An underwater production pressure reduction system for deepwater oil and gas fields and its pressure reduction method

Abstract

The present invention discloses an underwater production pressure reduction system for deepwater oil and gas fields and its pressure reduction method. The underwater production pressure reduction system for deepwater oil and gas fields includes an oil and gas production well, an underwater high-integrity pressure protection system, a buffer pipe section, a subsea pipe section, a deepwater riser section, and a platform. The pressure reduction method includes steps such as selecting an oil and gas production well with a high shut-in pressure as the target well, calculating the length of the buffer pipe section, installing an underwater high-integrity pressure protection system, setting the wall thickness of the deepwater riser to be greater than that of the tie-back subsea pipe, and setting pressure safety valves. The underwater production pressure reduction system for deepwater oil and gas fields and its pressure reduction method disclosed by the present invention can achieve pressure reduction of the underwater production system under the underwater production state, significantly reducing the design pressure of the subsea pipe section, its tie-back subsea pipe, and even the deepwater riser section, thereby reducing the wall thickness of the deepwater riser and the tie-back subsea pipe, and greatly reducing the project investment.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep - water oil and gas field development, and particularly relates to an underwater production pressure - reducing system for a deep - water oil and gas field and a pressure - reducing method thereof. Background Technique

[0002] During the development of deep - water oil and gas fields, the underwater well shut - in pressure is extremely high. During the process of connecting the underwater production system back to the collection and transportation of the relying platform, the over - pressure conditions are caused by the following two types of accidents: (1) The choke of the Christmas tree fails and opens fully; (2) Process accidents on the relying oil and gas production platform cause emergency production shutdown or hydrate blockage in the subsea pipeline due to low transportation temperature. When an over - pressure condition occurs, the pressure in the pipeline will accumulate to the shut - in pressure. Therefore, for the design pressure of underwater production facilities such as cross - connecting pipes, manifolds, and subsea pipelines between the underwater production wellhead and the platform shut - off valve, the maximum shut - in pressure value P1 of all single wells is usually adopted, that is, full - pressure design. Currently, the LW3 - 1 gas field and the Deepwater No. 1 gas field in production in China both adopt full - pressure design.

[0003] With full - pressure design, although the underwater production facilities and pipelines will not be over - pressured, for oil and gas fields with extremely high shut - in pressures, in the design stage, it is necessary to design deep - water risers with a greater hanging weight, return subsea pipes with a greater wall thickness, and manifolds with a greater weight. In the construction stage, deep - water risers with a large hanging weight are required, which increases the installation difficulty, raises the requirements for ship construction hoisting, reduces the selectivity of installation resources, and even restricts the feasibility of the floating platform development plan; return subsea pipes with a large wall thickness increase the welding difficulty and reduce the construction efficiency; manifolds with a large weight pose higher requirements for the hoisting capacity of installation ships. All of these undoubtedly increase the engineering investment cost of deep - water oil and gas field development. Summary of the Invention

[0004] The purpose of the present invention is to provide an underwater production pressure - reducing system for a deep - water oil and gas field and a pressure - reducing method thereof, so as to solve the problem of increasing the engineering investment cost of deep - water gas field development due to the current full - pressure design.

[0005] The underwater high - integrity pressure protection system of the present invention includes a supporting pipeline, a trigger, a logic solver, and a final execution facility; wherein, both ends of the supporting pipeline are respectively provided with a well - flow inlet and a well - flow outlet, the trigger is arranged upstream of the supporting pipeline, the final execution facility is arranged downstream of the supporting pipeline, and the trigger and the final execution facility are respectively connected by signal lines.

[0006] Further, the trigger includes a number of pressure sensors, and the number of pressure sensors are arranged in parallel on the supporting pipeline for measuring the pressure of the supporting pipeline; the final execution facility includes two shut-off valves, and the two shut-off valves are arranged in series in the supporting pipeline for controlling the shut-off in the supporting pipeline; the logic solver includes an independent control module, and the control module is connected to the pressure sensors of the trigger and the shut-off valves of the final execution facility through signal lines. Among them, the pressure sensors collect the pressure signals of the supporting pipeline and transmit the collected pressure signals to the control module of the logic solver, and the logic solver determines and issues a decision instruction to the shut-off valves of the final execution facility.

[0007] The present invention also relates to an underwater production pressure reduction system for deepwater oil and gas fields, including an oil and gas production well, a subsea pipeline section, a deepwater riser section and a platform. A tie-back subsea pipeline is provided at a section of the subsea pipeline section near the discharge end of the platform. The deepwater riser section is provided with a deepwater riser. The tie-back subsea pipeline is docked with the lower end of the deepwater riser of the deepwater riser section. The upper end of the deepwater riser is suspended on the platform. The underwater high-integrity pressure protection system and the buffer pipeline section described above are also included. The discharge port of the oil and gas production well is docked with the well flow inlet of the supporting pipeline of the underwater high-integrity pressure protection system; a buffer pipeline is connected between the well flow outlet of the supporting pipeline of the underwater high-integrity pressure protection system and the feed inlet of the subsea pipeline of the subsea pipeline section to form the buffer pipeline section.

[0008] Further, a platform access shut-off valve is provided at the upper end of the deepwater riser suspended on the platform.

[0009] Further, a pressure safety valve is provided at the top of the deepwater riser upstream of the platform access shut-off valve. When the pressure in the deepwater riser exceeds the set critical value, the pressure safety valve opens to release the fluid to achieve pressure relief.

[0010] Further, the wall thickness of the deepwater riser is greater than the wall thickness of the tie-back subsea pipeline.

[0011] Further, an oil production tree shut-off system is also included, and the oil production tree shut-off system and the underwater high-integrity pressure protection system are two independent overpressure protection systems.

[0012] The present invention also relates to a pressure reduction method for the above-mentioned underwater production pressure reduction system for deepwater oil and gas fields, including the following steps:

[0013] Step S1: Select the oil and gas production wells with high shut-in pressure as the target wells according to the reservoir characteristics, oil reservoir production allocation and well location distribution of each block of the gas field;

[0014] Step S2: Calculate the length of the buffer pipe section through dynamic simulation based on the fluid flow rate, pressure value flowing into the well flow inlet of the underwater high-integrity pressure protection system, and the shut-off time of the shut-off valve belonging to the final execution facility.

[0015] Step S3: Dock the discharge port of the target well with the well flow inlet of the supporting pipeline of the underwater high-integrity pressure protection system. Connect the well flow outlet of the supporting pipeline of the underwater high-integrity pressure protection system to the feed inlet of the subsea pipeline of the subsea pipe section through a buffer pipe section to complete the installation of the underwater high-integrity pressure protection system.

[0016] Step S4: Set the wall thickness of the deepwater riser to be greater than the wall thickness of the tie-back subsea pipe.

[0017] Step S5: Install a platform shut-off valve at the upper end of the deepwater riser suspended on the platform, and install a pressure safety valve at the top of the deepwater riser upstream of the platform shut-off valve.

[0018] Preferably, when the underwater high-integrity pressure protection system is operating, in the event of an overpressure condition, the Christmas tree shut-off system is activated first. Only when the Christmas tree shut-off system fails to effectively cut off the high-pressure source in a timely manner, the underwater high-integrity pressure protection system will be activated to protect the safety of downstream production facilities.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The present invention discloses an underwater production pressure reduction system and a pressure reduction method for deepwater oil and gas fields. Combining the reservoir characteristics of each block of the gas field, the oil reservoir production allocation, and the well location distribution, production wells with particularly high shut-in pressures are selected as target wells. Calculate the length of the buffer pipe section and complete the installation of the underwater high-integrity pressure protection system. The underwater high-integrity pressure protection system actively monitors the production pressure of the fluid medium in the pipeline. In the event of an overpressure condition, the valve of the underwater high-integrity pressure protection system can instantaneously and effectively cut off and isolate the high-pressure source to prevent the underwater production facilities from overpressurizing. The underwater production pressure reduction system and the pressure reduction method for deepwater oil and gas fields disclosed by the present invention can achieve the pressure reduction of the underwater production system during the underwater production state, significantly reducing the design pressures of the subsea pipe section, the long-distance tie-back subsea pipe, and the deepwater riser section inside the gas field. Thereby reducing the wall thickness of the deepwater riser and the tie-back subsea pipe, and significantly reducing the project investment. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the underwater high-integrity pressure protection system provided by Embodiment 1 of the present invention;

[0022] Figure 2 It is a schematic structural diagram of the underwater production pressure reduction system for deepwater oil and gas fields provided by Embodiment 2 of the present invention;

[0023] Figure 3 This is a schematic structural diagram of an application case of the subsea production pressure reduction system for deepwater oil and gas fields provided in Embodiment 2 of the present invention. Detailed implementation manners

[0024] The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0025] Embodiment 1: An underwater high integrity pressure protection system

[0026] Embodiment 1 provides an underwater high integrity pressure protection system, and its structure will be described in detail below with reference to the accompanying drawings.

[0027] The English name of the underwater high integrity pressure protection system A is "subsea high integrity pressure protection system", and its abbreviation is SHIPPS.

[0028] Reference Figure 1 , the underwater high integrity pressure protection system A includes a supporting pipeline 1, a trigger 2, a logic solver 3 and a final execution facility 4;

[0029] Among them, a well flow inlet 11 and a well flow outlet 12 are respectively arranged at both ends of the supporting pipeline 1, the trigger 2 is arranged upstream of the supporting pipeline 1, the final execution facility 4 is arranged downstream of the supporting pipeline 1, and the trigger 2 and the final execution facility 4 are respectively connected by signal lines.

[0030] Specifically, the trigger 2 includes a plurality of pressure sensors 20, and the plurality of pressure sensors 20 are arranged in parallel on the supporting pipeline 1 for measuring the pressure of the supporting pipeline 1. Usually, the 3oo2 or 4oo3 mode is adopted. Without affecting the execution of the safety function, it can not only allow one monitoring channel to fail to prevent misoperation, but also when multiple channels have dangerous failures, the safety function will fail, having a quite reliable hardware fault tolerance.

[0031] The logic solver 3 includes a set of independent control modules. The control modules are respectively connected to the pressure sensors 20 of the trigger 2 and the shut-off valve 40 of the final execution facility 4 by signal lines. Among them, the pressure sensors 20 collect the pressure signals of the supporting pipeline 1 and transmit the collected pressure signals to the control module of the logic solver 3, and the logic solver 3 determines and issues a decision instruction to the shut-off valve 40 of the final execution facility 4. The logic solver 3 is the core of the underwater high integrity pressure protection system A.

[0032] The final execution facility 4 includes two shut-off valves 40, which are arranged in series in the supporting pipeline 1 to control the shut-off in the supporting pipeline 1. Each shut-off valve 40 is equipped with complete accessories and testing equipment. The overall system adopts the "one in use and one standby" mode, is physically completely independent and multiplex redundant, ensures the reliability of series operation, and can effectively shut off in a very short time once triggered, ensuring the safety of downstream facilities.

[0033] Embodiment 2: An underwater production pressure reduction system for deepwater oil and gas fields

[0034] Embodiment 2 provides an underwater production pressure reduction system for deepwater oil and gas fields. Its structure will be described in detail below with reference to the drawings.

[0035] Reference Figure 2 and Figure 3 , the underwater production pressure reduction system for deepwater oil and gas fields includes an oil and gas production well O, the underwater high-integrity pressure protection system A of Embodiment 1, a buffer pipe section B, a subsea pipe section C, a riser section D, and a platform M.

[0036] Among them, the oil and gas production well O stores oil and gas inside and is a high-pressure pressure source; the subsea pipe section C is provided with underwater production facilities and is laid with subsea pipelines connecting the underwater production facilities; the platform M is an oil and gas production platform above sea level, and the deepwater riser section D is provided with a deepwater riser, and the upper end of the deepwater riser is suspended on the platform M.

[0037] Under normal circumstances, the discharge port of the oil and gas production well O is docked with the feed port of the subsea pipe section C. In order to realize the connection between the subsea pipe section C and the platform M, a tie-back subsea pipe C1 is provided at a section of the discharge end of the subsea pipe section C close to the platform M, and the tie-back subsea pipe C1 is docked with the lower end of the deepwater riser of the deepwater riser section D.

[0038] In order to control the shut-off of the oil and gas flow in the subsea pipeline, a platform access shut-off valve 5 is provided at the top of the deepwater riser suspended on the platform M.

[0039] Since under normal circumstances, when the high-pressure oil and gas flow of the oil and gas production well O flows through the tie-back subsea pipe C1 and the deepwater riser D, considering the occurrence of an overpressure condition, the pressure in the subsea pipe C1 and the deepwater riser D will accumulate to the shut-in pressure. In the design stage, a conservative approach is taken, and the design pressure of the deepwater riser and the tie-back subsea pipe C1 is taken as the maximum shut-in pressure value P1, resulting in a very large wall thickness.

[0040] However, the use of the subsea high-integrity pressure protection system A can achieve pressure reduction under subsea production conditions, significantly reducing the internal pressure of the deepwater riser in the deepwater riser section D of the subsea pipeline section C and its tie-back subsea pipeline C1, below the maximum shut-in pressure value P1. The internal pressure of the deepwater riser in the deepwater riser section D is taken as the subsea design pressure value P2, which thins the wall thickness of the deepwater riser and the tie-back subsea pipeline C1. Among them, the subsea design pressure value P2 is numerically equal to the shut-in pressure in a conventional well. The specific method is as follows:

[0041] The outlet of the oil and gas production well O is docked with the well flow inlet 11 of the supporting pipeline 1 of the subsea high-integrity pressure protection system A;

[0042] A buffer pipe section B is formed by connecting the well flow outlet 12 of the supporting pipeline 1 of the subsea high-integrity pressure protection system A and the inlet of the subsea pipeline of the subsea pipeline section C through a buffer pipeline.

[0043] The buffer pipe section B helps to reduce the impact on the pressure in the subsea pipeline section C after a cryogenic hydrate blockage occurs downstream during the response shutdown process of the subsea high-integrity pressure protection system A, so that the fluid pressure flowing out of the buffer section pipeline can be reduced to the subsea design pressure value P2. Specifically, during the response shutdown process of the subsea high-integrity pressure protection system A, a cryogenic hydrate blockage is likely to occur downstream, and the high-pressure fluid surges in, causing the pressure in the pipeline section between the installation position of the subsea high-integrity pressure protection system A and the blockage point to rise rapidly. Therefore, the buffer pipe section B is set so that the fluid pressure flowing out of the outlet of the buffer pipe section B is reduced to the subsea design pressure value P2. Among them, the length of the buffer pipe section B is obtained through dynamic simulation calculation based on the fluid flow rate, pressure value flowing into the well flow inlet 11 of the subsea high-integrity pressure protection system A, and the shutdown time of the shutdown valve 40 of the final execution facility 4.

[0044] To prevent internal leakage of the two shutdown valves 40 of the final execution facility 4 of the subsea high-integrity pressure protection system A, resulting in pressure accumulation, and also to avoid damage to the facilities of the platform M or casualties to personnel caused by overpressure failure of the deepwater riser section D, the wall thickness of the deepwater riser in the deepwater riser section D is greater than the wall thickness of the tie-back subsea pipeline C1; at the same time, a pressure safety valve 6 is set at the top of the deepwater riser upstream of the platform shutdown valve 5. When the pressure in the deepwater riser exceeds the set critical value, the pressure safety valve 6 opens to release the fluid and achieve pressure relief.

[0045] When the subsea production pressure reduction system of this deepwater oil and gas field is applied for pressure reduction, it also includes a Christmas tree shutdown system. The Christmas tree shutdown system and the subsea high-integrity pressure protection system A are two independent overpressure protection systems.

[0046] When the underwater high-integrity pressure protection system A is working, once overpressure is detected, the Christmas tree shutdown system is activated first. Only when the Christmas tree shutdown system fails to cut off the high-pressure source in time and effectively will the underwater high-integrity pressure protection system A be activated. For example, the shutdown pressure of the Christmas tree is set at 22 MPaA, and the shutdown pressure of the underwater high-integrity pressure protection system A is set at 25 MPaA.

[0047] The following introduces an application example of the underwater production pressure reduction system for deepwater oil and gas fields disclosed in the present invention. For a production well with a particularly high shut-in pressure, an underwater high-integrity pressure protection system is installed, and a corresponding buffer pipe section B and reasonable process parameter design are set. On the premise of ensuring safety, the design pressures of the manifold, conventional well cross-connection pipe, and submarine pipeline are significantly reduced, the installation difficulty of the manifold is reduced, and the laying efficiency of the submarine pipeline is improved. Among them, referring to Figure 3 , the underwater production facilities include a southern manifold, a submarine pipeline connecting the southern manifold to the northern manifold, a northern manifold, an underwater pig launcher, and a pipeline terminal connected in sequence. The southern manifold includes cross-connection pipes for several wells, and the northern manifold includes cross-connection pipes for several wells. The underwater production facilities are interconnected with the tie-back submarine pipeline C1 to form a subsea pipeline network. The design pressure in the subsea pipeline network is the shut-in pressure in the conventional well, and its pressure value should be equal to the subsea design pressure value P2. In a specific example, the subsea design pressure value P2 = 38.2 MPaA. The pipeline terminal is connected to the deepwater riser of the deepwater riser section D through the tie-back submarine pipeline C1. The length of the tie-back submarine pipeline C1 is 113 Km, and the internal pressure of the tie-back submarine pipeline C1 is 38.2 MPaA. The length of the connecting pipe of the submarine pipeline from the southern manifold to the northern manifold is 5.7 Km.

[0048] During use, to ensure normal operation and monitor its operating status, regular tests are required, including short-frequency tests and full-functional tests. Among them, short-frequency tests are usually carried out once every 3 to 6 months, including valve partial stroke tests, pressure sensor tests, etc., and can be tested during on-line production without shutting down the gas well. Full-functional tests are carried out once a year, including shutdown pressure response tests, shutdown valve tightness tests, etc. During the test process, the wellhead of the underwater high-integrity pressure protection system A needs to be shut down for production suspension.

[0049] Example 3: A pressure reduction method for an underwater production pressure reduction system in a deepwater oil and gas field

[0050] Example 3 provides a pressure reduction method for an underwater production pressure reduction system in a deepwater oil and gas field. Using the underwater production pressure reduction system provided in Example 2, combined with Figure 3 , this method includes the following steps:

[0051] Step S1: Select the oil and gas production well O with a high shut-in pressure as the target well according to the reservoir characteristics, oil reservoir production allocation, and well location distribution of each block in the gas field.

[0052] Step S2: Calculate the length of the buffer pipe section B through dynamic simulation based on the fluid flow rate, pressure value flowing into the well flow inlet 11 of the subsea high-integrity pressure protection system A, and the shutdown time of the shutdown valve 40 of the final execution facility 4.

[0053] Specifically, referring to Figure 3 , the design pressure of the subsea pipe section C and the deepwater riser D is the subsea design pressure value P2. Specifically, the subsea design pressure value P2 = 38.2 MPaA. The design pressures in the pipe of the well flow inlet 11 of the subsea high-integrity pressure protection system A and at the connection between the buffer section and the subsea pipe section C are both the maximum shut-in pressure value P1. Specifically, the maximum shut-in pressure value P1 = 58.8 MPaA. The buffer pipe section B can achieve a smooth transition of the design pressure from the maximum shut-in pressure P1 of the high-pressure well to the shut-in pressure in the conventional well, which helps to reduce the impact on the design pressure of the subsea pipe section C after the downstream low-temperature hydrate blockage occurs during the response shutdown process of the subsea high-integrity pressure protection system A.

[0054] Step S3: Connect the outlet of the target well to the well flow inlet 11 of the supporting pipe 1 of the subsea high-integrity pressure protection system A, and connect the well flow outlet 12 of the supporting pipe 1 of the subsea high-integrity pressure protection system A to the inlet of the subsea pipeline of the subsea pipe section C through the buffer pipe section B to complete the installation of the subsea high-integrity pressure protection system A.

[0055] Step S4: Set the wall thickness of the deepwater riser to be greater than the wall thickness of the tie-back subsea pipe C1.

[0056] Specifically, the outer diameter of the deepwater riser is 508 mm, and its wall thickness is designed according to the standard of Zone 2 and taken as 34.9 mm. The wall thickness of the tie-back subsea pipe C1 is taken as 31.8 mm.

[0057] Step S5: Set a platform shutdown valve 5 at the outlet of the deepwater riser suspended on the platform M, and set a pressure safety valve 6 at the top of the deepwater riser upstream of the platform shutdown valve 5.

[0058] Specifically, the opening pressure of the pressure safety valve 6 is set to 34 MPaA. Even if the two shutdown valves 40 of the final execution facility 4 have internal leakage of the valves, the pressure accumulation of the subsea production facility will not exceed the subsea design pressure value P2, that is, 38.2 MPaA.

[0059] When the subsea high-integrity pressure protection system A is working, once an overpressure condition occurs, the Christmas tree shutdown system will be activated first. Only when the Christmas tree shutdown system fails to cut off the high-pressure source in a timely and effective manner, will the subsea high-integrity pressure protection system A be activated.

[0060] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it on the basis of the present invention, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of the present invention claimed.

Claims

1. An underwater production pressure reduction system for deepwater oil and gas fields, comprising an oil and gas production well (O), a subsea pipeline section (C), a deepwater riser section (D), and a platform (M). A section of the subsea pipeline section (C) near the discharge end close to the platform (M) is provided with a tie-back subsea pipeline (C1). The deepwater riser section (D) is provided with a deepwater riser. The lower end of the tie-back subsea pipeline (C1) is docked with the lower end of the deepwater riser of the deepwater riser section (D), and the upper end of the deepwater riser is suspended on the platform (M). It is characterized in that, It also includes an underwater high-integrity pressure protection system (A) and a buffer pipe section (B). The underwater high-integrity pressure protection system (A) includes a supporting pipeline (1), a trigger (2), a logic solver (3), and a final execution facility (4). Both ends of the supporting pipeline (1) are respectively provided with a well flow inlet (11) and a well flow outlet (12). The trigger (2) is arranged upstream of the supporting pipeline (1), and the final execution facility (4) is arranged downstream of the supporting pipeline (1). The trigger (2) and the final execution facility (4) are respectively connected by signal lines. Among them, the trigger (2) includes a number of pressure sensors (20). A number of pressure sensors (20) are connected in parallel on the supporting pipeline (1) for measuring the pressure of the supporting pipeline (1). The final execution facility (4) includes two shut-off valves (40). The two shut-off valves (40) are arranged in series in the supporting pipeline (1) for controlling the shut-off in the supporting pipeline (1). The logic solver (3) includes an independent control module. The control module is respectively connected to the pressure sensor (20) of the trigger (2) and the shut-off valve (40) of the final execution facility (4) by signal lines. Among them, the pressure sensor (20) collects the pressure signal of the supporting pipeline (1) and transmits the collected pressure signal to the control module of the logic solver (3). The logic solver (3) makes a judgment and issues a decision instruction to the shut-off valve (40) of the final execution facility (4). The discharge port of the oil and gas production well (O) is docked with the well flow inlet (11) of the supporting pipeline (1) of the underwater high-integrity pressure protection system (A). A buffer pipe section (B) is formed by connecting the well flow outlet (12) of the supporting pipeline (1) of the underwater high-integrity pressure protection system (A) and the feed inlet of the subsea pipeline of the subsea pipe section (C) through a buffer pipeline.

2. The underwater production pressure reduction system for deepwater oil and gas fields according to claim 1, characterized in that, A platform access shut-off valve (5) is provided at the upper end of the deepwater riser section (D) suspended on the platform (M).

3. The underwater production pressure reduction system for deepwater oil and gas fields according to claim 2, characterized in that, A pressure safety valve (6) is provided at the top of the deepwater riser upstream of the platform access shut-off valve (5). When the pressure in the deepwater riser exceeds the set critical value, the pressure safety valve (6) opens to discharge fluid to achieve pressure relief.

4. The underwater production pressure reduction system for deepwater oil and gas fields according to claim 3, characterized in that, The wall thickness of the deepwater riser is greater than the wall thickness of the tie-back subsea pipe (C1).

5. The underwater production pressure reduction system for deepwater oil and gas fields according to claim 4, characterized in that, It also includes a Christmas tree shut-off system. The Christmas tree shut-off system and the underwater high-integrity pressure protection system (A) are two independent overpressure protection systems.

6. A method for reducing the pressure of underwater production equipment in deepwater oil and gas fields by using any one of the underwater production pressure reduction systems according to claims 1-5, characterized in that, It includes the following steps: Select the oil and gas production well (O) with a high shut-in pressure as the target well according to the reservoir characteristics, oil reservoir production allocation, and well location distribution of each block in the gas field. Calculate the length of the buffer pipe section (B). Dock the discharge port of the target well with the well flow inlet (11) of the supporting pipeline (1) of the underwater high-integrity pressure protection system (A). The well flow outlet (12) of the supporting pipeline (1) of the underwater high-integrity pressure protection system (A) is connected to the feed inlet of the subsea pipeline of the subsea pipe section (C) through the buffer pipe section (B) to complete the installation of the underwater high-integrity pressure protection system (A). Set the wall thickness of the deepwater riser to be greater than the wall thickness of the tie-back subsea pipeline (C1). Install a platform access shut-off valve (5) at the upper end of the deepwater riser suspended on the platform (M), and install a pressure safety valve (6) at the top of the deepwater riser upstream of the platform access shut-off valve (5).

7. The method according to claim 6, characterized in that, When the underwater high-integrity pressure protection system (A) is in operation, in the event of an overpressure condition, the Christmas tree shut-off system will be activated first. Only when the Christmas tree shut-off system fails to effectively cut off the high-pressure source in a timely manner, will the underwater high-integrity pressure protection system (A) be activated to protect the safety of downstream production facilities.

Images