Method, system and equipment for determining change characteristics of skin coefficient of water-drive reservoir

Abstract

The invention discloses a method, a system and equipment for determining the change characteristics of the skin coefficient of a water-drive reservoir, and the method comprises the steps: determining the flowing characteristics of reservoir fluid according to the relation among reservoir formation pressure, bottom hole flow pressure and yield, and determining Darcy flow according to the characteristics; based on the production materials meeting the Darcy flow, the bottom hole flowing pressure at the same reference depth at different times is calculated; calculating productivity data of the production well in different time periods after conversion; according to the oil reservoir parameters and the maximum and minimum values of the actual single well skin coefficient, the skin coefficient is calibrated in a preset range, and the relation between the skin coefficient of the target oil reservoir production well and the yield is obtained; and the productivity data and the pressure data of different production stages are projected into the skin coefficient and yield relation chart of the target oil reservoir, so that the change relation of the skin coefficient of the oil reservoir along with time is obtained. The problem of determining the skin coefficient change characteristics of the near wellbore zone of the production well in the oil reservoir water drive process is solved, and support is provided for oil reservoir dynamic analysis and productivity prediction.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and particularly to a method, system and device for determining the variation characteristics of the skin factor in a waterflood reservoir. Background Art

[0002] During the oilfield development process, the skin factor (S) is a key parameter that reflects the resistance of the formation near the wellhead to fluid flow. The change of this factor directly affects the productivity performance of the oil well. When injecting water to develop an oilfield, due to the action of the injected water, the skin factor near the production well will change with time, and this change has a significant impact on the productivity of a single well.

[0003] In the dynamic analysis of an oilfield, the prior art considers the influence of the skin factor on productivity by calculation. Specifically, the skin factor S of an oil well is usually expressed as the natural logarithm of the wellhead radius (r w ) divided by the reduced radius (r c ), that is, S = L n (r w / r c ). This formula shows that when the wellhead radius is equal to the reduced radius, the skin factor S is zero, meaning the oil well is perfect; when the wellhead radius is less than the reduced radius, the value of S is negative, indicating that the oil well is super-perfect; and when the wellhead radius is greater than the reduced radius, the value of S is positive, indicating that the oil well is imperfect.

[0004] Generally, the skin factor can be obtained through the pressure buildup curve, and the additional flow resistance generated by the skin is calculated by combining the slope of the pressure buildup curve. However, currently, for different reservoir types and well types, although there are various methods for calculating the skin factor, the results obtained by these methods are all static data. In reservoir monitoring, there has not yet been an effective method to track and analyze the change of the skin factor over time and predict the trend of this change. Therefore, a method for determining the variation characteristics of the skin factor in a waterflood reservoir is needed to obtain the variation law. Summary of the Invention

[0005] Embodiments of the present invention provide a method, system and device for determining the variation characteristics of the skin factor in a waterflood reservoir, which at least partially solve the technical problem that the monitoring of the reservoir in the prior art cannot track and analyze the change of the skin factor over time, and achieve the technical effect of accurately obtaining the variation law of the skin factor of the reservoir over time.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention discloses a method for determining the variation characteristics of the skin factor in a waterflood reservoir, including:

[0008] According to the relationship between reservoir formation pressure, bottom hole flowing pressure and production, the flow characteristics of reservoir fluid are determined based on the non-Darcy flow formula, and Darcy flow is determined based on the above characteristics;

[0009] Based on the production data that meets Darcy flow, calculate the bottom hole flowing pressure of the same production well at the same reference depth at different times;

[0010] Based on the converted bottom hole flowing pressure and production data, calculate the production capacity data of the production well in different time periods, and draw the change graphs of production capacity and pressure over time;

[0011] According to the reservoir parameters and the maximum value of the skin coefficient of the actual single well, the skin coefficient is calibrated within the preset range, and the relationship between the skin coefficient and the production of the target reservoir production well is obtained;

[0012] The production capacity data and pressure data of different production stages are projected onto the skin coefficient and production relationship chart of the target oil reservoir to obtain the relationship between the skin coefficient of the oil reservoir and time.

[0013] Optionally, the above non-Darcy flow formula includes:

[0014]

[0015] Among them, the above p r is the reservoir pressure, p wf is the bottom hole flowing pressure, q is the production rate, C and D are constants related to the flow characteristics.

[0016] Optionally, the step of calculating the bottom hole flowing pressure of the same production well converted to the same reference depth at different times specifically includes:

[0017] Select a reference depth as the basis for conversion;

[0018] Calculate the pressure gradient at different time points based on reservoir formation pressure and bottom hole flowing pressure data;

[0019] According to the pressure gradient and well depth information, the bottom hole flowing pressure at different time points is converted to the same reference depth;

[0020] Process the conversion results and organize them into tables or charts for easy analysis and comparison.

[0021] Optionally, the step of calculating the production capacity data of the production well in different time periods specifically includes:

[0022] The single-point method is used to calculate the production capacity data of production wells in different time periods.

[0023] Optionally, the step of obtaining the relationship between the skin coefficient and production of the target oil reservoir production well specifically includes:

[0024] Based on the above production data, obtain the productivity corresponding to different skin factors according to a preset formula, and plot the graph of the skin factor and production rate of the production wells in the target reservoir above to obtain the relationship between the skin factor and production rate of the production wells in the target reservoir above.

[0025] Optionally, the above preset formula includes:

[0026] Qw = J(p r -p wf )

[0027]

[0028] where Qw is the production rate, J is the productivity, p r is the reservoir pressure, p wf is the bottom-hole flowing pressure, k is the permeability, h is the effective thickness of the reservoir, r e is the control radius of the oil well, μ w is the fluid viscosity, B w is the volume coefficient of the fluid, r w is the wellbore radius, and s is the skin factor.

[0029] Optionally, before obtaining the relationship between the skin factor of the reservoir and time, it further includes:

[0030] Merge the graph of productivity change with time and the graph of pressure change with time according to actual requirements.

[0031] In a second aspect, the present invention discloses a system for determining the change characteristics of the skin factor of a waterflooded reservoir, including:

[0032] A Darcy flow judgment module, configured to determine the flow characteristics of the reservoir fluid based on the non-Darcy flow formula according to the relationship between the reservoir formation pressure, the bottom-hole flowing pressure and the production rate, and determine Darcy flow according to the above characteristics;

[0033] A conversion module, configured to calculate the bottom-hole flowing pressure of the same production well at the same reference depth at different times according to the production data satisfying Darcy flow;

[0034] A productivity data calculation module, based on the converted bottom-hole flowing pressure and production data, calculates the productivity data of the production well at different time periods, and respectively plots the graphs of productivity and pressure changing with time;

[0035] A skin factor acquisition module, configured to calibrate the skin factor within a preset range according to the reservoir parameters and the maximum and minimum values of the actual single-well skin factor, and obtain the relationship between the skin factor and production rate of the production wells in the target reservoir;

[0036] A variation relationship acquisition module is used to project the productivity data and pressure data at different production stages onto the skin factor and production relationship chart of the above-mentioned target reservoir, so as to obtain the variation relationship of the reservoir skin factor over time.

[0037] In a third aspect, the present invention discloses an electronic device, including a memory, a processor, and a computer program stored on the above-mentioned memory and executable on the above-mentioned processor. When the above-mentioned processor executes the above-mentioned computer program, the steps corresponding to the method in the first aspect are implemented.

[0038] In a fourth aspect, the present invention discloses a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the steps corresponding to the method in the first aspect are implemented.

[0039] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0040] In the technical solution of the present invention, the non-Darcy flow formula is used to determine the flow characteristics of reservoir fluids, and the production data that satisfies Darcy flow is used for analysis. During the analysis, the bottom-hole flowing pressure of the same production well at different times converted to the same reference depth is calculated, so as to avoid the pressures measured at different times not being the pressures at the same depth. Then, the productivity data of the production well in different time periods are calculated, and the variation diagrams of productivity and pressure over time are respectively drawn, so as to obtain the variation law of the skin factor rather than a static value. By giving a skin change range, the characteristics of the skin factor in the near-well zone of the reservoir can be intuitively judged by the position of the actual data on the graph. Finally, the productivity data and pressure data at different production stages are projected onto the skin factor and production relationship chart of the target reservoir to obtain the variation relationship of the reservoir skin factor over time. Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0042] Figure 1 It is a flow chart of a method for determining the variation characteristics of the skin factor of a waterflooded reservoir provided by the present invention;

[0043] Figure 2 It is a comparison schematic diagram of actual production dynamic data and relational expressions in the present invention;

[0044] Figure 3 It is a skin factor and production relationship chart of a production well in a target reservoir in the present invention;

[0045] Figure 4 This is a schematic diagram in the relationship chart of skin factor and production rate projected onto the target reservoir in the present invention;

[0046] Figure 5 This is a schematic structural diagram of a system for determining the variation characteristics of skin factor in a water - flooded reservoir provided by the present invention. Detailed implementation manners

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0048] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0049] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0050] It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solutions of this application, rather than limitations on the technical solutions of this application. Without conflict, the technical features in the embodiments of this application and the embodiments can be combined with each other.

[0051] In the embodiments of the present invention, there is provided a method for determining the variation characteristics of the skin factor in a water - flooded reservoir as shown in Figure 1 Figure [not shown], and the method includes steps S101 to S105:

[0052] Step S101: Based on the relationship between the formation pressure of the reservoir, the bottom - hole flowing pressure, and the production rate, and based on the non - Darcy flow formula, determine the flow characteristics of the reservoir fluid, and determine the Darcy flow according to the characteristics;

[0053] It should be noted that Darcy flow is selected to determine the variation law of the reservoir skin factor with time, rather than non-Darcy flow, mainly for the following reasons: 1. Darcy flow is an idealized model of fluid flow in porous media and is suitable for describing the flow behavior of oil in the reservoir. In reservoir engineering, Darcy flow is considered an effective model for describing the fluid flow in the reservoir. 2. Non-Darcy flow involves more complex fluid flow and may be affected by various factors such as pressure gradient, temperature, and fluid properties. In contrast, the assumptions of Darcy flow are relatively simple and can better reflect the basic flow characteristics of the reservoir. 3. By studying the Darcy flow model, it is more convenient to analyze the variation law of the skin factor and further understand the dynamic characteristics and development effects of the reservoir.

[0054] Therefore, in this embodiment, based on the relationship between the reservoir formation pressure, bottom-hole flowing pressure, and production rate, and based on the non-Darcy flow formula, the fluid flow characteristics of the reservoir are determined. Specifically, when the flow rate reaches a certain level, the seepage becomes non-Darcy flow, satisfying formula (1), and the pressure is proportional to the square of the production rate.

[0055]

[0056] For whether it is non-Darcy flow, its determination needs to be based on There is a linear relationship with q. According to formula (2), the curve of the actual production dynamics is plotted and compared with the relational expression to clarify whether it is non-Darcy flow. The actual production dynamics are as Figure 2 shown.

[0057]

[0058] Among them, p r is the reservoir pressure, p wf is the bottom-hole flowing pressure, q is the production rate, and C and D are constants related to the flow characteristics respectively.

[0059] Step S102: Calculate the bottom-hole flowing pressure of the same production well at different times converted to the same reference depth according to the production data that satisfies Darcy flow;

[0060] It should be noted that the reason for unifying the bottom-hole flowing pressure is that when using an electric submersible pump well for development, the position of the electric submersible pump will change, resulting in the pressures measured at different times not being the pressures at the same depth. Therefore, the reference depth can be any depth corresponding to a bottom-hole pressure test.

[0061] Specifically, a reference depth is selected as the conversion benchmark. Among them, the reference depth can be any depth corresponding to a bottom-hole pressure test.

[0062] Based on the reservoir formation pressure and bottom-hole flowing pressure data, calculate the pressure gradient at different time points. Among them, the pressure gradient refers to the pressure change value per unit depth and can be expressed by the following formula (3):

[0063]

[0064] Among them, is the pressure gradient, that is, the partial derivative of pressure with respect to depth, which describes the rate of change of pressure with depth (or distance); rho is the density, representing the ratio of the mass of a substance to its volume; g is the acceleration due to gravity; T is the temperature; C and K are constants.

[0065] According to the pressure gradient and well depth information, convert the bottom-hole flowing pressure at different time points to the same reference depth. The conversion formula is as follows:

[0066]

[0067] Among them, Pb is the converted bottom-hole flowing pressure, P1 is the initial bottom-hole flowing pressure, h1 is the depth before conversion, and h2 is the reference depth.

[0068] Finally, process the conversion results and organize them into a table or chart form for easy analysis and comparison.

[0069] Step S103, based on the converted bottom-hole flowing pressure and production data, calculate the productivity data of the production well in different time periods, and respectively draw the graphs of productivity and pressure changing with time.

[0070] Specifically, use the single-point method to calculate the productivity data of the production well in different time periods. That is, divide the production well output at a certain moment by the production pressure difference at this time to obtain the productivity. The specific formula is as follows:

[0071] J = Q / (p r - p wf ) (5)

[0072] Among them, J is the productivity, p r is the reservoir pressure, and p wf is the bottom-hole flowing pressure.

[0073] Step S104, according to the reservoir parameters and the maximum and minimum values of the actual single-well skin factor, calibrate the skin factor within the preset range and obtain the relationship between the skin factor and the production of the target reservoir production well. Among them, the reservoir parameters include reservoir permeability, reservoir thickness, fluid viscosity, volume coefficient, reservoir and wellbore radius, and reservoir average pressure and other parameters. According to the maximum and minimum values of the actual single-well skin factor in the reservoir, calibrate the skin factor within a reasonable range, and according to formulas (6) and (7), complete the calculation table of the single-well skin range, and draw the relationship chart of the skin factor and the production of the target reservoir production well based on the table. Formulas (6) and (7) are as follows:

[0074] Qw = J(p r -p wf ) (6)

[0075]

[0076] where Qw is the production rate, J is the production capacity, p r is the reservoir pressure, p wf is the bottom-hole flowing pressure, k is the permeability, h is the effective thickness of the reservoir, r e is the control radius of the oil well, μ w is the fluid viscosity, B w is the formation volume factor of the fluid, r w is the wellbore radius, and s is the skin factor.

[0077] For example, based on the data of the calibrated skin factor range of 20 - 75 calculated according to the above formulas (1) - (7), the relationship between the skin factor and the production rate of the production wells in the target reservoir is obtained as shown in Table 1 below.

[0078]

[0079] Table 1

[0080] Based on this table, the relationship chart of the skin factor and the production rate of this well is completed as Figure 3 shown.

[0081] Step S105: Project the production capacity data and pressure data at different production stages onto the relationship chart of the skin factor and the production rate of the target reservoir to obtain the variation relationship of the reservoir skin factor with time.

[0082] Specifically, based on the production data, the production capacity corresponding to different skin factors is obtained according to the preset formula, and the relationship chart of the skin factor and the production rate of the production wells in the target reservoir is drawn to obtain the relationship between the skin factor and the production rate of the production wells in the target reservoir. That is, the data in Table 1 is projected onto the relationship chart of the skin factor and the production rate of the target reservoir, and the characteristic prediction is completed in combination with the variation chart of pressure with time. In this embodiment, the skin factors at three time stages are tested, and the variation characteristics of the skin factor can be intuitively seen from the chart obtained by calculation, as Figure 4 shown.

[0083] Furthermore, before obtaining the variation relationship of the reservoir skin factor with time, it further includes: combining the variation chart of production capacity with time and the variation chart of pressure with time according to actual requirements. This step aims to integrate multiple data into one variation chart, making it more convenient for analysis and observation.

[0084] Based on the same inventive concept, a system for determining the variation characteristics of the skin factor in a waterflood reservoir as Figure 5 shown is provided, including:

[0085] The Darcy flow judgment module 201 is configured to determine the flow characteristics of reservoir fluids based on the non-Darcy flow formula according to the relationship between reservoir formation pressure, bottom-hole flowing pressure, and production rate, and determine Darcy flow according to the characteristics;

[0086] The conversion module 202 is configured to calculate the bottom-hole flowing pressure of the same production well at the same reference depth at different times according to the production data that satisfies Darcy flow;

[0087] The productivity data calculation module 203 calculates the productivity data of the production well at different time periods based on the converted bottom-hole flowing pressure and production data, and respectively draws the graphs of productivity and pressure changing with time;

[0088] The skin factor acquisition module 204 is configured to calibrate the skin factor within a preset range according to the reservoir parameters and the maximum and minimum values of the actual single-well skin factor, and obtain the relationship between the skin factor and production rate of the production wells in the target reservoir;

[0089] The variation relationship acquisition module 205 is configured to project the productivity data and pressure data at different production stages onto the graph of the relationship between the skin factor and production rate of the target reservoir to obtain the variation relationship of the reservoir skin factor with time.

[0090] Based on the same inventive concept, an embodiment of the present invention provides an electronic device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, a method for determining the variation characteristics of the skin factor of a waterflooded reservoir is implemented.

[0091] Based on the same inventive concept, an embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored. The program is characterized in that when it is executed by a processor, a method for determining the variation characteristics of the skin factor of a waterflooded reservoir is implemented.

[0092] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the specified functions in one Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0093] Although the preferred embodiments of the present invention have been described, additional changes and modifications can be made by those skilled in the art once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention.

[0094] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for determining the variation characteristics of the skin factor in a water - drive reservoir, characterized in that, The method includes: Based on the relationship between the reservoir formation pressure, bottom-hole flowing pressure and production rate, and based on the non-Darcy flow formula, determine the flow characteristics of the reservoir fluid, and determine the Darcy flow according to the characteristics; According to the production data that satisfies Darcy flow, calculate the bottom-hole flowing pressure of the same production well at different times converted to the same reference depth; Based on the converted bottom-hole flowing pressure and production data, calculate the productivity data of the production well in different time periods, and respectively draw the graphs of productivity and pressure changing with time; According to the reservoir parameters and the maximum and minimum values of the actual single-well skin factor, calibrate the skin factor within a preset range, and obtain the relationship between the skin factor and production rate of the production wells in the target reservoir; Project the productivity data and pressure data in different production stages onto the relationship chart of the skin factor and production rate of the target reservoir to obtain the changing relationship of the reservoir skin factor with time.

2. The method according to claim 1, wherein The non-Darcy flow formula includes: wherein, the p r is the reservoir pressure, p wf is the bottom-hole flowing pressure, q is the production rate, and C and D are constants related to the flow characteristics respectively.

3. The method according to claim 1, wherein The step of calculating the bottom-hole flowing pressure of the same production well at different times converted to the same reference depth specifically includes: Select a reference depth as the benchmark for conversion; According to the reservoir formation pressure and bottom-hole flowing pressure data, calculate the pressure gradients at different time points; According to the pressure gradients and well depth information, convert the bottom-hole flowing pressures at different time points to the same reference depth; Process the conversion results and organize them in the form of tables or charts for easy analysis and comparison.

4. The method according to claim 1, characterized in that The step of calculating the productivity data of the production well in different time periods specifically includes: Use the single-point method to calculate the productivity data of the production well in different time periods.

5. The method according to claim 1, characterized in that The step of obtaining the relationship between the skin factor and production rate of the production wells in the target reservoir specifically includes: Based on the production data, obtain the productivity corresponding to different skin factors according to a preset formula, and draw the chart of the skin factor and production rate of the production wells in the target reservoir to obtain the relationship between the skin factor and production rate of the production wells in the target reservoir.

6. The method according to claim 5, wherein The preset formula includes: Qw = J(p r -p wf ) Among them, Qw is the production rate, J is the production capacity, p r is the reservoir pressure, p wf is the bottom-hole flowing pressure, k is the permeability, h is the effective reservoir thickness, r e is the well control radius, μ w is the fluid viscosity, B w is the volume coefficient of the fluid, r w is the wellbore radius, and s is the skin factor.

7. The method according to any one of claims 1 to 6, characterized in that, Before obtaining the changing relationship of the reservoir skin factor with time, it further includes: Merge the graph of productivity changing with time and the graph of pressure changing with time according to actual requirements.

8. A system for determining the variation characteristics of skin factor in a waterflooded reservoir, characterized in that, The system includes: A Darcy flow judgment module, which is used to determine the flow characteristics of the reservoir fluid based on the relationship between the reservoir formation pressure, bottom-hole flowing pressure and production rate, and based on the non-Darcy flow formula, and determine the Darcy flow according to the characteristics; A conversion module, which is used to calculate the bottom-hole flowing pressure of the same production well at different times converted to the same reference depth according to the production data that satisfies Darcy flow; A productivity data calculation module, which calculates the productivity data of the production well in different time periods based on the converted bottom-hole flowing pressure and production data, and respectively draws the graphs of productivity and pressure changing with time; A skin factor acquisition module, which is used to calibrate the skin factor within a preset range according to the reservoir parameters and the maximum and minimum values of the actual single-well skin factor, and obtain the relationship between the skin factor and production rate of the production wells in the target reservoir; A changing relationship acquisition module, which is used to project the productivity data and pressure data in different production stages onto the relationship chart of the skin factor and production rate of the target reservoir to obtain the changing relationship of the reservoir skin factor with time.

9. An electronic device, characterized in that, The electronic device includes: a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method steps described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, the steps corresponding to the method described in any one of claims 1 to 7 are implemented.

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