Method and system for optimizing separation distance between partition plates for injecting carbon dioxide into shale oil reservoirs in subdivision mode

Abstract

The invention belongs to the technical field of shale oil reservoir development, and particularly relates to a shale oil reservoir subdivision carbon dioxide injection partition plate spacing optimization method and system. The problems of carbon dioxide gas channeling and low oil displacement efficiency caused by unreasonable separation distance of partition plates for injecting carbon dioxide in shale oil reservoir subdivisions at present are solved. According to the technical scheme, the method comprises the steps that a subdivision carbon dioxide injection exploitation physical model is built, the initial state of the subdivision carbon dioxide injection exploitation physical model is built, a subdivision carbon dioxide injection oil displacement experiment is carried out, the number of partition plates is continuously increased, and the carbon dioxide oil displacement efficiency under different partition plate intervals is obtained; a relation chart of different partition plate distances and carbon dioxide oil displacement efficiency and gas seeing time is established, the optimal partition plate distance of a sub-cabin carbon dioxide injection exploitation physical model can be obtained according to the chart, and the optimal partition plate distance of sub-cabin carbon dioxide injection of shale oil reservoirs in actual field production can be determined through a similarity criterion; according to the novel method, the shale oil reservoir development scheme can be optimized, and the overall economic benefit is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of shale oil reservoir development, and in particular relates to a method and system for optimizing the spacing between partitions for carbon dioxide injection in compartments of shale oil reservoirs. Background Art

[0002] Shale oil reservoirs are an unconventional oil and gas resource that is difficult to develop, and traditional water injection development methods have limited effects. In recent years, carbon dioxide recovery technology has gradually been applied in the development of shale oil reservoirs. By injecting carbon dioxide to increase reservoir pressure and improve oil fluidity, the recovery rate is increased.

[0003] After extensive research, the patent number CN202310774476.X, "A method for evaluating the effective displacement distance of carbon dioxide injection in low-permeability and tight oil reservoirs", analyzes the starting pressure gradient of cores with different permeabilities, establishes a mathematical relationship between it and the permeability, and calculates the effective displacement distance of the reservoir under different conditions, thereby determining the effective displacement distance of the actual carbon dioxide flooding in the oil field to optimize oil recovery efficiency; the patent number CN202410342868.3, "Carbon dioxide injection development optimization method and system based on non-complete miscibility characteristics", constructs a three-dimensional reservoir model containing fluid and reservoir characteristics, and analyzes the non-complete miscibility characteristics of carbon dioxide injection development based on the model, thereby achieving optimized development of the entire life cycle of carbon dioxide injection.

[0004] In general, there are many methods for injecting carbon dioxide into oil reservoirs. However, in the actual carbon dioxide injection process, due to the heterogeneity of shale oil reservoirs, carbon dioxide gas channeling is prone to occur, affecting the oil recovery effect. These methods have their own limitations. Therefore, it is very important to study a scientific method and system for optimizing the spacing of partitions for compartmentalized carbon dioxide injection in shale oil reservoirs, so as to solve the problem of carbon dioxide gas channeling in the existing technology, improve the recovery rate of shale oil reservoirs, and enhance the overall economic benefits of oil field development. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that unreasonable spacing of partitions for carbon dioxide injection in compartments of shale oil reservoirs leads to carbon dioxide gas channeling and low oil recovery efficiency. The present invention adopts a combination of experimental and theoretical means to build a physical model for carbon dioxide injection and exploitation in compartments, establish an initial state of the physical model for carbon dioxide injection and exploitation in compartments, conduct carbon dioxide injection and oil recovery experiments in compartments, continuously increase the number of partitions, obtain the carbon dioxide oil recovery efficiency under different partition spacings, establish a relationship chart between different partition spacings and carbon dioxide oil recovery efficiency and gas appearance time, and obtain the optimal partition spacing of the physical model for carbon dioxide injection and exploitation in compartments according to the chart. Through the similarity criterion, the optimal partition spacing of carbon dioxide injection in compartments of shale oil reservoirs in actual field production can be determined, and the calculation is convenient and the reliability is strong.

[0006] To achieve the above object, the present invention provides a method and system for optimizing the spacing between partitions for carbon dioxide injection in shale oil reservoir compartments, the method comprising the following steps:

[0007] The first step is to collect reservoir characteristic parameters of shale oil reservoirs, design a physical model for carbon dioxide injection in compartments, and build a physical model for carbon dioxide injection in compartments.

[0008] The second step is to set the temperature of the physical model of carbon dioxide injection for production in compartments to 90°C and the pressure to 50MPa, measure the total porosity of the physical model of carbon dioxide injection for production in compartments, and establish the initial oil saturation of the physical model of carbon dioxide injection for production in compartments, and obtain the total porosity and initial oil saturation of the physical model of carbon dioxide injection for production in compartments;

[0009] The third step is to start from no baffles and add one baffle at a time to obtain the CO2 recovery efficiency at different baffle spacings, and calculate the CO2 recovery efficiency at different baffle spacings;

[0010] The fourth step is to inject carbon dioxide for oil recovery without baffles. After carbon dioxide is injected, it advances rapidly along the area with good physical properties. After adding baffles, carbon dioxide cannot break through the baffles and advances evenly along the compartments between the baffles. A relationship chart of different baffle spacing and carbon dioxide oil recovery efficiency and gas time is established. With the increase of the number of baffles, the baffle spacing is shortened, and the carbon dioxide oil recovery efficiency and gas time gradually increase. When the baffle spacing is ≤l m When the CO2 flooding efficiency increases by less than 2%, the baffle spacing l can be determined. m Optimal bulkhead spacing for carbon dioxide injection in physical model compartments;

[0011] The fifth step is to obtain the optimal baffle spacing of the physical model of CO2 injection under experimental conditions. The optimal baffle spacing of CO2 injection in shale reservoirs in actual field production can be determined through similarity criteria.

[0012] ,

[0013] Among them, l z is the optimal partition spacing for on-site production, in m; l m is the optimal partition spacing of the physical model of carbon dioxide injection for sub-compartment production, in m; L is the length of the physical model of carbon dioxide injection for sub-compartment production, in m; L z It is the length of the on-site production horizontal well, in meters.

[0014] In the above-mentioned method and system for optimizing the spacing between partitions for compartmentalized carbon dioxide injection in shale oil reservoirs, the steps of building a physical model for compartmentalized carbon dioxide injection production are as follows:

[0015] The first step is to arrange horizontal wells of the same length in parallel along the longest side of a rectangular pressure vessel, and vertical partitions are arranged at equal intervals perpendicular to the axis of the horizontal wells, and the compartments between the partitions are independent of each other;

[0016] In the second step, quartz sand is filled around the horizontal well and consolidated after adding adhesive. The amount of adhesive is changed to make the physical model of compartmentalized carbon dioxide injection consistent with the actual shale oil reservoir characteristics.

[0017] In the above-mentioned method and system for optimizing the spacing between partitions for compartmentalized carbon dioxide injection in shale oil reservoirs, the step of obtaining the total porosity and initial oil saturation of the physical model for compartmentalized carbon dioxide injection production is as follows:

[0018] In the first step, the physical model of carbon dioxide injection for production in compartments in the pressure-resistant container is dried and weighed, and formation water is pressurized and injected into the pressure-resistant container to allow the formation water to fully enter the pore volume of the physical model. The physical model of carbon dioxide injection for production in compartments is weighed again, and the total porosity of the physical model of carbon dioxide injection for production in compartments is measured using the difference between the two weights.

[0019] In the second step, the physical model of carbon dioxide injection in compartments of saturated formation water is displaced by crude oil at a constant rate. When no water flows out of the physical model of carbon dioxide injection in compartments, the displacement process is stopped. At this time, the oil saturation is the initial oil saturation.

[0020] In the above-mentioned method and system for optimizing the partition spacing of compartmented carbon dioxide injection in shale oil reservoirs, the steps of calculating different partition spacings and carbon dioxide flooding efficiency are as follows:

[0021] The first step is to continuously increase the number of baffles. The baffles are arranged at equal intervals in the physical model of carbon dioxide injection and mining in the compartments. The calculation model with different baffle spacing can be established as follows:

[0022] ,

[0023] Among them, l i is the spacing between different baffles, in m; L is the length of the physical model of carbon dioxide injection mining in compartments, in m; i is the number of baffles, in pieces;

[0024] The second step is to conduct a carbon dioxide injection oil recovery experiment in compartments through a physical model of carbon dioxide injection in compartments, record the cumulative oil recovery volume and gas-seeking time under different baffle spacing, calculate the carbon dioxide oil recovery efficiency, and establish a calculation model for carbon dioxide oil recovery efficiency.

[0025] ,

[0026] Among them, R o is the CO2 flooding efficiency, unit: %V oiis the cumulative oil displacement of the i-th partition, in m³; B o is the crude oil volume coefficient, in dimensionless units; L is the length of the physical model for carbon dioxide injection in compartments, in m; D is the width of the physical model for carbon dioxide injection in compartments, in m; H is the height of the physical model for carbon dioxide injection in compartments, in m; P is the total porosity of the physical model for carbon dioxide injection in compartments, in %; S oi is the initial oil saturation, in %.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) enhanced flexibility and customization; (2) convenient and effective method with high work efficiency; (3) high reliability and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the attached picture:

[0029] Figure 1 It is the overall technical roadmap of the method;

[0030] Figure 2 This is a graph showing the relationship between different baffle spacing and gas-seeing time;

[0031] Figure 3 This is a graph showing the relationship between different baffle spacing and carbon dioxide flooding efficiency. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the embodiments and accompanying drawings;

[0033] The present invention provides a method and system for optimizing the spacing between partitions for carbon dioxide injection in shale oil reservoir compartments. Figure 1 It is the overall technical roadmap of the method, which includes the following steps:

[0034] The first step is to collect reservoir characteristic parameters of shale oil reservoirs, design a physical model for carbon dioxide injection in compartments, and build a physical model for carbon dioxide injection in compartments.

[0035] The second step is to set the temperature of the physical model of carbon dioxide injection for production in compartments to 90°C and the pressure to 50MPa, measure the total porosity of the physical model of carbon dioxide injection for production in compartments, and establish the initial oil saturation of the physical model of carbon dioxide injection for production in compartments, and obtain the total porosity and initial oil saturation of the physical model of carbon dioxide injection for production in compartments;

[0036] The third step is to start from no baffles and add one baffle at a time to obtain the CO2 recovery efficiency at different baffle spacings, and calculate the CO2 recovery efficiency at different baffle spacings;

[0037] The fourth step is to inject carbon dioxide for oil recovery without baffles. After carbon dioxide is injected, it advances rapidly along the area with good physical properties. After adding baffles, carbon dioxide cannot break through the baffles and advances evenly along the compartments between the baffles. A relationship chart of different baffle spacing and carbon dioxide oil recovery efficiency and gas time is established. With the increase of the number of baffles, the baffle spacing is shortened, and the carbon dioxide oil recovery efficiency and gas time gradually increase. When the baffle spacing is ≤l m When the CO2 flooding efficiency increases by less than 2%, the baffle spacing l can be determined. m Optimal bulkhead spacing for carbon dioxide injection in physical model compartments;

[0038] The fifth step is to obtain the optimal baffle spacing of the physical model of CO2 injection under experimental conditions. The optimal baffle spacing of CO2 injection in shale reservoirs in actual field production can be determined through similarity criteria.

[0039] ,

[0040] Among them, l z is the optimal partition spacing for on-site production, in m; l m is the optimal partition spacing of the physical model of carbon dioxide injection for sub-compartment production, in m; L is the length of the physical model of carbon dioxide injection for sub-compartment production, in m; L z It is the length of the on-site production horizontal well, in meters.

[0041] Furthermore, the steps of building a physical model of carbon dioxide injection production in compartments are:

[0042] The first step is to arrange horizontal wells of the same length in parallel along the longest side of a rectangular pressure vessel, and vertical partitions are arranged at equal intervals perpendicular to the axis of the horizontal wells, and the compartments between the partitions are independent of each other;

[0043] In the second step, quartz sand is filled around the horizontal well and consolidated after adding adhesive. The amount of adhesive is changed to make the physical model of compartmentalized carbon dioxide injection consistent with the actual shale oil reservoir characteristics.

[0044] Furthermore, the step of obtaining the total porosity and initial oil saturation of the physical model of carbon dioxide injection production in compartments is:

[0045] In the first step, the physical model of carbon dioxide injection for production in compartments in the pressure-resistant container is dried and weighed, and formation water is pressurized and injected into the pressure-resistant container to allow the formation water to fully enter the pore volume of the physical model. The physical model of carbon dioxide injection for production in compartments is weighed again, and the total porosity of the physical model of carbon dioxide injection for production in compartments is measured using the difference between the two weights.

[0046] In the second step, the physical model of carbon dioxide injection in compartments of saturated formation water is displaced by crude oil at a constant rate. When no water flows out of the physical model of carbon dioxide injection in compartments, the displacement process is stopped. At this time, the oil saturation is the initial oil saturation.

[0047] Further, the steps to calculate different baffle spacing and CO2 flooding efficiency are as follows:

[0048] The first step is to continuously increase the number of baffles. The baffles are arranged at equal intervals in the physical model of carbon dioxide injection and mining in the compartments. The calculation model with different baffle spacing can be established as follows:

[0049] ,

[0050] Among them, l i is the spacing between different baffles, in m; L is the length of the physical model of carbon dioxide injection mining in compartments, in m; i is the number of baffles, in pieces;

[0051] The second step is to conduct a carbon dioxide injection oil recovery experiment in compartments through a physical model of carbon dioxide injection in compartments, record the cumulative oil recovery volume and gas-seeking time under different baffle spacing, calculate the carbon dioxide oil recovery efficiency, and establish a calculation model for carbon dioxide oil recovery efficiency.

[0052] ,

[0053] Among them, R o is the CO2 flooding efficiency, unit: %V oi is the cumulative oil displacement of the i-th partition, in m³; B o is the crude oil volume coefficient, in dimensionless units; L is the length of the physical model for carbon dioxide injection in compartments, in m; D is the width of the physical model for carbon dioxide injection in compartments, in m; H is the height of the physical model for carbon dioxide injection in compartments, in m; P is the total porosity of the physical model for carbon dioxide injection in compartments, in %; S oi is the initial oil saturation, in %.

[0054] Taking a shale oil reservoir as an example, the reservoir burial depth of the reservoir reaches 4250m, the original reservoir pressure is 50MPa, the formation temperature is maintained at 90℃, the crude oil volume coefficient is 1.21, and the design length of the horizontal well section is 1200m. After obtaining the reservoir characteristic parameters of the shale oil reservoir, a compartment carbon dioxide injection production physical model is built, and its length, width and height are 2×0.5×0.5m. The basic parameters of the compartment carbon dioxide injection production physical model are shown in Table 1. Through the carbon dioxide injection oil recovery experiment, the carbon dioxide oil recovery efficiency and gas time under different baffle spacing are obtained, as shown in Table 2.

[0055] The relationship between different baffle spacing and CO2 flooding efficiency and gas appearance time is established. As the number of baffles increases, the baffle spacing decreases and the gas appearance time gradually increases. Figure 2 As shown in Figure 2, the CO2 flooding efficiency gradually increases and then slows down. Figure 3 As shown in the figure, when the baffle spacing is ≤0.33m, the increase in CO2 recovery efficiency is less than 2%. It can be determined that the optimal baffle spacing for sub-compartment CO2 injection in the physical model is 0.33m. Through the similarity criterion, it can be determined that the optimal baffle spacing for sub-compartment CO2 injection in shale oil reservoirs in actual field production is 198m.

[0056] Table 1 Basic parameters of the physical model for CO2 production by compartment injection

[0057]

[0058] Table 2 CO2 flooding efficiency and gas release time at different baffle spacings

[0059]

[0060] Compared with the prior art, the present invention has the following beneficial effects: (1) enhanced flexibility and customization; (2) convenient and effective method with high work efficiency; (3) high reliability and stability.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method and system for optimizing the spacing between partitions for carbon dioxide injection in shale oil reservoir compartments, characterized in that: The method comprises the following steps: S100, collecting reservoir characteristic parameters of shale oil reservoirs, designing a physical model for carbon dioxide injection production by compartments, and the steps of building the physical model for carbon dioxide injection production by compartments are as follows: S101, in a rectangular pressure vessel, horizontal wells of the same length are arranged in parallel along the longest side, vertical partitions are arranged perpendicular to the axis of the horizontal wells at equal intervals, and the compartments between the partitions are independent of each other; S102, quartz sand is filled around the horizontal well and consolidated after adding adhesive. The amount of adhesive is changed to make the physical model of CO2 injection in compartments consistent with the reservoir characteristics of the real shale oil reservoir; S200, setting the temperature of the physical model for carbon dioxide injection for production in compartments to 90°C and the pressure to 50MPa, measuring the total porosity of the physical model for carbon dioxide injection for production in compartments, and establishing the initial oil saturation of the physical model for carbon dioxide injection for production in compartments, the steps of obtaining the total porosity and initial oil saturation of the physical model for carbon dioxide injection for production in compartments are, S201, drying and weighing the physical model for carbon dioxide injection in the pressure container, injecting formation water into the pressure container under pressure to allow the formation water to fully enter the pore volume of the physical model, weighing the physical model for carbon dioxide injection in the compartments again, and measuring the total porosity of the physical model for carbon dioxide injection in the compartments using the difference between the two weights; S202, using crude oil constant rate displacement for the physical model of carbon dioxide injection in compartments for saturated formation water, and stopping the displacement process when no water flows out of the physical model of carbon dioxide injection in compartments, and the oil saturation at this time is the initial oil saturation; S300, starting from no baffle, adding one baffle at a time, and obtaining the carbon dioxide recovery efficiency at different baffle spacings. The steps for calculating different baffle spacings and carbon dioxide recovery efficiency are as follows: S301, continuously increase the number of baffles, and arrange the baffles at equal intervals in the physical model of carbon dioxide injection and mining in the compartments. The calculation model of different baffle spacings can be established as follows: ， Among them, l i is the spacing between different baffles, in m; L is the length of the physical model of carbon dioxide injection mining in compartments, in m; i is the number of baffles, in pieces; S302, through the physical model of carbon dioxide injection in compartments, a carbon dioxide injection oil recovery experiment is carried out, the cumulative oil recovery volume and gas-seeping time under different baffle spacing are recorded, and the carbon dioxide oil recovery efficiency is calculated at the same time, and a calculation model for the carbon dioxide oil recovery efficiency is established. ， Among them, R o is the CO2 flooding efficiency, unit is %; V oi is the cumulative oil displacement of the i-th partition, in m³; B o is the crude oil volume coefficient, in dimensionless units; L is the length of the physical model for carbon dioxide injection in compartments, in m; D is the width of the physical model for carbon dioxide injection in compartments, in m; H is the height of the physical model for carbon dioxide injection in compartments, in m; P is the total porosity of the physical model for carbon dioxide injection in compartments, in %; S oi is the initial oil saturation, unit is %; S400, CO2 flooding without baffles. After CO2 is injected, it advances rapidly along the area with good physical properties. After adding baffles, CO2 cannot break through the baffles and advances evenly along the compartments between the baffles. A relationship chart of different baffle spacings and CO2 flooding efficiency and gasification time is established. With the increase of the number of baffles, the baffle spacing is shortened, and the CO2 flooding efficiency and gasification time gradually increase. When the baffle spacing is ≤l m When the CO2 flooding efficiency increases by less than 2%, the baffle spacing l can be determined. m Optimal bulkhead spacing for carbon dioxide injection in physical model compartments; S500, under experimental conditions, obtains the optimal baffle spacing of the physical model of CO2 injection in compartments. Through similarity criteria, it can determine the optimal baffle spacing of CO2 injection in shale reservoirs in actual field production. ， Among them, l z is the optimal partition spacing for on-site production, in m; l m is the optimal partition spacing of the physical model of carbon dioxide injection for sub-compartment production, in m; L is the length of the physical model of carbon dioxide injection for sub-compartment production, in m; L z It is the length of the on-site production horizontal well, in meters.

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