A method and system for calculating permeability of a heterogeneous sand-shale reservoir

Abstract

This invention discloses a method and system for calculating the permeability of heterogeneous sandstone and mudstone reservoirs. Based on limited well information data from oilfield development wells, the spontaneous potential and natural gamma logging curves are first standardized and then normalized. The envelope area between the two is then calculated. Finally, a permeability logging interpretation model is established using a mathematical fitting method, combined with core analysis permeability, thereby enabling rapid quantitative calculation of permeability in predicted wells at continuous depths. This method is simple, universally applicable, and highly accurate, meeting the needs of oilfield production. It is operable by general interpreters and facilitates rapid large-scale application in production. Furthermore, it provides support for fluid identification and optimization of fracturing operations based on accurate permeability calculations.

Description

Technical Field

[0001] This invention belongs to the field of reservoir evaluation technology, and relates to a method and system for calculating the permeability of heterogeneous sandstone and mudstone reservoirs. Background Technology

[0002] Permeability is a crucial parameter for refined reservoir evaluation and plays a vital role in oilfield development. However, permeability is a rock physical parameter that is difficult to obtain directly through well logging methods; the parameters measured in well logging must be converted to calculate permeability. Generally, permeability increases with increasing porosity. In medium-to-high permeability sandstone and mudstone reservoirs, there is a good exponential function relationship between porosity and permeability, with a high correlation, making it easy to calculate permeability using porosity alone. However, for low-porosity, low-permeability, heterogeneous sandstone and mudstone reservoirs, the correlation between porosity and permeability is poor. The same porosity often exhibits different permeabilities, sometimes with differences of orders of magnitude, demonstrating severe heterogeneity both horizontally and vertically, making it difficult to characterize permeability using porosity alone.

[0003] With the development of logging technology and the advancement of mathematical methods, new imaging technologies such as nuclear magnetic resonance logging and dipole shear wave logging, as well as methods such as flow units, fractals, neural networks, and fuzzy mathematics, have been developed for permeability prediction, achieving certain results. However, these methods are based on abundant logging information and require a variety of curves, such as compensated density, compensated neutron, and imaging logging. For development wells, oilfields, considering costs, generally only collect natural gamma, spontaneous potential, sonic transit time, and resistivity logging curves. The scarcity of well information data leads to the lack of universality in newly developed permeability methods. Given the limited information available for development wells, there is an urgent need to develop new permeability logging interpretation models to improve the accuracy of permeability calculations and meet the production needs of oilfields. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method and system for calculating the permeability of heterogeneous sandstone and mudstone reservoirs, effectively solving the problems of low accuracy in permeability calculation of heterogeneous sandstone and mudstone reservoirs, limited data from development wells, and the inapplicability of new methods.

[0005] This invention is achieved through the following technical solution:

[0006] 1. A method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs, characterized by comprising the following steps:

[0007] Step 1: Obtain the porosity and permeability of core samples from the study area;

[0008] Step 2: Plot the porosity and permeability of the core analysis with the corresponding logging curves of spontaneous potential, spontaneous gamma, and sonic transit time on the same graph to correct and align the depth of the core analysis with the depth of the corresponding logging.

[0009] Step 3: After standardizing and normalizing the logging curves of the sonic transit time spontaneous potential and natural gamma of the corresponding well logs after depth alignment, calculate the envelope area of ​​the logging curves of the corresponding well logs after standardization and normalization.

[0010] Step 4: By standardizing and normalizing the envelope area of ​​the corresponding well logging spontaneous potential and natural gamma logging curves, and combining it with the permeability of the core analysis, a permeability logging interpretation model for the study area is established.

[0011] Step 5: Using the permeability logging interpretation model for the study area, the permeability of heterogeneous sandstone and mudstone reservoirs can be quantitatively calculated and predicted at continuous depths.

[0012] Preferably, in step 2, the alignment of the core analysis depth with the corresponding well logging depth is specifically achieved by: using the correlation between the porosity of the core analysis and the sonic transit time of the corresponding well logging, and utilizing the morphological characteristics of the core, the depth points of the core analysis are corrected. Positions with high porosity are moved towards positions with high sonic transit time, and positions with low porosity are moved towards positions with low sonic transit time, thereby achieving alignment between the core analysis depth and the corresponding well logging depth.

[0013] Preferably, the specific process for standardizing the spontaneous potential and natural gamma logging curves in step 3 is as follows: Select the same continuous and stable mudstone layer in the study area, use the frequency histogram method to count the characteristic peak values ​​of spontaneous potential and natural gamma for each well, take the average value of the characteristic peak values ​​of spontaneous potential and natural gamma among the various wells as the spontaneous potential and natural gamma values ​​of the mudstone layer in the study area, and take the difference between the characteristic peak values ​​of spontaneous potential and natural gamma and the average value of the characteristic peak values ​​of spontaneous potential and natural gamma for each well as the logging curve correction amount.

[0014] Preferably, the specific process of normalizing the spontaneous potential and natural gamma logging curves in step 3 is as follows: statistically study the distribution of spontaneous potential and natural gamma logging values, combine the geological characteristics of the study area and the logging response law, determine the left and right scales of the spontaneous potential and natural gamma logging curves, normalize the spontaneous potential and natural gamma logging curves, so that the normalized spontaneous potential curve is displayed with a linear scale [1 0], and the normalized natural gamma curve is displayed with a linear scale

[01] .

[0015] Preferably, the expression for the normalized natural potential is:

[0016]

[0017] In the formula, SP is the natural potential, with the unit being mV; SP L SP represents the range of values ​​on the left side of the scale for the natural potential. R The value represents the range of values ​​on the right side of the natural potential scale, in mV; SP n These are normalized data of natural potential, dimensionless.

[0018] Preferably, the expression for the natural gamma normalization is:

[0019]

[0020] In the formula, GR represents the natural gamma ray logging value, in API. L The range of values ​​for the left-hand scale of natural gamma; GR R The range of natural gamma values ​​on the right side of the scale, in API; GR n The data are normalized to natural gamma and are dimensionless.

[0021] Preferably, the formula for calculating the normalized envelope area of ​​the spontaneous potential and the spontaneous gamma logging curve is as follows:

[0022] mjc = 1 - SP n -GR n

[0023] In the formula, mjc is the normalized envelope area of ​​the spontaneous potential and natural gamma logging curves; SP n For natural potential normalized data, GR n Data is normalized to natural gamma.

[0024] Preferably, the permeability of the core analysis in step 5 needs to be normalized, and the expression is:

[0025]

[0026] In the formula, K is the permeability of the core analysis, in mD; K L The permeability scale range value on the left and K R The values ​​represent the permeability range on the right side of the scale, in mD; K n The data is normalized for penetration rate and is dimensionless.

[0027] Preferably, the expression for the permeability logging interpretation model in step 5 is:

[0028] K n =a×mjc b

[0029] In the formula, K nThe data represents normalized penetration rate data, which is dimensionless; mjc represents the envelope area; and a and b are model parameters, which are natural constants.

[0030] A permeability calculation system for heterogeneous sandstone and mudstone reservoirs, comprising:

[0031] The module includes a calculation module, a model building module, a plotting module, and a well logging curve processing module.

[0032] The calculation module is used to calculate the envelope area of ​​the corresponding well logging curves after standardization and normalization of the spontaneous potential and natural gamma.

[0033] The plotting module is used to plot the porosity and permeability of the core analysis on the same graph as the logging curves of the corresponding well logging spontaneous potential, spontaneous gamma, and sonic transit time.

[0034] The logging curve processing module is used to standardize and normalize the logging curves of the corresponding well spontaneous potential and natural gamma.

[0035] The model building module is used to build a permeability logging interpretation model for the study area.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] This invention provides a method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs. It utilizes the inverse relationship between natural gamma ray size and rock grain size, where variations in grain size lead to changes in formation permeability and spontaneous potential amplitude, to qualitatively classify permeable formations. Permeable formations exhibit significant anomalies, with larger anomalies indicating better permeability. Based on limited well information from development wells, the method first standardizes and then normalizes spontaneous potential and natural gamma ray logging curves, then calculates the envelope area between them. This envelope area includes not only formation permeability information reflected by spontaneous potential but also information caused by grain size, and its morphological characteristics show good consistency with formation permeability. Finally, combined with core analysis permeability, a mathematical fitting method is used to establish a permeability logging interpretation model, thereby achieving rapid and quantitative calculation of permeability in predictive wells at continuous depths. This effectively solves the problems of limited data from oilfield development wells and low accuracy in permeability calculation. The method is operable by operators and facilitates rapid large-scale application in production, demonstrating good universality and promotional value.

[0038] Furthermore, compared with existing background technologies, the calculation method of the present invention is simple, universal, and highly accurate, meeting the needs of oilfield production and facilitating rapid large-scale application in production. At the same time, it provides support for fluid identification and optimization of fracturing construction schemes based on accurate permeability calculation. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart of the permeability calculation method for heterogeneous sandstone and mudstone reservoirs according to the present invention;

[0041] Figure 2 This is a comparison chart of the permeability calculation results described in the embodiments of the present invention. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0043] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0044] A method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs, such as Figure 1 As shown, it includes the following steps:

[0045] Step 1 involves conducting routine physical property tests on the core samples from the study area to obtain porosity and permeability data for core analysis. The routine physical property tests for core analysis described in Step 1 are conducted according to the procedures outlined in the standard "Core Analysis Methods SY / T 5336-2006".

[0046] Step 2: Plot the porosity and permeability data from the core analysis along with the corresponding well logging curves on the same graph to align the core analysis depth with the corresponding well logging depth. The corresponding well logging curves include spontaneous potential (SP), natural gamma ray (GR), and sonic transit time (AC) curves. The SP, GR, and AC curves are obtained directly from the well logging data and have one set of depths. The core sample yields a different set of depths. Generally, there is a depth error between the core depth and the depth obtained from the well logging data; therefore, the core depth must be assigned to the corresponding well logging depth.

[0047] Step 3: Standardize the spontaneous potential and spontaneous gamma logging curves.

[0048] Step 4: Adjust the left and right scales of the spontaneous potential and natural gamma logging curves to normalize them.

[0049] Step 5: Calculate the spontaneous potential and the normalized envelope area of ​​the natural gamma logging curve for the corresponding well in the core analysis.

[0050] Step 6 analyzes the relationship between the permeability at the core measurement depth and the corresponding envelope area, and establishes a permeability logging interpretation model for the study area;

[0051] Step 7: Based on the aforementioned permeability logging interpretation model, and combining the sonic transit time, natural gamma (GR), and spontaneous potential logging curves in the predicted well, the permeability in the predicted well can be quickly and quantitatively calculated at continuous depths. The normalized envelope areas of the spontaneous potential and natural gamma logging curves in the predicted well are calculated from the sonic transit time, natural gamma (GR), and spontaneous potential logging curves in the predicted well, and then substituted into the established permeability logging interpretation model for the study area, allowing for rapid and continuous quantitative calculation of the permeability in the predicted well.

[0052] Furthermore, the porosity and permeability of the core analysis described in step 2 are plotted on the same graph as the corresponding well's spontaneous potential (SP), natural gamma (GR), and sonic transit time (AC) logging curves.

[0053] Specifically, the porosity and permeability of the core analysis are displayed in the figure using a bar chart.

[0054] Specifically, based on the correlation between porosity and acoustic transit time, depth correction is performed on the depth points of core analysis using morphological characteristics: locations with high porosity are moved towards locations with high acoustic transit time, and locations with low porosity are moved towards locations with low acoustic transit time.

[0055] Furthermore, the standardization of the spontaneous potential and spontaneous gamma logging curves in step 3 adopts the frequency histogram technique.

[0056] Specifically, the same set of continuous and stable mudstone layers in the study area are selected, and the characteristic peak values ​​of spontaneous potential and natural gamma of each well are statistically analyzed using frequency histograms. The average value is used as the spontaneous potential and natural gamma value of the mudstone in the study area. The difference between the characteristic peak value and the average value of each well is the logging curve correction amount for that well.

[0057] Furthermore, in step 4, since there is a difference in physical dimensions between spontaneous potential and natural gamma, the distribution of spontaneous potential and natural gamma logging values ​​is statistically studied. Combined with the geological characteristics of the study area and the logging response law, the left and right scales of spontaneous potential and natural gamma logging curves are determined, and the spontaneous potential and natural gamma logging curves are normalized so that their data are distributed between [0 1].

[0058] Specifically, the natural potential uses a linear scale, with a scale range of [SP]. L SP R The normalized expression is:

[0059]

[0060] In the formula, SP is the natural potential, in mV; SPL is the scale range value on the left side of the natural potential, SPR is the scale range value on the right side of the natural potential, in mV; and is the normalized data of the natural potential, dimensionless.

[0061] Specifically, natural gamma uses a linear scale, with a scale range of [GR]. L GR R The normalized expression is:

[0062]

[0063] In the formula, GR represents the natural gamma ray logging value, in API. L The range of values ​​for the left-hand scale of natural gamma; GR R The range of natural gamma values ​​on the right side of the scale, in API; GR n The data are normalized to natural gamma and are dimensionless.

[0064] Furthermore, in step 5, the curve after natural potential normalization is displayed on a linear scale [1 0], and the curve after natural gamma normalization is displayed on a linear scale [0 1], and the envelope area between the two is calculated.

[0065] Specifically, the normalized envelope area of ​​the spontaneous potential and spontaneous gamma logging curves is:

[0066] mjc = 1 - SP n -GR n

[0067] In the formula, mjc is the normalized envelope area of ​​the spontaneous potential and natural gamma logging curves; SP n For natural potential normalized data, GR n Data is normalized to natural gamma.

[0068] Furthermore, in step 6, a permeability logging interpretation model for the study area is established by relating the permeability at the core measurement depth point to the envelope area of ​​the corresponding well log.

[0069] Specifically, the permeability of the core analysis is normalized, and the expression is:

[0070]

[0071] In the formula, K is the permeability of the core analysis, in mD; K L The permeability scale range value on the left and K R The values ​​represent the permeability range on the right side of the scale, in mD; K n The data is normalized for penetration rate and is dimensionless.

[0072] Specifically, the normalized permeability logging interpretation model expression is as follows:

[0073] K n =a×mjc b

[0074] In the formula, K n The data represents normalized permeability data, which is dimensionless; mjc represents the envelope area; and a and b are model parameters, which are natural constants. After normalizing the permeability from the core analysis, the envelope area of ​​the corresponding well logging can be substituted into the formula model to obtain the well logging interpretation model for the permeability of the study area, providing a reference for subsequent prediction of permeability in well logging.

[0075] A permeability model is established based on the permeability and envelope area obtained from core analysis. During subsequent prediction, the envelope area obtained from well logging curves is used. This permeability model allows for the quantitative calculation of permeability in heterogeneous sandstone and mudstone reservoirs at continuous depths. The purpose of this invention is to effectively solve the problems of low accuracy in permeability calculation for heterogeneous sandstone and mudstone reservoirs, limited data from development wells, and the inapplicability of new methods. Based on limited well information from oilfield development wells, the spontaneous potential and natural gamma logging curves are first standardized and then normalized. The envelope area between the two is then calculated. Finally, a permeability logging interpretation model is established using a mathematical fitting method combined with core analysis permeability, thereby achieving rapid and quantitative calculation of permeability in predicted wells at continuous depths. This invention is simple, universally applicable, and highly accurate, meeting the needs of oilfield production. It is operable by general interpreters and facilitates rapid large-scale application in production. It also provides support for fluid identification and optimization of fracturing operation schemes based on accurate permeability calculations.

[0076] This invention also provides a permeability calculation system for heterogeneous sandstone and mudstone reservoirs, comprising,

[0077] The module includes a calculation module, a model building module, a plotting module, and a well logging curve processing module.

[0078] The calculation module is used to calculate the envelope area of ​​the corresponding well logging curves after standardization and normalization of the spontaneous potential and natural gamma.

[0079] The plotting module is used to plot the porosity and permeability of the core analysis on the same graph as the logging curves of the corresponding well logging spontaneous potential, spontaneous gamma, and sonic transit time.

[0080] The logging curve processing module is used to standardize and normalize the logging curves of the corresponding well spontaneous potential and natural gamma.

[0081] The model building module is used to build a permeability logging interpretation model for the study area.

[0082] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0083] The following detailed descriptions are all illustrative of embodiments and are intended to provide a further detailed explanation of the present invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present invention.

[0084] Specific Implementation Example 1,

[0085] See Figure 1 This invention provides a method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs, comprising the following steps:

[0086] Step one involves conducting routine physical property tests on core samples from the study area to obtain porosity and permeability data for core analysis. These routine physical property tests are performed according to the procedures outlined in the standard "Core Analysis Methods SY / T 5336-2006".

[0087] Step two, plot the porosity and permeability from the core analysis on the same graph as the corresponding well's spontaneous potential (SP) and compensated acoustic (AC) logging curves (e.g., ...). Figure 2 (As shown). Figure 2 From left to right, the first channel shows the spontaneous potential and spontaneous gamma ray logging curves, and the second channel shows the sonic transit time and porosity logging curves. The porosity from the core analysis is displayed using a bar chart. Figure 2 The 6th and 7th bars in the diagram represent the permeability of the core sample. Based on the correlation between porosity and acoustic transit time, depth correction was performed on the depth points of the core analysis using morphological characteristics: locations with high porosity moved towards locations with high acoustic transit time, and locations with low porosity moved towards locations with low acoustic transit time.

[0088] Step 3: Standardize the spontaneous potential (SP) and natural gamma ray (NGR) logging curves using frequency histogram technology. Selecting a continuous and stable mudstone layer within the study area, the frequency histogram is used to statistically analyze the characteristic peak values ​​of SP and NGR for each well. The average value is taken as the SP and NGR values ​​for the mudstone in the study area. The difference between the characteristic peak value and the average value for each well is the logging curve correction for that well. For the example well, the SP correction is -10 mV, and the NGR correction is -40 API. Figure 2 The third channel in the middle shows the standardized natural potential and natural gamma curve.

[0089] Step four: Combining the geological characteristics and logging response patterns of the study area, statistically analyze the distribution range of spontaneous potential (SP) and natural gamma logging values ​​in the study area. Adjust the left and right scales of the SP and natural gamma logging curves to normalize them, ensuring that their data are distributed between [0 1], thus eliminating the differences in physical dimensions between SP and natural gamma. A linear scale is used for SP, with a scale range of [-20, 100]; a linear scale is used for natural gamma, with a scale range of [0, 200].

[0090] The normalized expression for the spontaneous potential is as follows: Figure 2 SP in lane 4 n curve:

[0091]

[0092] In the formula, SP is the natural potential, mV; SP L and SP R The range of natural potential values, in mV; SP n Natural potential normalized data, dimensionless.

[0093] The natural gamma normalization expression is as follows: Figure 2 GR in Lane 4 n curve:

[0094]

[0095] In the formula, GR is the natural gamma logging value, API; GR L and GR R The natural gamma scale range, API; GR n , let dreams be normalized into data, dimensionless.

[0096] Step 5: Display the curve after natural potential normalization on a linear scale [1 0], and the curve after natural gamma normalization on a linear scale [0 1]. Calculate the envelope area between the two curves, as follows: Figure 2 The envelope area (MJ) curve for the fourth filling section and the sixth filling section:

[0097] MJ = 1 - SP n -GR n

[0098] Step six involves statistically analyzing the permeability at the core measurement depth points along with the corresponding normalized spontaneous potential and natural gamma data to establish a permeability logging interpretation model for the study area.

[0099] The permeability was measured on a logarithmic scale with a range of [0.01 100], and the permeability of the core analysis was normalized.

[0100]

[0101] In the formula, K is the permeability of the core analysis, in mD; K L and K R The permeability scale range is given by mD and K. n Penetration rate data is normalized and dimensionless.

[0102] The relationship between normalized core analysis permeability and the envelope area of ​​normalized spontaneous potential and natural gamma ray was analyzed, and the expression of the normalized permeability logging interpretation model was established as follows:

[0103] K n =a×mjc b

[0104] In the formula, K n The data represents normalized penetration rate data, which is dimensionless; mjc represents the envelope area; and a and b are model parameters, which are natural constants.

[0105] The two parameters a and b in the model were determined by statistical mathematical fitting, where a = 1.4530 and b = 1.2548, and the correlation coefficient of the model reached 0.8678.

[0106] Step 7: Based on the above permeability logging interpretation model, combined with the spontaneous potential and natural gamma logging curves in the predicted well, the permeability in the predicted well can be quickly and continuously calculated quantitatively at continuous depths.

[0107] In actual data processing, a method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs is implemented by writing a program. Figure 2 This image shows a comparison between the calculated permeability and the core analysis. Following steps one through six, the spontaneous potential and natural gamma are standardized, then normalized, and their envelope area is calculated. Finally, a mathematical fitting method is used to establish the relationship between the envelope area and the permeability from the core analysis, thus enabling rapid quantitative calculation of the predicted well permeability at continuous depths. Based on actual data processing results, the permeability accuracy calculated by this patent is significantly higher than previous methods. Figure 2 The calculation results (in the 7th section of the paper) are in good agreement with the core analysis measurements in terms of both shape changes and numerical values, demonstrating the feasibility of this method.

[0108] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs, characterized in that, Includes the following steps: Step 1: Obtain the porosity and permeability of core samples from the study area; Step 2: Plot the porosity and permeability of the core analysis with the corresponding logging curves of spontaneous potential, spontaneous gamma and sonic transit time on the same graph, and correct and align the depth of the core analysis with the depth of the corresponding logging. Step 3: After standardizing and normalizing the logging curves of the corresponding spontaneous potential and natural gamma after depth alignment, calculate the envelope area of ​​the corresponding logging curves of spontaneous potential and natural gamma after standardization and normalization. Step 4: By standardizing and normalizing the envelope area of ​​the corresponding well logging spontaneous potential and natural gamma logging curves, and combining it with the permeability of the core analysis, a permeability logging interpretation model for the study area is established. Step 5: Using the permeability logging interpretation model for the study area, the permeability of heterogeneous sandstone and mudstone reservoirs in the continuous depth logging is quantitatively calculated and predicted. In step 2, the core analysis depth is corrected and aligned with the corresponding well logging depth. The specific process is as follows: by using the correlation between the porosity of the core analysis and the sonic transit time of the corresponding well logging, the depth point of the core analysis is corrected using the morphological characteristics of the core. The location with high porosity is moved towards the direction with high sonic transit time, and the location with low porosity is moved towards the direction with low sonic transit time, thereby achieving the alignment of the core analysis depth with the corresponding well logging depth. The specific process of standardizing the spontaneous potential and natural gamma logging curves of the corresponding wells after depth alignment in step 3 is as follows: Select the same set of continuous and stable mudstone layers in the study area, use the frequency histogram method to count the characteristic peak values ​​of spontaneous potential and natural gamma of each well, take the average value of the characteristic peak values ​​of spontaneous potential and natural gamma among the wells as the spontaneous potential and natural gamma values ​​of the mudstone layers in the study area, and take the difference between the characteristic peak values ​​of spontaneous potential and natural gamma and the average value among the wells as the logging curve correction amount; The specific process of normalizing the spontaneous potential and natural gamma logging curves of the corresponding well logs after depth alignment in step 3 is as follows: Statistically study the distribution of spontaneous potential and natural gamma logging values, combine the geological characteristics of the study area and the logging response law, determine the left and right scales of the spontaneous potential and natural gamma logging curves, normalize the spontaneous potential and natural gamma logging curves, so that the curve after normalization of spontaneous potential is displayed with a linear scale [1 0], and the curve after normalization of natural gamma is displayed with a linear scale [0 1].

2. The method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs according to claim 1, characterized in that, The expression for the normalization of the natural potential is: In the formula, SP is the natural potential, with the unit being mV; SP L SP represents the range of values ​​on the left side of the scale for the natural potential. R This represents the range of values ​​on the right side of the natural potential scale, in mV. These are normalized data of natural potential, dimensionless.

3. The method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs according to claim 2, characterized in that, The expression for the natural gamma normalization is: In the formula, GR represents the natural gamma ray logging value, in API. L The range of values ​​for the left-hand scale of natural gamma; GR R This represents the range of natural gamma values ​​on the right side of the scale, in API. The data are normalized to natural gamma and are dimensionless.

4. The method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs according to claim 1, characterized in that, The formula for calculating the normalized envelope area of ​​the spontaneous potential and spontaneous gamma logging curves is as follows: In the formula, mjc The envelope area after normalization of spontaneous potential and spontaneous gamma logging curves; This is data normalized to natural potential. Data is normalized to natural gamma.

5. The method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs according to claim 2, characterized in that, The permeability of the core analysis in step 4 needs to be normalized. The specific expression is as follows: In the formula, K is the permeability of the core analysis, in mD; The permeability scale range values ​​on the left and The values ​​represent the permeability range on the right side of the scale, in mD. The data is normalized for penetration rate and is dimensionless.

6. The method for calculating the permeability of heterogeneous sandstone and mudstone reservoirs according to claim 1, characterized in that, The expression for the permeability logging interpretation model in step 4 of the study area is as follows: In the formula, The penetration rate data is normalized and dimensionless. mjc Let be the area of ​​the envelope, and a and b be model parameters, which are natural constants.

7. A permeability calculation device for heterogeneous sandstone and mudstone reservoirs, characterized in that, Based on the calculation method described in any one of claims 1-6 include, The module includes a calculation module, a model building module, a plotting module, and a curve processing module. The calculation module is used to calculate the envelope area of ​​the corresponding well logging curves after standardization and normalization of the spontaneous potential and natural gamma. The plotting module is used to plot the porosity and permeability of the core analysis on the same graph as the logging curves of the corresponding well logging spontaneous potential, spontaneous gamma, and sonic transit time. The curve processing module is used to standardize and normalize the logging curves of the corresponding well logging spontaneous potential and natural gamma. The model building module is used to build a permeability logging interpretation model for the study area.

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