Method for calculating effective volume of natural fracture network around well in fractured reservoir and related equipment

Abstract

The present application relates to the technical field of well test interpretation, and discloses a method for calculating the effective volume of a natural fracture network around a well in a fractured reservoir and related equipment, which is based on actual downhole pressure test data of a fractured reservoir, and by drawing a test well test curve and converting it into a rectangular coordinate curve, an analysis basis that fits the real seepage characteristics of the reservoir is constructed, thereby avoiding the limitations of traditional homogeneous assumption models and the non-uniform distribution of fractures in actual reservoirs. The effective volume of the natural fracture network is directly calculated based on the rectangular coordinate curve, thereby solving the problem of large errors in indirect calculation by traditional methods, and accurately representing the scale of the effective fracture network around the well, which provides reliable technical support for determining the distribution of dominant reservoirs, analyzing the main factors controlling productivity, and accurately calculating the oil and gas geological reserves, and helps to fine evaluation and development of fractured oil and gas reservoirs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of well test interpretation, in particular to a method for calculating the effective volume of a natural fracture network around a well in a fractured reservoir and related equipment. BACKGROUND

[0002] With the continuous deepening of oil and gas reservoir exploration and development, the development of shallow conventional oil and gas reservoirs has gradually entered the late stage of exploration and development. At present, the main target of increasing reserves and production of oil and gas is the development and utilization of unconventional and deep oil and gas reservoirs. These oil and gas reservoirs often have artificial fracture networks or natural fracture networks developed around the well. Among the currently determined reserves in the world, fractured oil and gas reservoirs account for about one fifth of the world's oil and gas reserves. In recent years, multiple fractured oil and gas reservoirs have been found in many places. These oil and gas reservoirs are often buried deep, or have lithology such as volcanic rock and metamorphic rock, and often have extremely poor matrix properties, and the reservoir and seepage channels of oil and gas are secondary fractures or weathering-tectonic fractures.

[0003] Therefore, for the above-mentioned oil and gas reservoirs, complex fracture networks are often distributed around the well, forming the space for oil and gas storage and seepage. Accurate evaluation of the effective fracture network volume around the well is of great significance for determining the distribution of dominant reservoirs and the main factors controlling productivity, developing future production prediction and optimizing production system, and calculating oil and gas geological reserves.

[0004] In the field of well test interpretation technology, previous studies have been conducted on matrix-fracture dual porosity medium models. For well test interpretation models of fractured reservoirs, homogeneity is often considered, that is, the fracture morphology is consistent, and the fractures are uniformly distributed in the matrix reservoir. At present, the dual porosity medium (pore and fracture) models established based on this concept mainly include the pseudo-steady state model, the spherical model and the plate-shaped model. However, the above-mentioned models can only obtain the storage ratio and the channeling coefficient to represent the fracture development and the flow capacity of the matrix system to the fracture network, respectively, and cannot directly obtain the effective fracture volume. The error of the indirectly calculated fracture volume is large. Therefore, it is necessary to establish a well test analysis technology for the effective fracture volume around the well from the seepage mechanism of the fractured reservoir, so as to provide a technical means for the fine evaluation of complex fractured oil and gas reservoirs. SUMMARY

[0005] The present application provides a method for calculating the effective volume of a natural fracture network around a well in a fractured reservoir and related equipment, which solves the problem of being unable to directly obtain the effective fracture volume and the large error of the indirectly calculated fracture volume.

[0006] To achieve the above object, the present application provides the following technical scheme:

[0007] The method for calculating the effective volume of a natural fracture network around a well in a fractured reservoir comprises:

[0008] obtaining downhole pressure test data of the fractured reservoir;

[0009] drawing the test well well test curve according to the downhole pressure test data of the fractured reservoir;

[0010] identifying the pseudo-steady flow stage according to the test well well test curve, and drawing the rectangular coordinate curve according to the pseudo-steady flow stage time and the pressure difference data;

[0011] obtaining the volume coefficient, the comprehensive compression coefficient and the actual yield of the well mouth of the fractured reservoir based on the linear regression of the rectangular coordinate curve;

[0012] calculating the effective volume of the natural fracture network around the well of the fractured reservoir according to the linear slope, the actual yield of the well mouth of the fractured reservoir, the volume coefficient and the comprehensive compression coefficient.

[0013] The further improvement of the present application is that the test well well test curve is drawn according to the downhole pressure test data of the fractured reservoir, and the specific method is as follows:

[0014] If the test object of the downhole pressure test data of the fractured reservoir is an oil-water layer, the downhole pressure test data is directly used for drawing;

[0015] If the test object of the downhole pressure test data of the fractured reservoir is a gas reservoir, the downhole pressure test data is replaced by pseudo-pressure to draw the test well well test curve again, and the pseudo-pressure is:

[0016]

[0017] In the formula, P is the atmospheric pressure; P is the atmospheric pressure ， P is the atmospheric pressure P is the original pressure, P is the original pressure, P is the original pressure, P is the pseudo-pressure, P is the pressure, P is the pressure p P is the pressure P is the pressure p P is the pressure P is the pressure

[0018] The further improvement of the present application is that, for the downhole pressure test data or the pseudo-pressure of the fixed-yield production stage, the double-logarithmic curve of the production pressure difference and the logarithmic derivative of the production pressure difference with respect to the production time is drawn, wherein the production pressure difference is the difference between the original pressure and the production pressure;

[0019] For the downhole pressure test data or the pseudo-pressure of the post-production shut-in stage, the double-logarithmic curve of the shut-in pressure difference and the logarithmic derivative of the shut-in pressure difference with respect to the shut-in time is drawn, wherein the shut-in pressure difference is the difference between the shut-in pressure and the shut-in instantaneous pressure.

[0020] The further improvement of the present application is that,

[0021] The pseudo-steady flow stage is characterized by a dip in the logarithmic derivative of the production pressure difference with respect to time in the well test curve, followed by a straight line segment with a slope of 1.

[0022] A further improvement of this invention lies in the method for obtaining the volume factor and overall compressibility factor of fractured reservoirs as follows:

[0023] Obtain formation fluid parameters and reservoir parameters of fractured reservoirs, and obtain volume factor and comprehensive compressibility factor based on formation fluid parameters and reservoir parameters of fractured reservoirs.

[0024] A further improvement of this invention lies in the method for obtaining the effective volume of the natural fracture network around the well based on the straight slope, the actual production rate of the fractured reservoir wellhead, the volume factor, and the comprehensive compressibility factor:

[0025]

[0026] In the formula: q For actual output, B This is the volume factor. C t The overall compression coefficient is... The effective volume of the natural fracture network around the well. The slope of the line.

[0027] A system for calculating the effective volume of natural fracture networks around a fractured reservoir well includes:

[0028] Data acquisition module: used to acquire downhole pressure test data of fractured reservoirs;

[0029] First plotting module: used to plot well test curves based on downhole pressure test data of fractured reservoirs;

[0030] The second plotting module is used to identify the quasi-steady flow stage based on the well test curves and to plot rectangular coordinate curves based on the quasi-steady flow stage time and pressure difference data.

[0031] Regression Acquisition Module: Used to perform linear regression based on rectangular coordinate curves to obtain the slope of the straight line, and to obtain the volume factor, comprehensive compressibility factor and actual wellhead production of fractured reservoirs;

[0032] Calculation module: Used to calculate the effective volume of the natural fracture network around the wellhead of a fractured reservoir based on the slope of the straight line, the actual production at the wellhead of the fractured reservoir, the volume factor, and the comprehensive compressibility factor.

[0033] A computer device includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of a method for calculating the effective volume of natural fracture networks around a fractured reservoir well.

[0034] A computer readable storage medium, having stored thereon a computer program, which, when executed by a processor, implements the steps of the method for calculating the effective volume of natural fracture network around a well in a fractured reservoir.

[0035] A computer program product, comprising a computer program, which, when executed by a processor, implements the steps of the method for calculating the effective volume of natural fracture network around a well in a fractured reservoir.

[0036] Compared with the prior art, the present application has the following beneficial effects: the present application provides a method for calculating the effective volume of natural fracture network around a well in a fractured reservoir, which is supported by downhole pressure test data of the fractured reservoir, and the analysis basis that fits the real seepage characteristics of the reservoir is constructed by drawing the test well test curve and converting it into a rectangular coordinate curve, thereby avoiding the limitations of the difference between the traditional homogeneous assumption model and the actual fracture distribution of the reservoir. The effective volume of the natural fracture network is directly calculated based on the rectangular coordinate curve, thereby solving the problem of large error in indirect calculation of the traditional method, and the size of the effective fracture network around the well can be accurately characterized, which provides reliable technical support for analyzing the main control factors of productivity and accurately calculating the oil and gas geological reserves, and helps the fine evaluation and development of the fractured oil and gas reservoir.

[0037] Further, starting from the seepage theory, linear regression analysis of the unsteady test data in the pseudo-steady flow stage is carried out by identifying the pseudo-steady flow stage, so that the effective natural fracture volume around the well can be accurately calculated according to the slope and reservoir parameters. Compared with the conventional method, the calculation method is simple and fast, fewer parameters are considered, the parameters are easy to obtain, and the calculation result is more accurate. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The flow chart of the method for calculating the effective volume of natural fracture network around a well in a fractured reservoir according to the present application is shown;

[0039] Figure 2 The test well test curve graph drawn by using the shut-in pressure test data according to the embodiment of the present application is shown;

[0040] Figure 3 The linear regression curve of the test data in the pseudo-steady flow stage according to the embodiment of the present application is shown;

[0041] Figure 4 The test well test curve graph according to the embodiment of the present application is shown;

[0042] Figure 5 The linear regression curve of the test data in another pseudo-steady flow stage according to the embodiment of the present application is shown;

[0043] Figure 6 The block diagram of the system for calculating the effective volume of natural fracture network around a well in a fractured reservoir according to the present application is shown. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0046] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0047] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0048] like Figure 1 As shown, this invention provides a method for calculating the effective volume of natural fracture networks around a fractured reservoir well, including:

[0049] S1 acquires downhole pressure test data for fractured reservoirs;

[0050] S2 plots well test curves based on downhole pressure test data of fractured reservoirs;

[0051] S3 identifies the pseudo-steady flow stage based on the test well curves and plots a rectangular coordinate curve based on the pseudo-steady flow stage time and pressure difference data.

[0052] S4 uses linear regression based on rectangular coordinate curves to obtain the slope of the straight line, and then obtains the volume factor, comprehensive compressibility factor and actual wellhead production of fractured reservoirs.

[0053] S5 calculates the effective volume of the natural fracture network around the wellhead of the fractured reservoir based on the straight slope, the actual production at the wellhead of the fractured reservoir, the volume factor, and the comprehensive compressibility factor.

[0054] Based on downhole pressure test data of fractured reservoirs, this study constructs an analytical foundation that closely reflects the actual seepage characteristics of the reservoir by plotting well test curves and converting them into rectangular coordinate curves. This avoids the limitations of traditional homogeneous assumption models that differ from the actual fracture distribution in reservoirs. The effective volume of the natural fracture network is directly calculated based on the rectangular coordinate curves, solving the problem of large errors in indirect calculations using traditional methods. This accurately characterizes the effective fracture network size around the well, providing reliable technical support for analyzing key factors controlling production capacity and accurately calculating oil and gas geological reserves, thus contributing to the refined evaluation and development of fractured oil and gas reservoirs.

[0055] The detailed steps are as follows:

[0056] The specific steps for plotting well test curves based on downhole pressure test data of fractured reservoirs are as follows:

[0057] If the downhole pressure test data of a fractured reservoir is used to test an oil-water layer, the downhole pressure test data can be used to plot the well test curve.

[0058] If the downhole pressure test data for fractured reservoirs is used to test gas reservoirs, replace the downhole pressure test data with pseudo-pressure and then plot the well test curve. The pseudo-pressure is:

[0059] (1).

[0060] In the formula: Atmospheric pressure, MPa; p i The original pressure is in MPa. The deviation coefficient under the original conditions is dimensionless. The viscosity of the fluid under the original conditions is given in mPa·s. The simulated pressure is in MPa. For pressure p The corresponding viscosity is below. For pressure p The corresponding deviation coefficient is below. For pressure.

[0061] For downhole pressure test data or simulated pressure during the production ramp-up phase, plot the production pressure differential. Logarithmic derivative of production pressure differential Regarding production time t The double logarithmic curve, in which the production pressure difference For the original pressure p i With production pressure difference;

[0062] For downhole pressure test data or simulated pressure during the post-production shut-in phase, plot the shut-in pressure differential. Logarithmic derivative of shut-in pressure difference The double logarithmic curve of the shut-in time Δ t , wherein the shut-in pressure difference is the shut-in pressure and the shut-in moment pressure p ws0 ;

[0063] The steps of drawing the rectangular coordinate curve according to the test well testing curve are specifically:

[0064] (1) The pseudo-steady flow stage is identified according to the derivative curve in the test well testing curve.

[0065] When there is a large-scale natural fracture network near the wellbore, the flow channeling characteristics are prone to occur, that is, the logarithmic derivative curve of the pressure difference about the logarithmic curve of the time appears concave, and then a straight line segment with a slope of 1 appears, which is the pseudo-steady flow stage.

[0066] (2) The rectangular coordinate curve is drawn by using the time and pressure difference data corresponding to the pseudo-steady flow stage in the test well testing curve.

[0067] The steps of calculating the effective volume of the natural fracture network around the well in the fractured reservoir based on the rectangular coordinate curve are specifically:

[0068] The slope of the straight line is obtained by linear regression of the rectangular coordinate curve.

[0069] For the downhole pressure testing data of the constant production production stage, the pressure or pressure difference changes linearly with time, and the wellhead production in this stage is derived from the elastic energy of the natural fracture network area, so:

[0070] (2).

[0071] is the production pressure, is the production time, is the effective volume of the natural fracture network around the well, C t is the comprehensive compressibility coefficient, B is the volume coefficient, q is the actual production.

[0072] After integration, we have:

[0073] (3).

[0074] wherein, is the initial pressure difference, is the production pressure difference.

[0075] It can be seen that the pressure difference curve changes with time in the rectangular coordinate, which is a straight line, and the slope is m , then formula (3) can be written as:

[0076] (4).

[0077] wherein is the slope of the straight line.

[0078] For the post-production shut-in stage:

[0079] (5)

[0080] wherein: is the pre-shut-in production time, is the shut-in pressure differential, is the shut-in time.

[0081] The pre-shut-in production time is long enough >>Δ t Equation (5) can be approximated as:

[0082] (6)

[0083] Therefore, equation (4) can also be written as:

[0084] (7)

[0085] wherein:

[0086] ; (8)

[0087] The effective volume of the natural fracture network around the well can be calculated according to the slope as:

[0088] (9)

[0089] wherein: is the actual production, m 3 / d; B is the volume coefficient, m 3 / m 3 ; C t is the overall compressibility, MPa -1 ; V f is the effective volume of the natural fracture network around the well, m 3 .

[0090] Another embodiment of the present application provides a method for calculating the effective volume of a natural fracture network around a well in a fractured reservoir, comprising: obtaining downhole pressure test data of the fractured reservoir, and drawing a test well test curve according to the downhole pressure test data of the fractured reservoir, as shown in Figure 2 ;

[0091] drawing a rectangular coordinate curve according to the test well test curve;

[0092] (1) According to the feature that the slope of the derivative curve in the test well test curve is 1, the pseudo-stable flow stage is identified Figure 2 .

[0093] (2) The time and pressure difference data corresponding to the pseudo-stable flow stage are used to draw a rectangular coordinate curve Figure 3 , and linear regression is performed to obtain the slope m of the straight line as 0.001.

[0094] The effective volume of the natural fracture network around the well in the fractured reservoir is calculated based on the rectangular coordinate curve.

[0095] The effective volume of the natural fracture network is calculated according to the pressure change formula of the pseudo-stable flow stage, and the parameter values involved are: the oil well production q is 157.4 m 3 / d, the volume coefficient B is 1.052 m 3 / m 3 , and the comprehensive compression coefficient C t is 0.0021 MPa -1 . Therefore, the effective volume of the natural fracture network is:

[0096] (10).

[0097] Another embodiment of the application provides a method for calculating the effective volume of the natural fracture network around the well in a fractured reservoir, comprising: obtaining downhole pressure test data of the fractured reservoir, and drawing a test well test curve according to the downhole pressure test data of the fractured reservoir, as shown in Figure 4 .

[0098] A rectangular coordinate curve is drawn according to the test well test curve.

[0099] (1) According to the feature that the slope of the derivative curve in the test well test curve is 1, the pseudo-stable flow stage is identified Figure 4 .

[0100] (2) The time and pressure difference data corresponding to the pseudo-stable flow stage are used to draw a rectangular coordinate curve Figure 5 , and linear regression is performed to obtain the slope m of the straight line as 0.0007.

[0101] The effective volume of the natural fracture network around the well in the fractured reservoir is calculated based on the rectangular coordinate curve.

[0102] The effective volume of the natural fracture network is calculated according to the pressure change formula of the pseudo-stable flow stage, and the parameter values involved are: the gas well production q is 648299 m 3 / d, the volume coefficient B is 0.0027 m 3 / m 3, comprehensive compression coefficient C t is 0.0062MPa -1 , fluid viscosity under original condition μ i is 0.0353mPa·s. Therefore, the effective volume of natural fracture network of the fracture type reservoir well is

[0103] (11).

[0104] As shown in Figure 6 , the application further provides a system for calculating the effective volume of natural fracture network around a fracture type reservoir well, comprising:

[0105] a data acquisition module for acquiring downhole pressure test data of the fracture type reservoir well;

[0106] a first drawing module for drawing a test well well test curve according to the downhole pressure test data of the fracture type reservoir well;

[0107] a second drawing module for identifying a pseudo-steady flow stage according to the test well well test curve, and drawing a rectangular coordinate curve according to the pseudo-steady flow stage time and differential pressure data;

[0108] a regression acquisition module for performing linear regression based on the rectangular coordinate curve to obtain a straight line slope, and acquiring a volume coefficient, a comprehensive compression coefficient and an actual yield of the wellhead of the fracture type reservoir;

[0109] a calculation module for calculating the effective volume of natural fracture network around the fracture type reservoir well according to the straight line slope, the actual yield of the wellhead of the fracture type reservoir, the volume coefficient and the comprehensive compression coefficient.

[0110] In the first drawing module, the test well well test curve is drawn according to the pressure test data around the fracture type reservoir well, specifically:

[0111] If it is an oil-water layer, the downhole pressure test data is directly used for drawing;

[0112] If it is a gas reservoir, the downhole pressure test data is replaced with pseudo-pressure for redrawing, and the pseudo-pressure is:

[0113] (12).

[0114] In the formula: is atmospheric pressure ， is original pressure, z i is a deviation factor under original condition, is fluid viscosity under original condition, is pseudo-pressure, is pressure p corresponding viscosity, P is pressure p The corresponding deviation coefficient is P is pressure.

[0115] In the first drawing module, for the pressure measurement data in the constant-rate production stage, a double logarithmic curve of the production pressure difference and the logarithmic derivative of the production pressure difference with respect to the production time is drawn, wherein the production pressure difference is the difference between the original pressure and the production pressure;

[0116] For the pressure measurement data in the post-production shut-in stage, a double logarithmic curve of the shut-in pressure difference and the logarithmic derivative of the shut-in pressure difference with respect to the shut-in time is drawn, wherein the shut-in pressure difference is the difference between the shut-in pressure and the shut-in instantaneous pressure.

[0117] In the second drawing module, the step of drawing the rectangular coordinate curve according to the test well testing curve is specifically:

[0118] The pseudo-steady flow stage is identified according to the test well testing curve, and the rectangular coordinate curve is drawn according to the time and pressure difference data of the pseudo-steady flow stage.

[0119] The pseudo-steady flow stage is a stage in which the derivative curve of the test well testing curve appears concave, and then gradually appears a straight line segment with a slope of 1.

[0120] In the calculation module, the step of calculating the effective volume of the natural fracture network around the well in the fractured reservoir based on the rectangular coordinate curve is specifically:

[0121] Based on the rectangular coordinate curve, linear regression is performed to obtain the slope of the straight line

[0122] The formation fluid parameters and reservoir parameters of the fractured reservoir are obtained, the volume coefficient and the comprehensive compressibility coefficient are obtained according to the formation fluid parameters and the reservoir parameters of the fractured reservoir, and the actual production of the wellhead of the fractured reservoir is obtained.

[0123] The effective volume of the natural fracture network around the well is obtained according to the slope of the straight line, the actual production of the wellhead of the fractured reservoir, the volume coefficient and the comprehensive compressibility coefficient.

[0124] In the calculation module, the method for obtaining the effective volume of the natural fracture network around the well according to the slope of the straight line, the actual production of the wellhead of the fractured reservoir, the volume coefficient and the comprehensive compressibility coefficient is:

[0125] (13).

[0126] In the formula: q Q is the actual production, B C is the volume coefficient, C t B is the comprehensive compressibility coefficient, V is the effective volume of the natural fracture network around the well, m is the slope of the straight line.

[0127] The computer device provided by an embodiment of the present application. The computer device of the embodiment comprises a processor, a memory, and a computer program stored in the memory and executable on the processor. The processor implements the steps in each of the above method embodiments when executing the computer program. Alternatively, the processor implements the functions of each module / unit in each of the above device embodiments when executing the computer program.

[0128] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present application.

[0129] The computer device can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. The computer device can include, but is not limited to, a processor and a memory.

[0130] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like.

[0131] The memory can be used to store the computer program and / or modules. The processor realizes various functions of the computer device by running or executing the computer program and / or modules stored in the memory, and calling data stored in the memory.

[0132] The modules / units integrated in the computer device, if realized in the form of software function units and sold or used as independent products, can be stored in a computer readable storage medium.

[0133] Based on such understanding, all or part of the processes in the above method embodiments can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. The computer program is executable by a processor to implement the steps of each of the above method embodiments.

[0134] The computer program comprises computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms, and the like.

[0135] The computer readable medium can include any entity or device capable of carrying the computer program codes, a recording medium, a USB key, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory, a random access memory, an electrical carrier signal, a telecommunications signal, and a software distribution package, etc. It should be noted that the computer readable medium contains contents that can be appropriately added or deleted according to the requirements of legislation and patent practices in a jurisdiction, for example, in some jurisdictions, according to legislation and patent practices, the computer readable medium does not include electrical carrier signals and telecommunications signals.

[0136] Although the embodiments of the present application are described above with reference to the drawings, the present application is not limited to the above-described specific embodiments and application fields, and the above-described specific embodiments are merely illustrative and instructive, but not restrictive. Those skilled in the art can make many forms under the guidance of the specification without departing from the scope of the claims of the present application, and these all belong to the protection of the present application.

Claims

1. A method for calculating the effective volume of a natural fracture network around a well in a fractured reservoir, characterized in that, The method comprises the following steps: obtaining downhole pressure test data of a fractured reservoir; plotting a test well test curve according to the downhole pressure test data of the fractured reservoir; identifying a pseudo-steady flow stage according to the test well test curve, and plotting a straight coordinate curve according to time and pressure difference data of the pseudo-steady flow stage; performing linear regression based on the straight coordinate curve to obtain a straight line slope, and obtaining a volume coefficient, a comprehensive compression coefficient and an actual yield of a wellhead of the fractured reservoir; calculating an effective volume of a natural fracture network around the well of the fractured reservoir according to the straight line slope, the actual yield of the wellhead of the fractured reservoir, the volume coefficient and the comprehensive compression coefficient; the pseudo-steady flow stage is that a logarithmic derivative of a production pressure difference of the test well test curve about time appears concave, and then a straight line segment with a slope of 1 gradually appears; the method for obtaining the effective volume of the natural fracture network around the well of the fractured reservoir according to the straight line slope, the actual yield of the wellhead of the fractured reservoir, the volume coefficient and the comprehensive compression coefficient comprises the following steps: where: q is the actual production, B is the volume factor, C t is the overall compressibility, is the effective volume of the natural fracture network around the well, is the slope of the straight line; the plotting of the test well test curve according to the downhole pressure test data of the fractured reservoir comprises the following steps: if the test object of the downhole pressure test data of the fractured reservoir is an oil-water layer, the downhole pressure test data is directly used for plotting; if the test object of the downhole pressure test data of the fractured reservoir is a gas reservoir, the downhole pressure test data is replaced by pseudo-pressure to plot the test well test curve, and the pseudo-pressure is: wherein: P is atmospheric pressure ， P0 is the original pressure, C0 is the deviation factor at the original conditions, μ0 is the fluid viscosity at the original conditions, P is the pseudo pressure, P is the pressure, P is the pressure p corresponding viscosity at the original conditions, P is the pressure p corresponding deviation factor at the original conditions; for downhole pressure test data or pseudo-pressure of a fixed-yield production stage, a double logarithmic curve of a production pressure difference and a logarithmic derivative of the production pressure difference about production time is plotted, wherein the production pressure difference is a difference between an original pressure and a production pressure; for downhole pressure test data or pseudo-pressure of a post-production shut-in stage, a double logarithmic curve of a shut-in pressure difference and a logarithmic derivative of the shut-in pressure difference about shut-in time is plotted, wherein the shut-in pressure difference is a difference between a shut-in pressure and a shut-in instantaneous pressure.

2. The method of claim 1, wherein, the method for obtaining the volume coefficient and the comprehensive compression coefficient of the fractured reservoir comprises the following steps: obtaining formation fluid parameters and reservoir parameters of the fractured reservoir, and obtaining the volume coefficient and the comprehensive compression coefficient according to the formation fluid parameters and the reservoir parameters of the fractured reservoir.

3. A system for calculating the effective volume of a natural fracture network surrounding a well in a fractured reservoir, the system comprising: The method for calculating the effective volume of the natural fracture network around the well of the fractured reservoir according to any one of claims 1-2 comprises the following steps: a data obtaining module for obtaining downhole pressure test data of a fractured reservoir; a first plotting module for plotting a test well test curve according to the downhole pressure test data of the fractured reservoir; a second plotting module for identifying a pseudo-steady flow stage according to the test well test curve, and plotting a straight coordinate curve according to time and pressure difference data of the pseudo-steady flow stage; a regression obtaining module for performing linear regression based on the straight coordinate curve to obtain a straight line slope, and obtaining a volume coefficient, a comprehensive compression coefficient and an actual yield of a wellhead of the fractured reservoir; a calculating module for calculating an effective volume of a natural fracture network around the well of the fractured reservoir according to the straight line slope, the actual yield of the wellhead of the fractured reservoir, the volume coefficient and the comprehensive compression coefficient.

4. A computer device comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program comprises instructions that, when executed by the processor, cause the processor to perform the method of any one of claims 1-3. The processor executes the computer program to implement the steps of the method for calculating the effective volume of the natural fracture network around the well of the fractured reservoir according to any one of claims 1-2.

5. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method for calculating the effective volume of the natural fracture network around the well of the fractured reservoir according to any one of claims 1-2.

6. A computer program product comprising a computer program, characterized in that, The computer program, when executed by a processor, implements the steps of the method for calculating the effective volume of a fracture network surrounding a well in a fractured reservoir according to any one of claims 1 to 2.

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