This invention relates in ^* general to the field of control devices for the operation of oilfield closing de¬ vices such as blowout preventers, diverters, valves and the like. In particular, the invention relates to control sys- terns for the emergency operation of blowout preventers. Prior art control systems for the operation of blowout preventers such as annular blowout preventers, ram blowout preventers, diverters and the like, have included a source of hydraulic power and a control valve system for di- recting closing or operating hydraulic pressure to the clos¬ ing device for an oil and gas well. In general, the source of hydraulic power includes accumulator bottles and hydraul¬ ic pumpso

Accumulator bottles are containers which store hy- draulic fluid under pressure for use in effecting blowout preventer closure„ Through the use of compressed nitrogen gas, these containers store energy which can be used to ef¬ fect rapid blowout preventer closure. The prior art systems have required that all blowout preventer closing units should be equipped with accumulator bottles with sufficient volumetric capacity to provide the usable hydraulic fluid volume (with the pumps inoperative) to close one pipe ram and an annular preventer in a blowout preventer stack plus the volume to open a hydraulic choke line valve. In gener- al, the accumulators are called upon to be able to close each ram preventer within thirty seconds. Closing time is generally required to not exceed thirty seconds for annular preventers which are smaller than twenty inches and forty- five seconds for annular preventers which are twenty inches in diameter and greater. Thus, the accumulators are called upon to close the annular and ram blowout preventers in an emergency situation, such as a well kick.

In general, the control system for a blowout pre¬ venter stack also requires a pump system. A general re- quirement is that if the accumulator system were to be re¬ moved from service, the pumps should be capable of closing

the annular preventer on the size drill pipe being used plus opening the hydraulically operated choke line valve and obtain a minimum of two hundred psi pressure above accumulator precharge pressure on the closing unit mani- fold within two minutes or less.

In general, the power for closing unit pumps should be available to the accumulator unit at all times such that the pumps will automatically start when the clos¬ ing unit manifold pressure has decreased to less than ninety percent of the accumulator operating pressure. Two or three independent sources of power are generally required on each closing unit. The dual source power system usually recom¬ mended is an air system plus an electrical system.

The source of hydraulic power passes through regu- lators and control valves before being applied to the indi¬ vidual annular or ram blowout preventers.

The prior art control systems as described above, although reliable, are not infallible. Pumps will not op¬ erate when their usual power sources are interrupted. It is conceivable that the electric pump and an air pump may si¬ multaneously fail. Accumulators do not function properly at times due to loss of gas precharge, due to closed block valves or due to operator failure to operate a proper mani¬ fold valve. In addition, regulators and fluid control valves of the control panel may at times be inoperative or fail.

This invention aims to provide an emergency system for the operation of oilfield closing devices to overcome the possible reliability problems of the prior art. The present invention therefore provides a system for operating an oilfield closing device comprising a solid propellant gas generator means for generating high pressure gas when actuated, a conduit connnected between the output of said gas generator means and the closing port of a gas driven piston of an oilfield closing device, and actuating means for activating said gas generator means, operably

causing said high pressure gas to be conducted via said conduit to said closing port.

One feature of the invention lies in the provision of an emergency system to generate control fluid for oil- field closing devices which requires no auxiliary power sources, which is easy to maintain, and which is relatively inexpensive to operate.

Further, the system of the invention is extremely simple in nature and operation and is therefore inherently more reliable than prior art systems.

Further features and advantages of the invention will be more apparent from the following description of pre¬ ferred embodiments of the invention taken together with the accompanying drawings, wherein: Figure 1 illustrates schematically the system for generating pressurized hydraulic fluid to operate an oil¬ field closing device wherein a tank of hydraulic fluid is provided to receive the pressurized gas from a solid pro¬ pellant gas generator; Figures 1A and IB illustrate alternative means for actuating the solid propellant gas generator according to the invention;

Figure 2 shows an alternative embodiment of the in¬ vention where gas from the solid propellant gas generator is applied directly to the closing chamber of an oilfield clos¬ ing device; and

Figure 3 illustrates a propellant cartridge dispos¬ ed in a structural breech and a detonator by which the car¬ tridge is actuated. Figure 1 shows a preferred embodiment of the inven¬ tion in which a solid propellant gas generator 30 is pro¬ vided with a pressure vessel 80 to apply pressurized hy¬ draulic fluid to the closing chamber 64 of an oilfield closing device 60. The oilfield closing device 60 may be an annular blowout preventer, a ram blowout preventer, a diver- ter or a similar device which has a hydraulically driven

piston 62. The solid propellant gas generator 30 in the embodiment illustrated in Figure 1 is actuated by means of a pulse of high pressure fluid applied via conduit 18 via an emergency switch 10. The actuation of the solid pro- pellant gas generator 30 causes high pressure gas to exit via conduit 16 and to be applied to the top of the high pressure vessel 80. The application of high pressure gas causes the hydraulic fluid 82 to be pressurized and applied via co ^' hduit 18 to the oilfield closing device 60. A check valve 50 is advantageously provided in the conduit 18 to prevent reverse flow in line 18. A relief valve 24 is con¬ nected to conduit 16 to relieve overpressure to high pres¬ sure fluid tank 18 from the gas generator 30. A rupture disk 22 is also applied to the conduit 16 to protect the system from maximum excess pressures generated by the gas generator 30. A combustion control orifice 14 is provided between the breech of the solid propellant gas generator 30 and the high pressure fluid tank 80 to control the propel¬ lant combustion pressure. Figure 1A illustrates an alternative means for ac¬ tuating the solid propellant gas generator 30. A current source I in circuit with switch S is connected by a conduc¬ tor path 90 to a detonating squib 92 which serves to actu¬ ate the gas generator 30. Figure IB illustrates a manual plunger 94 adapted to forcefully impact the detonator so as to mechanically actuate the detonator associated with the solid propellant gas generator 30.

Turning now to Figure 2, an alternative embodiment of the inventionis provided in which the output of the solid propellant gas generator 30 is applied directly to the closing chamber 64 of the oilfield closing device 60. The embodiment of Figure 2 is identical in construction to that illustrated in Figure 1 with the exception that the oilfield closing device 60 is operated by means of pressur¬ ized gas directly rather than using pressurized hydraulic

fluid. Thus, conduit 16 is connected directly between the output of the gas generator 30 and the closing chamber 64 of the oilfield closing device 60. The high pressure fluid source 20 and the emergency valve 10 of Figure 1 is identi- cal to that of the embodiment of the invention illustrated in Figure 2.

Figure 3 illustrates an exemplary configuration of a solid propellant gas generator 30 used in both embodiments of this invention. A solid propellant cartridge 31 is disposed within a structural breech 34 which is in turn surrounded by a 1/16 inch thick rubber sleeve 36. One eighth inch thick HTPB end inhibitors 42 are provided at each end of the car¬ tridge 31. Preferably, the propellant material of the car¬ tridge comprises a pyrotechnic compound such as RRC4115 com- mercially available from the Rocket Research Corporation. A polybag ignition booster package 38 is provided in the inte¬ rior 40 of the cartridge 31, which when actuated, causes the propellant to generate high pressure gases.

The structural steel 34 is closed at either end by perforated mild steel grain standoff plates 44 having holes provided at their centers. An aluminized mylar tape 46 seals the hole in the output end of the cartridge.

An initiator housing 48 fabricated of mild steel is welded to the end 41 of the structural breech 34. A port 48 for a hydraulic start signal is provided in the end of the initiator housing 48. A removable safety pin 52 protects the cartridge from accidental actuation. When pin 52 is re¬ moved, an 0-ring seal pistqn 54 is provided for detonating device when actuated by a hydraulic signal. Other detonat- ing means may be provided for electrical or mechanical actu¬ ation of the cartridge as schematically illustrated in Fig¬ ures 1A and IB.

There is provided a solid propellant gas generator for use in the system according to the invention which is designed for easy cartridge insertion into a structural breech and convenient spent cartridge removal.