mating with the hydraulic receptacle, at least one pod umbilical hydraulic connector hydraulically connected through umbilical connector piping to said hydraulic control pod, and at least one lower marine riser package umbilical hydraulic connector for hydraulically mating with said pod umbilical hydraulic connector and said subsea hydraulic umbilical line. When the system of the present invention is operated, a hydraulic flow path exists allowing hydraulic fluid to flow from the subsea hydraulic umbilical line through the lower marine riser package umbilical hydraulic connector through the pod umbilical hydraulic connector and into the hydraulic control pod which is hydraulically connected to the lower marine riser package hydraulic receptacle.

In one aspect, the invention relates to a hydraulic control pod with a male frustoconical hydraulic connector, adapted to be retrieved from a subsea BOP stack while the umbilical control hose remains attached to the drilling riser.

In another aspect, the invention relates to a method for converting a hydraulic control system to allow the subsea control pod to be retrieved while the umbilical control hose remains attached to the drilling riser.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A better understanding of the present invention can be obtained when the following detailed description of the disclosed embodiments is considered in conjunction with the following drawings, in which:

FIG. 1 is a perspective view of a subsea stack and Lower Marine Riser Package (LMRP) of the prior art.

FIG. 2 is a perspective view of an hydraulic control pod and associated female hydraulic receptacles on the LMRP and the subsea BOP stack, all of the prior art.

FIG. 3 is a section view of a preferred embodiment of the hydraulic control system of the present invention.

FIG. 3A is a section view of the preferred hydraulic control system shown in FIG. 3, at “A-A” in FIG. 3.

FIG. 3B is a section view of the preferred hydraulic control system shown in FIG. 3, in the landed and latched position.

FIG. 4A is a chart of hydraulic flows in a hydraulic control system of the prior art.

FIG. 4B is a chart of hydraulic flows of the preferred embodiment of the hydraulic control system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Refer now to FIG. 3, which shows a preferred embodiment of the present invention. Control pod 300 has umbilical junction plate 300A, male member 301 with latching mechanism 302, male hydraulic connector 303 with frustoconical surface 303A, and control pod deployment cable attachment point 304.

Control pod 300 also has radial connector brackets 305A and 305B, with attached pod umbilical connectors 306A and 306B, which have hydraulic ports 306C.

Pod umbilical connectors 306A and 306B are hydraulically connected to the valving inside the control pod 300 by umbilical connector piping 306D. As shown, umbilical connector piping 306D by-passes umbilical junction plate 300A; in this embodiment, umbilical junction plate 300A may be eliminated in order to save weight in control pod 300.

Alternately, umbilical junction plate 300A may be retained, and umbilical connector piping 306D may be run from pod umbilical connectors 306A and 306B to the hydraulic connectors on the top of umbilical junction plate 300A. Since the internal piping inside control pod 300A is often complex and convoluted, this approach may save time and money during a conversion. Furthermore, there may be circumstances when it is advantageous to retain umbilical junction plate 300A despite its added weight; for example, for a spare pod which a driller may wish to configure for either shallow water drilling (with umbical run separately from the riser) or for deepwater drilling (with the umbilical attached to the riser).

LMRP 307 has LMRP umbilical connectors 308A and 308B, attached to LMRP 307 by compliant suspension 309 and mounting brackets 310. The complaint suspension 309 as shown comprises coil springs and spherical bearings mounted between LMRP umbilical connectors 308A and 308B and corresponding mounting brackets 310, which allows LMRP umbilical connectors 308A and 308B to move about slightly when they are mated with pod umbilical connectors 306A and 306B. However, those skilled in the art will recognize that other mechanisms, such as elastomeric springs, Belleville washers, or hydraulic spring elements may be utilized without departing from the spirit of the invention.

LMRP umbilical connectors 308A and 308B are hydraulically connected to umbilical hoses 308C. Ideally, the umbilical hose may be configured such that the individual hoses within the umbilical bundle may be connected directly to LMRP umbilical connectors 308A and 308B without intervening hydraulic connections. In some circumstances, of course, the umbilical may have to be terminated on or near the riser, and jumper hoses (for example) used to connect the umbilical to the LMRP umbilical connectors.

LMRP 307 also has upper female hydraulic receptacle 311, which has inner hydraulic ports 312 and outer hydraulic ports 313 (not visible in this sectional view), inner frustoconical surface 312A, and outer frustoconical surface 313A.

Subsea BOP stack 314 has lower female hydraulic receptacle 315 with inner frustoconical surface 315A, and inner hydraulic ports 316 (not visible in this section view).

In the embodiment shown in FIG. 3, pod umbilical connectors 306A and 306B are male wedge-type connectors and LMRP umbilical connectors 308A and 308B. are mating female wedge-type connectors. In another embodiment, pod umbilical connectors 306A and 306B are female wedge-type connectors and LMRP umbilical connectors 308A and 308B are mating male wedge-type connectors. In still another embodiment, pod umbilical connectors 306A and 306B and LMRP umbilical connectors 308A and 308B are frustoconical type connectors, essentially versions of the hydraulic connectors beneath the control pod. Those skilled in the art will appreciate that the mating pod umbilical connectors and LMRP umbilical connectors may be any of many types of subsea wet-mateable hydraulic connectors known in the art.

Further, in the embodiment of the instant invention shown in FIG. 3, the control pod 300 is generally cylindrical in shape. Those skilled in the art will recognize that the control pod may be rectangular or another shape, and still be mated to a frustoconical male hydraulic connector 303.

In one embodiment of the instant invention, there are two radial connector brackets attached to the control pod. In another embodiment, there are more than two radial connector brackets.

In another embodiment of the instant invention, there are two radial connector brackets with associated pod umbilical connectors; one pod umbilical connector contains hydraulic circuits for LMRP controls and the other contains hydraulic circuits for the subsea BOP.

In yet another embodiment of the instant invention, there is only one radial connector bracket with an associated pod umbilical connector. In a related embodiment, the one radial connector bracket is arranged radially away from the well center.

Refer now to FIG. 3A, which shows a horizontal section through the pod (at “A-A” in FIG. 3). Control pod 300 has radial connector brackets 305A and 305B, with attached pod umbilical connectors 306A and 306B. In this embodiment, radial connector brackets 305A and 305B are substantially horizontally opposed on opposite sides of control pod 300 (that is, the inner included angle 319 between the brackets is 180 degrees), and a vertical plane 316 through radial connector brackets 305A and 305B is substantially tangential to well center axis 317 (which is coincident with the center of the riser 106B and the annular BOP 106A in FIG. 1).

In another embodiment of the instant invention, radial connector brackets 318A and 318B are each substantially tangential to well center axis 317.

In another embodiment which may provide the most compact installation, radial connector brackets 318A and 318B are each substantially tangential to well center axis 317, and the inner included angle (319 in FIG. 3A) between the brackets is minimized.

For a well center-to-pod center distance D (320 in FIG. 3A) and overall radial bracket length “L” (321 in FIG. 3A), a minimum inner included angle α is defined by the following equation: Equation 1 α=2(arc cos D/L)

In another embodiment of the instant invention, the included angle between the radial connector brackets will be between about 180 degrees and minimum inner included angle α as calculated by Equation 1.

Another embodiment of the instant invention consists of a method to convert an existing hydraulic control system to a system with retrievable control pods and an umbilical attached to the riser, comprising the steps of affixing one or more radial connector brackets and associated pod umbilical connector to the control pod, affixing mating LMRP umbilical connector and associated compliant suspension and mounting bracket to the LMRP, and plumbing the umbilical and control pod to the respective umbilical connectors.

Another embodiment of the method to convert an existing hydraulic control system further comprises the step of hydraulically by-passing the umbilical junction plate, and connecting the LMRP umbilical connectors directly to the valving within the control pod. In a related embodiment, the hydraulically by-passed umbilical junction plate may be permanently removed from the control pod in order to lower the weight of the pod, for example, for use in deep water.

In another embodiment, the method to convert an existing hydraulic control system comprises hydraulically connecting the individual hoses within the umbilical bundle directly to the LMRP umbilical connectors.

Generally, the most compact embodiment of the instant invention is preferred, for ease of retrofitting, compactness of the associated plumbing, and ease of subsea installation and retrieval. One such preferred embodiment comprises two pod connector brackets which are as short as practically possible (that is, with a small bracket length “L”), arrayed at the minimum interior angle α, and no junction plate 300A (colloquially known as the “kidney plate” after its shape) or associated hydraulic piping and connections, in order to save weight in the control pod.

FIG. 3B shows the embodiment of the instant invention shown in FIG. 3, with control pod 300 latched into LMRP 307, and the LMRP 307 landed and latched to the BOP stack 314. The umbilical hoses 308C are hydraulically connected to LMRP connectors 308A and 308B. LMRP connectors 308A and 308B are hydraulically connected to pod connectors 306A and 306B respectively. Pod connectors 306A and 306B are hydraulically connected directly to the valving in control pod 300 with umbilical connector piping 308C.

An existing hydraulic control pod may, according to the teachings of this disclosure, be modified to allow the control pod to be retrieved from the LMRP installed on the subsea stack without tripping the drilling riser and the attached umbilical control lines. In one embodiment, the method to convert an existing control pod may comprise the steps of attaching radial connector arms with hydraulic connectors to the control pod, attaching mating hydraulic connectors to the LMRP, and plumbing the umbilical hose bundle and the subsea control pod functions to the hydraulic connectors. In another embodiment, the method to modify a hydraulic control pod may comprise attaching the radial control arms at an inner included angle of between 180 degrees and the minimum inner included angle.

FIG. 4A shows hydraulic flows in hydraulic control systems of the prior art. Fluid from the umbilical 400 flows directly to the control pod 401. Upon a signal to actuate a function in the LMRP (such as opening or closing the annular BOP), fluid flows from the control pod 401 through the upper female connector 402 to the selected LMRP function 403. Upon a signal to actuate a function in the subsea BOP stack (such as opening or closing a ram BOP), fluid flows from the control pod 401 through the upper female connector 402 and the lower female connector 404 to the selected BOP stack function 405.

FIG. 4B shows the hydraulic flow paths in a hydraulic control system which is an embodiment of the instant invention. Fluid from the umbilical 400 flows to an LMRP connector 406 and a corresponding pod connector 407 to the control pod 407. Upon a signal to actuate a function in the LMRP (such as opening or closing the annular BOP), fluid flows from the control pod 401 through the upper female connector 402 to the selected LMRP function 403. Upon a signal to actuate a function in the subsea BOP stack (such as opening or closing a ram BOP), fluid flows from the control pod 401 through the upper female connector 402 and the lower female connector 404 to the selected BOP stack function 405.

In view of this disclosure, various other modifications may be made to the hydraulic control system of the instant invention by those of ordinary skill in the art without departing from the spirit of the invention. It should be understood, therefore, that the instant invention is not limited to the disclosed embodiments, but that the scope of the invention includes all embodiments within the following claims.

Claims

1. A hydraulic control system for a subsea retrievable control pod, comprising: a subsea hydraulic umbilical line;a lower marine riser package having a hydraulic receptacle;a hydraulic control pod having a hydraulic connector for hydraulically mating with the hydraulic receptacle;at least one pod umbilical hydraulic connector hydraulically connected through umbilical connector piping to said hydraulic control pod, andat least one lower marine riser package umbilical hydraulic connector for hydraulically mating with said pod umbilical hydraulic connector and said subsea hydraulic umbilical line;whereby when said system is operated, a hydraulic flow path exists allowing hydraulic fluid to flow from said subsea hydraulic umbilical line through said lower marine riser package umbilical hydraulic connector through said pod umbilical hydraulic connector and into said hydraulic control pod which is hydraulically connected to the lower marine riser package hydraulic receptacle.

2. The control system of claim 1 wherein said pod umbilical hydraulic connector being attached to said hydraulic control pod by a radial control bracket.

3. The control system of claim 1, comprising at least two pod umbilical hydraulic connectors, each connector being attached to said hydraulic control pod by a radial control bracket.

4. The control systems of claim 3 wherein at least two radial connector brackets being spaced between about 180 degrees apart and about 45 degrees apart.

5. The control system of claim 4, wherein the radial connector brackets are substantially horizontally opposed, with an inner included angle of about 180 degrees, and in which a vertical plane substantially through the radial connector brackets is substantially tangential to the well center axis.

6. The control system of claim 4, in which the radial connector brackets have the minimum inner included angle.

7. The control system of claim 1, wherein said pod umbilical hydraulic connectors being male wedge-type hydraulic connectors.

8. The control system of claim 1, wherein said pod umbilical hydraulic connectors being female wedge-type hydraulic connectors.

9. The control system of claim 1, wherein said pod umbilical hydraulic connectors are frustoconical-type connectors.

10. A method of converting a hydraulic control system for a subsea BOP stack and having a hydraulic umbilical line to allow a control pod to be retrieved without detaching the umbilical line, comprising the steps of: attaching at least one radial connector bracket to the control pod;attaching a pod umbilical hydraulic connector to the at least one radial connector bracket;attaching an umbilical hydraulic connector to a lower marine riser package, andplumbing the lower marine riser package umbilical hydraulic connector to the hydraulic umbilical line attached the drilling riser, and plumbing the pod umbilical hydraulic connector to a valve in the control pod.

11. The method of claim 10, in which there are two radial connector brackets with an included angle of between about 180 degrees and the minimum included angle.