Hydraulic power system

Abstract: A hydraulic system and method are provided for supplying high pressure hydraulic fluid to a cylinder for operating a ram, e.g a shearing and/or shut-off ram for a blowout preventer. It comprises means for supplying high pressure hydraulic fluid to the cylinder, said hydraulic fluid supply means comprising first (10) and second (11) storage means for storing hydraulic fluid under pressure, first conduit means (12) for supplying hydraulic fluid under pressure from said first storage means to the cylinder, a pressure sensing device (19) for determining the back pressure in said first conduit means, second conduit means (27) for supplying hydraulic fluid under pressure from said second storage means to the cylinder and valve means (25) for automatically opening said second conduit means when the back pressure in the first conduit means reaches a predetermined amount.

Description: This invention relates to a hydraulic power system and, more particularly, to a hydraulic power unit for actuating blowout preventers of the type having shearing and shut-off rams. Blowout preventers form a regular part of well drilling equipment as used, for example, in the drilling of oil wells and gas wells. Two major classes of blowout preventers are currently utilized to shut off uncontrolled flow of pressurized fluids: ram-type blowout preventers and spherical blowout preventers. In the ram-type blowout preventer, a hydraulic cylinder having a rod attached to its piston is utilized to move a ram, which acts as the closure element to close the passage of the pressurized fluid. A combination shearing and shut-off ram for a blowout preventer is described in US-A-3,736,982. This system is used in instances where a drill string must be cut and/or sealed to prevent damage to the well and associated equipment. It is important that the drill pipe be cut quickly. In order to shear some heavy wall, large diameter drill pipes, high pressures must be maintained on the rams while the shear rams are closed up against the drill pipe. Without this, there is the danger of not being able to shear the pipe or of damaging the rams. US-A-3,044,481 describes an automatic pressure fluid accumulator system for hydraulically or pneumatically operating pressure controlled devices, such as blowout preventers. The system utilizes first and second means for storing hydraulic fluid under pressure, respective first and second conduit means for supplying the fluid from each storage means to the device and valve means for opening and closing automatically the second conduit means in response to a balancing of pressures existing at different points in the system. US-A-3,804,175 relates to an inert gas fire fighting and blowout prevention system and provides flow conduits interconnecting a low and a high pressure source of inert gas to be supplied to the interior of the blowout preventer to mix with combustible gases leaking therefrom. The high pressure conduit is connected to the blowout preventer in response to an increased inert gas line pressure so as to force an elastic seal within the blowout preventer, against the drill string. It is the object of the present invention to provide a simple system for maintaining a high hydraulic pressure through the entire shearing sequence of the blowout preventer. The present invention relates to a hydraulic system for supplying high pressure hydraulic fluid to a cylinder for operating a ram, e.g. blowout preventer shearing and/or shut-off ram. The invention provides a hydraulically actuated shearing device in accordance with Claim 1. The invention also provides a method in accordance with Claim 7 for supplying high pressure hydraulic fluid to a cylinder for operating a shearing and/or shut-off ram for a blowout preventer. The device has particular utility when associated with a blowout preventer comprising a shearing blade, a hydraulically actuated cylinder operatively connected to the blade and means for supplying high pressure hydraulic fluid to the cylinder. It typically consists of two separate banks of accumulator bottles that are charged by a common pumping source, but are discharged separately. The banks of accumulator bottles are typically charged to about 20685 Pa (3,000 psi). The first bank of accumulator bottles is then utilized for supplying fluid to stroke the rams closed and up against the drill pipe. As the rams begin to push up against the drill pipe, a back pressure is created and when this back pressure reaches in the order of about 5516 Pa (800 psi), this causes a valve to automatically open permitting an immediate strong flow from the second bank of accumulator bottles. This means that as the blade is commencing its cut through the drill pipe, a fresh supply of hydraulic fluid is sent to the rams causing a rapid shearing of the pipe at full hydraulic pressure. While reference is made above to drill pipe, it will be understood that the invention applies to the shearing of elongated members generally extending down into a wellbore, e.g. pipes, tubes, sucker rods and wireline. The two separate banks of accumulator bottles can be connected to the cylinder by various conduit configurations. Thus, totally separate conduits may be used, but preferably the second conduit connects into the first conduit. It is also preferable to provide a one way flow valve in the first conduit between the first bank of accumulator bottles and the connection to the second conduit and a one way flow valve in the second conduit. According to another preferred embodiment, the two banks of accumulator bottles are connected by a conduit to permit simultaneous charging of the two banks. This conduit also preferably includes a one way flow valve which prevents flow in the direction from the second bank to the first bank of accumulator bottles. Certain preferred embodiments of the present invention are illustrated by the attached drawings in which: Figure 1 is a schematic flow sheet of one embodiment of the hydraulic system of this invention; Figure 2 is an isometric illustration of typical shear rams which utilizes the hydraulic system of Figure 1; Figure 3 is a schematic illustration of a pipe shearing system with the shear rams partially closed, and Figure 4 is a schematic illustration of a pipe shearing system with the shear rams fully closed. The system as shown in Figure 1 includes a first bank of accumulator bottles 10 and a second bank of accumulator bottles 11. Hydraulic fluid from supply line 14 is pumped into the bottles at a pressure of about 20685 Pa (3,000 psi) from line 14 and through line 12. A one way flow valve 13 is provided in line 12 between accumulator bottles 10 and 11 to prevent fluid flow in the direction between the second accumulator bottles 11 and the first accumulator bottles 10. A branch line 15 extends from line 12 and it includes a one way flow valve 16 preventing flow toward line 12. A pair of further branch lines 17 and 18 extend off line 15. A branch line 23 extends off line 17 and this connects to bypass valve 22 shown in the flow position from line 23 in Figure 1. Thus, the fluid flow comes down through line 23, through valve 22 and continues in line 39. From line 39 it travels via either branch line 33 or valve 31 or branch line 34. These valves 31 and 32 are selectively individually used with valve 31 having outlets 37 and 38 connecting to the closed and open sides of the cylinder respectively and valve 32 having outlets 35 and 36 connecting the closed and open sides of the cylinder respectively. The lines 35 and 37 connect via lines 30 and 29 respectively to a selector valve 28. A single line 27 also connects at one end to valve 28 and at the other end to a hydraulic pilot operated control valve 25 which is actuated by a pressure build up in line 27. The pressure buildup in line 27 is caused by a pressure buildup in line 35 or 37 connecting to the cylinder. Valve 25 is typically a Koomey hydraulic pilot operated SPM control valve and is shown in the closed position in Figure 1. When the back pressure builds up to a predetermined level, e.g. 5516 Pa (800 psi), in line 35 or 37, valve 25 is automatically actuated so that it moves to the flow position permitting outflow from accumulator bottles 11 through valve 24, line 26 and then through line 23, valve 22, line 39 and valve 31 or 32. Line 26 preferably also includes a one way flow valve 49 preventing flow back toward bottles 11. Line 18 connects to hydraulic regulator 19 which utilizes an external hydraulic pilot signal to set the regulated output pressure in line 21. Line 20 is the hydraulic pilot signal line which is set and maintained at a predetermined operating pressure either from a remote location or on the unit itself. When fluid is supplied through lines 18 and 21, the rams are typically used as blind rams, e.g. for testing with no drill pipe in the hole. When fluid is passed through lines 17 and 23 and through valve 22, high pressure from line 15 bypasses the regulator 19 and thus, valve 22 is known as the bypass valve. The shear rams are well known in the industry and will be described only briefly as shown in Figures 2-4. They include a lower holder 41 and an upper holder 44. The lower holder 41 includes a shear blade 40, a lower block member 42 and a lower rubber seal 43. The upper holder 44 includes an upper block 45 and an upper rubber seal 46. The operation of the shear rams is shown in Figures 3 and 4, with Figure 3 showing the rams closing and commencing to engage a pipe P. Thus, the shear blade 40 in Figure 3 is commencing to compress the pipe P. The closing motion of the upper holder 44 pushes the horizontal seal 47 forward and downward on top of the shear blade, resulting in a tight sealing contact. The horizontal seal 47 has a molded-in support plate 46 which holds it in place when the rams are open.

Claims: A hydraulically actuated shearing device for shearing an elongated member (P) extending downhole into the wellbore comprising a shearing blade (40), a hydraulically actuated cylinder operatively connected to the blade (40) and means for supplying high pressure hydraulic fluid to the cylinder, said hydraulic fluid supply means comprising first and second storage means (10,11) for storing hydraulic fluid under pressure, first conduit means (21) for supplying hydraulic fluid under pressure from said first storage means (10) to the cylinder, a pressure sensing device (19) for determining the back pressure in said first conduit means (21), second conduit means (26) for supplying hydraulic fluid under pressure from said second storage means (11) to the cylinder and valve means (25) for automatically opening said second conduit means (21) when the back pressure in the first conduit means reaches a predetermined amount. A device according to Claim 1 wherein the first and second storage means comprise first and second banks of accumulator bottles (10,11). A device according to Claim 1 or Claim 2 wherein said second conduit means (26) connects to said first conduit means (21). A device according to any one of Claims 1 - 3 wherein the valve means comprises a hydraulic pilot operated control valve (25). A system according to any one of Claims 1 - 4 which includes a third conduit means (12) flow connecting the first and second storage means (10,11), said third conduit means including a one-way flow valve (13) to prevent fluid flow in the direction between the second storage means (11) and the first storage means (10). A system according to Claim 3 wherein said first and second conduit means (10,11) each includes a one-way flow valve (16,49) to prevent fluid flow in the direction of each respective storage means. A method for supplying high pressure hydraulic fluid to a cylinder for operating a shearing and/or shut-off ram for a blowout preventer, which comprises supplying the fluid from first and second high pressure hydraulic storage means (10,11) by way of first and second conduit means (21,26), and including the steps of initially supplying fluid to the cylinder from the first storage means (10) via the first conduit means (21) until a back pressure develops in said first conduit means, sensing the back pressure by means of a pressure sensing device, generating a signal when the back pressure reaches a predetermined value, said signal causing a valve (25) to automatically open in the second conduit (26) thereby providing an immediate strong flow of fluid from the second storage means to the cylinder. A method as defined in Claim 7, further comprising the steps of interconnecting the first and second high pressure hydraulic storage means (10,11) by way of third conduit means (12), and preventing fluid flow along the third conduit means in the direction from the second storage means (11) to the first storage means (10). A method as defined in Claim 7 or Claim 8, further including the steps of connecting the second conduit means (10) to the first conduit means (11), and preventing fluid flow in both the first and second conduit means in the direction toward its respective storage means.

Inventors: DOWNIE R JAMES, WACHOWICZ STANLEY W, DOWNIE, R. JAMES, WACHOWICZ, STANLEY W.
Applicants: BAROID TECHNOLOGY INC, BAROID TECHNOLOGY, INC.
Application year: 1990
Main classification: E21B33
IPC codes: E21B33, E21B29, E21B34