Shale porosity logging calculation method with variable skeleton parameters

Abstract

The invention discloses a shale porosity logging calculation method with variable skeleton parameters, and relates to the technical field of logging. According to the method, on the basis of total rock X diffraction core analysis scale lithology scanning logging, core porosity, mineral volume content, a density logging value in logging information, skeleton density and kerogen volume are obtained and combined into a density rock physical volume model, and clay mineral skeleton parameters are obtained; the method comprises the following steps: determining a clay mineral skeleton parameter which changes along with diagenesis such as compaction, obtaining a density porosity volume model by using the changed clay mineral skeleton parameter, replacing a micro neutron logging value with the density logging value to obtain a neutron pore volume model, and combining the obtained density and neutron pore volume models to obtain the porosity. According to the method, the porosity of the shale reservoir with high clay mineral content can be accurately calculated, the framework parameters of the clay minerals under different burial depths are obtained, the calculation precision of the porosity of the shale reservoir is effectively improved, and the reservoir evaluation requirement is met.

Description

Technical Field

[0001] The invention relates to the technical field of well logging, and more particularly to a shale porosity well logging calculation method with variable skeleton parameters. Background Art

[0002] Shale oil is an unconventional oil and gas reservoir. Currently, the rock physics volume model used to calculate shale porosity is mostly a mud sandstone model. Mud sandstone consists of a skeleton (mainly quartz and feldspar), mud (cement) and pores. Compared with mud sandstone, shale reservoirs are rich in organic matter and have a large clay mineral content. Since clay minerals are non-crystalline minerals, their skeleton parameters will change with diagenesis such as compaction under different burial depth conditions, resulting in large changes in rock physical properties, such as density skeleton and neutron skeleton values. Therefore, the use of mud sandstone rock physics volume model to evaluate shale porosity has the following disadvantages:

[0003] 1. This model is applied to conventional reservoirs, which have simple mineral composition and low clay mineral content, which is very different from shale reservoirs, which are rich in organic matter and have high clay mineral content;

[0004] 2. The changes in clay mineral skeleton parameters and kerogen correction were not considered, resulting in poor calculation accuracy.

[0005] The invention patent application published on December 30, 2015, with publication number CN105205296A, entitled "A method for obtaining the porosity of shale gas reservoirs", discloses a method for calculating the porosity of shale gas reservoirs using ESC element logging curves. This method can obtain the reservoir rock skeleton density value that varies with depth, but does not consider the influence of shale's organic-rich characteristics on porosity. The invention patent application published on December 17, 2021, with publication number CN113805249A, entitled "A shale gas-oil ratio evaluation method that eliminates the influence of organic matter and mud content", discloses a method for calculating the effective porosity of shale that eliminates the influence of organic matter and mud content. This method considers the influence of organic matter on porosity. However, neither of these two methods considers the phenomenon that clay minerals as a skeleton change with depth, let alone the law of clay minerals as a skeleton changing with depth. Summary of the invention

[0006] In order to overcome the defects and deficiencies in the above-mentioned prior art, the present invention provides a shale porosity logging calculation method with variable skeleton parameters. The purpose of the present invention is to avoid the problem of difficult selection of clay mineral skeleton parameters and poor calculation accuracy when calculating porosity in conventional rock physics volume model method. Based on the whole rock X-ray diffraction core analysis scale lithology scanning logging, the present invention converts the mineral mass percentage into volume content, calculates the skeleton density of crystalline minerals and clay minerals as supporting skeletons, and converts the TOC content percentage into kerogen, combines the core porosity, mineral volume content, density logging value, skeleton density and kerogen volume obtained from the experiment into the density rock physics volume model, and obtains the clay mineral skeleton parameters; analyzes the difference of each clay mineral skeleton parameter caused by the sedimentation depth, obtains the clay mineral skeleton parameter that changes with the compaction and other diagenetic effects, uses the clay mineral skeleton parameter to obtain the density porosity volume model, replaces the above density logging value with the neutron logging value to obtain the neutron pore volume model, and finally, combines the obtained density and neutron pore volume models to obtain the porosity. The present invention can accurately calculate the porosity of shale reservoirs with high clay mineral content, and combine density and neutron logging response equations to obtain clay mineral skeleton parameters at different burial depths, effectively improving the calculation accuracy of shale reservoir porosity and meeting reservoir evaluation requirements.

[0007] In order to solve the problems existing in the above-mentioned prior art, the present invention is implemented through the following technical solutions.

[0008] The present invention provides a shale porosity logging calculation method with variable skeleton parameters, the method comprising the following steps:

[0009] S1. Based on the whole-rock X-ray diffraction core analysis scale lithology scanning logging, the mineral mass percentage is converted into the mineral volume content, the skeleton density of the crystalline minerals and clay minerals as the supporting skeleton is calculated, and the TOC content percentage is converted into kerogen;

[0010] S2. Integrate the core porosity, mineral volume content, density logging value, skeleton density and kerogen volume obtained from the experiment into the density rock physics volume model to obtain various clay mineral skeleton parameters;

[0011] S3. Analyze the differences in clay mineral skeleton parameters caused by sedimentation depth to obtain clay mineral skeleton parameters that change with diagenesis;

[0012] S4, substituting the clay mineral skeleton parameters obtained in step S3 into the skeleton density calculation formula in step S1 to obtain a new skeleton density, and substituting the new skeleton density into the density rock physics volume model in step S2 to obtain a density pore volume model;

[0013] S5, replacing the density logging values ​​in the above steps S2, S3 and S4 with neutron logging values, and performing the same operations as the above steps S2 to S3 to obtain a neutron pore volume model;

[0014] S6. The density pore volume model obtained in step S4 and the neutron pore volume model obtained in step S5 are combined to calculate the porosity.

[0015] Further preferably, in step S1, based on the whole-rock X-ray diffraction core analysis scale lithology scanning logging, the mineral mass percentage is converted into the mineral volume content, the continuous mineral profile that changes with depth is obtained, the skeleton density of crystalline minerals and clay minerals as the supporting skeleton is calculated, and the TCO content percentage is converted into kerogen.

[0016] More preferably, in step S1, the calculation formula of the skeleton density is:

[0017] In the formula, ρ ma Indicates skeleton density, g / cm 3 ; m represents the number of crystalline minerals, n represents the number of clay minerals, M csti Indicates the mass percentage of the i-th crystal type mineral, %; M clj represents the mass percentage of the jth clay mineral, %; ρ csti Indicates the density logging skeleton parameter of the ith crystal type mineral, g / cm 3 ρ clj represents the density logging skeleton parameter of the clay mineral in the jth layer, g / cm 3 .

[0018] More preferably, in step S1, the calculation formula for converting the mineral mass percentage into the mineral volume content is: Where V i Indicates the volume content of the mineral in the i-th element, %; M i Indicates the mass percentage of the i-th mineral, %; ρ i Represents the density logging skeleton parameter of the i-th crystal type mineral, g / cm 3 .

[0019] More preferably, in step S1, the conversion formula for converting the TOC content percentage to kerogen is:

[0020] In the formula, ρ ker represents the kerogen density parameter; k represents the conversion coefficient; ρ b Indicates the logging density value, g / cm 3 ; V ker Indicates kerogen volume content, %.

[0021] More preferably, the conversion coefficient k=1.2.

[0022] Further preferably, in step S2, the core porosity, the density logging value in the logging data, the skeleton density and the kerogen volume are combined into the density rock physics volume model, and the optimization algorithm is used to obtain various clay mineral skeleton parameters. The specific formula is as follows:

[0023] ρ b =ρ ma ×(1-V ker -φ)+ρ ker ×V ker +ρ fl ×φ;

[0024] In the formula, ρ ma Indicates skeleton density, g / cm 3 ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ; φ represents the core porosity, %.

[0025] Further preferably, step S3 specifically includes finding the laws of various clay mineral skeleton parameters under different burial depths and reservoir formation conditions, and establishing a formula for clay mineral skeleton parameters affected by compaction.

[0026] More preferably, the clay mineral skeleton parameter formula affected by compaction is:

[0027] ρ cli =a i ×DEPTH; where DEPTH represents the burial depth, m; a i represents the correction coefficient of clay mineral in the ith layer; ρ cli represents the density logging skeleton parameter after correction of clay minerals in the ith layer, g / cm 3 .

[0028] Further preferably, in step S5, the established neutron pore volume model is

[0029] CNL=CNL ma ×(1-V ker -φ N )+CNL ker ×V ker +CNL fl ×φ N ;

[0030] Where, CNL represents the neutron logging value, %; CNL ma Indicates the neutron value of the mineral skeleton, %; V ker Indicates kerogen volume content, %; φ N Indicates porosity, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

[0031] Further preferably, in step S6, the density pore volume model obtained in step S4 and the neutron pore volume model obtained in step S5 are combined to calculate the porosity, and the specific formula is:

[0032]

[0033] In the formula, φ D Indicates the porosity calculated from density logging value, %; φ N Indicates the porosity calculated by neutron logging value, %; φ t represents the calculated porosity, %; ρ ma Indicates skeleton density, g / cm 3 ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ;CNL represents neutron logging value, %;CNL ma Indicates the neutron value of the mineral skeleton, %; V ker Indicates kerogen volume content, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

[0034] Compared with the prior art, the beneficial technical effects brought by the present invention are as follows:

[0035] The present invention provides a shale logging porosity calculation method with variable clay mineral skeleton parameters. The method can accurately calculate the porosity of shale reservoirs with a large clay mineral content. The technology avoids the shortcomings of the conventional rock physics volume model method, that is, the difficulty in selecting clay mineral skeleton parameters and the poor calculation accuracy when calculating porosity. The clay mineral skeleton parameters at different burial depths are obtained by combining density and neutron logging response equations, thereby effectively improving the calculation accuracy of shale reservoir porosity and meeting reservoir evaluation requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1A flow chart of a shale porosity logging calculation method with variable skeleton parameters provided by the present invention;

[0037] Figure 2 A diagram of a shale porosity rock physics model used in an embodiment of the present invention;

[0038] Figure 3 This is a graph showing the variation of clay mineral density logging skeleton parameters with sedimentation depth in an embodiment of the present invention;

[0039] Figure 4 This is a graph showing the variation of clay mineral neutron logging skeleton parameters with deposition depth in an embodiment of the present invention;

[0040] Figure 5 This is a graph of the porosity logging calculation results of the first section of the core sampling of the XX well obtained by using the method of the present invention in an embodiment of the present invention;

[0041] Figure 6 This is a graph of the porosity logging calculation results of the second section of the core sampling of the XX well obtained by using the method of the present invention in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following is an exemplary embodiment of the present invention that helps to fully understand the claims and their equivalents in conjunction with the accompanying drawings, wherein the specific details will be considered as exemplary only, and do not limit the scope of the present invention. Therefore, those of ordinary skill in the art can make various changes and modifications to the embodiments without departing from the scope and spirit of the present invention.

[0043] Example 1

[0044] As a preferred embodiment of the present invention, refer to the attached specification Figure 1 As shown, this embodiment discloses a shale porosity logging calculation method with variable skeleton parameters, the method comprising the following steps:

[0045] S1. Based on the whole-rock X-ray diffraction core analysis scale lithology scanning logging, the mineral mass percentage is converted into the mineral volume content, the skeleton density of the crystalline minerals and clay minerals as the supporting skeleton is calculated, and the TOC content percentage is converted into kerogen;

[0046] S2. Integrate the core porosity, mineral volume content, density logging value, skeleton density and kerogen volume obtained from the experiment into the density rock physics volume model to obtain various clay mineral skeleton parameters;

[0047] S3. Analyze the differences in clay mineral skeleton parameters caused by sedimentation depth to obtain clay mineral skeleton parameters that change with diagenesis;

[0048] S4, substituting the clay mineral skeleton parameters obtained in step S3 into the skeleton density calculation formula in step S1 to obtain a new skeleton density, and substituting the new skeleton density into the density rock physics volume model in step S2 to obtain a density pore volume model;

[0049] S5, replacing the density logging values ​​in the above steps S2, S3 and S4 with neutron logging values, and performing the same operations as the above steps S2 to S3 to obtain a neutron pore volume model;

[0050] S6. The density pore volume model obtained in step S4 and the neutron pore volume model obtained in step S5 are combined to calculate the porosity.

[0051] Example 2

[0052] As another preferred embodiment of the present invention, this embodiment further elaborates and supplements the technical solution of the present invention on the basis of the above-mentioned embodiment 1. In this embodiment, in step S1, based on the whole rock X-ray diffraction core analysis scale lithology scanning logging, the mineral mass percentage is converted into the mineral volume content, the continuous mineral profile that changes with depth is obtained, the skeleton density of the crystalline minerals and clay minerals as the supporting skeleton is calculated, and the TCO content percentage is used to convert it into kerogen.

[0053] In step S1, the calculation formula of skeleton density is:

[0054] In the formula, ρ ma Indicates skeleton density, g / cm 3 ; m represents the number of crystalline minerals, n represents the number of clay minerals, M csti Indicates the mass percentage of the i-th crystal type mineral, %; M clj represents the mass percentage of the jth clay mineral, %; ρ csti Indicates the density logging skeleton parameter of the ith crystal type mineral, g / cm 3 ρ clj represents the density logging skeleton parameter of the clay mineral in the jth layer, g / cm 3 .

[0055] In step S1, the calculation formula for converting mineral mass percentage into mineral volume content is: Where V i Indicates the volume content of the mineral in the i-th element, %; M i Indicates the mass percentage of the i-th mineral, %; ρ i Represents the density logging skeleton parameter of the i-th crystal type mineral, g / cm 3 .

[0056] In step S1, the conversion formula for converting TOC content percentage to kerogen is:

[0057] In the formula, ρ ker represents the kerogen density parameter; k represents the conversion coefficient; ρ b Indicates the logging density value, g / cm 3 ; V ker Indicates kerogen volume content, %.

[0058] As an example, the conversion coefficient k=1.2.

[0059] Example 3

[0060] As another preferred embodiment of the present invention, this embodiment is a further detailed supplement and elaboration of the technical solution of the present invention based on the above-mentioned embodiment 1 or embodiment 2. In this embodiment, in step S2, the core porosity, the density logging value in the logging data, the skeleton density and the kerogen volume are combined into the density rock physics volume model, and the optimization algorithm is used to obtain various clay mineral skeleton parameters. The specific formula is as follows:

[0061] ρ b =ρ ma ×(1-V ker -φ)+ρ ker ×V ker +ρ fl ×φ;

[0062] In the formula, ρ ma Indicates skeleton density, g / cm 3 ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ; φ represents the core porosity, %.

[0063] The specific step S3 is to find the law of various clay mineral skeleton parameters under different burial depths and reservoir formation conditions, and establish a formula for clay mineral skeleton parameters affected by compaction.

[0064] More preferably, the clay mineral skeleton parameter formula affected by compaction is:

[0065] ρ cli =a i ×DEPTH; where DEPTH represents the burial depth, m; a irepresents the correction coefficient of clay mineral in the ith layer; ρ cli represents the density logging skeleton parameter after correction of clay minerals in the ith layer, g / cm 3 .

[0066] In step S5, the neutron pore volume model is established as

[0067] CNL=CNL ma ×(1-V ker -φ N )+CNL ker ×V ker +CNL fl ×φ N ;

[0068] Where, CNL represents the neutron logging value, %; CNL ma Indicates the neutron value of the mineral skeleton, %; V ker Indicates kerogen volume content, %; φ N Indicates porosity, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

[0069] In step S6, the density pore volume model and the neutron pore volume model obtained in step S4 are combined to calculate the porosity. The specific formula is:

[0070]

[0071] In the formula, φ D Indicates the porosity calculated from density logging value, %; φ N Indicates the porosity calculated by neutron logging value, %; φ t represents the calculated porosity, %; ρ ma Indicates skeleton density, g / cm 3 ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ;CNL represents neutron logging value, %;CNL ma Indicates the neutron value of the mineral skeleton, %; V ker Indicates kerogen volume content, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

[0072] Example 4

[0073] As another preferred embodiment of the present invention, please refer to the attached specification. Figure 1 To Attachment Figure 6 As shown, a shale porosity logging calculation method with variable skeleton parameters includes the following steps:

[0074] Step 1: Based on the whole-rock X-ray diffraction core analysis scale lithology scanning logging, the mineral mass percentage is converted into volume content, and the continuous mineral profile that changes with depth is obtained. The skeleton density of crystalline minerals and clay minerals as the supporting skeleton is calculated and converted into kerogen using the TOC content percentage. The specific process will be carried out according to the following formula: In the formula, ρ ma Indicates skeleton density, g / cm 3 ; m represents the number of crystalline minerals, n represents the number of clay minerals, M csti Indicates the mass percentage of the i-th crystal type mineral, %; M clj represents the mass percentage of the jth clay mineral, %; ρ csti Indicates the density logging skeleton parameter of the ith crystal type mineral, g / cm 3 ρ clj represents the density logging skeleton parameter of the clay mineral in the jth layer, g / cm 3 .

[0075] The formula for converting mineral mass percentage to mineral volume content is: Where V i Indicates the volume content of the mineral in the i-th element, %; M i Indicates the mass percentage of the i-th mineral, %; ρ i Represents the density logging skeleton parameter of the i-th crystal type mineral, g / cm 3 .

[0076] The conversion formula for TOC content percentage to kerogen is:

[0077] In the formula, ρ ker represents the kerogen density parameter; k represents the conversion coefficient, generally k=1.2; ρ b Indicates the logging density value, g / cm 3 ; V ker Indicates kerogen volume content, %.

[0078] From the whole rock X-ray diffraction core analysis and lithology scanning logging, it is known that the main mineral components of Well XX are quartz, illite, chlorite, potassium feldspar, albite, dolomite, calcite, pyrite and siderite. The mineral mass percentage is converted into volume content, and the continuous mineral profile of Well XX with depth is obtained. The following Table 1 is the skeleton fixed value parameter table used in Well XX; Figure 5 , Figure 6 The 6th track is a continuous mineral profile.

[0079] Table 1 is the skeleton setting parameter table used in XX well

[0080] Rock Type Density(g / cm3) neutron(%) Calcite 2.71 0 dolomite 2.847 2.5 Potassium feldspar 2.57 -0.6 Sodium feldspar 2.61 -0.5 Pyrite 4.987 -1.9 quartz 2.65 -5 Siderite 3.96 18.4 Kerogen 1.2 50 fluid 0.95 96 Step 2: Substitute the core porosity, density logging value, skeleton density and kerogen volume into the established density rock physics volume model formula, and use the optimization algorithm to obtain various clay mineral skeleton parameters. The specific formula is as follows:

[0081] ρ b =ρ ma ×(1-V ker -φ)+ρ ker ×V ker +ρ fl ×φ;

[0082] In the formula, ρ ma Indicates skeleton density, g / cm 3 ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ; φ represents the core porosity, %.

[0083] Step 3: Analyze the differences in the skeleton parameters of various clay minerals caused by the sedimentation depth, and obtain the clay mineral skeleton parameters that change with the compaction and other diagenetic effects. Specifically, find the law of various clay mineral skeleton parameters under different burial depth accumulation conditions (see Figure 3 , Figure 4 ), and establish the clay mineral skeleton formula affected by compaction.

[0084] The clay mineral skeleton parameter formula affected by compaction is:

[0085] ρ cli =a i ×DEPTH; where DEPTH represents the burial depth, m; a i represents the correction coefficient of clay mineral in the ith layer; ρ cli represents the density logging skeleton parameter after correction of clay minerals in the ith layer, g / cm 3 .

[0086] Figure 3 , Figure 4This is a graph showing the changes in clay mineral density and neutron logging skeleton parameters with sedimentation depth for Well XX and its adjacent wells.

[0087] Step 4: Substitute the clay mineral skeleton parameters obtained in step 3 into the skeleton density calculation formula in step 1 to obtain a new skeleton density, and substitute the new skeleton density into the density rock physics volume model in step 2 to obtain a density pore volume model.

[0088] Step 5: Replace the density logging values ​​in steps 2, 3, and 4 with neutron logging values, and use the same operation as in the above steps to obtain the neutron pore volume model. The established neutron pore volume model is

[0089] CNL=CNL ma ×(1-V ker -φ N )+CNL ker ×V ker +CNL fl ×φ N ;

[0090] Where, CNL represents the neutron logging value, %; CNL ma Indicates the neutron value of the mineral skeleton, %; Vk er Indicates kerogen volume content, %; φ N Indicates porosity, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

[0091] Step 6: The density pore volume model obtained in step 4 and the neutron pore volume model obtained in step 5 are combined to calculate the porosity. The specific formula is:

[0092]

[0093] In the formula, φ D Indicates the porosity calculated from density logging value, %; φ N Indicates the porosity calculated by neutron logging value, %; φ t represents the calculated porosity, %; ρ ma Indicates skeleton density, g / cm 3 ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ;CNL represents neutron logging value, %;CNL maIndicates the neutron value of the mineral skeleton, %; V ker Indicates kerogen volume content, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

[0094] Figure 5 , Figure 6 Track 2 is the lithofacies of the coring section, Tracks 3-5 are conventional logging curves, Track 6 is the continuous mineral profile, and Track 7 is the core porosity and calculated porosity.

[0095] While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the claims.

Claims

1. A shale porosity logging calculation method with variable skeleton parameters, characterized in that: The method comprises the following steps, S1. Based on the whole-rock X-ray diffraction core analysis scale lithology scanning logging, the mineral mass percentage is converted into the mineral volume content, the skeleton density of the crystalline minerals and clay minerals as the supporting skeleton is calculated, and the TOC content percentage is converted into kerogen; S2. Integrate the core porosity, mineral volume content, density logging value, skeleton density and kerogen volume obtained from the experiment into the density rock physics volume model to obtain various clay mineral skeleton parameters; S3. Analyze the differences in clay mineral skeleton parameters caused by sedimentation depth to obtain clay mineral skeleton parameters that change with diagenesis; S4, substituting the clay mineral skeleton parameters obtained in step S3 into the skeleton density calculation formula in step S1 to obtain a new skeleton density, and substituting the new skeleton density into the density rock physics volume model in step S2 to obtain a density pore volume model; S5, replacing the density logging values ​​in the above steps S2, S3 and S4 with neutron logging values, and performing the same operations as the above steps S2 to S3 to obtain a neutron pore volume model; S6. The density pore volume model obtained in step S4 and the neutron pore volume model obtained in step S5 are combined to calculate the porosity.

2. The shale porosity logging calculation method with variable skeleton parameters according to claim 1, characterized in that: In step S1, based on the whole-rock X-ray diffraction core analysis scale lithology scanning logging, the mineral mass percentage is converted into mineral volume content, the continuous mineral profile that changes with depth is obtained, the skeleton density of crystalline minerals and clay minerals as the supporting skeleton is calculated, and the TCO content percentage is converted into kerogen.

3. The shale porosity logging calculation method with variable skeleton parameters according to claim 2, characterized in that: In step S1, the calculation formula of skeleton density is: In the formula, ρ ma Indicates skeleton density, g / cm 3 ; m represents the number of crystalline minerals, n represents the number of clay minerals, M csti Indicates the mass percentage of the i-th crystal type mineral, %; M clj represents the mass percentage of the jth clay mineral, %; ρ csti Indicates the density logging skeleton parameter of the ith crystal type mineral, g / cm 3 ; ρ clj represents the density logging skeleton parameter of the clay mineral in the jth layer, g / cm 3 .

4. The shale porosity logging calculation method with variable skeleton parameters according to claim 2, characterized in that: In step S1, the calculation formula for converting mineral mass percentage into mineral volume content is: Where V i represents the volume content of the mineral in the ith position, %; M i Indicates the mass percentage of the i-th mineral, %; ρ i Represents the density logging skeleton parameter of the i-th crystal type mineral, g / cm 3 .

5. The shale porosity logging calculation method with variable skeleton parameters according to claim 2, characterized in that: In step S1, the conversion formula for converting TOC content percentage to kerogen is: In the formula, ρ ker represents the kerogen density parameter; k represents the conversion coefficient; ρ b Indicates the logging density value, g / cm 3 ; V ker Indicates kerogen volume content, %.

6. The shale porosity logging calculation method with variable skeleton parameters according to claim 5, characterized in that: The conversion coefficient k=1.

2.

7. A shale porosity logging calculation method with variable skeleton parameters according to any one of claims 1 to 6, characterized in that: In step S2, the core porosity, density logging values ​​in the logging data, skeleton density and kerogen volume are combined into the density rock physics volume model, and the optimization algorithm is used to obtain various clay mineral skeleton parameters. The specific formula is as follows: r b =ρ ma ×(1-V ker -φ)+ρ ker ×V ker +r fl ×φ; In the formula, ρ ma Indicates skeleton density, g / cm 3 ; ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ; φ represents the core porosity, %.

8. A shale porosity logging calculation method with variable skeleton parameters according to any one of claims 1 to 6, characterized in that: The specific step S3 is to find the law of various clay mineral skeleton parameters under different burial depths and reservoir formation conditions, and establish a formula for clay mineral skeleton parameters affected by compaction.

9. The shale porosity logging calculation method with variable skeleton parameters according to claim 8, characterized in that: The clay mineral skeleton parameter formula affected by compaction is: ρ cli =a i ×DEPTH; where DEPTH represents the burial depth, m; a i represents the correction coefficient of clay mineral in the ith layer; ρ cli represents the density logging skeleton parameter after correction of clay minerals in the ith layer, g / cm 3 .

10. A shale porosity logging calculation method with variable skeleton parameters according to any one of claims 1 to 6, characterized in that: In step S5, the neutron pore volume model is established as CNL=CNL ma ×(1-V ker -φ N )+CNL ker ×V ker +CNL fl ×φ N ; Where, CNL represents the neutron logging value, %; CNL ma Indicates the neutron value of the mineral skeleton, %; V ker Indicates kerogen volume content, %; φ N Indicates porosity, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

11. The shale porosity logging calculation method with variable skeleton parameters according to claim 10, characterized in that: In step S6, the density pore volume model obtained in step S4 and the neutron pore volume model obtained in step S5 are combined to calculate the porosity. The specific formula is: In the formula, φ D Indicates the porosity calculated from density logging value, %; φ N Indicates the porosity calculated by neutron logging value, %; φ t represents the calculated porosity, %; ρ ma Indicates skeleton density, g / cm 3 ; ρ b Indicates the logging density value, g / cm 3 ; V ker represents the volume content of kerogen, %; ρ ker Represents kerogen density parameter, g / cm 3 ρ fl Indicates fluid density parameter, g / cm 3 ;CNL represents neutron logging value, %;CNL ma Indicates the neutron value of the mineral skeleton, %; V ker Indicates kerogen volume content, %; CNL ker represents kerogen neutron parameter, %; CNL fl Represents the fluid neutron parameter, %.

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