Blowout prevention system for oil well

Abstract

The invention relates to the technical field of oil well sucker rod well control, in particular to an oil well blowout prevention system, which is characterized in that a blow-off pipe and a blow-off valve are additionally arranged between a traditional ram blowout preventer and an annular blowout preventer, the pressure in a well is relieved, and after the blow-off pipe is additionally arranged, the function of the traditional blowout preventer is expanded. Risk control in the lifting process of the sucker rod is achieved, the function of the blowout preventer is expanded, and the application scene of the blowout preventer is changed. Through the combined action of the ram blowout preventer, the annular blowout preventer and the blowout valve, an oil well pressure control structure is formed, and meanwhile, a technical scheme for recovery of exploitation is provided for a closed oil well.

Description

Technical Field

[0001] The present application relates to the technical field of oil well sucker rod well control, and in particular to an oil well blowout prevention system. Background Art

[0002] Well control safety is the foundation of oil well operations, and wellhead blowout prevention is the bottom-line mechanism for well control safety. Wellhead blowout prevention relies on the blowout preventer installed at the wellhead.

[0003] The lack of a circulation channel between the casing and the tubing prevents the well from balancing the kill pressure when a sucker rod gets stuck or the tubing becomes clogged, ultimately forcing the well to be shut down because the sucker rod cannot be safely raised. Installing a blowout preventer at the wellhead can prevent oil from gushing out of the well, but it still cannot prevent the well from being shut down. Furthermore, a blowout preventer is only a mandatory or backup measure to enforce well safety. It does not fundamentally change the well's pressure mechanism and cannot save wells that still have potential for recovery.

[0004] Focusing on existing blowout preventers themselves, they still have some flaws in their blowout prevention process. For example, the blowout prevention mechanism of traditional sucker rod ram blowout preventers only supports full or partial sealing of the dual rams, and cannot seal off different-diameter tools such as couplings and centralizers. If different-diameter tools become stuck in the rams, the blowout preventer will fail. Another example is the annular blowout preventer, which uses a hydraulic annular rubber to achieve rapid well shut-in, but its pressure-bearing capacity is extremely low, making it unable to meet the needs of long-term high-pressure well shutdown.

[0005] Chinese utility model patent CN201568027U provides a rod inspection device that places two annular BOPs one above the other and connects them via a blind pipe to enable pressure testing. However, this technical solution does not eliminate the potential pressure hazards; its applicable pressure range depends on the pressure-bearing parameters of the annular BOPs, and it also fails to address the problems of the aforementioned background technology. Summary of the Invention

[0006] The present application provides an oil well blowout prevention system, which combines a ram blowout preventer and an annular blowout preventer to expand the function of the blowout preventer, and adds a pressure channel to the oil well blowout prevention structure to balance the oil well pressure.

[0007] The technical solution of this application is as follows: An oil well blowout prevention system includes a ram blowout preventer connected to an oil wellhead, the ram blowout preventer having an upwardly open discharge port, the discharge port being upwardly connected to a discharge pipe, the discharge pipe being a three-way structure and having a downwardly directed first discharge end, an upwardly directed second discharge end, and a horizontal third discharge end; The first discharge nozzle end is connected to the discharge nozzle; The second blowout end is connected to an annular blowout preventer; The third spraying end is connected to the spraying valve; The first discharge spray end, the second discharge spray end and the third discharge spray end are all provided with a switch valve.

[0008] Furthermore, the blow-off valve is connected to a blow-off pipeline, and the blow-off pipeline is connected to a blow-off tank for storing oil.

[0009] Furthermore, the diameter of the nozzle is larger than the diameter of the oil pipe.

[0010] Furthermore, the switch valve is a valve with adjustable opening.

[0011] In a second aspect, the present application provides an operating method for an oil well blowout prevention system. The method is used in an oil well high-pressure working condition during the process of lifting a pumping rod. Before the oil well high-pressure working condition occurs, the switch valves are all in an open state. The method is characterized in that it includes the following steps: Step 1: When the tubing pressure exceeds the warning value and the oil well is under high pressure, the annular blowout preventer is closed and forced tripping is performed; Step 2: Determine whether the tool in the ram BOP is a different-diameter tool. If so, lift the different-diameter tool to within the nozzle height range, control the ram BOP to maintain a semi-closed state, open the annular BOP to lift the different-diameter tool out of the annular BOP, and then close the annular BOP to continue the forced tripping operation. If not, proceed to the next step. Step 3: During the forced lifting operation, after the sucker rod is unstuck, the gate blowout preventer is controlled to remain in the open state so that the oil flows to the blowout tank through the blowout valve and the blowout pipeline; Step 4: When the oil pipe pressure returns to below the warning value, drain the oil in the spray tank, reopen the annular blowout preventer, and resume operation.

[0012] Furthermore, the warning value of the oil pipe pressure is 0.6 MPa.

[0013] Furthermore, in step three, after the sucker rod is unstuck, it is determined whether the tubing pressure is lower than the warning value. If so, the annular blowout preventer is opened while the ram blowout preventer remains open; if not, the annular blowout preventer is kept closed.

[0014] Due to the adoption of the above technical solution, the beneficial effects of this application are as follows: 1. This application achieves risk control during the sucker rod lifting process. A single sucker rod blowout preventer (BOP) lacks the conditions for implementing risk control, and therefore serves only as a safety net for risk control. Furthermore, the BOP merely mitigates or shelves the risk, without proactively intervening to eliminate it. In this application, risk control is achieved by leveraging the ram BOP's higher blowout prevention pressure and dual closed / semi-closed functions, combined with the annular BOP's adaptability to varying diameters. Specifically, the ram BOP possesses a high blowout prevention capability, enabling it to utilize its own blowout prevention function in the event of pressure anomalies, providing a safety net for risk control. Furthermore, the ram BOP's semi-closed function facilitates the lifting of varying diameter tools: the annular BOP can perform forced lifting and lowering operations on varying diameter tools, but due to its insufficient pressure-bearing capacity, it lacks the conditions for independent forced lifting operations. When these two functions are combined, the ram BOP's semi-closed state complements the annular BOP's pressure-bearing capacity, improving the overall system's pressure-bearing capacity and effectively adding a "forced lifting" function to the annular BOP. In summary, the technical solution of this application provides risk control for sucker rod lifting in the following ways: controlling the risk of different-diameter equipment getting stuck in the gate blowout preventer during abnormal pressure periods; and limiting the high pressure of the oil well during forced lifting operations. Furthermore, risk control is also reflected in the pressure relief measures after the oil is blown out. When the forced lifting operation is completed, the oil layer pressure enters the blowout tank through the blowout valve, dissipating the oil layer pressure and handling the abnormal pressure condition. After the oil in the blowout tank is discharged, the blowout system returns to normal working condition, and the oil well can continue to be mined.

[0015] 2. The technical solution of this application expands the function of the blowout preventer, changing its application scenarios. Existing blowout preventers are used to prevent oil from erupting from the well under abnormal pressure conditions. They have a single function and are almost disposable. In this application, the blowout prevention function of the blowout preventer is weakened, and its control function is expanded. Specifically, the blowout preventer of this application acts as a control mechanism to adjust the movement of the sucker rod and can be used repeatedly for a long time. Furthermore, traditional ram blowout preventers can only seal sucker rods of conventional sizes and cannot seal different-diameter tools, which greatly limits the blowout prevention function of the ram blowout preventer. To compensate for the shortcomings of the ram blowout preventer, this application designs a nozzle to provide travel space for different-diameter tools, allowing the ram blowout preventer to delay the use of its blowout prevention function, rather than directly failing after being stuck. Traditional annular blowout preventers can be used for different-diameter tools, but their blowout prevention effect is insufficient and they lack the ability to force the sucker rod to lift. After connecting the ram blowout preventer, the ram blowout preventer acts as a pressure controller, and the annular blowout preventer can forcibly lift the sucker rod under safe conditions.

[0016] 3. This application forms an oil well pressure control structure through the combined action of a gate blowout preventer, an annular blowout preventer, and a blowout valve. After the blowout valve is installed, it always remains open and will not be closed in any form. The oil well pressure is always in a pressure relief state, and the risk of abnormal pressure in the oil well is significantly reduced. The on-off valve at the blowout valve is an adjustable valve. By adjusting the opening of the on-off valve, the pressure relief pressure can be controlled, further making the oil well pressure controllable.

[0017] 4. This application provides a technical solution for resuming production in closed oil wells. Installing this system in addition to the ram BOP in a closed oil well can relieve pressure within the well and enable continued production under risk control through the annular BOP and blowout pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0019] Figure 1 A schematic diagram of the structure of an oil well blowout prevention system provided in this application; Figure 2 A flow chart of an operating method of an oil well blowout prevention system provided in this application; In the attached figure: 1. Oil well; 2. Ram blowout preventer; 2-1. Blowout port; 3. Blowout pipe; 3-1. First blowout end; 3-2. Second blowout end; 3-3. Third blowout end; 4. Annular blowout preventer; 5. Blowout valve; 6. Switch valve. DETAILED DESCRIPTION

[0020] Based on the background technology, traditional blowout preventers do not have risk control capabilities, have relatively simple functions and can only serve as a safety net for oil well risk control. The present application provides an oil well blowout prevention system, including a gate blowout preventer 2 connected to the wellhead of an oil well 1, wherein the gate blowout preventer 2 has a blowout port 2-1 open to the top and the blowout port 2-1 is upwardly connected to a blowout pipe 3, the blowout pipe 3 is a three-way structure and has a downward first blowout end 3-1, an upward second blowout end 3-2 and a horizontal third blowout end 3-3; the first blowout end 3-1 is connected to the blowout port 2-1; the second blowout end 3-2 is connected to an annular blowout preventer 4; the third blowout end 3-3 is connected to a blowout valve 5; the first blowout end 3-1, the second blowout end 3-2 and the third blowout end 3-3 are all provided with a switch valve 6.

[0021] The main structure of the ram BOP 2 is the housing, with the ram as its core component. It also includes a sealing assembly, a power mechanism, a labor-saving mechanism, and a retraction device. The housing is typically cast or forged from high-strength alloy steel and can withstand extremely high wellhead pressures. The ram, the core sealing component of the BOP, is categorized into different types based on its function: fully sealed rams and semi-sealed rams. The sealing assembly is the ram sealant core, made of a high-temperature and high-pressure-resistant elastic material (such as nitrile rubber or fluororubber). It is installed at the front end of the ram and forms a seal when in contact with the drill pipe or wellbore. The power mechanism is a handwheel-screw system. Rotating the handwheel drives the screw, which propels the ram laterally. The labor-saving mechanism is a lever-gear system that utilizes the principle of leverage or gear reduction to amplify operating force, reducing manpower requirements. The locking device is equipped with a self-locking nut or ratchet mechanism to prevent the ram from retracting.

[0022] The annular BOP 4 is forged or cast from a single piece of high-strength alloy steel, offering high-pressure resistance. Its structure generally consists of a cylindrical shell, connected to the wellhead assembly at the top and bottom by flanges or clamps. Inside, it houses a hydraulic chamber and a space for the rubber core. The rubber core of the annular BOP 4 is made of a high-temperature (-50°C to 150°C) and hydrogen sulfide-resistant elastomer (such as NBR or HNBR). The top section features a conical structure with a tapered rubber core, while the bottom section contacts the piston, which deforms toward the center under pressure. The annular BOP 4 hydraulically propels the piston upward, compressing the rubber core to achieve a seal.

[0023] Both the annular blowout preventer 4 and the ram blowout preventer 2 can be realized by existing technologies.

[0024] As attached Figure 1 As shown, a ram BOP 2 is connected to the wellhead via an on-off valve 6. The ram BOP 2 has a double-layer structure and can be used in either a semi-closed or fully closed configuration. The ram BOP 2 has a higher blowout pressure, typically between 21 MPa and 35 MPa. Compared to the annular BOP 4, the ram BOP 2's blowout prevention capability is three to five times greater. Both semi-closed and fully closed configurations of the ram BOP 2 provide the same blowout prevention pressure. Both configurations are used to shut in the well to prevent blowouts, but the traditional usage scenarios for fully and semi-closed and closed configurations differ. Furthermore, after shutting in the well, the oil well is difficult to reopen due to the inability to relieve pressure.

[0025] The top of the ram BOP 2 is connected to the blowout pipe 3 via a switch valve 6, and the blowout pipe 3 is further connected to the blowout valve 5 and the annular BOP 4 via two other switch valves 6. The blowout valve 5 is connected to the blowout pipe 3 line, and the blowout pipe 3 line is connected to the blowout tank for storing oil. The blowout pipe 3 line and the tank are existing technologies. Figure 1Not shown. The blowout pipe 3 is a buffer space provided between the annular BOP 4 and the ram BOP 2. The advantages of the ram BOP 2 are its high blowout prevention pressure and its dual operating modes, but its disadvantage is its inability to accommodate unusually shaped equipment. The advantage of the annular BOP 4 is its adaptability to unusually shaped equipment, but its blowout prevention capability is insufficient. Given the different blowout prevention pressures of the two, a simple mechanical connection between them is clearly not engineering-sounding and cannot compensate for the shortcomings of the ram BOP 2. The blowout pipe 3 of this application, after connecting the ram BOP 2 and the annular BOP 4, provides space for the movement of equipment of varying diameters, enabling the annular BOP 4 to be operated with a forced start, while also expanding the protective function of the ram BOP 2. Finally, this application forms an oil well pressure control structure through the combined action of the ram BOP 2, the annular BOP 4, and the blowout valve 5. After installation, the blowout valve 5 remains open and will not be closed in any manner, maintaining a constant pressure relief state within the oil well, significantly reducing the risk of pressure anomalies within the well. The on-off valve 6 at the blowout valve 5 is an opening-adjustable valve. By adjusting the opening of the on-off valve 6, the pressure relief pressure can be controlled, thereby further making the oil well pressure controllable.

[0026] As a preferred embodiment of the present application, the diameter of the nozzle 3 is larger than the diameter of the oil pipe. The main function of the nozzle 3 is the connection function, which gives the blowout preventer an expansion function and exerts the ability to control oil well risks.

[0027] As a preferred embodiment of the present application, the switch valve 6 is an opening-adjustable valve, which can be adjusted by adjusting the opening of the switch valve 6 .

[0028] Based on the above oil well blowout prevention system structure, as shown in the attached Figure 2 As shown, the present application provides a method for operating an oil well blowout prevention system. This method is used to prevent high-pressure conditions in the oil well during the process of raising the pump rod. Before the high-pressure condition occurs, the switch valve 6 is in the open state. The high-pressure condition refers to the oil pipe pressure exceeding the warning value. In this embodiment, the warning value is 0.6 MPa. Based on engineering experience, when the oil pipe pressure exceeds 0.8 MPa, oil will be ejected from the oil well.

[0029] This method comprises the following steps: Step 1: When the oil pipe pressure exceeds the warning value, the oil well is in a high-pressure working condition, and the annular blowout preventer 4 is closed for forced tripping. During normal operation, the blowout preventer is kept open.

[0030] Step 2: Determine whether the tool in the gate blowout preventer 2 is a different-diameter tool. If so, lift the different-diameter tool to within the height range of the nozzle 3, control the gate blowout preventer 2 to remain in a semi-closed state, open the annular blowout preventer 4 to lift the different-diameter tool out of the annular blowout preventer 4, and then close the annular blowout preventer 4 to continue the forced lifting operation; if not, execute the steps downward. The forced lifting operation is to forcibly lift the pumping rod when the annular blowout preventer 4 is closed. For a single gate blowout preventer 2 structure, this process is impossible to achieve and there is a risk of blowout. However, in the oil well blowout prevention system structure on which this method is based, the pressure in the well can be relieved in time.

[0031] Step 3: During the forced lifting operation, after the sucker rod is unstuck, the ram BOP 2 is controlled to remain open, allowing oil to flow through the blowout valve 5 and blowout pipe 3 to the blowout tank. In this step, if the sucker rod is unstuck, it can be determined whether the oil pipeline pressure is below the warning value. If so, the annular BOP 4 is opened while the ram BOP 2 remains open. If not, the annular BOP 4 remains closed.

[0032] Step 4: When the oil pipe pressure recovers to below the warning value, the oil in the spray tank is discharged, and the annular blowout preventer 4 is reopened to resume operation.

[0033] In this method, all the switch valves 6 are open, but the switch valve 6 at the blowout valve 5 can adjust the opening to control the pressure relief pressure. The present application realizes risk control during the sucker rod lifting process. A single sucker rod blowout preventer does not have the conditions to implement risk control, so the blowout preventer can only serve as a safety net for risk control; and the blowout preventer only weakens or puts the risk on hold, without actively intervening to eliminate the risk. In the present application, risk control is achieved by relying on the higher blowout prevention pressure and the dual functions of closed / semi-closed of the gate blowout preventer 2 and the different-diameter adaptability effect of the annular blowout preventer 4. Specifically, the gate blowout preventer 2 has a higher blowout prevention capability, which can play its own blowout prevention function when the pressure is abnormal, providing a safety net for risk control. Furthermore, the semi-sealed function of the ram BOP 2 creates conditions for reducing tools: the annular BOP 4 can perform forced lifting and lowering operations on reducing tools, but due to its insufficient pressure-bearing capacity, it is unable to perform forced lifting operations independently. When these two functions are combined, the semi-sealed state of the ram BOP 2 can supplement the pressure-bearing capacity of the annular BOP 4, improving the overall system's pressure-bearing capacity, effectively adding a "forced lifting" function to the annular BOP 4. In summary, the technical solution of this application provides risk control for pump rod lifting by: controlling the risk of reducing tools becoming stuck in the ram BOP 2 during abnormal pressure periods; and limiting the high pressure in the well during forced lifting operations. Furthermore, risk control is also reflected in the pressure relief measures after the oil is ejected. After the forced lifting operation is completed, the oil formation pressure enters the blowout tank through the blowout valve 5, dissipating the oil formation pressure and resolving the abnormal pressure condition. After the oil in the blowout tank is discharged, the blowout system returns to normal operation, and the well can resume production.

[0034] This application provides a technical solution for resuming production in closed oil wells. Installing this system in addition to the ram blowout preventer 2 in a closed oil well can relieve pressure within the well and enable continued production under risk control through the annular blowout preventer 4 and blowout pipe 3.

[0035] Anything not described in this application can be achieved by adopting or drawing on existing technologies.

[0036] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. An oil well blowout prevention system, comprising a ram blowout preventer connected to the wellhead of the oil well, characterized in that: The ram blowout preventer has a discharge port that opens upwards and is upwardly connected to a discharge pipe, the discharge pipe being a three-way structure and having a downward first discharge end, an upward second discharge end, and a horizontal third discharge end; The first discharge nozzle end is connected to the discharge nozzle; The second blowout end is connected to an annular blowout preventer; The third spraying end is connected to the spraying valve; The first discharge spray end, the second discharge spray end and the third discharge spray end are all provided with a switch valve.

2. The oil well blowout prevention system according to claim 1, characterized in that: The spray valve is connected to a spray line, and the spray line is connected to a spray tank for storing oil.

3. The oil well blowout prevention system according to claim 1, characterized in that: The diameter of the nozzle is larger than the diameter of the oil pipe.

4. The oil well blowout prevention system according to claim 1, characterized in that: The switch valve is an opening-adjustable valve.

5. An operating method for the oil well blowout prevention system according to claim 4, wherein the method is used in the process of lifting the pumping rod during the high-pressure working condition of the oil well. Before the high-pressure working condition of the oil well occurs, the switch valves are all in the open state, and the method is characterized in that: The following steps are involved: Step 1: When the tubing pressure exceeds the warning value and the oil well is under high pressure, the annular blowout preventer is closed and forced tripping is performed; Step 2: Determine whether the tool in the ram BOP is a different-diameter tool. If so, lift the different-diameter tool to within the nozzle height range, control the ram BOP to maintain a semi-closed state, open the annular BOP to lift the different-diameter tool out of the annular BOP, and then close the annular BOP to continue the forced tripping operation. If not, proceed to the next step. Step 3: During the forced lifting operation, after the sucker rod is unstuck, the gate blowout preventer is controlled to remain in the open state so that the oil flows to the blowout tank through the blowout valve and the blowout pipeline; Step 4: When the oil pipe pressure returns to below the warning value, drain the oil in the spray tank, reopen the annular blowout preventer, and resume operation.

6. The method for operating an oil well blowout prevention system according to claim 5, characterized in that: The warning value of the oil pipe pressure is 0.6MPa.

7. The method for operating an oil well blowout prevention system according to claim 5, characterized in that: In step three, after the sucker rod is unstuck, determine whether the tubing pressure is lower than the warning value. If so, open the annular BOP while keeping the ram BOP open; if not, keep the annular BOP closed.

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