FPSO natural gas reinjection post-production prediction method

Abstract

The application provides a FPSO natural gas reinjection post-production prediction method, which is applied to a floating production storage and offloading (FPSO) with an underwater high-pressure separator, and comprises the following steps: S101, self-defined coding of FPSO natural gas reinjection post-production prediction; and S102, combining the self-defined coding with a water-gas alternation numerical file to predict future production of reservoirs and single wells after the underwater high-pressure separator is added. The self-defined coding of FPSO natural gas reinjection post-production prediction and the combination of the self-defined coding with the water-gas alternation numerical file can accurately predict future production of reservoirs and single wells after the underwater high-pressure separator is added to the FPSO, thereby providing a basis for preparing an oilfield development plan and providing a basis for managers to make a reasonable production plan.

Description

Technical Field

[0001] This invention relates to the field of natural gas production prediction technology, and in particular to a method for predicting production after natural gas reinjection into an FPSO. Background Technology

[0002] Offshore oil development has made significant progress over the past few decades. With the exploitation of onshore and shallow-water resources becoming increasingly saturated, the oil industry has shifted its focus to deepwater and ultra-deepwater areas. Through innovative solutions such as drilling technologies, subsea structures, and floating production storage and offloading (FPSO) vessels, oil and gas have been successfully extracted from depths of hundreds or even thousands of meters. One of the key areas in offshore oil development is subsea production technology. The continuous development of equipment and processes, including subsea wellhead trees, oil and gas separation and processing systems, subsea pipelines, and storage facilities, has significantly improved the efficiency and production capacity of subsea oil and gas resources.

[0003] An FPSO (Floating Production Storage and Offloading) is a comprehensive offshore oil and gas production facility capable of conducting oil and gas extraction, processing, storage, and unloading operations at sea. Each FPSO has a specific oil and gas processing capacity. For example, the first domestically built ultra-large floating production storage and offloading (FPSO) – the Bakaru – built by Dalian Shipbuilding Industry Group, has a daily processing capacity of 220,000 barrels of crude oil, 150,000 cubic meters of natural gas, 150,000 barrels of water injection, and a storage capacity of 1.6 million barrels of crude oil. With oil field development, the gas-to-oil ratio increases, and natural gas production may exceed the FPSO's processing capacity, thus affecting crude oil production. Currently, some companies have developed subsea high-pressure separators to separate the oil and gas mixture before it flows to the FPSO, reinjecting the separated natural gas. This reduces the FPSO's gas processing capacity, thereby increasing crude oil production. However, the addition of high-pressure separators makes it difficult to predict oil production in reservoir numerical simulation schemes. Existing numerical simulation methods cannot handle this problem; it is necessary to calculate the actual amount of natural gas flowing to the FPSO and determine the specific values ​​of fuel gas, external gas, and reinjected gas at each time point. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a method for predicting the production of FPSO natural gas after reinjection, which is based on numerical simulation of water-gas alternating drive and completes the FPSO production prediction by custom-written production calculation formula.

[0005] To achieve the above-mentioned objective, this invention provides a method for predicting production after natural gas reinjection into an FPSO. This method is applied to a floating production storage and offloading (FPSO) vessel equipped with a subsea high-pressure separator, and includes the following steps:

[0006] S101, Custom coding for production prediction after FPSO natural gas reinjection;

[0007] S102. Combine custom coding with water-gas alternation numerical files to predict the future production of reservoirs and single wells after the addition of subsea high-pressure separators.

[0008] Furthermore, custom coding is performed for FPSO natural gas reinjection production forecasting, specifically including the following steps:

[0009] S201. Set the conditions for the underwater high-pressure separator, and set the separator option of the production well connected to the underwater high-pressure separator to the corresponding underwater high-pressure separator.

[0010] S202. Calculate the amount of natural gas separated by the underwater high-pressure separator;

[0011] S203. Calculate the gas production on the FPSO;

[0012] S204. Calculate the actual gas handling capacity of the FPSO after adding an underwater high-pressure separator.

[0013] S205. Calculate the gas injection volume of other water-gas alternating wells, excluding the injection well of the subsea high-pressure separator.

[0014] Furthermore, the conditions for the underwater high-pressure separator include the name, number of stages, temperature, and pressure of the underwater high-pressure separator.

[0015] Furthermore, the FPSO connects to eight production wells (P1-P8) and six injection wells (I1-I6). P1-P6 are connected to the FPSO, and P7-P8 are connected to the subsea high-pressure separator. Injection wells I1-I5 are connected to the FPSO, and I6 is connected to the subsea high-pressure separator. The oil, gas, and water produced by P7-P8 pass through the subsea high-pressure separator, and the separated gas is directly reinjected into the formation via I6.

[0016] Furthermore, the amount of natural gas separated by the underwater high-pressure separator, GUM1S1, is calculated using the following formula:

[0017] The natural gas output of the underwater high-pressure separator GUM1S1 = primary separation capacity GG1PR - gas processing capacity.

[0018] Furthermore, the gas production rate GUM1 on the FPSO is calculated using the following formula:

[0019] FPSO gas production GUM1 = Total gas production of this unit - Injection volume of injection well I6.

[0020] Furthermore, the actual gas handling capacity of the FPSO after adding the underwater high-pressure separator is calculated using the following formula:

[0021] Actual gas handling capacity of FPSO = reinjection volume of injection well I6 + designed gas handling capacity of FPSO.

[0022] Furthermore, the gas injection rate of other water-gas alternating wells, excluding the subsea high-pressure separator injection well, is calculated, including:

[0023] The gas injection rate GUWAGM1 for other water-gas alternating wells is calculated using the following formula:

[0024] Other water-gas alternating well gas injection volume GUWAGM1 = Total gas production of this unit - Reinjection volume of injection well I6 - Fuel gas volume - Sales volume;

[0025] Using well group control, the injection volume of water-gas alternating well groups and separator injection wells is defined.

[0026] Furthermore, the custom coding for predicting the production output after FPSO natural gas reinjection also includes: determining whether the total gas production of the production unit exceeds the gas processing capacity of the FPSO; when the total gas production exceeds the gas processing capacity of the FPSO, adjusting the control mode to change from fixed liquid or fixed oil production to fixed FPSO maximum gas processing capacity production.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] This invention provides a method for predicting production after natural gas reinjection in FPSOs. By custom coding the production prediction after natural gas reinjection in FPSOs and combining the custom coding with water-gas alternation numerical files, the future production of reservoirs and individual wells after the addition of subsea high-pressure separators to FPSOs can be accurately predicted. This provides a basis for the preparation of oilfield development plans and a foundation for managers to formulate reasonable production plans. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only preferred embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the overall process of a method for predicting the production of FPSO natural gas after reinjection, provided in an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the overall structure of the FPSO provided in an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the overall process of custom coding provided in an embodiment of the present invention. Detailed Implementation

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The listed embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0034] Reference Figure 1 This embodiment provides a method for predicting the production output after natural gas reinjection into an FPSO. The method is applied to a floating production storage and offloading vessel (FPSO) equipped with a subsea high-pressure separator, and includes the following steps:

[0035] S101. Custom coding for production prediction after FPSO natural gas reinjection.

[0036] S102. Combine custom coding with water-gas alternation numerical files to predict the future production of reservoirs and single wells after the addition of subsea high-pressure separators.

[0037] Reference Figure 2 In this embodiment, the FPSO connects to eight production wells (P1-P8) and six injection wells (I1-I6). Wells P1-P6 are connected to the FPSO, and wells P7-P8 are connected to a subsea high-pressure separator. Injection wells I1-I5 are connected to the FPSO, and well I6 is connected to the subsea high-pressure separator. The oil, gas, and water produced by wells P7-P8 pass through the subsea high-pressure separator, and the separated gas is directly reinjected into the formation via well I6. Due to the reinjection via the subsea high-pressure separator, it is necessary to know the actual gas production on the FPSO at each time step.

[0038] Reference Figure 3 As an optional implementation method, custom coding for FPSO natural gas reinjection production prediction includes the following steps:

[0039] S201. Set the conditions for the underwater high-pressure separator by setting the separator option of the production well connected to the underwater high-pressure separator to the corresponding underwater high-pressure separator. For example, the conditions for the underwater high-pressure separator include the name, number of stages, temperature, and pressure of the underwater high-pressure separator.

[0040] S202. Calculate the amount of natural gas separated by the underwater high-pressure separator, GUM1S1. The calculation formula is:

[0041] The natural gas output of the underwater high-pressure separator GUM1S1 = primary separation capacity GG1PR - gas processing capacity.

[0042] S203. Calculate the gas production rate GUM1 on the FPSO. The calculation formula is:

[0043] FPSO gas production GUM1 = Total gas production of this unit - Injection volume of injection well I6.

[0044] S204. Calculate the actual gas handling capacity of the FPSO after adding the underwater high-pressure separator. The calculation formula is as follows:

[0045] Actual gas handling capacity of FPSO = reinjection volume of injection well I6 + designed gas handling capacity of FPSO.

[0046] S205. Calculate the gas injection volume of other water-gas alternating wells, excluding the injection well of the subsea high-pressure separator.

[0047] As an optional implementation, the gas injection rate of other water-gas alternating wells besides the subsea high-pressure separator injection well is calculated, specifically including:

[0048] The gas injection rate GUWAGM1 for other water-gas alternating wells is calculated using the following formula:

[0049] Other water-gas alternating well gas injection volume GUWAGM1 = Total gas production of this unit - Injection volume of injection well I6 - Fuel gas volume - Sales volume.

[0050] Using well group control, the injection volume of water-gas alternating well groups and separator injection wells is defined.

[0051] The injection rate of a water-gas alternating well can be expressed as: M1_WAG GAS RATE GUWAGM1M1_PRO.

[0052] The injection volume of the separator injection well can be expressed as: M1_HS_I GAS RATE GUM1S1M1_HS_P.

[0053] Simultaneously, it is necessary to consider that the total gas production of this production unit cannot exceed the gas processing capacity of the FPSO. In this embodiment, all production wells and injection wells are grouped into one production unit. When the gas production exceeds the gas processing capacity of the FPSO, the control mode needs to be adjusted, changing from constant liquid or constant oil production to production at the maximum gas processing capacity of the FPSO, which can be expressed as:

[0054] ACTIONG

[0055] ACT1 M1_PRO GUGASM1>150000 (FPSO gas handling capacity)

[0056] GCONPROD

[0057] M1_PRO GRAT 2*GUM1 /

[0058] ENDACTIO

[0059] At this point, the custom coding for FPSO natural gas reinjection production prediction is complete. By combining the water-gas alternation numerical simulation file and defining the relevant parameters of the production unit in the production control section of the numerical simulation software, the above custom coding is inserted to accurately predict the future production of the reservoir and individual wells after the addition of the subsea high-pressure separator. This provides a basis for developing oilfield development plans and for managers to formulate reasonable production plans. For example, professional petroleum industry numerical simulation software can be used, such as Eclipse, Intersect, CMG, and tNavigator, which are commonly used in the market.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting production after natural gas reinjection into an FPSO, characterized in that, The method is applied to a floating production storage and offloading (FPSO) vessel equipped with a subsea high-pressure separator, and the method includes the following steps: S101, Custom coding for production prediction after FPSO natural gas reinjection; S102. Combine custom coding with water-gas alternation numerical files to predict the future production of reservoirs and single wells after the addition of subsea high-pressure separators; Custom coding for FPSO natural gas reinjection production forecasting includes the following steps: S201. Set the conditions for the underwater high-pressure separator, and set the separator option of the production well connected to the underwater high-pressure separator to the corresponding underwater high-pressure separator. S202. Calculate the amount of natural gas separated by the underwater high-pressure separator; S203. Calculate the gas production on the FPSO; S204. Calculate the actual gas handling capacity of the FPSO after adding an underwater high-pressure separator. S205. Calculate the gas injection rate of other water-gas alternating wells, excluding the injection well of the subsea high-pressure separator. The FPSO connects to eight production wells (P1-P8) and six injection wells (I1-I6). Wells P1-P6 are connected to the FPSO, and wells P7-P8 are connected to the subsea high-pressure separator. Injection wells I1-I5 are connected to the FPSO, and well I6 is connected to the subsea high-pressure separator. The oil, gas, and water produced by wells P7-P8 pass through the subsea high-pressure separator, and the separated gas is directly reinjected into the formation via well I6.

2. The method for predicting FPSO natural gas reinjection production according to claim 1, characterized in that, The conditions for the underwater high-pressure separator include its name, number of stages, temperature, and pressure.

3. The method for predicting FPSO natural gas reinjection production according to claim 1, characterized in that, The formula for calculating the amount of natural gas GUM1S1 separated by the underwater high-pressure separator is as follows: The natural gas output of the underwater high-pressure separator is GUM1S1 = primary separation volume GG1PR - gas processing capacity.

4. The method for predicting FPSO natural gas reinjection production according to claim 3, characterized in that, The gas production rate GUM1 on the FPSO is calculated using the following formula: FPSO gas production GUM1 = Total gas production of this unit - Injection volume of injection well I6.

5. The method for predicting FPSO natural gas reinjection production according to claim 4, characterized in that, The actual gas handling capacity of the FPSO after adding the underwater high-pressure separator is calculated using the following formula: Actual gas handling capacity of FPSO = reinjection volume of injection well I6 + designed gas handling capacity of FPSO.

6. The method for predicting FPSO natural gas reinjection production according to claim 5, characterized in that, Calculate the gas injection rate for water-gas alternating wells other than the subsea high-pressure separator injection well, including: The gas injection rate GUWAGM1 for other water-gas alternating wells is calculated using the following formula: Other water-gas alternating well gas injection volume GUWAGM1 = Total gas production of this unit - Reinjection volume of injection well I6 - Fuel gas volume - Sales volume; Using well group control, the injection volume of water-gas alternating well groups and separator injection wells is defined.

7. The method for predicting FPSO natural gas reinjection production according to claim 1, characterized in that, The custom coding for predicting production after FPSO natural gas reinjection also includes: determining whether the total gas production of the production unit exceeds the gas processing capacity of the FPSO; when the total gas production exceeds the gas processing capacity of the FPSO, adjusting the control mode to change from fixed liquid or fixed oil production to fixed FPSO maximum gas processing capacity production.

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