Extrusion stress reservoir oil and gas reservoir saturation calculation method, equipment and medium

Abstract

The invention discloses an extrusion stress reservoir oil and gas reservoir saturation calculation method, equipment and a medium, and aims to solve the technical problem that the calculation accuracy of the oil and gas reservoir saturation of an extrusion stress reservoir is reduced due to the fact that the influence of a pore structure on resistivity is not considered in the prior art. The method comprises the following steps: collecting block samples, and calculating a relationship between stress difference and water-saturated resistivity increase multiple under different pore structures; establishing a saturated water resistivity curve under the condition of no stress difference according to the Archie formula; calculating an apparent water-containing resistivity curve; and performing back calculation to obtain the real oil-gas saturation of the stratum. According to the method, the influence of the pore structures on the resistivity is considered, and the actual condition of the stratum is reflected more accurately by classifying different pore structures and establishing the corresponding resistivity and stress relation.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration and development, specifically to a method, equipment, and medium for calculating the saturation of oil and gas reservoirs under compression stress. Background Technology

[0002] In the field of oil and gas exploration and development, accurately assessing the hydrocarbon saturation of reservoirs is crucial. This indicator directly relates to the commercial value and development potential of oil and gas reservoirs, and has a decisive impact on optimizing the exploitation of oil and gas resources. With the continuous advancement of exploration technology, the types of oil and gas reservoirs and their geological conditions are becoming increasingly complex, especially in reservoirs under compressional stress conditions, where accurate calculation of hydrocarbon saturation has become a technical challenge. The main indicator for evaluating reservoir hydrocarbon saturation is rock resistivity. However, studies by scholars both domestically and internationally have found that the resistivity of reservoirs under strong compressional stress is generally higher, resulting in the inaccurate reflection of formation information when directly using resistivity data to calculate saturation.

[0003] Patents CN106802433 and CN109901238 introduce laboratory methods for measuring resistivity under different stresses simulating tensile and compressive stresses in formations. Based on the stress-resistivity relationship and combined with conventional physical property data, a method for correcting the true resistivity of formations is established. Patent CN106285651 obtains the maximum horizontal principal stress, minimum horizontal principal stress, and horizontal principal stress difference in the formation; establishes a relationship between the apparent resistivity of tight sandstone formations and the horizontal principal stress difference; then determines the true resistivity of the formation based on the horizontal principal stress difference, the apparent resistivity of the tight sandstone formation, and the relationship; finally, it determines the fluid properties of the tight sandstone formation based on the true resistivity of the tight sandstone.

[0004] The papers "Mechanism of Influence of Geostress on Resistivity of Tight Sandstone and Establishment of Geostress Correction Resistivity Model" and "Well Logging Resistivity Correction Method under Strong Extrusion Stress Conditions in Kuqa Foreland Basin" derive, based on Archie's formula, that there is a correlation between the horizontal principal stress difference and resistivity under extrusion stress conditions. Through a large number of resistivity measurement experiments, a resistivity correction method based on the horizontal principal stress difference is established, thereby realizing the determination of the true resistivity of the formation and carrying out accurate calculation of fluid identification and reservoir saturation.

[0005] The methods described above all utilize corrected resistivity for saturation calculations. However, in practical applications, it has been found that, on the one hand, these techniques suffer from difficulties in selecting empirical parameters during resistivity correction; on the other hand, due to the influence of multiple factors such as lithology, physical properties, and fractures, the pore structure of rocks varies significantly, and none of the methods consider the impact of pore structure on resistivity. Therefore, it is necessary to further refine and improve resistivity correction methods under strong compressive stress conditions to achieve accurate calculation of reservoir hydrocarbon saturation. Summary of the Invention

[0006] The purpose of this invention is to provide a method, equipment, and medium for calculating the saturation of oil and gas reservoirs under compression stress, so as to overcome the shortcomings of the prior art which does not consider the influence of pore structure on resistivity, thus reducing the accuracy of calculating the saturation of oil and gas reservoirs under compression stress.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for calculating the saturation of oil and gas reservoirs under compressional stress, characterized by comprising the following steps: S1. Collect block samples to conduct stress difference and resistivity experiments, and calculate the relationship between stress difference and the increase factor of water-saturated resistivity under different pore structures. S2: Collect high-temperature and high-pressure rock electrical data from the block, calculate porosity and formation water resistivity using well logging, and establish saturated water resistivity curves under stress-free conditions based on Archie's formula. ; S3. Based on the established relationship between stress difference and the increase factor of saturated water resistivity, and the saturated water resistivity curve without stress difference, calculate the apparent saturated water resistivity. curve; S4, combined with formation resistivity and apparent water saturation resistivity The true oil and gas saturation of the formation is obtained by reverse calculation.

[0008] Furthermore, determining the relationship between stress difference and the increase factor of saturated water resistivity includes the following steps: S101, measure the core porosity and permeability of the sample, change the pressure difference between axial pressure and confining pressure, and measure the resistivity under different stress differences; S102, Calculate the increase factor of core water-saturated resistivity under different stress conditions based on resistivity.

[0009] In the formula, i represents the number of experiments conducted with stress difference as the variable. Let be the factor by which the apparent water-saturated resistivity of the sample increases under the i-th stress difference. Let be the water-saturated resistivity of the core under the i-th stress difference. The resistivity of the core saturated with water under a stress difference of 0 MPa; S103. Based on the measured porosity and permeability, the core pore structure parameters are calculated, and the samples are classified according to the calculated core pore structure parameters.

[0010] In the formula, These are the core pore structure parameters. To measure porosity in rock cores, To measure permeability from rock cores; S104. Based on the pore structure classification results and the calculated increase factor of core saturated resistivity, a relationship between the increase factor of core saturated resistivity and stress under different pore structures is established.

[0011] In the formula, j represents the number of pore structure categories. The factor by which the apparent water-saturated resistivity increases under different pore structures; The difference is the horizontal principal stress. , is a coefficient, an empirical coefficient for different pore structures, specifically determined based on experimental data.

[0012] Furthermore, the increase factor of the apparent water-saturated resistivity is obtained by measuring with a resistivity logging instrument.

[0013] Furthermore, the values ​​of i are 1, 2, 3, and 4, which correspond to stress differences of 0 MPa, 10 MPa, 30 MPa, and 50 MPa, respectively.

[0014] Furthermore, based on the core pore structure parameters The samples were classified into four types of porous structures.

[0015] Furthermore, the apparent water saturation resistivity The method for calculating the curve includes the following steps: S301, to measure the tectonic stress coefficient, overlying strata pressure, and pore pressure of the rock strata in the study area in the directions of maximum and minimum horizontal stress; S302, Calculate the maximum horizontal principal stress Minimum horizontal principal stress and horizontal principal stress difference ,

[0016]

[0017]

[0018] In the formula, PR is Poisson's ratio. , These represent the tectonic stress coefficients of the rock strata in the study area along the directions of maximum and minimum horizontal geostress, respectively. For the pressure of the overlying strata, The Biot elastic modulus is... Pore ​​pressure; S303, based on well logging calculated porosity and well logging calculated permeability, calculate the pore structure parameter PER.

[0019] In the formula, POR is the porosity calculated from well logging, and PERM is the permeability calculated from well logging. S304. Based on the increase factor of apparent saturated water resistivity under different pore structures and the saturated water resistivity curve under no stress difference, a continuous apparent saturated water resistivity is obtained. curve,

[0020] In the formula, j is the number of pore structure categories. Based on the pore structure parameters calculated by S304 and combined with the pore structure classification characterization established by S104, the pore structure type to which the depth point belongs is determined, and thus the corresponding j is determined.

[0021] Furthermore, the resistivity curve of water saturation under no stress difference The calculation formula is as follows:

[0022] In the formula, a, b, m are Archie's formula coefficients, which need to be determined based on the high-temperature and high-pressure rock electrical experimental data of the study block; Rw is the formation water resistivity, which is determined based on the water sample analysis data of the study block; POR is the porosity calculated by well logging.

[0023] Furthermore, the back-calculation process for the true hydrocarbon saturation of the formation includes the following steps: S401, the water saturation index of the formation under compressive stress conditions is obtained according to Archie's formula.

[0024] In the formula, a, b, m, n are Archie's formula coefficients, which need to be determined based on the high-temperature and high-pressure rock electrical experimental data of the study block; Rw is the formation water resistivity, which is determined based on the water sample analysis data of the study block; POR is the porosity calculated from well logging. Formation resistivity; S402, when the strata are saturated with water At this time, the formation resistivity This can be understood as the resistivity of saturated water under compressive stress, leading to the relationship between formation water saturation and saturated water resistivity under compressive stress.

[0025] In the formula, This is obtained from S3; S403, based on the formulas described in S401 and S402, yields the formula for calculating formation water saturation.

[0026] Thus, the formula for calculating formation oil and gas saturation is obtained:

[0027] In the formula, This represents the water saturation level of the formation. This represents the oil and gas saturation level at the bottom layer.

[0028] An electronic device, comprising: One or more processors; Memory; One or more applications, wherein the one or more applications are stored in the memory and configured to be executed by the one or more processors, the one or more applications being configured to perform the above-described computational methods.

[0029] A computer-readable medium storing processor-executable program code that, when executed by the processor, causes the processor to perform the above-described calculation method.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method, equipment, and medium for calculating the saturation of oil and gas reservoirs under compression stress. By conducting resistivity measurement experiments under different stress conditions and pore structures, a more accurate stress-resistivity relationship is established, thereby improving the accuracy of oil and gas saturation calculations. The relationship established through experimental data avoids the difficulty in selecting empirical parameters in existing technologies, making the calculation process more objective and reliable. It also considers the influence of pore structure on resistivity, classifying different pore structures and establishing corresponding resistivity-stress relationships to more accurately reflect the actual formation conditions. By providing a more accurate method for calculating oil and gas saturation, this invention helps to more effectively assess and develop oil and gas resources, reduce development risks, and improve economic benefits. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a method for calculating the saturation of a squeeze-stressed oil and gas reservoir according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram illustrating the process of determining the relationship between stress difference and the increase factor of saturated water resistivity in the method for calculating the saturation of squeezed stress reservoirs in this embodiment of the invention.

[0033] Figure 3 The apparent saturated water resistivity in the method for calculating the saturation of oil and gas reservoirs under compression stress in this embodiment of the invention. A flowchart illustrating the curve calculation method.

[0034] Figure 4 This is a schematic diagram illustrating the back-calculation process of the actual oil and gas saturation of the formation in the method for calculating the saturation of oil and gas reservoirs under compression stress in an embodiment of the present invention.

[0035] Figure 5 This is a diagram showing the relationship between stress and resistivity under different pore structures in embodiments of the present invention.

[0036] Figure 6 The diagram shows the calculation results of the maximum horizontal principal stress, minimum horizontal principal stress, and difference between horizontal principal stresses in the embodiments of the present invention.

[0037] Figure 7 This is a diagram showing the calculated pore structure parameters in an embodiment of the present invention.

[0038] Figure 8 This is a diagram showing the calculated results of formation oil and gas saturation in an embodiment of the present invention.

[0039] Figure 9 This is a schematic diagram of an electronic device according to an embodiment of the present invention.

[0040] Figure 10 This is a schematic diagram of a computer-readable medium according to an embodiment of the present invention. Detailed Implementation

[0041] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a number" means two or more, unless otherwise explicitly specified.

[0045] Example 1: like Figures 1 to 4 The figure shows a method for calculating the saturation of a squeeze-stressed oil and gas reservoir provided in an embodiment of the present invention, including the following steps: S1. Collect block samples to conduct stress difference and resistivity experiments, and calculate the relationship between stress difference and the increase factor of water-saturated resistivity under different pore structures. S2: Collect high-temperature and high-pressure rock electrical data from the block, calculate porosity and formation water resistivity using well logging, and establish saturated water resistivity curves under stress-free conditions based on Archie's formula. ; S3. Based on the established relationship between stress difference and the increase factor of saturated water resistivity, and the saturated water resistivity curve without stress difference, calculate the apparent saturated water resistivity. curve; S4, combined with formation resistivity and apparent water resistivity The true oil and gas saturation of the formation is obtained by reverse calculation.

[0046] Preferably, in this embodiment, determining the relationship between stress difference and the increase factor of saturated water resistivity includes the following steps: S101, measure the core porosity and permeability of the sample, change the pressure difference between axial pressure and confining pressure, and measure the resistivity under different stress differences; S102, Calculate the increase factor of core water-saturated resistivity under different stress conditions based on resistivity.

[0047] In the formula, i represents the number of experiments conducted with stress difference as the variable. Let be the factor by which the apparent water-saturated resistivity of the sample increases under the i-th stress difference. Let be the water-saturated resistivity of the core under the i-th stress difference. The resistivity of the core saturated with water under a stress difference of 0 MPa; S103. Based on the measured porosity and permeability, the core pore structure parameters are calculated, and the samples are classified according to the calculated core pore structure parameters.

[0048] In the formula, These are the pore structure parameters of the rock core. To measure porosity in rock cores, To measure permeability from rock cores; S104. Based on the pore structure classification results and the calculated increase factor of core saturated resistivity, a relationship between the increase factor of core saturated resistivity and stress under different pore structures is established.

[0049] In the formula, j represents the number of pore structure categories. The factor by which the apparent water-saturated resistivity increases under different pore structures; The difference is the horizontal principal stress. , is a coefficient, an empirical coefficient for different pore structures, specifically determined based on experimental data.

[0050] Preferably, in this embodiment, the increase factor of the apparent water-saturated resistivity is obtained by measuring the resistivity logging instrument.

[0051] Preferably, in this embodiment, i takes the values ​​1, 2, 3, and 4, which correspond to stress differences of 0 MPa, 10 MPa, 30 MPa, and 50 MPa, respectively.

[0052] Preferably, in this embodiment, the core pore structure parameters are used. The samples were classified into four types of porous structures.

[0053] Preferably, the apparent water-saturated resistivity described in this embodiment The method for calculating the curve includes the following steps: S301, to measure the tectonic stress coefficient, overlying strata pressure, and pore pressure of the rock strata in the study area in the directions of maximum and minimum horizontal stress; S302, Calculate the maximum horizontal principal stress Minimum horizontal principal stress and horizontal principal stress difference ,

[0054]

[0055]

[0056] In the formula, PR is Poisson's ratio. , These represent the tectonic stress coefficients of the rock strata in the study area along the directions of maximum and minimum horizontal geostress, respectively. For the pressure of the overlying strata, The Biot elastic modulus is... Pore ​​pressure; S303, based on well logging calculated porosity and well logging calculated permeability, calculate the pore structure parameter PER.

[0057] In the formula, POR is the porosity calculated from well logging, and PERM is the permeability calculated from well logging. S304. Based on the increase factor of apparent saturated water resistivity under different pore structures and the saturated water resistivity curve under no stress difference, a continuous apparent saturated water resistivity is obtained. curve,

[0058] In the formula, j is the number of pore structure categories. Based on the pore structure parameters calculated by S304 and combined with the pore structure classification characterization established by S104, the pore structure type to which the depth point belongs is determined, and thus the corresponding j is determined.

[0059] Preferably, the water-saturated resistivity curve under no stress difference described in this embodiment The calculation formula is as follows:

[0060] In the formula, a, b, m are Archie's formula coefficients, which need to be determined based on the high-temperature and high-pressure rock electrical experimental data of the study block; Rw is the formation water resistivity, which is determined based on the water sample analysis data of the study block; POR is the porosity calculated by well logging.

[0061] Preferably, the back-calculation process for the true hydrocarbon saturation of the formation in this embodiment includes the following steps: S401, the water saturation index of the formation under compressive stress conditions is obtained according to Archie's formula.

[0062] In the formula, a, b, m, n are Archie's formula coefficients, which need to be determined based on the high-temperature and high-pressure rock electrical experimental data of the study block; Rw is the formation water resistivity, which is determined based on the water sample analysis data of the study block; POR is the porosity calculated from well logging. Formation resistivity; S402, when the strata are saturated with water At this time, the formation resistivity This can be understood as the resistivity of saturated water under compressive stress, leading to the relationship between formation water saturation and resistivity of saturated water under compressive stress.

[0063] In the formula, This is obtained from S3; S403, based on the formulas described in S401 and S402, yields the formula for calculating formation water saturation.

[0064] Thus, the formula for calculating formation oil and gas saturation is obtained:

[0065] In the formula, This represents the water saturation level of the formation. This represents the oil and gas saturation level at the bottom layer.

[0066] Example 2: This embodiment provides an application scenario for a method to calculate the saturation of oil and gas reservoirs under compressional stress.

[0067] The reservoir lithology of the DB block in a domestic oilfield is mainly composed of lithic sandstone and feldspathic lithic sandstone, with matrix porosity ranging from 4% to 12% and matrix permeability from 0.17 to 9.89 mD. Fractures are well-developed. This block is affected by tectonic movements, resulting in strong compressive stress and a complex overall pore structure. The resistivity is influenced by multiple factors, including compressive stress and the complex pore structure, and cannot directly reflect the true formation information, leading to low accuracy in saturation calculations. This embodiment uses... Figure 1 The method shown is for calculating the saturation of oil and gas reservoirs under compression stress in this block.

[0068] The relationship between stress difference and the increase in resistivity under different pore structures was obtained based on stress difference and resistivity experiments.

[0069] The core saturated water resistivity measurement experiment was conducted according to the procedure specified in the standard "Core Analysis Methods SY / T 5385-2007". This experiment, while maintaining a constant axial pressure (10 MPa), measured the resistivity of saturated formation water at confining pressures of 10 MPa, 20 MPa, 40 MPa, and 60 MPa. The formation water salinity was determined to be 40,000 mg / L based on test data from this block, and the formation temperature was 144℃. After obtaining the experimental data, the calculation method for the relationship between stress difference and the increase in saturated water resistivity under different pore structures is as follows: Based on the confining pressure and axial pressure of this experiment, the core water-saturated resistivity of each sample under stress differences of 0 MPa, 10 MPa, 30 MPa, and 50 MPa can be obtained. The increase factor of the core water-saturated resistivity under different stress differences is calculated based on the core water-saturated resistivity measured under different pressure differences for each sample, using the following formula:

[0070] In the formula, i takes values ​​of 1, 2, 3, and 4, which correspond to stress differences of 0 MPa, 10 MPa, 30 MPa, and 50 MPa, respectively. Let be the factor by which the apparent water-saturated resistivity of the sample increases under the i-th stress difference. Let be the water-saturated resistivity of the core under the i-th stress difference, in Ω·m. The resistivity of the core sample saturated with water at 0 MPa is expressed in Ω·m.

[0071] The pore structure parameters of the core were calculated based on the measured porosity and permeability, and the samples were then classified according to these calculated parameters. The formulas for calculating the core pore structure parameters are as follows:

[0072] In the formula, These are the pore structure parameters of the rock core. Porosity was measured in core samples, in percentages (%). Permeability measured from rock cores, in mD.

[0073] like Figure 5 As shown, based on the porosity and permeability measured in this experiment, the samples were classified into four types of pore structures, as shown in the table below: Classification Standards for Pore Structure Parameters

[0074] Based on the pore structure classification results and the calculated increase factor of core saturated resistivity, the relationship between the increase factor of core saturated resistivity and stress under different pore structures is established, as follows:

[0075] In the formula, j represents the number of pore structure categories. The factor by which the apparent water-saturated resistivity increases under different pore structures; The difference in horizontal principal stresses is expressed in MPa. , is a coefficient, an empirical coefficient for different pore structures, specifically determined based on experimental data, and is dimensionless.

[0076] like Figure 6As shown, based on the corresponding pore structure classification, the relationship between the stress difference and the increase in saturated water resistivity under different pore structures is obtained. From... Figure 6 As can be seen, Type I pore structure is the best, with the largest change in resistivity increase factor. This indicates that as the stress difference increases, the pore structure gradually deteriorates, leading to an increase in water-saturated resistivity and a larger increase in the corresponding resistivity factor. Type IV pore structure is the worst, with a smaller change in resistivity increase factor. Analysis suggests that the rock with this pore structure has poor electrical conductivity; as the stress difference increases, the pore structure does not change significantly, and the corresponding resistivity does not change significantly either, resulting in a small change in the resistivity increase factor.

[0077] In advance, high-temperature and high-pressure rock electrical data of the block were collected, and porosity and formation water resistivity were calculated using well logging. The saturated water resistivity curve under stress-free conditions was then calculated using Archie's formula. ,

[0078] In the formula, a, b, m are Archie's formula coefficients, determined based on rock electrical experimental data of the block: a = 1.4291, b = 1.2003, m = 1.4303, n = 1.6583; Rw is the formation water resistivity, calculated to be 0.05 Ω·m based on the formation water salinity and formation temperature of this block; POR is the porosity calculated from well logging, in units of %.

[0079] Apparent water resistivity The curve calculation method is as follows: Stress curves, including maximum horizontal principal stress, were calculated based on conventional well logging data. Minimum horizontal principal stress and horizontal principal stress difference The calculation formula is as follows:

[0080]

[0081]

[0082] In the formula: PR is Poisson's ratio, which is dimensionless; , , respectively, are the tectonic stress coefficients of the rock strata in the study area in the directions of maximum and minimum horizontal geostress, and are dimensionless; The pressure of the overlying strata is expressed in MPa. The Biot elastic coefficient is dimensionless. This represents pore pressure, in MPa.

[0083] like Figure 6As shown, the maximum horizontal principal stress calculated in this well is mainly distributed between 120 MPa and 170 MPa, and the minimum horizontal principal stress is mainly distributed between 87 MPa and 120 MPa. The calculated difference in horizontal principal stress is mainly distributed between 26 MPa and 37 MPa, indicating that the overall stress in this block is very strong. It is necessary to consider the influence of stress on resistivity when calculating the saturation parameters.

[0084] Pore ​​structure parameters are calculated based on conventional well logging data, using the following formulas:

[0085] In the formula, POR is the porosity calculated from well logging, in percentage, and PERM is the permeability calculated from well logging, in mD.

[0086] like Figure 7 As shown, the porosity calculated from the well logging data is mainly distributed between 1% and 8.5%, and the permeability is mainly distributed between 0.03 mD and 2 mD, which belongs to a low-porosity and low-permeability reservoir. The calculated pore structure parameters are between 0.1 and 1.

[0087] Based on the increase factor of apparent saturated water resistivity under different pore structures and the saturated water resistivity curves under no stress difference, a continuous apparent saturated water resistivity is obtained. Curves, such as Figure 8 The electrical conductivity curves are shown in a series.

[0088]

[0089] In the formula, j represents the number of pore structure categories. Based on the calculated pore structure parameters and the established pore structure classification characterization, the pore structure type to which the depth point belongs is determined, and thus the corresponding j is determined.

[0090] According to Archie's formula, under compressive stress conditions, the formation resistivity and saturation have the following relationship:

[0091] When the strata are saturated with water ( At this time, the formation resistivity This can be understood as the resistivity of water saturated under compressive stress conditions, i.e., the calculated apparent resistivity of water saturated. The relationship between formation water saturation and resistivity of saturated water under compressive stress was derived:

[0092] The relationship between formation resistivity and saturation under combined compressive stress and the relationship between formation water saturation and saturated water resistivity under compressive stress can be used to derive the formula for calculating formation water saturation as follows:

[0093] The formation's hydrocarbon saturation can then be obtained using the following formula:

[0094] like Figure 8 As shown in the figure, the saturation column represents the actual oil and gas saturation of the formation calculated according to the present invention. It can be seen from the figure that the calculated oil and gas saturation is in very high agreement with the saturation obtained by laboratory mercury intrusion porosimetry, indicating that the method has good reliability.

[0095] Example 3: like Figure 9 The diagram shown is a structural block diagram of an electronic device provided in an embodiment of the present invention. This electronic device can be a smartphone, tablet computer, e-reader, or other electronic device capable of running applications. The electronic device in this application may include one or more of the following components: a processor, a memory, and one or more applications, wherein the one or more applications may be stored in the memory and configured to be executed by one or more processors, and the one or more applications are configured to perform the methods described in the foregoing method embodiments.

[0096] A processor may include one or more processing cores. The processor connects various parts within the electronic device using various interfaces and lines, and performs various functions and processes data by running or executing instructions, programs, code sets, or instruction sets stored in memory, and by calling data stored in memory. Optionally, the processor may be implemented using at least one hardware form of Digital Signal Processing (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor may integrate one or a combination of several of the following: Central Processing Unit (CPU), Graphics Processing Unit (GPU), and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the displayed content; and the modem handles wireless communication. It is understood that the modem may also be implemented separately as a communication chip, without being integrated into the processor.

[0097] The memory may include random access memory (RAM) or read-only memory (ROM). The memory can be used to store instructions, programs, code, code sets, or instruction sets. The memory may include a program storage area and a data storage area. The program storage area may store instructions for implementing an operating system, instructions for implementing at least one function, instructions for implementing the various method embodiments described below, etc. The data storage area may also store data created by the terminal during use.

[0098] Example 4: like Figure 10 The diagram shows a structural block diagram of a computer-readable storage medium provided in an embodiment of the present invention. This computer-readable medium stores program code that can be invoked by a processor to execute the methods described in the above method embodiments. The computer-readable storage medium can be an electronic memory such as flash memory, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM, hard disk, or ROM. Optionally, the computer-readable storage medium includes a non-transitory computer-readable storage medium. The computer-readable storage medium has storage space for program code that performs any of the method steps described above. This program code can be read from or written to one or more computer program products. The program code can be compressed, for example, in a suitable form.

[0099] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the saturation of oil and gas reservoirs under compressional stress, characterized in that, Includes the following steps: S1. Collect block samples to conduct stress difference and resistivity experiments, and calculate the relationship between stress difference and the increase factor of water-saturated resistivity under different pore structures. S2: Collect high-temperature and high-pressure rock electrical data from the block, calculate porosity and formation water resistivity using well logging, and establish saturated water resistivity curves under stress-free conditions based on Archie's formula. ; S3. Based on the established relationship between stress difference and the increase factor of saturated water resistivity, and the saturated water resistivity curve without stress difference, calculate the apparent saturated water resistivity. curve; S4, combined with formation resistivity and apparent water saturation resistivity The true oil and gas saturation of the formation is obtained by reverse calculation.

2. The method for calculating the saturation of a squeeze-stressed oil and gas reservoir according to claim 1, characterized in that, Determining the relationship between stress difference and the increase factor of saturated water resistivity includes the following steps: S101, measure the core porosity and permeability of the sample, change the pressure difference between axial pressure and confining pressure, and measure the resistivity under different stress differences; S102, Calculate the increase factor of core water-saturated resistivity under different stress conditions based on resistivity. In the formula, i represents the number of experiments conducted with stress difference as the variable. Let be the factor by which the apparent water-saturated resistivity of the sample increases under the i-th stress difference. Let be the water-saturated resistivity of the core under the i-th stress difference. The resistivity of the core saturated with water under a stress difference of 0 MPa; S103. Based on the measured porosity and permeability, the core pore structure parameters are calculated, and the samples are classified according to the calculated core pore structure parameters. In the formula, These are the pore structure parameters of the rock core. To measure porosity in rock cores, To measure permeability from rock cores; S104. Based on the pore structure classification results and the calculated increase factor of core saturated resistivity, a relationship between the increase factor of core saturated resistivity and stress under different pore structures is established. In the formula, j represents the number of pore structure categories. The factor by which the apparent water-saturated resistivity increases under different pore structures; The difference is the horizontal principal stress. , is a coefficient, an empirical coefficient for different pore structures, specifically determined based on experimental data.

3. The method for calculating the saturation of a squeeze-stressed oil and gas reservoir according to claim 2, characterized in that, The increase in apparent water-saturated resistivity was obtained by measuring resistivity logging instruments.

4. The method for calculating the saturation of a squeeze-stressed oil and gas reservoir according to claim 2, characterized in that, The values ​​of i are 1, 2, 3, and 4, which correspond to stress differences of 0 MPa, 10 MPa, 30 MPa, and 50 MPa, respectively.

5. The method for calculating the saturation of a squeeze-stressed oil and gas reservoir according to claim 2, characterized in that, Based on core pore structure parameters The samples were classified into four types of porous structures.

6. The method for calculating the saturation of a squeeze-stressed oil and gas reservoir according to claim 2, characterized in that, The apparent water-saturated resistivity The method for calculating the curve includes the following steps: S301, to measure the tectonic stress coefficient, overlying strata pressure, and pore pressure of the rock strata in the study area in the directions of maximum and minimum horizontal stress; S302, Calculate the maximum horizontal principal stress Minimum horizontal principal stress and horizontal principal stress difference , In the formula, PR is Poisson's ratio. , These represent the tectonic stress coefficients of the rock strata in the study area along the directions of maximum and minimum horizontal geostress, respectively. For the pressure of the overlying strata, The Biot elastic modulus is... Pore ​​pressure; S303, based on well logging calculated porosity and well logging calculated permeability, calculate the pore structure parameter PER. In the formula, POR is the porosity calculated from well logging, and PERM is the permeability calculated from well logging. S304, based on the increase factor of apparent saturated water resistivity under different pore structures and the saturated water resistivity curve under no stress difference, a continuous apparent saturated water resistivity is obtained. curve, In the formula, j is the number of pore structure categories. Based on the pore structure parameters calculated by S304 and combined with the pore structure classification characterization established by S104, the pore structure type to which the depth point belongs is determined, and thus the corresponding j is determined.

7. The method for calculating the saturation of a squeeze-stressed oil and gas reservoir according to claim 1, characterized in that, The resistivity curve of water saturation under no stress difference The calculation formula is as follows: In the formula, a, b, m are Archie's formula coefficients, which need to be determined based on the high-temperature and high-pressure rock electrical experimental data of the study block; Rw is the formation water resistivity, which is determined based on the water sample analysis data of the study block; POR is the porosity calculated by well logging.

8. The method for calculating the saturation of a squeeze-stress reservoir oil and gas reservoir according to claim 1, characterized in that, The back-calculation process for the true hydrocarbon saturation of the formation includes the following steps: S401, the water saturation index of the formation under compressive stress conditions is obtained according to Archie's formula. In the formula, a, b, m, n are Archie's formula coefficients, which need to be determined based on the high-temperature and high-pressure rock electrical experimental data of the study block; Rw is the formation water resistivity, which is determined based on the water sample analysis data of the study block; POR is the porosity calculated from well logging. Formation resistivity; S402, when the strata are saturated with water At this time, the formation resistivity This can be understood as the resistivity of saturated water under compressive stress, leading to the relationship between formation water saturation and saturated water resistivity under compressive stress. In the formula, This is obtained from S3; S403, based on the formulas described in S401 and S402, yields the formula for calculating formation water saturation. Thus, the formula for calculating the oil and gas saturation of a formation is obtained: In the formula, This represents the water saturation level of the formation. This represents the oil and gas saturation level at the bottom layer.

9. An electronic device, characterized in that, include: One or more processors; Memory; One or more applications, wherein the one or more applications are stored in the memory and configured to be executed by the one or more processors, the one or more applications being configured to perform the method described in any one of claims 1-8.

10. A computer-readable medium, characterized in that, The computer-readable medium stores processor-executable program code, which, when executed by the processor, causes the processor to perform the method described in any one of claims 1-8.

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