Evaluation method for organic carbon content of coal-series hydrocarbon source rock

Abstract

The invention belongs to the technical field of unconventional oil and gas exploration, development and evaluation, and relates to a method for evaluating the organic carbon content of a coal series hydrocarbon source rock, which comprises the following steps of: determining the sound wave and resistivity conversion coefficient of a shale reservoir through core scale sound wave and resistivity curve enveloping; and further considering the influence of sedimentary environment indication and organic carbon source difference on the organic carbon content, constructing an environment influence factor, and forming a new transition phase shale organic carbon evaluation method and calculation model. Compared with a traditional delta LogR theoretical model and a multiple regression calculation model with poor regional universality, the new model not only can reflect the sedimentary change and reservoir feature difference of the sea-land transition phase shale, but also fills the blank of the organic carbon calculation method of the type of the sea-land transition phase shale; the calculation result provides a solid data basis for favorable area optimization and resource quantity evaluation of the sea-land transition phase shale, and the method has good popularization and use values.

Description

Technical Field

[0001] The present invention belongs to the technical field of unconventional oil and gas exploration, development and evaluation, and specifically relates to a method for evaluating the organic carbon content of coal-bearing hydrocarbon source rocks. Background Art

[0002] In the field of self-generated and self-stored unconventional shale oil and gas, organic carbon is an important part of the source rock property evaluation. It is an important parameter for clarifying oil and gas-bearing shale layers. Its content is related to the gas content of the shale. It is also one of the key indicators for optimizing favorable shale oil and gas areas and evaluating resource quantities.

[0003] There are two main methods for obtaining organic carbon content:

[0004] The first type is to obtain measurement data by burning and analyzing rock samples under laboratory conditions with the help of an organic carbon analyzer. Due to the limited number of rock samples, high experimental costs and long time periods, it is difficult to obtain continuous organic matter content data in the vertical direction of a single well, and it is impossible to quickly promote it to neighboring wells over a large area.

[0005] The second method is to use logging and core data to calibrate each other, and realize the quantitative calculation of organic matter abundance in the whole well section through inherent theoretical formulas or regional empirical formulas or machine intelligence algorithms. Regional empirical formulas such as Schmoker, Fertl, Hu Huiting and others proposed to use natural gamma, density, uranium curves and rock sample data to establish empirical formulas for specific research areas. Due to regional limitations, it is difficult to promote; although the machine intelligence algorithm has high calculation accuracy, it relies more on sample data and lacks theoretical basis, making it difficult to adjust according to actual conditions; and the more commonly used theoretical formula is the ΔLogR method proposed by Passey et al. in 1990, and the calculation formula is as follows:

[0006] ΔLogR=lg(R t / R t基线 )+K×(Δt-Δt 基线 )

[0007] TOC=ΔLogR×10 (2.29-0.1688*LOM )

[0008] Where: R t is the formation resistivity, Ω·m; R t基线 is the resistivity of the non-source rock section, Ω·m; Δt is the acoustic time difference, us / ft; Δt 基线 is the acoustic time difference of the non-source rock section, us / ft; LOM is the organic matter maturity index, dimensionless; K is the scale ratio coefficient of resistivity and porosity, dimensionless; TOC is the organic carbon content, %; ΔLogR is the difference coefficient of acoustic wave and resistivity at the baseline.

[0009] The application background of the ΔLogR method is a marine sedimentary environment with simple structure, mainly reducing environment, stable shale distribution, large continuous thickness, low clay content, and relatively homogeneous and complete. Compared with marine shale gas, the marine-continental transitional shale gas, which is concentrated in large basins such as Ordos and Sichuan and accounts for 25% of my country's total shale gas resources, has not yet been developed on a large scale. The reason is that marine-continental transitional shale is mainly formed in sedimentary environments such as tidal flats, lagoons, swamps, and deltas. Affected by changes in sedimentary environment, the thickness and distribution of shale are unstable, the clay content is high, the lithology is diverse and changes rapidly in the vertical direction, and it is often associated with coal seams. A small amount of organic carbon comes from marine plankton, and more comes from terrestrial plants, resulting in great differences in organic carbon content. The results calculated directly using the ΔLogR method have large errors. At present, there is no accurate and effective method to evaluate the organic carbon in marine-continental transitional shale. Summary of the invention

[0010] The purpose of the present invention is to provide a method for evaluating the organic carbon content of coal-bearing source rocks, thereby solving the problem that there is no accurate and effective method for evaluating the organic carbon content of marine-continental transitional shale.

[0011] The present invention is achieved through the following technical solutions:

[0012] The present invention discloses a method for evaluating the organic carbon content of coal-bearing hydrocarbon source rocks, comprising the following steps:

[0013] S1. Obtaining organic carbon experimental data and mineral component experimental data of the same batch of rock samples in the target layer of the target area;

[0014] Obtain the natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curves of each sampling point in the target layer of the target area;

[0015] S2. Using the uranium and thorium curves, the sedimentary environment indicator curves of each sampling point are obtained;

[0016] S3, using the organic carbon experimental data obtained in S1 and the uranium curve of each sampling point to calibrate the core depth, obtain the rock sample depth data after the calibrated ...

[0017] S4, using the organic carbon experimental data obtained in S1, the acoustic wave curve and resistivity curve of each sampling point, and the rock sample depth data after the homing correction obtained in S3 to determine the non-source rock section of the target layer in the target area;

[0018] S5, calculating the acoustic wave and resistivity scale ratio coefficient of the non-source rock section of the target layer in the target area according to the resistivity curve and acoustic wave curve of each sampling point obtained in S1;

[0019] S6. Establish the final clay content calculation formula based on the natural gamma, thorium, neutron and density curves obtained in S1;

[0020] According to the final clay content calculation formula, a true resistivity calculation model for the target layer in the target area is established;

[0021] S7, improving ΔLogR according to the acoustic wave and resistivity scale coefficient of the non-source rock section of the target layer in the target area obtained in S5 and the true resistivity calculation model of the target layer in the target area obtained in S6, to obtain an improved ΔLogR_JZ;

[0022] S8. Establish an organic carbon genesis indicator curve based on the relationship between organic carbon and mineral components;

[0023] S9, constructing an environmental impact factor curve using the sedimentary environment indicator curve obtained in S2 and the organic carbon genesis indicator factor curve obtained in S8;

[0024] S10. Determine the organic carbon calculation formula for each sampling point based on the environmental impact factor curve obtained in S9 and the ΔLogR_JZ obtained in S7.

[0025] Furthermore, in S2, the calculation formula corresponding to the sedimentary environment indicator curve of each sampling point is:

[0026] RTHU = TH / U;

[0027] Where: TH is the thorium curve; U is the uranium curve, and RTHU is the sedimentary environment indicator curve.

[0028] Furthermore, S3 specifically includes the following processes:

[0029] Put the organic carbon experimental data and the uranium curve in the same curve track, and move the organic carbon experimental data up and down as a whole according to the positive linear scale. When the numerical change trends of the two are consistent, the depth correction amount at this time is the rock sample depth data after the homeostasis correction;

[0030] Taking the rock sample depth data after homing correction as the standard, obtain the natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curve data at the same depth point;

[0031] The resistivity curve is a deep lateral resistivity curve or a deep induction resistivity curve.

[0032] Further, S5 is specifically as follows: using the non-source rock section determined in S4, establishing the acoustic wave-resistivity cross-plot of each sampling point in the non-source rock section, and obtaining the relationship between the two, as follows:

[0033] LqCy t =aAC+b

[0034] Where: R tis the resistivity curve, Ω·m; AC is the acoustic wave curve, us / m; a and b are fitting constants;

[0035] The proportional coefficient between the sound wave and the resistivity scale is K = -a.

[0036] Furthermore, in S6, the expression of the true resistivity calculation model of the target layer in the target area is:

[0037] R t _Vsh=ce -dVsh ;

[0038] Where: R t_Vsh is the resistivity of the non-source rock section after clay correction; Vsh is the final clay content of the target layer in the target area; c and d are fitting constants;

[0039] The calculation formula for the final clay content of the target layer in the target area is:

[0040] Vsh=(Vsh_GR+Vsh_TH+Vsh_ND) / 3;

[0041] Where: Vsh_GR is the clay content calculated by natural gamma, Vsh_TH is the clay content calculated by energy spectrum thorium, and Vsh_ND is the clay content calculated by neutron density.

[0042] Furthermore, the calculation formula for clay content calculated by spectral thorium is:

[0043]

[0044]

[0045] Where: TH is the energy spectrum thorium curve value; TH ma is the thorium curve value of the pure lithology of the target layer; TH sh is the thorium curve value of pure mudstone in the target layer; C is the formation coefficient; TH_index is a process variable, dimensionless.

[0046] Furthermore, the formula for calculating the clay content by natural gamma calculation is:

[0047]

[0048]

[0049] Where: GR is the natural gamma curve value; GR ma is the natural gamma curve value of the pure lithology of the target layer; GR sh is the natural gamma curve value of pure mudstone in the target layer; GR_index is a process variable, dimensionless.

[0050] Furthermore, the calculation formula for clay content calculated by neutron density is:

[0051]

[0052] Where: CNL is the neutron curve value; CNL ma is the neutron curve value of the pure lithology of the target layer; CNL f is the neutron curve value of the formation pore fluid; CNL sh is the neutron curve value of pure mudstone in the target layer; DEN is the density curve; DEN ma DEN is the pure lithology density curve value of the target layer; f is the density curve value of the formation pore fluid; DEN sh is the density curve value of pure mudstone in the target layer.

[0053] Further, in S7, the calculation formula is:

[0054] ΔLogR_JZ=lg(R t _Vsh / R t_Vsh基线 )-a×(Δt-Δt 基线 )

[0055] Where: R t_Vsh is the resistivity after clay correction; ΔLogR_JZ is the difference coefficient of the corrected acoustic wave and resistivity at the baseline; R t_Vsh基线 is the resistivity of the non-source rock section after clay correction; Δt 基线 is the acoustic time difference of the non-source rock section, Δt is the acoustic time difference; a=-K, K is the scale ratio coefficient of the acoustic wave and resistivity.

[0056] Furthermore, in S8, the calculation formula of the organic carbon genesis indicator curve is as follows:

[0057]

[0058] ORID is the organic carbon origin indicator factor curve, dimensionless; Vsh min Vsh is the minimum clay content; max is the maximum clay content;

[0059] In S9, the expression of the environmental impact factor curve is:

[0060]

[0061] EIF is the environmental impact factor curve, and RTHU is the sedimentary environment indicator curve;

[0062] In S10, the calculation formula for organic carbon at each sampling point is:

[0063] TOC = ΔLogR_JZ × EIF + m;

[0064] Where: TOC is the organic carbon content, EIF is the environmental impact factor curve, and m is the fitting constant.

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

[0066] The present invention provides a method for evaluating the organic carbon content of coal-bearing source rocks. The acoustic wave and resistivity conversion coefficients of shale reservoirs are determined by core calibration acoustic waves and resistivity curve envelopes. On the basis of clarifying the true resistivity of the formation, the effects of sedimentary environmental indications and differences in organic carbon sources on the organic carbon content are further considered, and environmental impact factors are constructed to form a new transitional phase shale organic carbon evaluation method and calculation model. In the analysis and application of actual well data, compared with the traditional ΔLogR theoretical model and the multivariate regression calculation model with poor regional universality, the new model can not only reflect the sedimentary changes and reservoir characteristic differences of marine-continental transitional phase shales, but also fill the gap in the calculation method of organic carbon of this type of marine-continental transitional phase shales. The calculation results provide a solid data basis for the optimization of favorable areas and resource assessment of marine-continental transitional phase shales, and the model method has good promotion and use value. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a flow chart of a method for evaluating the organic carbon content of coal-bearing source rocks provided by an embodiment of the present invention;

[0068] Figure 2 It is a schematic diagram of core depth homing provided by an embodiment of the present invention;

[0069] Figure 3 is a schematic diagram of determining a non-source rock section provided by an embodiment of the present invention;

[0070] Figure 4 It is a relationship diagram of the acoustic wave and resistivity ratio calibration coefficients for determining the non-hydrocarbon source rock section provided by an embodiment of the present invention;

[0071] Figure 5 is a relationship diagram between environmental impact factors and organic carbon provided by an embodiment of the present invention;

[0072] Figure 6 is an organic carbon content calculation model provided by an embodiment of the present invention;

[0073] Figure 7 It is a comparison chart of the calculation results of the new organic carbon model provided by the embodiment of the present invention and the experimental data. DETAILED DESCRIPTION

[0074] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0075] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0076] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or equipment.

[0077] The purpose of the present invention is to establish a sedimentary environment indicator curve using logging data, and to redetermine the acoustic wave, resistivity conversion coefficient and formation true resistivity of the marine-continental transitional phase shale reservoir on the basis of considering the high clay content and strong lithofacies heterogeneity of the marine-continental transitional phase shale reservoir, so as to obtain an improved ΔLogR calculation method, and finally construct an evaluation method for the organic carbon content of coal-bearing source rocks by combining the sedimentary environment indication and the difference in organic carbon sources, so as to solve the problem that the marine-continental transitional phase shale is affected by sedimentary changes, the organic carbon content varies greatly, and the quantitative calculation is inaccurate, so as to provide technical support for the optimization of sweet spots and favorable areas of the marine-continental transitional phase shale and the resource assessment.

[0078] The features and performances of the present invention are further described in detail below in conjunction with the embodiments.

[0079] See also Figure 1 The present invention provides a method for evaluating the organic carbon content of coal-bearing source rocks, which is performed according to the following steps:

[0080] Step 1: Carry out organic carbon and mineral composition experiments on rock samples of the A formation in the X study area according to the process specified in the "Technical Specification for Shale Gas Well Logging Evaluation Q / SY 16847-2020" standard to obtain experimental data on the organic carbon and clay content of the rock samples; obtain the natural gamma, uranium, and thorium curves of each sampling point from the natural gamma ray spectrum logging data by conventional means, and obtain the acoustic wave, density, neutron, and deep induction resistivity curves of each sampling point from the conventional logging data.

[0081] Step 2: Using the uranium and thorium curves, the sedimentary environment indicator curve of each sampling point is calculated according to formula (1);

[0082] RTHU=TH / U (1)

[0083] Where: TH is the thorium curve; U is the uranium curve.

[0084] Step 3: Use the organic carbon experimental data obtained in step 1 to calibrate the uranium curve of each sampling point, return the core depth, and obtain the rock sample depth data and its corresponding logging curve data after the return correction;

[0085] Specifically, the organic carbon experimental data and the uranium curve are placed in the same curve track, and the two are moved up and down as a whole according to the positive linear scale. When the numerical change trends of the two are consistent, the depth correction amount at this time is the rock sample depth data after the homeostasis correction, such as Figure 2 shown.

[0086] Furthermore, the natural gamma, uranium, thorium, acoustic wave, density, neutron, deep lateral or deep induction resistivity curve data of the same depth point are obtained based on the depth data of the rock sample after the homing correction.

[0087] Step 4: Determine the non-source rock section of the target layer in the target area by using the acoustic wave and resistivity curves of each sampling point obtained in step 1, the organic carbon experimental data, and the rock sample depth data after the homing correction obtained in step 3;

[0088] When performing step 4, the key is to scale the acoustic wave and resistivity curves of each sampling point in the form of reverse linear and forward logarithmic, respectively, so that the acoustic wave and resistivity curves overlap in the non-source rock section.

[0089] The overlap of non-source rock sections is based on the following criteria: the organic carbon content after correction for the corresponding depth is less than 0.75%, such as Figure 3 shown.

[0090] Step 5: Calculate the acoustic wave and resistivity scale coefficients of the non-source rock section of the target layer in the target area;

[0091] Specifically, using the non-source rock segment determined in step 4, the acoustic wave and resistivity cross-plots of each sampling point in the non-source rock segment are established to obtain the relationship between the two, as shown in Figure 4 As shown, the details are as follows:

[0092] LqCy t =aAC+b (2)

[0093] In formula (2): R t is the resistivity curve, Ω·m; AC is the acoustic wave curve, us / m; a and b are fitting constants.

[0094] The acoustic wave and resistivity scale proportional coefficient K = -a = 0.0092.

[0095] Step 6: Establish a true resistivity calculation model for the target layer in the target area;

[0096] Specifically, using the clay mineral content obtained in step 1 and the resistivity curve value corresponding to the depth after the core is returned in step 3, a relationship between the two is further established, as follows:

[0097] R t _Vsh=ce -dVsh (3)

[0098] Where: R t_Vsh is the resistivity of the non-source rock section after clay correction, Ω·m; Vsh is the final clay content of the target layer in the target area, decimal; c and d are fitting constants.

[0099] When carrying out step six, the key is to establish a calculation formula for the final clay content of the target layer in the target area: use the natural gamma, thorium, neutron and density curves obtained in step one to establish the clay content calculation formula respectively.

[0100] The clay content calculated by spectral thorium is as follows:

[0101]

[0102]

[0103] Where: TH is the energy spectrum thorium curve value, ppm; TH ma is the thorium curve value of the pure lithology (sandstone or carbonate rock, etc.) of the target layer, ppm; TH sh is the thorium curve value of pure mudstone in the target layer, ppm; Vsh_TH is the clay content calculated by spectral thorium, decimal; C is the formation coefficient, which is 3.7 for Tertiary formations and 2 for old formations; TH_index is a process variable, dimensionless.

[0104] If the lithology of the target layer is known in advance, the corresponding lithology value can be directly read from the curve, and the TH ma , TH sh Specifically, for the target layer in the target area, TH ma Take 5; TH sh Take 35; take 2 for C.

[0105] The clay content calculated by natural gamma is as follows:

[0106]

[0107]

[0108] Where: GR is the natural gamma curve value, API; GR ma is the natural gamma curve value of the pure lithology (sandstone or carbonate rock, etc.) of the target layer, API; GR sh is the natural gamma curve value of pure mudstone in the target layer, API; Vsh_GR is the clay content calculated by natural gamma, decimal; GR_index is a process variable, dimensionless.

[0109] If the lithology of the target layer is known in advance, the corresponding lithology value can be directly read from the curve, and the GR ma , GR sh Specifically, for the target area and target layer, GR ma Take 65;GR sh Take 180.

[0110] The clay content formula for neutron density calculation is as follows:

[0111]

[0112] Where: CNL is the neutron curve value, decimal; CNL ma The neutron curve value of the pure lithology (sandstone or carbonate rock, etc.) of the target layer, decimal; CNL f is the neutron curve value of the formation pore fluid, decimal; CNL sh is the neutron curve value of pure mudstone in the target layer, decimal; DEN is the density curve, g / cm 3 ;DEN ma is the density curve value of the pure lithology (sandstone or carbonate rock, etc.) of the target layer, g / cm 3 ;DEN f is the density curve value of the formation pore fluid, g / cm 3 ;DEN sh is the density curve value of pure mudstone in the target layer, g / cm 3 ; Vsh_ND is the clay content calculated by neutron density, a decimal.

[0113] Specifically, for the target area and target layer, CNL ma Take -0.1; CNL f Take 1; CNL sh Take 0.4; DEN ma Take 2.65; DEN f Take 1; DEN sh Take 2.4.

[0114] Finally, the average weighted method is used to obtain the final clay content calculation formula (9):

[0115] Vsh=(Vsh_GR+Vsh_TH+Vsh_ND) / 3 (9)

[0116] Where: Vsh is the final calculated clay content, a decimal.

[0117] Step 7: Use formulas (2) to (9) to improve the traditional ΔLogR and obtain the improved ΔLogR_JZ;

[0118] Specifically, the calculation formula is:

[0119] ΔLogR_JZ=lg(R t _Vsh / R t_Vsh基线 )-a×(Δt-Δt 基线 ) (10)

[0120] Where: R t_Vsh is the resistivity after clay correction; ΔLogR_JZ is the difference coefficient of the corrected acoustic wave and resistivity at the baseline; R t_Vsh基线 is the resistivity of the non-source rock section after clay correction; Δt 基线 is the acoustic time difference of the non-source rock section, Δt is the acoustic time difference; a=-K, K is the scale ratio coefficient of the acoustic wave and resistivity.

[0121] Step 8. Considering that a small amount of organic carbon in the marine-continental transitional phase shale comes from marine plankton and more comes from terrestrial plant debris, the higher the organic carbon content is in the mature stage of shale, the higher the clay mineral content is, indicating that it is clay mineral-based. The calculation formula for defining the organic carbon genesis indicator factor curve is as follows:

[0122]

[0123] Where: ORID is the organic carbon origin indicator curve, dimensionless; Vsh min Vsh is the minimum clay content; max The clay content is the maximum.

[0124] Step 9: Use the sedimentary environment indicator curve RTHU obtained in step 2 and the organic carbon genesis indicator factor ORID obtained in step 8 to construct an environmental impact factor curve.

[0125] The key to constructing the environmental impact factor curve is to establish a consistent relationship between the sedimentary environment indicator curve and the organic carbon genesis indicator factor and the organic carbon content by analyzing the relationship between the two. The specific calculation formula is:

[0126]

[0127] Where: EIF is the environmental impact factor curve, dimensionless.

[0128] Step 10: Figure 5 The relationship diagram between environmental impact factors and organic carbon is constructed as shown in the figure. According to the environmental impact factors obtained in step nine and the corrected ΔLogR_JZ obtained in step seven, the organic carbon calculation formula for each sampling point is determined, as shown in FIG. Figure 6 As shown;

[0129] Specifically, the calculation formula is as follows:

[0130] TOC=ΔLogR_JZ×EIF+m (13)

[0131] Where: TOC is the organic carbon content, %, and m is the fitting constant.

[0132] Figure 7 This is a comparison chart of the organic carbon calculation results obtained based on the present invention and the core experimental data, which shows that the method of the present invention is reliable, practical and effective.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating the organic carbon content of coal-bearing source rocks, characterized in that: The following steps are involved: S1. Obtaining organic carbon experimental data and mineral component experimental data of the same batch of rock samples in the target layer of the target area; Obtain the natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curves of each sampling point in the target layer of the target area; S2. Using the uranium and thorium curves, the sedimentary environment indicator curves of each sampling point are obtained; S3, using the organic carbon experimental data obtained in S1 and the uranium curve of each sampling point to calibrate the core depth, obtain the rock sample depth data after the calibrated ... S4, using the organic carbon experimental data obtained in S1, the acoustic wave curve and resistivity curve of each sampling point, and the rock sample depth data after the homing correction obtained in S3 to determine the non-source rock section of the target layer in the target area; S5, calculating the acoustic wave and resistivity scale ratio coefficient of the non-source rock section of the target layer in the target area according to the resistivity curve and acoustic wave curve of each sampling point obtained in S1; S6. Establish the final clay content calculation formula based on the natural gamma, thorium, neutron and density curves obtained in S1; According to the final clay content calculation formula, a true resistivity calculation model for the target layer in the target area is established; S7, improving ΔLogR according to the acoustic wave and resistivity scale coefficient of the non-source rock section of the target layer in the target area obtained in S5 and the true resistivity calculation model of the target layer in the target area obtained in S6, to obtain an improved ΔLogR_JZ; S8. Establish an organic carbon genesis indicator curve based on the relationship between organic carbon and mineral components; S9, constructing an environmental impact factor curve using the sedimentary environment indicator curve obtained in S2 and the organic carbon genesis indicator factor curve obtained in S8; S10. Determine the organic carbon calculation formula for each sampling point based on the environmental impact factor curve obtained in S9 and the ΔLogR_JZ obtained in S7.

2. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 1, characterized in that: In S2, the calculation formula corresponding to the sedimentary environment indicator curve of each sampling point is: RTHU = TH / U; Where: TH is the thorium curve; U is the uranium curve, and RTHU is the sedimentary environment indicator curve.

3. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 1, characterized in that: S3 specifically includes the following processes: Put the organic carbon experimental data and the uranium curve in the same curve track, and move the organic carbon experimental data up and down as a whole according to the positive linear scale. When the numerical change trends of the two are consistent, the depth correction amount at this time is the rock sample depth data after the homeostasis correction; Taking the rock sample depth data after homing correction as the standard, obtain the natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curve data at the same depth point; The resistivity curve is a deep lateral resistivity curve or a deep induction resistivity curve.

4. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 1, characterized in that: S5 is specifically as follows: using the non-source rock section determined in S4, establish the acoustic wave-resistivity cross-plot of each sampling point in the non-source rock section, and obtain the relationship between the two, as follows: LgR t =aAC+b Where: R t is the resistivity curve, Ω·m; AC is the acoustic wave curve, us / m; a and b are fitting constants; The proportional coefficient between the sound wave and the resistivity scale is K = -a.

5. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 1, characterized in that: In S6, the true resistivity calculation model of the target layer in the target area is expressed as: R t _What=what -dVsh ; Where: R t_Vsh is the resistivity of the non-source rock section after clay correction; Vsh is the final clay content of the target layer in the target area; c and d are fitting constants; The calculation formula for the final clay content of the target layer in the target area is: Vsh=(Vsh_GR+Vsh_TH+Vsh_ND) / 3; Where: Vsh_GR is the clay content calculated by natural gamma, Vsh_TH is the clay content calculated by energy spectrum thorium, and Vsh_ND is the clay content calculated by neutron density.

6. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 5, characterized in that: The calculation formula of clay content calculated by spectral thorium is: Where: TH is the energy spectrum thorium curve value; TH ma is the thorium curve value of the pure lithology of the target layer; TH sh is the thorium curve value of pure mudstone in the target layer; C is the formation coefficient; TH_index is a process variable, dimensionless.

7. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 5, characterized in that: The formula for calculating the clay content by natural gamma calculation is: Where: GR is the natural gamma curve value; GR ma is the natural gamma curve value of the pure lithology of the target layer; GR sh is the natural gamma curve value of pure mudstone in the target layer; GR_index is a process variable, dimensionless.

8. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 5, characterized in that: The calculation formula for clay content calculated by neutron density is: Where: CNL is the neutron curve value; CNL ma is the neutron curve value of the pure lithology of the target layer; CNL f is the neutron curve value of the formation pore fluid; CNL sh is the neutron curve value of pure mudstone in the target layer; DEN is the density curve; DEN ma DEN is the pure lithology density curve value of the target layer; f is the density curve value of the formation pore fluid; DEN sh is the density curve value of pure mudstone in the target layer.

9. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 5, characterized in that: In S7, the calculation formula is: ΔLogR_JZ=lg(R t _Vsh / R t_Vsh基线 )-a×(Δt-Δt 基线 ) Where: R t_Vsh is the resistivity after clay correction; ΔLogR_JZ is the difference coefficient of the corrected acoustic wave and resistivity at the baseline; R t_Vsh基线 is the resistivity of the non-source rock section after clay correction; Δt 基线 is the acoustic time difference of the non-source rock section, Δt is the acoustic time difference; a=-K, K is the scale ratio coefficient of the acoustic wave and resistivity.

10. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 1, characterized in that: In S8, the calculation formula of the organic carbon genesis indicator factor curve is as follows: ORID is the organic carbon origin indicator factor curve, dimensionless; Vsh min is the minimum clay content; Vsh max is the maximum clay content; In S9, the expression of the environmental impact factor curve is: EIF is the environmental impact factor curve, and RTHU is the sedimentary environment indicator curve; In S10, the calculation formula for organic carbon at each sampling point is: TOC = ΔLogR_JZ × EIF + m; Where: TOC is the organic carbon content, EIF is the environmental impact factor curve, and m is the fitting constant.

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