System, method, device and medium for evaluating effectiveness of mudstone biogas reservoir

Abstract

The present application relates to the technical field of unconventional oil and gas reservoir effectiveness logging interpretation and evaluation, in particular to a mudstone biogas reservoir effectiveness evaluation system, method, device and medium. The correlation between the sand content index and the shale content is used to establish a shale content calculation model for high shale formation, and the shale content is calculated. This method greatly improves the calculation accuracy of shale content and effectively solves the problems of reservoir leakage and other problems in the process of calculating shale content in the prior art. Then, the shale content is used to calculate the effective porosity, the shale content and the effective porosity are used to calculate the permeability, and the effective porosity and the permeability are used to evaluate the effectiveness of the mudstone biogas reservoir. The shale content and reservoir physical property parameters calculated by the above method have good consistency with core analysis data, can truly reflect the formation conditions, and the evaluation results are more accurate, providing a reliable basis for subsequent oil and gas exploitation. The problem of low accuracy of mudstone biogas reservoir judgment in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of unconventional oil and gas reservoir effectiveness logging interpretation and evaluation, in particular to a mudstone biogas reservoir effectiveness evaluation system, method, device and medium. BACKGROUND

[0002] The mudstone biogas potential tapping interval has the characteristics of weak diagenesis, weak cementation, loose lithology, high argillaceous content and thin reservoir. The reservoir characteristics are quite different from those of the main gas layer. From the mudstone gas wells that have been produced, the argillaceous content of the mudstone biogas target interval is higher than that of the main gas reservoir as a whole, and is mainly thin interbedded. The argillaceous content calculated by the natural gamma curve of the main gas reservoir cannot be identified and divided into reservoirs in the mudstone gas interval, resulting in the loss of gas layers. From the core physical property analysis data, the total porosity of sandstone and mudstone is similar, both around 35%. The total porosity and permeability calculated by the main model in the mudstone interval cannot reflect the differences between the reservoir and the surrounding rock, and between the reservoirs, especially in the high argillaceous content formation of the mudstone biogas reservoir. The main model cannot effectively evaluate the reservoir.

[0003] At present, the main methods for determining argillaceous content at home and abroad are as follows:

[0004] The determination of argillaceous content Vsh is of great significance in the quantitative interpretation of argillaceous sandstone reservoirs. Over the years, many theories and methods for calculating argillaceous content Vsh have been proposed. At present, the methods for calculating argillaceous content Vsh can be divided into two categories. One is based on rock physical experiments, and each measurement point is calculated to obtain an argillaceous content Vsh, and then the best value is obtained. The other is based on logging curves. When the rock contains argillite, various logging curves are more or less affected by argillite, and the degree of influence is determined by the argillaceous content Vsh. When evaluating the characteristics of the rock, only when the argillaceous content Vsh is known, the influence of argillite can be corrected.

[0005] Generally speaking, natural gamma or gamma spectrum or spontaneous potential is better for calculating argillaceous content, but natural gamma requires that the other substances in the reservoir do not contain radioactive minerals except argillite. The spontaneous potential requires that the formation water resistivity remains unchanged, and the composition of argillite in the reservoir is the same as that of the adjacent mudstone. The calculation of argillaceous content by other logging curve methods requires more stringent conditions, and the resistivity method requires that the porosity and water saturation of the reservoir are small.

[0006] Due to the characteristics of weak diagenesis, high argillaceous matter and thin interbedding of the mudstone biogas target layer, the variation range of the logging natural gamma and natural potential curve is small; the traditional model of calculating argillaceous content Vsh by using natural gamma is adopted: Larionov (1969), Steiber (1970), Clavier (1971), when there are high gamma non-clay minerals such as potassium feldspar and mica, the argillaceous content Vsh calculated by using natural gamma is high. SUMMARY

[0007] In view of the low precision of the existing mudstone biogas reservoir effectiveness evaluation, the present application provides a mudstone biogas reservoir effectiveness evaluation method.

[0008] To achieve the above purpose, the present application adopts the following technical solutions:

[0009] The present application provides a mudstone biogas reservoir effectiveness evaluation method, comprising the following steps:

[0010] Obtaining the neutron curve and the natural gamma curve of the logging;

[0011] Normalizing the neutron curve to obtain the normalized neutron curve, and normalizing the natural gamma curve to obtain the normalized natural gamma curve;

[0012] Combining the normalized neutron curve and the normalized natural gamma curve to construct a sand content index curve;

[0013] Calculating the argillaceous content by using the sand content index curve;

[0014] Calculating the effective porosity by using the argillaceous content;

[0015] Calculating the permeability by using the argillaceous content and the effective porosity;

[0016] Evaluating the effectiveness of the mudstone biogas reservoir by using the effective porosity and the permeability.

[0017] Further, the method for normalizing the neutron curve to obtain the normalized neutron curve is:

[0018] Obtaining the maximum value of the neutron curve and the minimum value of the neutron curve;

[0019] Calculating the normalized neutron curve value by using the maximum value of the neutron curve and the minimum value of the neutron curve, and the method is:

[0020] DCN=(CNmax-CN) / (CNmax-CNmin) (1)

[0021] Wherein, DCN is the normalized neutron curve value, CNmax is the neutron curve maximum value, CNmin is the neutron curve minimum value, and CN is the neutron curve value;

[0022] The normalized neutron curve is constructed by using the normalized neutron curve value.

[0023] Further, the method for normalizing the natural gamma curve to obtain the normalized natural gamma curve is:

[0024] The maximum value of the natural gamma curve and the minimum value of the natural gamma curve are obtained.

[0025] The normalized natural gamma curve value is calculated by using the maximum value of the natural gamma curve and the minimum value of the natural gamma curve, and the method is:

[0026] DGR=(GRmax-GR) / (GRmax-GRmin) (2)

[0027] Wherein, DGR is the normalized neutron curve value, GRmax is the maximum value of the natural gamma curve, GRmin is the minimum value of the natural gamma curve, and GR is the natural gamma curve value.

[0028] The normalized natural gamma curve is constructed by using the normalized natural gamma curve value.

[0029] Further, the method for combining the normalized neutron curve and the normalized natural gamma curve to construct the sand content index curve is:

[0030] The normalized neutron curve value and the normalized natural gamma curve value are obtained.

[0031] The sand content index curve model is constructed by using the normalized neutron curve value and the normalized natural gamma curve value, and the sand content index is calculated by using the sand content index curve model, and the method is:

[0032] FSD=DCN-DGR (3)

[0033] Wherein, FSD is the sand content index, DCN is the normalized neutron curve value, and DGR is the normalized natural gamma curve value.

[0034] The sand content index curve is constructed by using the sand content index.

[0035] Further, the method for calculating the shale content by using the sand content index curve is:

[0036] The core analysis shale content data is obtained.

[0037] The core analysis shale content data is fitted with the sand content index curve to establish a shale content calculation model, and the method is:

[0038] Vsh=a×eb×FSD (4)

[0039] Wherein, Vsh is the shale content, a and b are the index function coefficients, and FSD is the sand index;

[0040] The shale content is calculated by using the shale content calculation model.

[0041] Further, the method for calculating the effective porosity by using the shale content is:

[0042] The correlation between the clay porosity and the shale content obtained by core analysis is acquired;

[0043] The clay porosity calculation model is established according to the correlation between the clay porosity and the shale content obtained by core analysis;

[0044] The clay porosity is calculated by using the clay porosity calculation model;

[0045] The density curve and the neutron curve of the well logging are acquired;

[0046] The total porosity is calculated by using the density curve and the neutron curve of the well logging;

[0047] The effective porosity is calculated by using the clay porosity and the total porosity.

[0048] Further, the method for calculating the permeability by using the shale content and the effective porosity is:

[0049] The correlation between the irreducible water saturation obtained by core analysis and the shale content and the effective porosity is acquired;

[0050] The irreducible water saturation calculation model is established according to the correlation between the irreducible water saturation obtained by core analysis and the shale content and the effective porosity;

[0051] The irreducible water saturation is calculated by using the irreducible water saturation calculation model;

[0052] The correlation between the permeability obtained by core analysis and the effective porosity and the irreducible water saturation is acquired;

[0053] The permeability calculation model is established according to the correlation between the permeability obtained by core analysis and the effective porosity and the irreducible water saturation;

[0054] The permeability is calculated by using the permeability calculation model.

[0055] A mudstone biogas reservoir evaluation system, comprising:

[0056] The data acquisition module is configured to acquire the neutron curve and the natural gamma curve of the well logging;

[0057] The normalization processing module is configured to normalize the neutron curve to obtain a normalized neutron curve, and normalize the natural gamma ray curve to obtain a normalized natural gamma ray curve.

[0058] The sand index curve construction module is configured to combine the normalized neutron curve and the normalized natural gamma ray curve to construct a sand index curve.

[0059] The shale content calculation module is configured to calculate the shale content by using the sand index curve.

[0060] The effective porosity calculation module is configured to calculate the effective porosity by using the shale content.

[0061] The permeability calculation module is configured to calculate the permeability by using the shale content and the effective porosity.

[0062] The shale gas reservoir effectiveness evaluation module is configured to evaluate the effectiveness of the shale gas reservoir by using the effective porosity and the permeability.

[0063] A terminal device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the above method when executing the computer program.

[0064] A computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the above method.

[0065] Compared with the prior art, the present application has the following beneficial effects:

[0066] The present application provides a method for evaluating the effectiveness of mudstone biogas reservoirs, which adopts rock physical experiment analysis data and logging response characteristics for comparative analysis, and finds that when the shale content increases, the formation irreducible water increases as a whole, and the neutron logging value increases accordingly, so the neutron curve can reflect the formation sand content to a certain extent. The method combines the neutron curve and the natural gamma curve to construct a calculation model of the sand content index of the favorable reservoir in the mudstone section to calculate the sand content index. When the sand content index is less than or equal to 0, it represents a high shale cap rock, and when the sand content index is greater than 0, it represents a sandstone reservoir. The greater the sand content index, the more sand the formation contains and the less shale the formation contains. Accordingly, the favorable gas-bearing layer section can be divided in the high shale formation. The correlation between the sand content index and the shale content is used to establish a shale content calculation model for the high shale formation to calculate the shale content. The method greatly improves the calculation accuracy of the shale content and effectively solves the problems of reservoir loss and the like in the process of calculating the shale content in the prior art. Then, the shale content is used to calculate the effective porosity, the shale content and the effective porosity are used to calculate the permeability, and the effective porosity and the permeability are used to evaluate the effectiveness of the mudstone biogas reservoir. The method takes the sand content index as the core, establishes a reservoir physical parameter model, forms a fine model for calculating the clay porosity, the effective porosity, the irreducible water saturation and the permeability based on the sand content index, and provides a new method for evaluating the effectiveness of the mudstone biogas reservoir based on the sand content index. The shale content and the reservoir physical parameters calculated by the above method have good consistency with the core analysis data, can truly reflect the formation conditions, the mudstone biogas reservoir can be identified by the sand content index model, the shale content, the effective porosity, the irreducible water saturation and the permeability are used to evaluate the effectiveness of the mudstone biogas reservoir, and the evaluation result is more accurate and reliable, thereby providing a reliable basis for subsequent oil and gas exploitation.

[0067] The present application also provides a mudstone biogas reservoir evaluation system, which is provided with a data acquisition module, a normalization processing module, a sand content index curve construction module, a shale content calculation module, an effective porosity calculation module, a permeability calculation module and a mudstone biogas reservoir effectiveness evaluation module, realizes the normalization processing of the neutron curve to obtain a normalized neutron curve, the normalization processing of the natural gamma curve to obtain a normalized natural gamma curve, the combination of the normalized neutron curve and the normalized natural gamma curve to construct a sand content index curve, the calculation of the shale content, the effective porosity and the permeability based on the sand content index curve, and the effectiveness evaluation of the mudstone biogas reservoir based on the effective porosity and the permeability, thereby achieving high evaluation efficiency and high evaluation accuracy and reliability.

[0068] The present application also provides a terminal device, which comprises a memory, a processor, a computer program stored in the memory and executable on the processor, and realizes the above-mentioned method steps.

[0069] The application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the method. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 A schematic diagram of a mudstone biogas reservoir effectiveness evaluation method of the application.

[0071] Figure 2 A core analysis shale content data and sand index curve fitting diagram in shale content calculation in the mudstone biogas reservoir effectiveness evaluation of the application.

[0072] Figure 3 A nuclear magnetic analysis clay porosity data and shale content curve fitting diagram in clay porosity calculation in the mudstone biogas reservoir effectiveness evaluation of the application.

[0073] Figure 4 A core analysis irreducible water saturation value and effective porosity and shale content ratio data fitting diagram in permeability calculation in the mudstone biogas reservoir effectiveness evaluation of the application.

[0074] Figure 5 A well mudstone biogas logging interpretation result diagram obtained by the mudstone biogas reservoir effectiveness evaluation system of the application. DETAILED DESCRIPTION

[0075] In order to make the objects, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described below in connection with the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. The components of the embodiments of the application described and shown in the drawings can be arranged and designed in various different configurations.

[0076] Therefore, the detailed description of the embodiments of the application provided in the drawings below is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the application without creative labor are within the scope of protection of the application.

[0077] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0078] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0079] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0080] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0081] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0082] See also Figure 1 The present invention discloses a method for evaluating the effectiveness of a mudstone biogas reservoir, comprising the following steps:

[0083] S1: Obtain neutron and natural gamma ray curves of well logging;

[0084] S2: Normalize the neutron curve to obtain a normalized neutron curve, and normalize the natural gamma curve to obtain a normalized natural gamma curve, specifically:

[0085] The neutron curve is normalized to obtain the normalized neutron curve as follows:

[0086] Get the maximum value and minimum value of the neutron curve;

[0087] The normalized neutron curve value is calculated using the maximum and minimum values ​​of the neutron curve as follows:

[0088] DCN=(CNmax-CN) / (CNmax-CNmin) (1)

[0089] The normalized neutron curve is constructed by using the normalized neutron curve value.

[0090] The normalized gamma ray curve is obtained by normalizing the natural gamma ray curve.

[0091] The maximum value of the natural gamma ray curve and the minimum value of the natural gamma ray curve are obtained.

[0092] The normalized natural gamma ray curve value is calculated by using the maximum value of the natural gamma ray curve and the minimum value of the natural gamma ray curve, and the method is:

[0093] DGR=(GRmax-GR) / (GRmax-GRmin) (2)

[0094] The normalized natural gamma ray curve is constructed by using the normalized natural gamma ray curve value.

[0095] Wherein, DCN is the normalized neutron curve, CNmax is the maximum value of the neutron curve, CNmin is the minimum value of the neutron curve, and CN is the neutron curve; DGR is the normalized neutron curve, GRmax is the maximum value of the natural gamma ray curve, GRmin is the minimum value of the natural gamma ray curve, and GR is the natural gamma ray curve.

[0096] S3: The normalized neutron curve and the normalized natural gamma ray curve are combined to construct a sand content index curve, and the specific method is:

[0097] The normalized neutron curve value and the normalized natural gamma ray curve value are obtained.

[0098] The sand content index curve model is constructed by using the normalized neutron curve value and the normalized natural gamma ray curve value, and the sand content index is obtained by using the sand content index curve model, and the method is:

[0099] FSD=DCN-DGR (3)

[0100] The sand content index curve is constructed by using the sand content index.

[0101] Wherein, FSD is the sand content index, DCN is the normalized neutron curve value, and DGR is the normalized natural gamma ray curve value.

[0102] In actual production, through the comparison and analysis of the data of rock physical experiment analysis and logging response characteristics, it is found that when the shale content increases, the formation bound water increases as a whole, the neutron logging value increases accordingly, so the neutron curve can reflect the formation sand content to a certain extent. The shale section is divided to build a sand content index calculation model of favorable reservoir. When the sand content index is less than or equal to 0, it represents high shale cap rock; when the sand content index is greater than 0, it represents sandstone reservoir. The greater the sand content index, the more sand the formation contains and the less shale the formation contains. Accordingly, the sand content index can be used as an indication of favorable reservoir in the shale biogas target well section.

[0103] S4: Calculate the shale content by using the sand content index curve, specifically as follows:

[0104] Obtain the core analysis shale content data; the core analysis shale content data can be obtained through X-ray diffraction whole rock experiment analysis;

[0105] Fit the core analysis shale content data with the sand content index curve to establish a shale content calculation model, see Figure 2 , the method is as follows:

[0106] Vsh=a×e b×FSD (4)

[0107] Wherein, Vsh is the shale content, a and b are the coefficients of the exponential function, and FSD is the sand content index;

[0108] Calculate the shale content by using the shale content calculation model.

[0109] S5: Calculate the effective porosity by using the shale content, specifically as follows:

[0110] Obtain the clay porosity obtained by core experiment nuclear magnetic analysis;

[0111] Obtain the correlation between the clay porosity obtained by core analysis and the shale content;

[0112] Since the clay porosity obtained by nuclear magnetic analysis has good correlation with the shale content, the clay porosity model is established by data fitting according to the clay porosity data obtained by nuclear magnetic analysis and the shale content curve, the clay porosity is calculated by using the clay porosity model, see Figure 3 , the method is as follows:

[0113] Φclay=c×Vsh (5)

[0114] Wherein, Φclay is the clay porosity, c is a constant, and Vsh is the shale content;

[0115] Obtain the total porosity obtained by core analysis, the density curve and the neutron curve of logging;

[0116] The total porosity model is established by using the binary linear data fitting of the total porosity obtained by core analysis and the density curve and the neutron curve obtained by logging, and the total porosity is calculated, and the method is:

[0117] Φt=a×CN+b×DEN+c (6)

[0118] Wherein, Φt is the total porosity, CN is the neutron curve value, DEN is the density curve value, a is the neutron coefficient, b is the density coefficient, and c is the constant;

[0119] The effective porosity is calculated by using the clay porosity and the total porosity, and the method is:

[0120] The effective porosity model is established by carrying out shale correction on the total porosity Φt, and the effective porosity is calculated, and the method is:

[0121] Φe=Φt-Φclay (7)

[0122] Wherein, Φe is the effective porosity, Φt is the total porosity, and Φclay is the clay porosity.

[0123] S6: The permeability is calculated by using the shale content and the effective porosity, and the method is:

[0124] The core analysis permeability and the irreducible water saturation are obtained;

[0125] The correlation between the core analysis irreducible water saturation, the shale content and the effective porosity is obtained according to the core analysis permeability and the irreducible water saturation;

[0126] The irreducible water saturation calculation model is established according to the correlation between the core analysis irreducible water saturation, the shale content and the effective porosity, and the method is: the data fitting is carried out on the core analysis irreducible water saturation value and the ratio of the effective porosity to the shale content, the irreducible water saturation model is established, and the irreducible water saturation is calculated, and reference is made to Figure 4 , and the method is:

[0127]

[0128] Wherein, Swi is the irreducible water saturation, a and b are the exponential function coefficients, Φe is the effective porosity, and Vsh is the shale content.

[0129] The ratio of the core analysis permeability and the effective porosity to the irreducible water saturation is linearly fitted, the permeability calculation model is established, and the permeability is calculated, and the method is:

[0130]

[0131] Wherein, K is the permeability, a is the coefficient, Φe is the effective porosity, and Swi is the irreducible water saturation.

[0132] S7: evaluating the effectiveness of the mudstone biogas reservoir using the effective porosity and the permeability. The lower limit criterion of the effective reservoir porosity is 23%, and the lower limit criterion of the permeability is 20 mD.

[0133] A mudstone biogas reservoir evaluation system comprises:

[0134] A data acquisition module is configured to acquire a neutron curve and a natural gamma curve of a well log.

[0135] A normalization processing module is configured to normalize the neutron curve to obtain a normalized neutron curve and normalize the natural gamma curve to obtain a normalized natural gamma curve.

[0136] A sand content index curve construction module is configured to combine the normalized neutron curve and the normalized natural gamma curve to construct a sand content index curve.

[0137] A shale content calculation module is configured to calculate the shale content using the sand content index curve.

[0138] An effective porosity calculation module is configured to calculate the effective porosity using the shale content.

[0139] A permeability calculation module is configured to calculate the permeability using the shale content and the effective porosity.

[0140] An effectiveness evaluation module of the mudstone biogas reservoir is configured to evaluate the effectiveness of the mudstone biogas reservoir using the effective porosity and the permeability.

[0141] The effectiveness evaluation data and the evaluation results obtained by the system are described below with reference to a well log. Figure 5 and the following table:

[0142]

[0143] Compared with the actual detection results, the results are consistent with the mudstone biogas reservoir data measured by the actual core analysis, and can truly reflect the formation conditions.

[0144] The terminal device comprises a processor, a memory, and a computer program stored in the memory and executable on the processor. The processor executes the computer program to implement the steps in each method embodiment. Alternatively, the processor executes the computer program to implement the functions of each module / unit in each device embodiment.

[0145] 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.

[0146] The terminal device can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. The terminal device can include, but is not limited to, a processor and a memory.

[0147] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like.

[0148] The memory can be used to store the computer programs and / or modules, and the processor can realize various functions of the terminal device by running or executing the computer programs and / or modules stored in the memory, and calling data stored in the memory.

[0149] The modules / units integrated in the terminal 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. Based on this understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the processor executes the computer program, the steps of the above-mentioned various method embodiments can be realized. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc. It should be noted that the computer readable medium can include or exclude contents according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.

[0150] In summary, the present application combines the neutron curve and the natural gamma curve, constructs a shale section division favorable reservoir sand content index calculation model, and represents the sandstone reservoir. The greater the sand content index, the more sand the formation contains, and the less mud the formation contains. Accordingly, the sand content index can be used as an indication of a favorable reservoir in a shale biogas target well section. A reservoir physical parameter model is established with the sand content index as the core, the correlation between effective porosity, permeability and clay bound water saturation is analyzed, and a fine model for calculating shale content, effective porosity, bound water saturation and permeability with the sand content index as the core is formed. The method greatly improves the calculation accuracy of shale content and effectively solves the problem of reservoir leakage.

[0151] The above merely describes the preferred embodiments of the present application and is not intended to limit the technical solutions of the present application in any way. Those skilled in the art should understand that the technical solutions can be modified and replaced in several simple ways without departing from the spirit and principles of the present application, and these modifications and replacements are also within the protection scope of the claims.

Claims

1. A method for evaluating the effectiveness of a mudstone biogas reservoir, characterized in that: The following steps are involved: Obtain neutron curves and natural gamma ray curves of well logging; Normalizing the neutron curve to obtain a normalized neutron curve, and normalizing the natural gamma curve to obtain a normalized natural gamma curve; The normalized neutron curve and the normalized natural gamma ray curve are combined to construct the sand index curve; Use the sand index curve to calculate the mud content; Use the mud content to calculate the effective porosity; Calculate permeability using shale content and effective porosity; The effectiveness of mudstone biogas reservoirs is evaluated using effective porosity and permeability.

2. The method for evaluating the effectiveness of a mudstone biogas reservoir according to claim 1, wherein: The neutron curve is normalized to obtain the normalized neutron curve as follows: Get the maximum value and minimum value of the neutron curve; The normalized neutron curve value is calculated using the maximum and minimum values ​​of the neutron curve as follows: DCN=(CNmax-CN) / (CNmax-CNmin) (1) Wherein, DCN is the normalized neutron curve value, CNmax is the maximum value of the neutron curve, CNmin is the minimum value of the neutron curve, and CN is the neutron curve value; The normalized neutron curve value is used to construct a normalized neutron curve.

3. The method for evaluating the effectiveness of a mudstone biogas reservoir according to claim 1, wherein: The method of normalizing the natural gamma curve to obtain the normalized natural gamma curve is: Get the maximum value and minimum value of the natural gamma curve; The normalized natural gamma curve value is calculated using the maximum value and the minimum value of the natural gamma curve as follows: DGR=(GRmax-GR) / (GRmax-GRmin) (2) Wherein, DGR is the normalized neutron curve value, GRmax is the maximum value of the natural gamma curve, GRmin is the minimum value of the natural gamma curve, and GR is the natural gamma curve value; Construct a normalized natural gamma curve using the normalized natural gamma curve value.

4. The method for evaluating the effectiveness of a mudstone biogas reservoir according to claim 1, wherein: The method of constructing the sand index curve by combining the normalized neutron curve and the normalized natural gamma curve is as follows: Obtain normalized neutron curve values ​​and normalized natural gamma curve values; The normalized neutron curve value and the normalized natural gamma ray curve value are used to construct a sand index curve model, and the sand index is calculated using the sand index curve model. The method is as follows: FSD=DCN-DGR (3) Among them, FSD is the sand content index, DCN is the normalized neutron curve value, and DGR is the normalized natural gamma curve value; Using the sand content index, a sand content index curve is constructed.

5. The method for evaluating the effectiveness of a mudstone biogas reservoir according to claim 1, wherein: Using the sand index curve, the method for calculating the mud content is: Obtain shale content data from core analysis; The core analysis mud content data was fitted with the sand index curve to establish a mud content calculation model. The method is as follows: Vsh=a×e b×FSD (4) Where Vsh is the shale content, a and b are the coefficients of the exponential function, and FSD is the sand content index; The mud content is calculated using the mud content calculation model.

6. The method for evaluating the effectiveness of a mudstone biogas reservoir according to claim 1, wherein: The method for calculating effective porosity using mud content is: Obtain core analysis to determine the correlation between clay porosity and mud content; Based on the correlation between clay porosity and mud content from core analysis, a clay porosity calculation model was established; Calculate the clay porosity using the clay porosity calculation model; Obtain density curve and neutron curve of well logging; Calculate total porosity using density and neutron log curves; Using clay porosity and total porosity, effective porosity is calculated.

7. The method for evaluating the effectiveness of a mudstone biogas reservoir according to claim 1, wherein: The method for calculating permeability using mud content and effective porosity is: Obtain core analysis to determine the correlation between irreducible water saturation, shale content, and effective porosity; Based on the correlation between irreducible water saturation, mud content and effective porosity from core analysis, a calculation model for irreducible water saturation was established; Calculate irreducible water saturation using irreducible water saturation calculation model; Obtain correlation between core analysis permeability and effective porosity and irreducible water saturation; Based on the correlation between permeability, effective porosity and irreducible water saturation obtained from core analysis, a permeability calculation model was established; Calculate the permeability using the permeability calculation model.

8. A mudstone biogas reservoir evaluation system, characterized in that: include: Data acquisition module: used to obtain neutron curves and natural gamma ray curves of well logging; Normalization processing module: used for normalizing the neutron curve to obtain a normalized neutron curve, and normalizing the natural gamma curve to obtain a normalized natural gamma curve; Sand index curve construction module: used to combine the normalized neutron curve and the normalized natural gamma ray curve to construct the sand index curve; Mud content calculation module: used to calculate mud content using sand index curve; Effective porosity calculation module: used to calculate effective porosity using mud content; Permeability calculation module: used to calculate permeability using mud content and effective porosity; Mudstone biogas reservoir effectiveness evaluation module: used to evaluate the effectiveness of mudstone biogas reservoirs using effective porosity and permeability.

9. A terminal device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

Images