System and Method for Rescuing a Malfunctioning Subsea Blowout Preventer
A pair of rescue vehicles are deployed on deployment cables to force the shear ram of a sub-sea BOP to shut if it should malfunction. The rescue vehicles may be provided with a camera for remote operation from the surface. The rescue vehicles include securing arms to mate with receiving means on the BOP or its enclosure. The securing arms actuate hydraulic means to release the BOP shear ram piston from hydraulic lock. The rescue vehicles carry their own hydraulic fluid under pressure, or hydraulic fluid pressure may be supplied from the surface or from an ROV, in order to actuate a rod which strikes the accessible BOP shear ram tail rod, forcing the shear ram shut. The rescue vehicles also carry their own securing wedges to slide down behind the vehicle rod, securely holding the BOP shear ram shut.
The present invention relates generally to the field of sub-sea blowout preventers and, more particularly, to a system and a method for assisting the shutting of such a blowout preventer should it fail to properly shut.
BACKGROUND OF THE INVENTIONA blowout preventer (BOP) for deep subsea oil and/or gas well work is commonly hydraulically operated. The hydraulic pressure may be electrically generated downhole or provided from a surface source. Commonly used hydraulic control valves require electrical power to actuate. The signal for actuation may be by way of a hard wire, an acoustic signal, or by radio frequency signal transmission. Failure of any of (1) power to supply the hydraulic pressure, (2) the signal circuit, (3) any of several control valves, or (4) leakage of hydraulic fluid supply will render the BOP inoperative.
Such a BOP is provided for subsea drilling operations which may experience a blowout, i.e. an uncontrolled flow of formation fluids into the drilling well. A blowout can cause loss of life, pollution, damage to drilling equipment, and loss of well production. In the event of a blowout, a shear ram within the BOP is designed to rapidly shear the drill pipe and thus shut off the well. The BOP also includes monitoring equipment to indicate to operators on the surface the status of the various rams of the BOP, including the shear rams.
A riser pipe carries formation fluids from the BOP at the sea floor to a surface drilling vessel and circulates drilling fluids down through a drill bit at the bottom of the drill string. The marine riser pipe connects to the BOP through the lower marine riser package (“LMRP”), which contains a device to connect to the BOP, an annular seal for well control, and flow control devices to supply hydraulic fluids for the operation of the BOP. Many BOP functions are hydraulically controlled, with piping attached to the riser supplying hydraulic fluids and other well control fluids. In deeper water installations, other functions as electrically controlled, with a battery on the BOP providing DC electricity for these functions. Typically, a central control unit allows an operator to monitor and control the BOP functions from the surface. An operator aboard a surface vessel typically operates the flow control components and the BOP functions via an electronic multiplex control system.
Certain drilling or environmental situations require an operator to disconnect the LMRP from the BOP and retrieve the riser and LMRP to the surface vessel. The BOP functions must contain the well when a LMRP is disconnected so that formation fluids do not escape into the environment. To increase the likelihood that a well will be contained in an upset or disconnect condition, companies typically include redundant systems designed to prevent loss of control if one control component fails. Usually, companies provide redundancy by installing multiple independent central control units to back up all critical control units. Only one control unit is used at a time, with the other providing backup.
In U.S. Pat. No. 7,757,772, Donohue et al. proposed a system and method to allow backup or alternate fluid flow routes around malfunctioning components using removable, modular component sets. The system and method of Donohue et al. were directed to providing operational redundancy, in contrast to safety redundancy, which has been focus of most prior art systems. In one embodiment in Donohue et al., an ROV establishes a backup hydraulic flow to a BOP function by attaching one end of a hose to a modular valve block and the other end to an intervention shuttle valve, thus circumventing and isolating malfunctioning components. A compound intervention shuttle valve is provided that comprises first and second primary inlets, first and second secondary inlets, and an outlet. A modular valve block is provided that comprises a directional control valve, a pilot valve, a manifold pressure regulator, a pilot pressure regulator, stab type hydraulic connections and an electrical wet-make connection.
While the system proposed by Donohue et al. does indeed provided additional operational redundancy, it is not effective in shutting a malfunctioning shear ram if the problem is not of the type requiring hydraulic backup. For example, if the hydraulic system is still intact, but the shear ram failed to shut because it was jammed or otherwise failed to shut, then the system of Donohue et al. would be ineffective. Thus, there remains a need for a simple, robust system to provide a rescue shutting force to a shear ram in the event of a failure. The present invention is directed to filling that need in the art.
SUMMARY OF THE INVENTIONThe present invention addresses these and other needs in the sub-sea blowout preventer art by providing a pair of BOP rescue vehicles. Before the BOP is deployed to the sea bottom, it is modified so as to be ready to receive the rescue vehicles. First, the tail rods of the shear rams are made accessible outside the BOP body, if they are not already accessible by design. The rescue system of this invention is equally applicable to other types of BOP rams. Second, means is provided to mechanically receive the rescue vehicles and securely hold the vehicles to the BOP for operation. This receiving means may alternatively be provided on the lower marine riser package. And third, a five-way valve is provided to isolate the primary hydraulic system and to bypass the BOP's shear ram piston so that it is not hydraulically locked and can be made to shut by external means provided by the rescue vehicles.
The rescue vehicles are deployed on deployment cables, and may be provided with a camera for remote operation from the surface. The rescue vehicles include securing arms to mate with the receiving means which were a part of the modification of the BOP. The securing arms actuate the hydraulic five-way valve to release the BOP shear ram piston from hydraulic lock. The rescue vehicles may carry their own hydraulic fluid under pressure in order to actuate a rod which strikes the accessible BOP shear ram tail rod, forcing the shear ram shut. Alternatively, a battery powered pump may be installed on the BOP, to be activated by the rescue vehicles, a stab-in connection may provide hydraulic pressure from the surface or from the rescue vehicles, or other pressure sources may be provided. The rescue vehicles also carry their own securing wedges to slide down behind the vehicle rod, securely holding the BOP shear ram shut.
These and other features and objects will be readily apparent to those of skill in the art from a review of the following detailed description, along with the accompanying drawings.
BOP comprises a body 22 including an axial bore 24 arranged along an axis 26. Drill pipe, coiled tubing, or the like (not shown) is run through the bore 24. A pair of bores 28 extend laterally from the bore 24 and retain two halves 30 and 32 of a shear ram. The shear ram halves 30 and 32 are each attached to a respective rod 34 which is attached to or integrally formed with a respective piston 36. Each piston is retained within its own cylinder 38. As used herein, the term “ram” alone may represent the two ram halves, whether a shear ram, a slip ram, or other type.
Throughout the following description, it is to be understood that the BOP includes a pair of opposing shear ram halves, and thus substantially identical structure is called for on either side of the BOP, including the structure of the rescue system of the present invention. For example, a structural element may be identified in the singular, where it is to understood that the same structure is called for on the other side of the BOP.
The BOP of
Each piston 36 includes a tail rod 54, either attached to the piston or integrally formed with the piston. The tail rod extends through an opening 56 in the body 22 of the BOP so that it is accessible outside the BOP.
The BOP 20 also includes a latching wedge 58 adjacent each tail rod 54. The wedge 58 is operated by a wedge piston 60 which is enclosed within a wedge cylinder 62. An open line 64 is in fluid communication with the open line 50, and ports fluid pressure to a side of the piston 60 which tends to hold the wedge 58 in an open position. A shut line 66 is in fluid communication with the shut line 52 so that porting hydraulic fluid pressure so as to shut the shear ram also ports pressure tending to move the wedge down into a latching position. Once the ram moves in enough to clear the tail rod away from the wedge, the wedge will shut, if everything works as intended.
This is shown in
The action thus described may fail for a number of reasons. Loss of hydraulic fluid and pressure due to any one of the seals or in the pipe and fittings will render the BOP useless. Furthermore, supplying a backup fluid supply will have no effect if additional hydraulic fluid pressure is simply bled off in a leak. In addition, failure of the signal to reach the controller which operates the control valve 44, or failure the 4-way valve itself, will also cause BOP failure. The fail-safe position of the system maintains fluid pressure from the source 40 to keep the BOP rams in the open position.
If the BOP should fail to operate for any of these or other reason, a BOP rescue vehicle 68 of this invention may be employed, as shown in
The second way that the shutting of the BOP rams is accomplished involves moving the tail rods 54. For this purpose, an assist open line 72 and an assist shut line 74 are provided in each rescue vehicle 69. Hydraulic fluid pressure is provided by an assist pressure source 76, as shown and described below in relation to
Referring briefly now to
Referring now to
Referring now to both
As previously described,
Referring next to
The locking of the vehicles into place, ready for operation in accordance with this invention, is shown in
To this point, the system and method of this invention have been described as applied to a BOP in which the tail rod is accessible from outside the body of the BOP. However, some BOP's are made in which the tail rod is not so accessible, with the tail rod within the body of the BOP or enclosed within a tail rod enclosure affixed to the body of the BOP. Such a BOP 200 is shown in
The BOP 200 is hydraulically operated in the same manner as previously described in respect of
In order to operate with the rescue vehicles as previously described, the BOP 200 must be modified, such as the modification shown in
The BOP 200 is also modified to include the 5-way valves 16 in the same manner as previously described in respect of
In all previous drawing figures, the BOP body itself has been modified to receive the rescue vehicles. However, as previously stated, the modifications may preferably be made to the structure which supports the BOP. This embodiment of the invention is illustrated in
Preferably, the BOP rescue system is packaged to be stored on the surface aboard a fire boat, supply vessel, or other easily deployed water craft away from the drilling rig, until the rescue system is needed. If a blowout occurs, and the shear ram fails to shut, the rescue system is needed and it is then lowered from surface into position at the BOP. One method of lowering the rescue system is on coiled tubing, rather than the deployment cable previously described. The coiled tubing may then also provide a conduit for surface generated hydraulic power, with no electric power required at the BOP. This does not preclude the option of installing via cable, and electric cable to generate hydraulic power at the BOP.
The principles, preferred embodiment, and mode of operation of the present invention have been described in the foregoing specification. This invention is not to be construed as limited to the particular forms disclosed, since these are regarded as illustrative rather than restrictive. Moreover, variations and changes may be made by those skilled in the art without departing from the spirit of the invention.
Claims
1. A blowout preventer and rescue system in combination, comprising:
- a. a blowout preventer including a body and at least one pair of rams;
- b. a hydraulic system to operate the ram, the hydraulic system including a tail rod accessible from outside the body of the blowout preventer;
- c. means associated with the blowout preventer arranged to receive a rescue vehicle; and
- d. a rescue vehicle arranged to secure to the receiving means associate with the blowout preventer, the rescue vehicle including means to forcefully contact the tail rod from outside the blowout preventer body, thereby shutting the shear ram.
2. The system of claim 1, wherein the ram is a shear ram.
3. The system of claim 2, wherein the hydraulic system to operate the shear ram including an open line and a shut line, and wherein the system further comprises a control valve in the open and shut lines to controllably disable the hydraulic system.
4. The system of claim 1, wherein the means to receive a rescue vehicle comprises a plurality of horizontally oriented posts arranged on the blowout preventer.
5. The system of claim 1, further comprising a support structure for the blowout preventer, and wherein the means to receive a rescue vehicle comprises a plurality of horizontally oriented posts arranged on the support structure for the blowout preventer.
6. The system of claim 1, wherein the rescue vehicle includes a port securing arm and a starboard securing arm, the arms arranged to secure to the receiving means.
7. The system of claim 4, wherein the rescue vehicle includes a port securing arm and a starboard securing arm, the arms arranged to secure to posts.
8. The system of claim 5, wherein the rescue vehicle includes a port securing arm and a starboard securing arm, the arms arranged to secure to the receiving means.
9. The system of claim 3, further comprising a contactor of the rescue vehicle arranged to contact the control valve in the open and shut lines to controllably disable the hydraulic system.
10. The system of claim 1, further comprising an assist pressure source on the rescue vehicle.
11. The system of claim 1, further comprising a hydraulic coupling on the rescue vehicle to receive hydraulic fluid under pressure from an external source.
12. The system of claim 1, further comprising a deployment cable adapted to couple to the rescue vehicle.
13. The system of claim 1, wherein the means to forcefully contact the tail rod from outside the blowout preventer body includes a hydraulically operated assist rod, and further comprising a locking wedge aboard the rescue vehicle arranged to lock the assist rod when the ram has been operated.
Type: Application
Filed: Sep 8, 2010
Publication Date: Mar 8, 2012
Inventor: Denzal Wayne Van Winkle (Santa Maria, CA)
Application Number: 12/877,586
International Classification: E21B 29/12 (20060101);