Method for determining gathering and transportation process of produced liquid of carbon dioxide flooding oil field

Abstract

The invention relates to the technical field of oil field surface engineering produced liquid gathering and transportation treatment processes, in particular to a method for determining a carbon dioxide flooding oil field produced liquid gathering and transportation process. The method comprises the following steps: selecting a plurality of oil wells as target wells, presetting basic data, pipeline parameters and inter-station parameters of the target wells, respectively inputting the basic data, the pipeline parameters and the inter-station parameters into three computational simulation software to establish gathering and transportation system mechanism models, presetting gathering and transportation process technical parameters of a plurality of groups of target wells, respectively inputting each group of data into three gathering and transportation system mechanism models, selecting a target inter-well station, determining calculation software of the target inter-well station according to an actual gas-liquid ratio condition in the target inter-well station, inputting preset parameters of the target inter-well station into the software and establishing a model, inputting gathering and transportation process technical parameters of the target inter-well station into the model, and determining process parameters of the carbon dioxide flooding oilfield produced liquid gathering and transportation process according to a calculation result. The method provided by the invention effectively ensures the production stability of the carbon dioxide flooding gathering and transportation system, and is more economical and practical.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield surface engineering produced liquid gathering and transportation processing technology, and in particular to a method for determining a carbon dioxide driven oilfield produced liquid gathering and transportation technology. Background Art

[0002] Crude oil gathering and transportation is one of the central links of oilfield surface engineering. It mainly involves gathering and transporting oil, gas and water from oil wells to processing stations using wellhead back pressure. For Daqing Oilfield, Jilin Oilfield, Shengli Oilfield, etc., the wax precipitation point of crude oil is between 31℃ and 50℃, the buried depth of single-well oil gathering and water mixing pipeline is generally about 1.0m, and the lowest ground temperature in winter is about -2℃. The pipeline environment temperature is low and the thermal conditions are poor. In actual production, in order to ensure normal production and operation, the oil gathering process of water mixing or seasonal water mixing is usually adopted. The oil gathering process of water mixing process can meet the needs of gathering and transportation of crude oil in carbon dioxide flooding.

[0003] CCUS-EOR technology is not only an important measure for my country to achieve "carbon peak and carbon neutrality", but also a strategic successor technology for significantly improving the recovery rate of low permeability oil fields. It can create a harmonious win-win situation for energy and environment, and is highly consistent with the green and low-carbon development strategy. Therefore, the promotion and application of this technology is of great significance.

[0004] Carbon dioxide flooding and storage is the core link of CCUS-EOR industrial promotion. Due to the application of carbon dioxide flooding, as carbon dioxide is injected into the formation, the oil layer is affected by a large amount of carbon dioxide returning, and the change of oil-gas ratio of the wellhead produced liquid affects the wellhead produced liquid gathering and transportation system. The physical properties of the produced liquid, the wellhead oil temperature and pressure are all changed compared with conventional water flooding, polymer flooding and other displacement methods. The conventional gathering and transportation processing technology cannot meet the production control needs well. Therefore, a method for determining the gathering and transportation process of produced liquid in carbon dioxide flooding oil fields is proposed. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention provides a method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field. According to the particularity of carbon dioxide flooding produced liquid, by comparing the differences in the calculation results of three softwares, the gathering and transportation system mechanism model calculation software is optimized, and the gathering and transportation process technology suitable for the gas-liquid ratio of carbon dioxide flooding produced liquid at different stages is determined, so as to ensure the production stability of the carbon dioxide flooding gathering and transportation system and help promote the application of CCUS-EOR.

[0007] (II) Technical solution

[0008] In order to solve the above problems, the present invention provides a method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field, comprising:

[0009] Step S1: Select multiple oil wells as target wells, and preset basic data, pipeline parameters and inter-station parameters of the target wells;

[0010] Step S2: input the target well data preset in step S1 into OLGA software, Pipephase software and Pipesim software respectively, and establish the gathering and transportation system mechanism model respectively;

[0011] Step S3: Preset multiple groups of gathering and transportation process technical parameters of target wells, input each group of data into the three gathering and transportation system mechanism models of step S2, and compare the calculation results output by the three calculation models under each group of data;

[0012] Step S4: Select a target inter-well station, and determine the software for performing calculation simulation on the target inter-well station according to the actual gas-liquid ratio condition in the target inter-well station and the difference between the three calculation models obtained in step S3;

[0013] Step S5: presetting the basic data, pipeline parameters and station-to-station parameters of the target inter-well station, and inputting the preset parameters of the target inter-well station into the software determined in step S4 to establish a gathering and transportation system mechanism model;

[0014] Step S6: Determine the gathering and transportation process technical parameters of the target well station, input them into the gathering and transportation system mechanism model of step S5, and use the output calculation results to determine the process parameters of the CO2 flooding oil field produced liquid gathering and transportation process.

[0015] Preferably, in step S1, the basic data of the target well include the wellhead oil output temperature and the single well water injection amount, the pipeline parameters of the target well include the length and diameter of a single oil collecting ring, and the inter-station parameters of the target well include the length and diameter of the inter-station oil collecting pipeline, the station inlet pressure and the water injection temperature in the metering room.

[0016] Preferably, in step S2, the modeling of the OLGA software, Pipephase software and Pipesim software all utilizes a black oil model, which is a calculation model established by basic differential equations, wherein the basic differential equations include Darcy's law and the law of conservation of matter.

[0017] Preferably, the Darcy's law is an experimental law that reflects the law of water seepage in rock and soil pores, and its calculation expression is:

[0018]

[0019] Wherein, h: friction loss along the pipeline, m; l: pipeline length, m; V: medium flow velocity, m / s; d: pipeline inner diameter, m; g: gravitational acceleration; λ: friction coefficient.

[0020] Preferably, in step S3, the gathering and transportation process technical parameters of the target well include gas-liquid ratio, oil gathering ring liquid production and oil gathering ring length.

[0021] Preferably, in step S3, the calculation results of the gathering and transportation system mechanism model of the target well include the highest back pressure and oil return temperature at the wellhead.

[0022] Preferably, in step S5, the basic data of the target inter-well station include the number of metering rooms, the number of oil wells in the metering room, the wellhead oil outlet temperature and the water injection amount of a single well, the pipeline parameters of the target inter-well station include the length and diameter of a single oil collecting ring, and the inter-station parameters of the target inter-well station include the length and diameter of the inter-station oil collecting pipeline, the station inlet pressure and the water injection temperature of the metering room.

[0023] Preferably, in step S6, the gathering and transportation process technical parameters of the target well station include liquid production, oil production and oil gathering radius.

[0024] Preferably, in step S6, the calculation results of the gathering and transportation system mechanism model of the target well station include the gas-liquid ratio and the highest back pressure at the wellhead.

[0025] Preferably, in step S6, the process parameters include oil and gas transmission method, oil collection radius, metering method and pipeline material.

[0026] (III) Beneficial effects

[0027] The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field provided by the present invention aims at the particularity of carbon dioxide flooding produced liquid, compares the differences in the calculation results of three softwares, and optimizes the gathering and transportation system mechanism model calculation software. Through modeling calculation and actual on-site production conditions in the early stage of pilot tests, it can not only ensure the production stability of the carbon dioxide flooding oil gathering and transportation system, but also be more economical and practical, which plays an important role in ensuring the promotion and application of CCUS-EOR. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flow chart of a method for determining a carbon dioxide flooding oil field produced liquid gathering and transportation process according to an embodiment of the present invention;

[0029] Figure 2 The oil-gas ratio of the method for determining the carbon dioxide flooding oil field produced liquid gathering and transportation process in the embodiment of the present invention is 400m 3 / t, DN50, trend diagram of the highest wellhead back pressure under different fluid production;

[0030] Figure 3 The oil-gas ratio of the method for determining the carbon dioxide flooding oil field produced liquid gathering and transportation process in the embodiment of the present invention is 400m 3 / t, DN50, trend diagram of the highest wellhead temperature under different fluid production;

[0031] Figure 4 The oil-gas ratio of the method for determining the carbon dioxide flooding oil field produced liquid gathering and transportation process in the embodiment of the present invention is 100m 3 / t, maximum wellhead back pressure diagram for different pipe diameters and different production fluids;

[0032] Figure 5 The oil-gas ratio of the method for determining the carbon dioxide flooding oil field produced liquid gathering and transportation process in the embodiment of the present invention is 100m 3 / t, the inter-circulation temperature trend diagram of different pipe diameters and different produced fluids;

[0033] Figure 6 The oil-gas ratio of the method for determining the gathering and transportation process of the produced liquid of the carbon dioxide flooding oil field according to the embodiment of the present invention is 600m 3 / t, trend chart of the highest wellhead back pressure for different pipe diameters and different production fluids;

[0034] Figure 7 The oil-gas ratio of the method for determining the gathering and transportation process of the produced liquid of the carbon dioxide flooding oil field according to the embodiment of the present invention is 600m 3 / t, the inter-circulation temperature trend diagram of different pipe diameters and different produced fluids;

[0035] Figure 8 The maximum wellhead back pressure trend diagram of the method for determining the gathering and transportation process of the produced liquid of the carbon dioxide flooding oil field according to the embodiment of the present invention, with an oil-gas ratio of 800m3 / t, different pipe diameters, and different produced liquids;

[0036] Fig. 9 The oil-gas ratio of the method for determining the carbon dioxide flooding oil field produced liquid gathering and transportation process in the embodiment of the present invention is 800m 3 / t, inlet temperature trend chart of different pipe diameters and different produced fluids;

[0037] Fig.10 The inlet temperature trend diagram under different liquid production and oil-gas ratios of the method for determining the carbon dioxide flooding oil field produced liquid gathering and transportation process according to the embodiment of the present invention;

[0038] Fig.11 It is a trend diagram of wellhead back pressure under different liquid production and oil-gas ratios of the method for determining the production liquid gathering and transportation process of a carbon dioxide flooding oil field in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Figure 1 The flowchart of the method for determining the gathering and transportation process of produced liquid from a carbon dioxide flooding oil field according to an embodiment of the present invention is as follows: Figure 1 As shown, the present invention provides a method for determining a production liquid gathering and transportation process of a carbon dioxide flooding oil field, comprising:

[0041] Step S1: Select multiple oil wells as target wells, and preset basic data, pipeline parameters and inter-station parameters of the target wells.

[0042] In practical applications, the characteristics of carbon dioxide flooding oil fields are high CO2 content in associated gas, low wellhead oil temperature and high oil-gas ratio. Therefore, priority is given to the relevant data of the target well. In this determination method, the basic data of the target well include the wellhead oil temperature and the water injection amount of a single well. The pipeline parameters of the target well include the length and diameter of a single oil gathering ring. The inter-station parameters of the target well include the length and diameter of the inter-station oil gathering pipeline, the station inlet pressure and the water injection temperature of the metering room.

[0043] In this embodiment, the basic data part: the oil outlet temperature at the wellhead is generally 15-30°C according to the empirical value. For carbon dioxide flooding, the oil outlet temperature at the wellhead is set to 5°C, and the water injection rate for a single well is 0.6m 3 / h, viscosity-temperature curve, density, water content; pipeline parameters: the length of a single oil collecting ring is 2000m, the pipe diameter is DN50 / DN65, ground temperature, considering that carbon dioxide flooding uses non-metallic pipes, so the heat transfer coefficient and friction resistance of the pipeline are adaptively adjusted; inter-station parameters: the length of the inter-station oil gathering pipeline is 1000m, the pipe diameter is DN100, the inlet pressure is set to 0.3MPa, and the water mixing temperature in the metering room is 63℃.

[0044] Step S2: input the target well data preset in step S1 into OLGA software, Pipephase software and Pipesim software respectively, and establish the gathering and transportation system mechanism model respectively.

[0045] In practical applications, PipePhase software is a strict steady-state multiphase flow simulator for oil and gas production networks and pipeline transmission and distribution system calculations. It has a huge physical property database and thermodynamic calculation methods, and can accurately simulate huge network models with wells, pipelines and other connecting equipment. PipePhase uses experience and mechanical methods to analyze multiphase flow phenomena in pipelines. It combines fluid models with strict energy balance and has detailed heat transfer analysis capabilities.

[0046] At the same time, OLGA software is used to simulate the instantaneous motion state of oil, gas and water in production systems such as oil and gas wells, pipelines and processing equipment. It is the world's standard software for transient multiphase flow simulation. It can simulate the entire flow path of the fluid from output to the processing plant, including the flow assurance issues in the near-well area, the wellbore and the gathering and transportation pipeline network, and maximize the actual flow space. It has been widely used in all areas of flow assurance. It provides an effective basis for oilfield mixed transportation technology solutions and further development and transformation of oilfields. In addition, the fluid component tracking module of the OLGA software can simulate the transient characteristics in the pipeline, the gas-liquid conversion process and the supercritical state motion characteristics. Typical applications are carbon dioxide design and simulation of steam-assisted production.

[0047] In addition, Pipesim software is mainly used for multiphase fluid analysis, and can perform computational simulations on oil, gas, and water three-phase, gas-liquid two-phase, and single-phase liquid. The biggest feature is the system's integration and openness, sharing heat transfer, multiphase flow, and fluid behavior methods to ensure data quality and consistency between steady-state and transient analysis. And the proportions of different components of pollutants CO2, H2S, N2, H2, and CO can be input during calculation.

[0048] In this method, Table 1 is a comparison table of three computing software. As shown in Table 1, the reasons for selecting three computing simulation software in practical applications are analyzed based on the contents of the table.

[0049] In practical applications, OLGA software, Pipephase software and Pipesim software all use the black oil model for modeling and calculation. The black oil model is a calculation model established through basic differential equations, which include Darcy's law and the law of conservation of matter. The black oil model assumes that there are three phases of oil, gas and water in the reservoir, and each phase obeys Darcy's law. The oil and gas phases in the reservoir reach a phase equilibrium state instantaneously, and oil and water are immiscible; natural gas is also assumed to be insoluble in water.

[0050] It should be noted that Darcy's law is an experimental law that reflects the law of water seepage in rock and soil pores, and its calculation expression is:

[0051]

[0052] Wherein, h: friction loss along the pipeline, m; l: pipeline length, m; V: medium flow velocity, m / s; d: pipeline inner diameter, m; g: gravitational acceleration; λ: friction coefficient.

[0053] Table 1 Comparison of three computing software

[0054]

[0055] In practical applications, the law of conservation of matter shows that the net mass flow rate flowing into the control body is equal to the mass increased per unit time due to the density change in the control body. Then, by fixing the terminal pressure and starting temperature, that is, the inlet metering room pressure and the wellhead temperature, the Darcy formula and the continuity equation are used to iteratively calculate the maximum back pressure at the wellhead and the inlet room temperature.

[0056] Step S3: Preset multiple groups of gathering and transportation process technical parameters of target wells, input each group of data into the three gathering and transportation system mechanism models of step S2, and compare the calculation results output by the three calculation models under each group of data.

[0057] In this determination method, the target well's gathering and transportation process technical parameters include gas-liquid ratio, oil gathering ring liquid production and oil gathering ring length, and the calculation results of the gathering and transportation system mechanism model of the target well include the highest wellhead back pressure and oil return temperature.

[0058] In practical applications, the oil-gas ratio is 400m 3 / t is taken as an example, crude oil from a production plant in Daqing Oilfield is selected for trial calculation, and a gathering and transportation system mechanism model is established for 4 oil wells. Table 2 is a table of crude oil properties. As shown in Table 2, when establishing the gathering and transportation system mechanism model, the physical property data of crude oil are also required.

[0059] Table 2 Crude oil properties

[0060]

[0061] Three softwares were used to calculate the maximum back pressure at the wellhead and the inter-return temperature when the oil-gas ratio was 400m3 / t, with different pipe diameters, liquid production rates, and oil gathering ring lengths. The maximum back pressure at the wellhead and the inter-return temperature when the oil-gas ratio was 400m3 / t, DN50, and with different liquid production rates and oil gathering ring lengths were plotted.

[0062] In this embodiment, considering that the oil collecting ring production is 10, 20 and 30 t / d respectively; the oil collecting ring length is 1.0 km, 1.5 km, 2.0 km, 3.0 km and 4.0 km, the maximum back pressure and oil return temperature of each target well are calculated.

[0063] Table 3 is a calculation table of the oil gathering ring of an oil field under the condition of an oil-gas ratio of 400m3 / t. As shown in Table 3, three softwares are used to calculate the maximum back pressure and back temperature of the wellhead under the conditions of an oil-gas ratio of 400m3 / t, different pipe diameters, liquid production, and oil gathering ring lengths. The calculation results of the oil gathering ring of an oil field under the three calculation simulation software can be obtained, and the maximum back pressure and back temperature of the wellhead under the oil-gas ratio of 400m3 / t, DN50, different liquid production and oil gathering ring lengths are plotted respectively, as shown in Table 3. Figure 2 and Figure 3As shown in the figure, the values ​​calculated by the software Olga<Pipesim<Pipephase. Under the same oil-gas ratio, production rate and oil gathering radius, the hydraulic conditions calculated by the software Olga are better and the thermal conditions are worse; the hydraulic conditions calculated by the software Pipephase are worse and the thermal conditions are better. The calculation differences between the software are within 20%, so Olga and Pipephase are selected again to calculate the maximum back pressure at the wellhead and the inlet temperature at different oil-gas ratios.

[0064] Table 3 Calculation table of oil gathering ring of a certain oil field under oil-gas ratio of 400m3 / t

[0065]

[0066] In this example, a simulation calculation is performed on an oil collecting ring, which governs four oil wells and considers that the oil-gas ratio is 100m 3 / t、600m 3 / t、800m 3 / t; the oil gathering ring production is 10, 20, and 30 t / d respectively; the oil gathering ring length is 1.0 km, 1.5 km, 2.0 km, 3.0 km, and 4.0 km, calculate the maximum back pressure and oil return temperature at the wellhead.

[0067] like Figures 4 to 9 As shown in the figure, under the same oil-gas ratio, production, and oil gathering radius, the hydraulic conditions calculated by Olga software are better and the thermal conditions are worse; the hydraulic conditions calculated by Pipephase software are worse and the thermal conditions are better; when the gas-oil ratio is 100m 3 / t, both software can meet the demand when the liquid production reaches 30t / d, the pipe diameter is DN65 / DN50, the oil gathering radius is 3000m, and the wellhead back pressure is less than 1MPa; when the gas-oil ratio is 600m 3 / t, when the liquid production reaches 30t / d, the oil gathering radius is 2000m calculated by Pipephase, and the pipe diameter is DN65, and the wellhead back pressure is less than 1MPa.

[0068] By comparing the various indicators of the software simulation results, it can be seen that the simulation results of the Pipephase software are higher than those of the other two software. From the perspective of actual production, the conditions simulated by the Pipephase software are more stringent, and the production process selected through the Pipephase software simulation is more inclusive.

[0069] Step S4: Select a target inter-well station, and determine the software for performing calculation simulation on the target inter-well station according to the actual gas-liquid ratio condition in the target inter-well station and the difference between the three calculation models obtained in step S3.

[0070] In this embodiment, after comprehensive consideration of various aspects, especially to ensure the CO2 flooding in the later stage, that is, the gas-liquid ratio is greater than 400m 3 / tAfter stable production, Pipephase software is preferred.

[0071] Step S5: preset the basic data, pipeline parameters and station-to-station parameters of the target inter-well station, and input the preset parameters of the target inter-well station into the software determined in step S4 to establish a gathering and transportation system mechanism model.

[0072] In the present determination method, in step S5, the basic data of the target inter-well station include the number of metering rooms, the number of oil wells in the metering room, the wellhead oil output temperature and the water injection amount of a single well, the pipeline parameters of the target inter-well station include the length and diameter of a single oil collecting ring, and the inter-station parameters of the target inter-well station include the length and diameter of the inter-station oil collecting pipeline, the station inlet pressure and the water injection temperature of the metering room.

[0073] In this embodiment, for different gas-liquid ratios, Pipephase software is used, and the basic data of the target inter-well station are as follows: the oil transfer station has 5 metering rooms, each metering room has 20 wells, the wellhead oil temperature is set to 5°C, and the water injection rate of a single well is 0.6m3 / h; the pipeline parameters of the target inter-well station: the length of a single oil collecting ring is 2000m~3000m, and the pipe diameter is DN50 / DN65; the inter-station parameters of the target inter-well station: the water injection temperature of the metering room is 63°C, the inlet pressure is set to 0.3MPa, the length of the inter-station oil gathering pipeline is 1000m, and the pipe diameter is DN100.

[0074] Step S6: Determine the gathering and transportation process technical parameters of the target well station, input them into the gathering and transportation system mechanism model of step S5, and use the output calculation results to determine the process parameters of the CO2 flooding oil field produced liquid gathering and transportation process.

[0075] In the present determination method, in step S6, the gathering and transportation process technical parameters of the target inter-well station include liquid production, oil production and oil gathering radius, and the calculation results of the gathering and transportation system mechanism model of the target inter-well station include gas-liquid ratio and wellhead maximum back pressure, wherein the process parameters include oil and gas transmission mode, oil gathering radius, metering method and pipeline material.

[0076] Table 4.1 Calculation table of maximum wellhead back pressure and inlet temperature under different liquid production / oil production and oil-gas ratio

[0077]

[0078] Table 4.2 Calculation table of the maximum back pressure at the wellhead and the inlet temperature at different liquid production / oil production and oil-gas ratio

[0079]

[0080] Tables 4.1 and 4.2 are calculation tables for the maximum back pressure at the wellhead and the inlet temperature under different liquid production / oil production and oil-gas ratios. As shown in Tables 4.1 and 4.2, the liquid production, oil production and oil gathering radius are input into the target well station according to the gathering and transportation system mechanism model established by Pipephase, and the relevant calculation results are obtained.

[0081] In practical applications, the maximum back pressure at the wellhead and the inlet temperature under different oil-gas ratios and different liquid production rates are plotted, such as Fig.10 As shown in the figure, under the same oil-gas ratio, the lower the liquid production / oil production, the higher the inlet temperature. At the same time, under the same liquid production, the higher the oil-gas ratio, the lower the inlet temperature. Fig.11 As shown, under the same oil-gas ratio, the higher the liquid production / oil production, the higher the wellhead back pressure. At the same time, under the same liquid production, the higher the oil-gas ratio, the higher the wellhead back pressure.

[0082] In this embodiment, by simulating and calculating the above conditions and combining the actual production situation of carbon dioxide flooding in Daqing Yushulin Oilfield, the process parameters of the process technology of the low permeability oilfield carbon dioxide flooding produced liquid gathering and transportation system can be determined.

[0083] In practical applications, when the oil-gas ratio is low at the initial stage of gas injection, the oil-gas ratio is less than 400m 3 / t, adopt oil and gas mixed transportation mode, in the later stage when the oil and gas are relatively high, the oil and gas ratio is> 400m 3 / t, in order to meet the production needs, oil and gas distribution is adopted at the wellhead.

[0084] At the same time, in order to improve the hydraulic conditions of the oil gathering pipeline and shorten the oil gathering radius as much as possible, we draw on the previous engineering practice of carbon dioxide flooding and use one ring for every 3 to 4 oil wells. Generally speaking, the length of the oil gathering ring should be less than 3.0 km. When the production well is far away from the processing station, the metering room is connected in series to the station.

[0085] In addition, the oil wells use the wellhead dynamometer diagram oil measurement method, and the metering separator combined with the integrator is used for metering in the metering room, and the dynamometer diagram oil measurement is calibrated.

[0086] It should be noted that the carbon dioxide contained in the produced fluid can easily cause pipeline corrosion. In order to prevent pipeline corrosion, oil collection and water blending pipelines are made of non-metallic pipes with strong corrosion resistance.

[0087] In addition to the embodiments described above, this determination method is applied in the following oil fields, and the relevant results obtained are as follows:

[0088] In actual application, Hailar Oilfield carried out CO2 drive experiments in 2016, and constructed 101 CO2 drive oil wells. An independent oil gathering system was built for the CO2 drive production wells, and a small ring water injection process was adopted. 2 to 3 oil wells were independently formed into a ring, and the length of the oil gathering ring was less than 1.5 km. The length of the oil gathering ring of remote wells was less than 2.0 km, and an oil and gas mixed transportation method was adopted.

[0089] In addition, the feasibility study of the "Daqing Aonan Oilfield CCUS Phase I Development Plan" was completed in 2022, and the design work is currently underway. The infrastructure CO2 drive has produced 479 oil wells. Through software simulation calculations, there is one ring for every 3 to 4 oil wells, and the length of the oil gathering ring is less than 3.0 km. In the initial stage of gas injection, the oil-gas ratio is less than 400m 3 / t, the oil-gas mixed transmission method is adopted, and in the later stage, when the oil-gas ratio is greater than 400m 3 / t, oil and gas distribution method is adopted at the wellhead.

[0090] The CCUS oil collection system of Aonan Oilfield has been further optimized on the basis of the original CO2 flooding and transportation process, which can save 25.1 million yuan in investment and ensure that the oil collection system meets the development and production needs. At the same time, it has effectively guaranteed the "Aonan Oilfield Phase I CCUS-EOR" oil recovery and storage project, and achieved the smooth implementation of the demonstration project with an annual injection capacity of 900,000 tons and a built production capacity of 296,000 tons / year.

[0091] The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field provided by the present invention optimizes the gathering and transportation system mechanism model calculation software, comprehensively considers factors such as the medium, gathering and transportation radius, and process flow of the crude oil gathering and transportation system, establishes a hydraulic and thermal model of the gathering and transportation system, determines the gathering and transportation process technology suitable for the gas-liquid ratio of produced liquid in carbon dioxide flooding at different stages, ensures the production stability of the carbon dioxide flooding gathering and transportation system, and promotes the promotion and application of CCUS-EOR.

[0092] By implementing this method, the following beneficial effects are effectively achieved: First, the oil gathering technology realizes closed oil gathering, which reduces the loss of associated gas and is beneficial to environmental protection; second, through modeling calculations and actual on-site production conditions in the early stage of pilot tests, the number of wells under the jurisdiction of the annular process and the setting of the annular length are given to solve the gathering and transportation problem of low oil outlet temperature at the wellhead, effectively ensuring the stability of the production system and, at the same time, improving the economy of the oil gathering system construction; third, through modeling calculations, the gathering and transportation technology of mixed transportation in the early stage and separate transportation in the later stage is implemented, and the gas-oil ratio content of the produced liquid is used as the technical limit, and the gas-oil ratio values ​​of the separate transportation and mixed transportation of the gathering and transportation system are given, which is well adapted to the development characteristics of large changes in the gas-oil ratio of the produced liquid in carbon dioxide drive, and at the same time, effectively reduces the one-time engineering investment.

[0093] The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A method for determining the collection and transportation process of produced liquid in a carbon dioxide flooding oil field, characterized in that: include: Step S1: Select multiple oil wells as target wells, and preset basic data, pipeline parameters and inter-station parameters of the target wells; Step S2: input the target well data preset in step S1 into OLGA software, Pipephase software and Pipesim software respectively, and establish the gathering and transportation system mechanism model respectively; Step S3: Preset multiple groups of gathering and transportation process technical parameters of target wells, input each group of data into the three gathering and transportation system mechanism models of step S2, and compare the calculation results output by the three calculation models under each group of data; Step S4: Select a target inter-well station, and determine the software for performing calculation simulation on the target inter-well station according to the actual gas-liquid ratio condition in the target inter-well station and the difference between the three calculation models obtained in step S3; Step S5: presetting the basic data, pipeline parameters and station-to-station parameters of the target inter-well station, and inputting the preset parameters of the target inter-well station into the software determined in step S4 to establish a gathering and transportation system mechanism model; Step S6: Determine the gathering and transportation process technical parameters of the target well station, input them into the gathering and transportation system mechanism model of step S5, and use the output calculation results to determine the process parameters of the CO2 flooding oil field produced liquid gathering and transportation process.

2. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In step S1, the basic data of the target well includes the wellhead oil output temperature and the single well water injection amount, the pipeline parameters of the target well include the length and diameter of a single oil collecting ring, and the inter-station parameters of the target well include the length and diameter of the inter-station oil collecting pipeline, the station inlet pressure and the water injection temperature in the metering room.

3. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In the step S2, the modeling of the OLGA software, Pipephase software and Pipesim software all utilizes the black oil model, which is a calculation model established by basic differential equations, and the basic differential equations include Darcy's law and the law of conservation of matter.

4. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 3, characterized in that: The Darcy's law is an experimental law that reflects the law of water seepage in rock and soil pores, and its calculation expression is: Wherein, h: friction loss along the pipeline, m; l: pipeline length, m; V: medium flow velocity, m / s; d: pipeline inner diameter, m; g: gravitational acceleration; λ: friction coefficient.

5. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In step S3, the gathering and transportation process technical parameters of the target well include gas-liquid ratio, oil gathering ring liquid production and oil gathering ring length.

6. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In step S3, the calculation results of the gathering and transportation system mechanism model of the target well include the highest back pressure at the wellhead and the oil return temperature.

7. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In step S5, in step S5, the basic data of the target inter-well station include the number of metering rooms, the number of oil wells in the metering room, the wellhead oil output temperature and the water injection amount of a single well, the pipeline parameters of the target inter-well station include the length and diameter of a single oil collecting ring, and the inter-station parameters of the target inter-well station include the length and diameter of the inter-station oil collecting pipeline, the station inlet pressure and the water injection temperature of the metering room.

8. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In step S6, the gathering and transportation process technical parameters of the target well station include liquid production, oil production and oil gathering radius.

9. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In step S6, the calculation results of the gathering and transportation system mechanism model of the target well station include the gas-liquid ratio and the highest back pressure at the wellhead.

10. The method for determining the gathering and transportation process of produced liquid in a carbon dioxide flooding oil field according to claim 1, characterized in that: In step S6, the process parameters include oil and gas transmission method, oil collection radius, metering method and pipeline material.

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