A method for evaluating reasonable well spacing for shale gas development based on post-fracture fracture network distribution

Abstract

This application provides a method for evaluating reasonable shale gas development well spacing based on post-pressure fracture network distribution, including: conducting analysis and evaluation of the post-pressure fracture network extension of gas wells at test well spacing; constructing a hydraulic fracture model; optimizing fracture network parameters; using non-normalized blocks to evaluate the reformed half-fracture length and reservoir reformed volume parameters within the work area, and clarifying the scope of gas well reform within the work area; determining the three-dimensional morphology of the post-pressure fracture network, and clarifying the extension of inter-well fractures within the work area; clarifying whether there is communication between the post-pressure fracture networks of test wells at small well spacing; clarifying the economic limit well spacing within the work area; using the economic evaluation well spacing as the lower limit and the post-pressure simulated fracture length as the upper limit, combining numerical simulation, unstable production analysis, small well spacing test, and interference well test results, to obtain reasonable development well spacing data results for the block. This method can clarify reasonable development well spacing and achieve economic and efficient shale gas development.

Description

Technical Field

[0001] The present application relates to the field of shale gas development, and in particular to a method for evaluating reasonable shale gas development well spacing based on post-compression fracture network distribution. Background Art

[0002] my country boasts abundant shale gas resources, with recoverable reserves estimated at 25 trillion cubic meters, representing enormous potential for development. However, domestic shale gas development is just beginning. Due to differences in geological conditions, development technologies, and policies, there are no successful experiences to draw upon. Therefore, it is imperative to establish applicable theories and technical approaches to effectively develop shale gas.

[0003] However, determining the optimal well spacing for shale gas development is a complex process. If the well spacing is too large, some areas between horizontal wells cannot be effectively fractured, and reserves cannot be fully utilized, resulting in a waste of resources. If the well spacing is too small, there may be increased investment, severe interference between wells, and overlapping gas supply radii, which affects the efficiency of gas field development. While the development model adopted abroad, which initially produces with large well spacing and then intensifies the well network later, can reduce the risks associated with shale gas development, the production of intensified wells that come into production later is generally lower than that of the parent wells, reducing the overall effectiveness of shale gas development. Therefore, clarifying the optimal well spacing for shale gas horizontal well development is crucial to maximizing the effectiveness of volume fracturing on formation transformation. Summary of the Invention

[0004] This application provides a method for evaluating reasonable shale gas development well spacing based on post-fracture fracture network distribution, aiming to solve the problem of low development efficiency caused by insufficient shale gas reserves.

[0005] The technical solution of this application is:

[0006] A method for evaluating reasonable well spacing for shale gas development based on post-fracture fracture network distribution includes the following steps:

[0007] S1: Obtain the statistical results of microseismic monitoring of the test well group in the work area, and conduct analysis and evaluation of the fracture network extension of the gas well after pressure reduction at the test well spacing;

[0008] S2, using numerical simulation software to import the gas well fracturing drilling and completion parameters, production performance data, and related attribute parameters in the work area to construct a hydraulic fracture model; randomly generate an activated natural fracture grid based on the imported microseismic geometry data to form an interactive fracture system, and further optimize the post-fracture fracture network parameters based on the historical fitting results of the production performance data in the work area;

[0009] S3, based on the production status of the gas wells in the work area, perform a dynamic analysis of the gas well production using an unstable production analysis method, combine the production stage division and flow pattern analysis of the gas wells, and use a non-normal scale block to evaluate the stimulated half-fracture length and reservoir stimulated volume parameters in the work area to determine the scope of gas well stimulation in the work area;

[0010] S4, using a discrete fracture network simulation method to simulate and analyze the post-fracturing fracture network, inputting fracturing fluid properties, support properties, and pumping procedures, determining the three-dimensional shape of the post-fracturing fracture network, and clarifying the extension of interwell fractures in the work area;

[0011] S5, analyzing the well-to-well interference of the small-well-spacing test in the work area, tracking the pressure changes of the interference test wells in the work area, comparing the pressure, gas production, and water production changes of the test wells during the production test to analyze the well-to-well interference, and determining whether there is communication between the fracture networks after pressure-pressurization of the test wells under the small-well-spacing condition; if there is communication, it indicates that there is overlap between the fractures in the fracture networks after pressure-pressurization, that is, there is overlap in the gas supply range, the well spacing of the test wells under the small-well-spacing condition is too small, and the reasonable development well spacing should be greater than the test well spacing;

[0012] S6. Determine the economic limit of the well spacing for a single well in the block. Establish a gas well production decline model within the work area using an unstable production analysis method. Comprehensively consider parameters such as single well investment, production, gas prices, national financial subsidies, and operating costs. Establish a correlation chart between gas well investment and well spacing, a correlation chart between internal rate of return and well spacing, and a correlation chart between recovery factor and well spacing. Clearly, the value of recoverable reserves controlled by a single well is equal to the well spacing at the time of drilling and production test investment.

[0013] S7, based on the data obtained in step S2, step S3, step S4, step S5 and step S6, with the economic evaluation well spacing as the lower limit and the simulated fracture length after fracturing as the upper limit, combined with the results of numerical simulation, unstable production analysis, small well spacing test and interference well test, further narrow the range of well spacing values to obtain the data results of reasonable development well spacing for the block.

[0014] As a technical solution of the present application, in step S2, the monitoring statistical data of the gas well fracturing microseismic data includes the length, width, height and orientation of the fracturing cracks.

[0015] As a technical solution of the present application, in step S2, the drilling and completion parameters include wellhead coordinates, inclined depth, vertical depth, well inclination, azimuth, fracturing stage, number of clusters, sand addition amount and liquid addition amount; the production dynamic data includes gas well gas production, pressure and water production; the related attribute parameters include porosity, gas saturation, rock physical parameters, permeability and adsorption and desorption parameters.

[0016] As a technical solution of the present application, in step S3, the gas well production stage and flow state analysis includes the division of fracture linear flow, formation and fracturing fracture dual linear flow, formation to fracture linear flow, transition flow, peripheral linear flow and boundary flow.

[0017] As a technical solution of the present application, in step S4, the post-compression fracture network simulation analysis simulates the extension of artificial fractures, the interweaving of artificial and natural fractures, and the process of fracture network formation based on discrete fracture networks, finite elements, extended finite elements, and boundary elements.

[0018] As a technical solution of the present application, in step S5, the close-well spacing test involves selecting a test well group with a spacing smaller than the designed well spacing and conducting an interference well test and an interference dynamic analysis test. The interference dynamic analysis test includes the interference of the test well's fracturing on the production performance of adjacent wells, and whether the production performance of the test well after production is put into production remains consistent with that of the adjacent wells or affects each other.

[0019] As a technical solution of the present application, in step S7, the reasonable development well spacing of the block is determined after comprehensive consideration of numerical simulation, unstable production analysis, well-to-well interference analysis, and economic evaluation methods.

[0020] Beneficial effects of this application:

[0021] This application provides a method for evaluating reasonable shale gas development well spacing based on post-fracture distribution. It identifies the extension of artificial fractures and the coupling of artificial and natural fractures, clarifies the appropriate well spacing for shale gas horizontal wells, and guides the preparation of shale gas development plans and the deployment of development wells. This method fully utilizes the inter-well stimulation volume and avoids excessive overlap in gas supply ranges between wells, saving drilling and fracturing investment, significantly improving block reserve utilization and gas field development efficiency, and providing a reference for determining appropriate well spacing in shale blocks. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the implementation methods of the present application, the following is a brief introduction to the drawings required for use in the implementation methods. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A flowchart of a method for evaluating reasonable shale gas development well spacing based on post-fracture network distribution provided in an embodiment of the present application;

[0024] Figure 2 This is a chart showing the correlation between the gas well recovery rate, internal rate of return and economic limit well spacing of the test well group in the work area provided in the embodiment of the present application. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without making any creative efforts shall fall within the scope of protection of the present application.

[0027] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0028] In the description of this application, it should be noted that the terms "upper" and "lower" etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the invented product is usually placed when in use. These are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0029] In addition, in this application, unless otherwise expressly specified or limited, the phrase "a first feature is above or below a second feature" may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, the phrases "above, above, and above the second feature" may include the first feature being directly above and obliquely above the second feature, or simply indicate that the first feature is higher in level than the second feature. The phrases "below, below, and below the second feature" may include the first feature being directly below and obliquely below the second feature, or simply indicate that the first feature is lower in level than the second feature.

[0030] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0031] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0032] Example:

[0033] Please refer to Figure 1 , with reference Figure 2 The present invention provides a method for geosteering a shale gas well in a middle gas layer, comprising the following steps:

[0034] S1. Obtain statistical results of microseismic monitoring of the test well group within the work area, including parameters such as segmented fracture length, fracture height, and fracture width, and conduct analysis and evaluation of fracture network extension after gas well pressure reduction at the test well spacing;

[0035] S2. Using numerical simulation software to import the hydraulic fracturing drilling and completion parameters, production performance data, and related attribute parameters of the gas wells in the work area, a hydraulic fracture model is constructed. Based on the imported microseismic geometry data, an activated natural fracture grid is randomly generated to form an interactive fracture system. Based on this, the fracture network parameters are further optimized based on the historical fitting results of the production performance data.

[0036] S3. Based on the gas well production situation, conduct a dynamic analysis of gas well production using the unstable production analysis method. Combined with the gas well production stage division and flow pattern analysis, use a non-standard scale to evaluate parameters such as the stimulated half-fracture length and reservoir stimulation volume to determine the gas well stimulation scope.

[0037] S4. Use the discrete fracture network (DFN) simulation method to simulate and analyze the fracture network after fracturing. Input the fracturing fluid properties, support and performance, and pumping program to determine the three-dimensional morphology of the fracture network after fracturing and clarify the extension of interwell fractures.

[0038] S5. Analyze the inter-well interference during the small-well-spacing test, track changes in the interference test well pressure, and compare changes in pressure, gas production, and water production during the test production of the test wells to analyze the inter-well interference. Determine whether there is communication between the fracture networks after pressure-pressurization in the small-well-spacing test wells. If there is communication, it indicates that there is overlap between the fractures in the pressure-pressurized fracture network, that is, there is overlap in the gas supply range. The well spacing in the small-well-spacing test wells is too small, and the reasonable development well spacing should be greater than the test well spacing.

[0039] S6. Determine the economic limit of well spacing for a single well in the block. Establish a production decline model for gas wells within the work area using an unstable production analysis method. Comprehensively consider parameters such as single well investment, production, gas prices, national financial subsidies, and operating costs. Develop correlation charts for gas well investment and well spacing, internal rate of return and well spacing, and recovery factor and well spacing. This ensures that the value of recoverable reserves controlled by a single well is equal to the well spacing at the time of the drilling and production test investment.

[0040] S7. Based on the data obtained in steps S2, S3, S4, S5, and S6, with the economic evaluation well spacing as the lower limit and the simulated fracture length after fracturing as the upper limit, the well spacing range is further narrowed by fully combining the results of numerical simulation, unstable production analysis, small well spacing test, and interference well test to obtain a reasonable development well spacing for the block and realize efficient utilization of the block.

[0041] It should be noted that in step S2, the statistical data of microseismic monitoring of gas wells include the length, width, height and orientation of the fracturing cracks, that is, the extension width of the fracturing cracks perpendicular to the wellbore direction in the plane, the extension height of the fracturing cracks perpendicular to the wellbore direction in the cross section, and the extension length along the wellbore direction.

[0042] At the same time, it should be noted that in step S2, the drilling and completion parameters include wellhead coordinates, inclined depth, vertical depth, well inclination, azimuth, fracturing stage, number of clusters, sand addition amount, liquid addition amount, etc., production dynamic data include gas well gas production, pressure, water production, etc., and related attribute parameters include porosity, gas saturation, rock physical parameters, permeability, adsorption and desorption parameters, etc.

[0043] In addition, in step S3, the production stage and flow pattern analysis includes the division of flow stages such as fracture linear flow, formation and hydraulic fracture dual linear flow, formation to fracture linear flow, transition flow, peripheral linear flow, and boundary flow.

[0044] It should be noted that in step S4, the post-fracture simulation fracture network analysis method is mainly based on discrete fracture network, finite element, extended finite element, boundary element and other mathematical methods to simulate the extension of artificial fractures, the interweaving of artificial and natural fractures, and the process of fracture network formation.

[0045] Furthermore, in step S5, the close-well spacing test primarily involves selecting a test well group with a spacing smaller than the planned well spacing to conduct interference testing and interference dynamic analysis testing. The interference dynamic analysis test includes the impact of fracturing in the test well on the production performance of adjacent wells, and whether the production performance of the test well after commissioning remains consistent with that of adjacent wells or whether there is a mutual impact.

[0046] In addition, in step S7, the final reasonable well spacing is determined after comprehensive consideration of numerical simulation, unstable production analysis, well interference analysis, and economic evaluation methods.

[0047] In summary, this application provides a method for evaluating reasonable shale gas development well spacing based on post-fracture distribution. It identifies the extension of artificial fractures and the coupling of artificial and natural fractures, clarifies the appropriate well spacing for shale gas horizontal wells, and guides the preparation of shale gas development plans and the deployment of development wells. This method fully utilizes the inter-well stimulation volume and avoids excessive overlap in gas supply ranges between wells, saving drilling and fracturing investment, significantly improving block reserve utilization and gas field development efficiency, and providing a reference for determining appropriate well spacing in shale blocks.

[0048] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for evaluating reasonable well spacing for shale gas development based on post-fracture fracture network distribution, characterized in that: The following steps are involved: S1: Obtain the statistical results of microseismic monitoring of the test well group in the work area, and conduct analysis and evaluation of the fracture network extension of the gas well after pressure reduction at the test well spacing; S2, using numerical simulation software to import the gas well fracturing drilling and completion parameters, production performance data, and related attribute parameters in the work area to construct a hydraulic fracture model; randomly generate an activated natural fracture grid based on the imported microseismic geometry data to form an interactive fracture system, and further optimize the post-fracture fracture network parameters based on the historical fitting results of the production performance data in the work area; S3, based on the production status of the gas wells in the work area, perform a dynamic analysis of the gas well production using an unstable production analysis method, combine the production stage division and flow pattern analysis of the gas wells, and use a non-normal scale block to evaluate the stimulated half-fracture length and reservoir stimulated volume parameters in the work area to determine the scope of gas well stimulation in the work area; S4, using a discrete fracture network simulation method to simulate and analyze the post-fracturing fracture network, inputting fracturing fluid properties, support properties, and pumping procedures, determining the three-dimensional shape of the post-fracturing fracture network, and clarifying the extension of interwell fractures in the work area; S5, analyzing the well-to-well interference of the small-well-spacing test in the work area, tracking the pressure changes of the interference test wells in the work area, comparing the pressure, gas production, and water production changes of the test wells during the production test to analyze the well-to-well interference, and determining whether there is communication between the fracture networks after pressure-pressurization of the test wells under the small-well-spacing condition; if there is communication, it indicates that there is overlap between the fractures in the fracture networks after pressure-pressurization, that is, there is overlap in the gas supply range, the well spacing of the test wells under the small-well-spacing condition is too small, and the reasonable development well spacing should be greater than the test well spacing; S6. Determine the economic limit of the well spacing for a single well in the block. Establish a gas well production decline model in the work area using an unstable production analysis method. Taking into account the single well investment, production, gas price, national financial subsidies, and operating cost parameters, establish a correlation chart between gas well investment and well spacing, a correlation chart between internal rate of return and well spacing, and a correlation chart between recovery factor and well spacing. It is clear that the value of recoverable reserves controlled by a single well is equal to the well spacing at the time of drilling and production test investment. S7, based on the data obtained in step S2, step S3, step S4, step S5 and step S6, with the economic evaluation well spacing as the lower limit and the simulated fracture length after fracturing as the upper limit, combined with the results of numerical simulation, unstable production analysis, small well spacing test and interference well test, further narrow the range of well spacing values to obtain the data results of reasonable development well spacing for the block.

2. The method for evaluating reasonable shale gas development well spacing based on post-fracture distribution according to claim 1, characterized in that: In step S2, the monitoring statistics of the gas well fracturing microseismic data include the length, width, height and orientation of the fracturing cracks.

3. The method for evaluating reasonable shale gas development well spacing based on post-fracture distribution according to claim 1, characterized in that: In step S2, the drilling and completion parameters include wellhead coordinates, inclined depth, vertical depth, well inclination, azimuth, fracturing stage, number of clusters, sand addition amount, and liquid addition amount; the production dynamic data include gas well gas production, pressure, and water production; the related attribute parameters include porosity, gas saturation, rock physical parameters, permeability, and adsorption and desorption parameters.

4. The method for evaluating reasonable shale gas development well spacing based on post-fracture distribution according to claim 1, characterized in that: In step S3, the gas well production stage and flow pattern analysis includes the division of fracture linear flow, formation and hydraulic fracture dual linear flow, formation to fracture linear flow, transition flow, peripheral linear flow and boundary flow.

5. The method for evaluating reasonable shale gas development well spacing based on post-fracture distribution according to claim 1, characterized in that: In step S4, the post-compression fracture network simulation analysis is to simulate the extension of artificial fractures, the interweaving of artificial and natural fractures, and the process of fracture network formation based on discrete fracture networks, finite elements, extended finite elements, and boundary elements.

6. The method for evaluating reasonable shale gas development well spacing based on post-fracture distribution according to claim 1, characterized in that: In step S5, the small well spacing test is to select a test well group with a well spacing smaller than the designed well spacing and carry out interference well testing and interference dynamic analysis tests. The interference dynamic analysis test includes the interference of the test well fracturing on the production dynamics of the adjacent wells, and whether the production dynamics of the test well after it is put into production remain consistent with those of the adjacent wells or affect each other.

7. The method for evaluating reasonable shale gas development well spacing based on post-fracture distribution according to claim 1, characterized in that: In step S7, the reasonable development well spacing of the block is determined by comprehensively considering various methods such as numerical simulation, unstable production analysis, well interference analysis, and economic evaluation.

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