A management method suitable for efficient operation of a deepwater high pour point oilfield

Abstract

The present application belongs to the technical field of flow safety guarantee for deepwater oil and gas field development, and discloses a management method suitable for efficient operation of deepwater high pour-point oil field. The method adds a blocking valve and a diesel injection point in a double-pipe loop system, sets a free selection valve group on a manifold, and keeps the continuous flow of hot water in a non-production pipeline during single-pipe operation, thereby solving the technical problems of high pour-point and high gas-liquid ratio oil field in single-pipe and double-pipe operation modes and their switching process. The present application replaces the conventional diesel replacement scheme by continuously injecting hot water with appropriate flow and temperature conditions in the non-production pipeline, thereby reducing diesel consumption, ensuring safe and stable operation of the system, and improving the development efficiency and economic benefits of deepwater high pour-point oil field.

Description

Technical Field

[0001] This invention belongs to the field of deepwater oil and gas field development flow safety assurance technology, and more specifically, it relates to a management method suitable for the efficient operation of deepwater high-pour-point oil fields. Background Technology

[0002] In the development of deepwater oil and gas fields, especially for large-scale oilfields, subsea production systems are typically implemented in conjunction with floating production storage and offloading (FPSO) units. Considering the total oilfield production, FPSO riser size limitations, and the need for flow safety assurance during shutdowns and inspections (such as pigging and replacement operations), the dual-pipe loop system has become a standard and mature technical solution. This system typically connects multiple subsea manifolds in series via two parallel pipes, with a pigging loop installed at the end manifold to achieve loop connectivity.

[0003] This technical solution faces severe challenges for the development of high-pour-point crude oil fields. High-pour-point crude oil is characterized by its high pour point. In the typically 2-4°C deep-water cryogenic environment, a significant temperature difference exists between the high-temperature fluid inside the pipeline and the surrounding seawater, leading to rapid heat loss. If the fluid velocity or flow rate within the pipeline is insufficient, its temperature may drop below the pour point during transport, triggering wax crystal precipitation, crude oil gelation, and ultimately pipeline blockage. To mitigate this risk, it is essential to ensure that the actual throughput of the pipeline does not fall below a critical "minimum safe throughput" to maintain the fluid temperature within the pipeline consistently within a safe range.

[0004] In the development of large-scale high-pour-point oilfields, a phased production model is typically adopted. In the early stages of development, only the first or a few manifolds are connected to production, resulting in relatively low total output that cannot simultaneously meet the minimum safe throughput requirements of both pipelines in a dual-pipeline loop. To expedite oilfield production and achieve early economic benefits, a single-pipeline transportation mode is commonly used in engineering. This involves concentrating all production in one pipeline to ensure that the temperature of that pipeline meets the safety requirement of being above the pour point, while the other pipeline remains in a non-production state. Once other manifolds are subsequently put into operation, increasing the total oilfield output and enabling the simultaneous fulfillment of the minimum safe throughput requirements of both pipelines, the operation mode is switched to a dual-pipeline parallel transportation mode to fully utilize the system's transportation capacity, forming a dynamic switching mode of "initial single-pipeline operation, mid-to-late-stage dual-pipeline operation."

[0005] This model, when applied to the development of deepwater oilfields with high pour point and high gas-liquid ratio, presents complex technical challenges and management difficulties: (1) Safety of single-pipe operation in the early stage of production: Since the pipeline is transported with high-pour-point oil, it is necessary to preheat the pipeline before production, select the preheating fluid and effectively manage the fluid in the non-production pipeline to prevent contact with high-pour-point oil or natural gas in the operating pipeline during the replacement process, which may cause oil condensation blockage or hydrate blockage, so as to ensure the smooth operation of the replacement condition.

[0006] (2) Complex switching between different modes: When switching from single-pipe to dual-pipe mode, the backup pipeline needs to be started smoothly and safely, and the fluid in the dual-pipe circuit needs to be managed safely to avoid oil condensation or hydrate blockage during the replacement process.

[0007] (3) Mid-to-late stage dual-pipe operation flow allocation: During the design phase, the target pipes for each single well to be connected to the two pipelines are given according to the production allocation to maintain the basic consistency of the flow and status of the two pipelines. However, the actual production allocation after commissioning is often different from the design phase. Measures need to be taken to ensure that the flow of both pipelines meets the minimum flow and increase flexibility.

[0008] Therefore, there is a need for a technical method that can systematically, efficiently, and safely manage high-pour-point and high-gas-liquid-ratio oilfields in single and dual-pipe operation modes and their switching processes, in order to fill the technological gap in the development of existing deep-water high-pour-point oilfields. Summary of the Invention

[0009] This invention aims to address at least one of the technical problems existing in the prior art. To this end, this invention provides a management method suitable for the efficient operation of deep-water high-pour-point-rate oilfields, aiming to solve the technical gaps faced in the development of existing deep-water high-pour-point-rate oilfields, particularly the technical difficulties and management challenges in single and dual-pipe operation modes and their switching processes for high-pour-point-rate, high-gas-liquid-ratio oilfields.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: a management method suitable for efficient operation of deep-water high-pour-point oilfields, comprising: The steps for single-pipe operation in the initial stage of production: Piping system preparation: Select two pipes of the same diameter, the first pipe and the second pipe, and connect the FPSO to multiple manifolds distributed underwater; add a first isolation valve, a second isolation valve and a diesel injection point at the double loop of the end manifold, and add a hot water pump on the platform side of the second pipe. Manifold configuration: Install a selectable valve assembly on the first manifold, and use a single valve scheme for the remaining manifolds, connecting them to the target pipes specified by the first and second pipelines; Pipe preheating: Start the hot water pump to inject preheated hot water into the first and second pipes for preheating; Initial production: When only the production wells in the first manifold are put into production, all production wells can be connected to the first pipeline for production by freely selecting valve groups, and the single-pipe production mode is operated. Non-production pipeline management: After the preheating process is completed, continue to maintain the continuous flow of preheated water in the second pipeline, while adjusting and reducing the preheated water flow rate to ensure that the preheated water temperature before mixing with the material in the first pipeline can guarantee that the fluid temperature in the first pipeline is higher than the wax precipitation point. The steps for dual-tube operation in the mid-to-late stages: Assess the throughput: After the production wells of the remaining manifolds are put into operation, assess the total throughput to confirm whether the conditions for the dual-pipeline operation mode are met. Switching preparation: Shut down the hot water pump, stop supplying preheated hot water to the second pipe, and close the first isolation valve to isolate the dual-pipe circuit; Diesel replacement: Inject diesel fuel at the diesel injection point to replace the water in the dual-pipeline circuit with safe diesel fuel. After the replacement is completed, close the second isolation valve. Wellhead switching: Based on the principle of flow balance, the production wells on the first manifold are switched from the first pipeline to the second pipeline to ensure that the flow of the first pipeline and the second pipeline is basically balanced.

[0011] Preferably, the selectable valve assembly can provide three optional material flow paths for the production well within the first manifold: All logistics are connected to the first pipeline; All logistics are connected to the second pipeline; The logistics portion is connected to the first pipeline, while the rest is connected to the second pipeline.

[0012] As a preferred option, the specific connection method of the freely selectable valve group depends on the difference between the actual production of each well after commissioning and the production estimated during the design phase, including the following three cases: When the flow rate of other manifolds connected to the first pipeline is less than the flow rate of the second pipeline minus the output of the wells under the jurisdiction of the first manifold, all the logistics of the first manifold will be connected to the first pipeline. When the flow rate of other manifolds connected to the second pipeline is less than the flow rate of the first pipeline minus the output of the wells under the jurisdiction of the first manifold, all the logistics of the first manifold will be connected to the second pipeline. When the absolute value of the difference between the flow rate of other manifolds connected to the second pipeline and the flow rate of other manifolds connected to the first pipeline is less than the flow rate of the first manifold, based on the production output of the wells under the jurisdiction of the first manifold, some production wells enter the first pipeline and the other production wells enter the second pipeline, so as to maintain a basic balance in the flow rates of the two pipelines.

[0013] As a preferred option, the principles for adjusting the preheated hot water flow rate in the second pipeline include: The preheated water flow rate should be reduced to a level where the preheated water temperature before mixing with the production flow in the first pipeline ensures that the fluid temperature in the first pipeline is above the wax precipitation point. The preheating water flow rate should ensure that, after the oilfield is shut down, the mixture flow in the first pipeline does not drop to the pour point of the high-pour-point crude oil within the allowable safe shutdown time; The preheating water temperature should be adjusted according to the ambient temperature, the pour point of the high-pour-point crude oil, and the wax precipitation point.

[0014] As a preferred option, it also includes steps for stopping and restarting the dual-pipe production mode and managing the preheated water in the dual-pipe loop, specifically: Start the hot water pump to inject preheated hot water into the first and second pipes for preheating; After preheating is complete, shut off the first isolation valve to isolate the dual-pipe circuit; Start production at the production well on the first pipeline side; Diesel fuel is injected at the diesel injection point to displace the preheated water in the dual-pipe circuit; After the displacement is completed, the second isolation valve is shut off to completely isolate the dual-pipe circuit; Start production at the production well on the second pipeline side.

[0015] As a preferred option: during the production process, both the first isolation valve and the second isolation valve are in the open state, and the preheated hot water from the process system enters the second pipeline through the hot water pump, and the preheated hot water is kept circulating throughout the entire underwater production system.

[0016] As a preferred option, after the oilfield is shut down, an isolation pig is launched from the FPSO's launch tube to replace the high-pour-point production fluid in the second pipeline and the water in the second pipeline. Since the second pipeline was preheated before shutdown, the temperature at the interface between the first and second pipelines is high, and there are no issues with oil condensation blockage or hydrates.

[0017] The present invention has the following advantages due to the adoption of the above technical solutions: 1. This invention addresses the management of non-production pipelines in oil and gas fields with a small number of producing wells under the underwater dual-pipeline development model. It replaces the conventional method of replacing diesel fuel by continuously injecting preheated water with appropriate flow rate and temperature into the non-production pipelines, thereby reducing diesel fuel consumption.

[0018] 2. By adding a first isolation valve and a second isolation valve, this invention ensures that the well's material is distributed into the first or second pipe, avoiding the problem of uneven flow caused by the well's material randomly passing through the double pipe loop and being freely distributed, which could lead to one pipe being completely liquid and the other being completely gaseous under extreme operating conditions.

[0019] 3. The present invention provides three selectable flow paths for the production well in the first manifold by adding a free-selection valve group on the first manifold, which solves the problem of imbalance between the flow rate, safe shutdown time and erosion flow safety factors in the two pipelines.

[0020] 4. After the preheating process is completed, the present invention continues to maintain the continuous flow of preheated water in the non-production pipeline of the dual-loop pipeline transportation system, and adjusts and reduces the flow rate of the preheated water. The reduction of the flow rate must ensure that the temperature of the preheated water before mixing with the production material in the production pipeline is higher than the wax precipitation point, so as to avoid frequent periodic wax removal in daily production and increase the workload of on-site production operations.

[0021] 5. In the process of switching from a single pipe to a dual pipe production, the present invention injects diesel fuel through the diesel fuel injection point, replacing the non-flowing water in the dual pipe circuit with safe diesel fuel, thus avoiding the problems of oil condensation blockage caused by contact with high-pour-point oil or hydrate blockage caused by contact with natural gas.

[0022] 6. The present invention uses a dual-pipe mode shutdown and restart scheme, which uses diesel injection points to inject diesel fuel to replace preheated water, thus ensuring the safety and reliability of the dual-pipe mode shutdown and restart process. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings: Figure 1 This is a schematic diagram of the management method for efficient operation of deep-water high-pour-point oilfields provided by the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] This invention provides a management method for the efficient operation of deep-water, high-pour-point-rate oilfields. This method solves the technical challenges of single- and dual-pipe operation modes and their switching processes in high-pour-point-rate, high-gas-liquid-ratio oilfields by adding isolation valves and diesel injection points to a dual-pipe loop system, installing selectable valve assemblies on the manifold, and maintaining continuous flow of hot water in non-production pipelines during single-pipe operation. This invention replaces the conventional diesel replacement scheme by continuously injecting hot water at appropriate flow rates and temperatures into non-production pipelines, reducing diesel consumption while ensuring the safe and stable operation of the system, thus improving the development efficiency and economic benefits of deep-water, high-pour-point-rate oilfields.

[0026] The following is a detailed description, with reference to the accompanying drawings, of the management method for efficient operation of deep-water high-pour-point oilfields provided by embodiments of the present invention.

[0027] This invention provides a management method suitable for the efficient operation of deepwater high-pour-point oilfields, which mainly includes the following six aspects: First, regarding the pipeline system structure design, this invention selects two pipes, 1 and 2, of the same diameter, and connects the FPSO in series with multiple underwater manifolds 1201, 1202, and 1203 to form a dual-loop pipeline system. Compared to traditional dual-loop systems, isolation valves 1 and 2 are added at the end of manifold 1203 to ensure that the well's fluid is distributed into pipe 1 or pipe 2, preventing the well's fluid from randomly flowing through the dual-loop system and causing flow deviation, which could lead to one pipe being entirely liquid and the other entirely gaseous under extreme operating conditions. Furthermore, a diesel injection point DIV2 is added at the dual-loop system to displace the fluid in the dual-loop system, thus preventing condensation of the fluid in the dual-loop system during shutdown. A hot water pump is added to the platform side of pipe 2 (i.e., unit 1: FPSO), which can be used to preheat the pipeline before commissioning or restarting, or to keep the fluid in non-production pipelines in a flowing state during the initial single-pipe operation phase of production.

[0028] Secondly, regarding the pipeline allocation scheme for low throughput in the initial stage of production, when only wells A1 to A6 within manifold 1201 are in operation and the throughput is low, a selectable valve group is added to manifold 1201. By opening the valve on one side of pipeline 1 and closing the valve on the other side of pipeline 2, wells A1 / A2 / A3 and A4 / A5 / A6 are all connected to pipeline 1 for production, ensuring the minimum safe throughput requirement of the pipeline. To maintain basic consistency in the throughput and status of the two pipelines during production, and to reduce the installation weight of the manifolds and the number of valves to reduce investment, manifolds 1202 and 1203 adopt a single-valve scheme, connecting to the designated target pipes of pipelines 1 and 2.

[0029] Third, the optional valve group added to manifold 1201 provides three optional logistics routes for wells A1-A6 within manifold 1201: (1) all logistics are connected to pipeline 1; (2) all logistics are connected to pipeline 2; (3) some logistics are connected to pipeline 1, and the rest are connected to pipeline 2. The specific connection method depends on the difference between the actual output of each well after commissioning and the output estimated in the design stage. This measure solves the problem of imbalance between the flow rate, safe shutdown time and erosion flow safety factors in the two pipelines.

[0030] In practice, the operation of the valve assembly can be freely selected according to the following three situations: (1) If the flow rate of manifolds 1202 and 1203 connected to pipeline 1 (wells A10 / A11 / A12 and A13 / A14 / A15) is lower than "the flow rate of manifolds 1202 connected to pipeline 2 (wells A7 / A8 / A9 and A16 / A17 / A18) minus the output of wells under the jurisdiction of manifold 1201 (wells A1 / A2 / A3 and A4 / A5 / A6)," then all valves of manifold 1201 on one side of pipeline 1 will be opened, and all the material flow of manifold 1201 will be connected to pipeline 1. (2) If the flow rate of manifolds 1202 and 1203 connected to pipeline 2 (wells A7 / A8 / A9 and A16 / A17 / A18) is lower than the flow rate of manifolds 1 connected to pipeline 1 (wells A10 / A11 / A12 and A13 / A14 / A15) minus the output of wells (wells A1 / A2 / A3 and A4 / A5 / A6) under the jurisdiction of manifold 1201, then the valve on the side of pipeline 2 of manifold 1201 will be opened, and all the material flow of manifold 1201 will be connected to pipeline 2; (3) If the absolute value of the difference between the flow rate of manifold 1202 and manifold 1203 connected to pipeline 2 (wells A7 / A8 / A9 and A16 / A17 / A18) and the flow rate of manifold 1 connected to pipeline 1 (wells A10 / A11 / A12 and A13 / A14 / A15) is less than the flow rate of manifold 1201, then according to the production output, some wells on the manifold 1 will enter pipeline 1 by opening the valve on one side of pipeline 1, and other wells will enter pipeline 2 by opening the valve on one side of pipeline 2, so as to maintain the basic balance of the flow rates of the two pipelines.

[0031] Fourth, regarding pipeline management during single-pipe operation, in the development of large-scale high-pour-point oilfields, a phased production model is typically adopted. In the early stages of development, only manifold 1201 is connected to production, resulting in a relatively low total output. This cannot simultaneously meet the minimum safe throughput requirements of both pipelines in a dual-pipeline loop, and production can only be carried out in pipeline 1. Because the pipeline transports high-pour-point oil, it needs to be preheated before production. The preheating medium is preheated water. After preheating, the non-production pipeline 2 contains water. If preheating is stopped, the temperature will be lowered to seabed temperature. If the oilfield stops supplying oil and isolation valves 1 and 2 are opened, the cold water will come into contact with the high-pour-point oil and natural gas in pipeline 1, causing oil condensation blockage or hydrate blockage. To avoid this flow safety issue, the conventional practice is to replace the water in the non-production pipeline with low-pour-point diesel oil as a safe medium.

[0032] After the preheating process, this invention maintains the continuous flow of preheated water in pipe 2 of the dual-loop pipeline system, while adjusting and reducing the flow rate. This reduction must ensure that the preheated water temperature before mixing with the production fluid in pipe 1 is above the wax precipitation point, thus avoiding frequent periodic wax removal during daily production and reducing on-site workload. Furthermore, after oilfield shutdown, the mixture in pipe 1 will not decrease to its freezing point within the permissible safe shutdown time. After shutdown, an isolation pig can be launched from the platform's launch tube to replace the high-freezing-point production fluid in pipe 1 and the water in pipe 2. Because pipe 2 was preheated water before shutdown, the temperature at the interface between pipes 1 and 2 is high, preventing oil condensation blockage and hydrate issues. During production, both isolation valves 1 and 2 are in the open state.

[0033] In practice, the preheated water from the process system enters pipe 2 through a hot water pump. The preheated water circulates throughout the entire production system. The isolation valve is open. Pipe 1 contains the production fluid and the continuously flowing hot water in pipe 2. The preheated water circulates within the system.

[0034] The control of the preheated water flow rate in pipe 2 should be based on the following principles: 1) The flow rate of the preheated water should be reduced to a level where the temperature of the preheated water before mixing with the production flow in pipe 1 can ensure that the temperature of the fluid in pipe 1 is higher than the wax precipitation point; 2) The preheating water flow rate should ensure that after the oilfield is shut down, the mixture flow in pipeline 1 does not drop to the pour point of the high-pour-point crude oil within the allowable safe shutdown time; 3) The preheating water temperature should be adjusted according to parameters such as ambient temperature, pour point and wax precipitation point of high-pour-point crude oil to ensure the safety of the system.

[0035] Fifth, regarding the process of switching from single-pipe production mode to dual-pipe production mode, after the manifold 1203 is put into operation, the throughput increases, requiring adjustment to two pipelines. This involves shutting down the hot water pump, closing isolation valve 1, and switching the upper section of manifold 1201 from pipeline 1 to pipeline 2 for production. To prevent residual preheated water in the dual-pipe loop from contacting high-temperature, high-pour-point oil and natural gas during the replacement process after shutdown, thus avoiding oil condensation blockage and hydrate blockage, isolation valve 1 is closed during the switch to dual-pipe production mode. Diesel is injected at diesel injection point DIV2 to replace the non-flowing water in the dual-pipe loop with safe diesel (which will not contact high-pour-point oil causing oil condensation blockage or natural gas causing hydrate blockage). After the preheated water in the dual-pipe loop has been replaced, isolation valve 2 is closed. Closing isolation valves 1 and 2 prevents fluid at the subsea wellhead from freely distributing on the manifold, causing flow deviation problems.

[0036] In practice, the process of switching from a single-pipe production mode to a dual-pipe production mode can be carried out according to the following steps: S1. Assess the current output to confirm whether the dual-pipe operation conditions are met; S2. Turn off the hot water pump and stop supplying preheated hot water to pipe 2; S3. Shut down isolation valve 1 to isolate the dual-pipe circuit; S4. Inject diesel fuel at diesel injection point DIV2; S5. Monitor the diesel replacement process to ensure that the water in the dual-pipeline circuit is completely replaced; S6. Shut off isolation valve 2 to completely isolate the dual-pipe circuit; S7. Switch the production of the upper part of the manifold 1201 from pipeline 1 to pipeline 2.

[0037] Sixth, regarding the restart plan for the dual-pipe production mode, when restarting the dual-pipe production mode, preheating with preheated hot water is required. After preheating, shut off isolation valve 1, start the wellhead on the side of pipeline 1, and inject diesel fuel at diesel injection point DIV2 in the dual-pipe circuit to displace the preheated hot water in the dual-pipe circuit. After the displacement is completed, shut off isolation valve 2 and start the wellhead on the side of pipeline 2.

[0038] In practice, the restart process for the dual-pipe production mode after shutdown can be carried out according to the following steps: S1. Start the hot water pump to inject preheated hot water into pipes 1 and 2 for preheating; S2. After preheating is complete, shut off isolation valve 1 to isolate the dual-pipe circuit; S3. Start production at the production well on side 1 of pipeline; S4. Inject diesel fuel at diesel injection point DIV2 to displace the preheated hot water in the dual-pipe circuit; S5. After the displacement is completed, shut off isolation valve 2 to completely isolate the dual-pipe circuit; S6. Start production wells on both sides of the pipeline to begin production.

[0039] The implementation process of this invention will be explained in detail below with a specific application example: Suppose a deep-water high-pour-point oilfield has three manifolds (manifold 1201, manifold 1202, and manifold 1203), each manifold has 6 production wells, and the management method provided by this invention is used for development.

[0040] Phase 1: Initial single-pipe operation during the initial production phase 1) Piping System Preparation: Install two pipes, 1 and 2, of the same diameter, and connect manifolds 1201, 1202, and 1203 in series. Install isolation valves 1 and 2 at the U-bend double-pipe loop on the right side of manifold 1203, and add a diesel injection point DIV2. Add a hot water pump on the platform side of pipe 2 (i.e., unit 1: FPSO).

[0041] 2) Manifold configuration: Install a selectable valve group on manifold 1201. Manifold 1202 and manifold 1203 adopt a single valve scheme and are connected to the target pipes specified by pipes 1 and 2.

[0042] 3) Pipe preheating: Start the hot water pump to inject preheated hot water into the two pipes for preheating, monitor the pipe temperature, and ensure that the safety requirements are met.

[0043] 4) Initial production: Only wells A1 to A6 within manifold 1201 will be put into production. All production logistics will be connected to pipeline 1 through freely selectable valve groups to ensure the minimum safe throughput requirements of the pipeline.

[0044] 5) Non-production pipeline management: After the preheating process is completed, continue to maintain the continuous flow of preheated water in pipeline 2, adjust and reduce the preheated water flow rate, and ensure that the temperature of the preheated water before mixing with the production logistics in pipeline 1 can guarantee that the temperature of the flowing fluid in pipeline 1 is higher than the wax precipitation point.

[0045] Phase Two: Mid-to-Late Stage Dual-Pipe Operation 1) Assess the throughput: After manifold 1202 and manifold 1203 are put into operation, assess the total throughput to confirm whether the conditions for dual-pipe operation are met.

[0046] 2) Switching preparation: Shut down the hot water pump and stop supplying preheated hot water to pipe 2. Close isolation valve 1 to isolate the dual-pipe circuit.

[0047] 3) Diesel replacement: Inject diesel at diesel injection point DIV2 to replace the water in the dual-pipe circuit with safe diesel medium. After the replacement is completed, shut off isolation valve 2.

[0048] 4) Wellhead switching: According to the principle of supply balance, the upper part of the well in manifold 1201 will be switched from pipeline 1 to pipeline 2 for production, so as to ensure that the supply of the two pipelines is basically balanced.

[0049] Phase 3: Shutdown and restart of dual-pipe production mode 1) Shutdown preparation: Shut down the system as planned, assess the system status, and confirm the reason for the shutdown and the expected shutdown time.

[0050] 2) System shutdown: Shut down the system according to the normal shutdown procedure to ensure safe system shutdown.

[0051] 3) Restart preparation: Check the status of each component of the system to confirm that each component is normal and undamaged.

[0052] 4) System preheating: Start the hot water pump to inject preheated hot water into the two pipes for preheating, monitor the pipe temperature, and ensure that the safety requirements are met.

[0053] 5) Step-by-step start-up: After preheating, close isolation valve 1 and start the wellhead on the pipeline 1 side. Inject diesel fuel at the diesel injection point to displace the preheated water in the dual-pipeline circuit. After displacement, close isolation valve 2 and start the wellhead on the pipeline 2 side.

[0054] The above application examples demonstrate that the management method provided by this invention can effectively solve the technical challenges in single and dual-pipe production modes and their switching processes in deep-water high-pour-point oilfields, improve oilfield operating efficiency, reduce operating costs, and enhance system safety.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A management method suitable for efficient operation in deep-water high-pour-point oilfields, characterized in that, include: The steps for single-pipe operation in the initial stage of production: Select two pipes of the same diameter, the first pipe and the second pipe, and connect the FPSO to multiple manifolds distributed underwater; add a first isolation valve, a second isolation valve and a diesel injection point at the double loop of the end manifold, and add a hot water pump on the platform side of the second pipe. Install a selectable valve assembly on the first manifold, and use a single valve scheme for the remaining manifolds, connecting them to the target pipes specified by the first and second pipelines; Start the hot water pump to inject preheated hot water into the first and second pipes for preheating; When only the production well in the first manifold is put into production, all production wells can be connected to the first pipeline for production by freely selecting valve groups, and the single-pipe production mode is operated. After the preheating process is completed, the preheated water in the second pipe continues to flow continuously, while the preheated water flow rate is adjusted and reduced to ensure that the temperature of the preheated water before mixing with the material in the first pipe can guarantee that the temperature of the fluid in the first pipe is higher than the wax precipitation point. The steps for dual-tube operation in the mid-to-late stages: After the production wells of the remaining manifolds are put into operation, the total throughput is assessed to confirm whether the conditions for dual-pipe operation mode are met. Shut down the hot water pump, stop supplying preheated hot water to the second pipe, and close the first isolation valve to isolate the dual-pipe circuit; Inject diesel fuel at the diesel injection point to replace the water in the dual-pipeline circuit with safe diesel fuel. After the replacement is complete, shut off the second isolation valve. Based on the principle of supply balance, the production wells on the first manifold will be switched from the first pipeline to the second pipeline to ensure that the supply of the first pipeline and the second pipeline are basically balanced.

2. The management method according to claim 1, characterized in that, The selectable valve assembly provides three alternative material flow paths for the production well within the first manifold: All logistics are connected to the first pipeline; All logistics are connected to the second pipeline; The logistics portion is connected to the first pipeline, while the rest is connected to the second pipeline.

3. The management method according to claim 2, characterized in that, The specific connection method of the freely selectable valve group depends on the difference between the actual production of each well after commissioning and the production estimated during the design phase, including the following three situations: When the flow rate of other manifolds connected to the first pipeline is less than the flow rate of the second pipeline minus the output of the wells under the jurisdiction of the first manifold, all the logistics of the first manifold will be connected to the first pipeline. When the flow rate of other manifolds connected to the second pipeline is less than the flow rate of the first pipeline minus the output of the wells under the jurisdiction of the first manifold, all the logistics of the first manifold will be connected to the second pipeline. When the absolute value of the difference between the flow rate of other manifolds connected to the second pipeline and the flow rate of other manifolds connected to the first pipeline is less than the flow rate of the first manifold, based on the production output of the wells under the jurisdiction of the first manifold, some production wells enter the first pipeline and the other production wells enter the second pipeline, so as to maintain a basic balance in the flow rates of the two pipelines.

4. The management method according to claim 1, characterized in that, The principles for adjusting the preheating water flow rate in the second pipeline include: The preheated water flow rate should be reduced to a level where the preheated water temperature before mixing with the production flow in the first pipeline ensures that the fluid temperature in the first pipeline is above the wax precipitation point. The preheating water flow rate should ensure that, after the oilfield is shut down, the mixture flow in the first pipeline does not drop to the pour point of the high-pour-point crude oil within the allowable safe shutdown time; The preheating water temperature should be adjusted according to the ambient temperature, the pour point of the high-pour-point crude oil, and the wax precipitation point.

5. The management method according to claim 1, characterized in that, It also includes steps for stopping and restarting the dual-pipe production mode and managing the preheated water in the dual-pipe loop, specifically: Start the hot water pump to inject preheated hot water into the first and second pipes for preheating; After preheating is complete, shut off the first isolation valve to isolate the dual-pipe circuit; Start production at the production well on the first pipeline side; Diesel fuel is injected at the diesel injection point to displace the preheated water in the dual-pipe circuit; After the displacement is completed, the second isolation valve is shut off to completely isolate the dual-pipe circuit; Start production at the production well on the second pipeline side.

6. The management method according to claim 1, characterized in that, During the production process, both the first and second isolation valves are open. The preheated water from the process system enters the second pipeline through the hot water pump, and the preheated water circulates throughout the entire underwater production system.

7. The management method according to claim 1, characterized in that, After the oilfield shuts down, an isolation pig is launched from the FPSO's launch tube to replace the high-pour-point production fluid in the second pipeline and the water in the second pipeline. Because the second pipeline was preheated before shutdown, the temperature at the interface between the first and second pipelines is high, and there are no issues with oil condensation blockage or hydrates.

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