Method for evaluating organic carbon content of coal measure source rock

Abstract

The present application belongs to the field of unconventional oil and gas exploration and evaluation technology, and relates to a method for evaluating the organic carbon content of coal measure source rock. The method determines the sonic wave and resistivity conversion coefficient of shale reservoirs through core calibration sonic wave and resistivity curve envelope, further considers the influence of sedimentary environment indication and organic carbon source difference on the organic carbon content on the basis of determining the true resistivity of the stratum, constructs an environmental impact factor, and forms a new transitional phase shale organic carbon evaluation method and calculation model. Compared with the traditional DeltaLogR theoretical model and the poor regional universality of the multiple regression calculation model, the new model can not only reflect the sedimentary change and reservoir characteristic difference of the transitional phase shale, but also fill the gap of the organic carbon calculation method of the transitional phase shale, and the calculation result provides a solid data basis for the favorable area optimization and resource quantity evaluation of the transitional phase shale, and has good popularization and use value.

Description

Technical Field

[0001] The present invention belongs to the technical field of unconventional oil and gas exploration, development and evaluation, and particularly 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 identifying 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 the optimization of favorable shale oil and gas areas and resource assessment.

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

[0004] The first method involves burning and analyzing rock samples in the laboratory using an organic carbon analyzer. However, due to limitations in the number of rock samples available, high experimental costs, and long experimental cycles, it is difficult to obtain continuous vertical organic matter content data for a single well, and this data cannot be rapidly replicated across adjacent wells.

[0005] The second method is to use the mutual calibration of logging and core data to achieve quantitative calculation of organic matter abundance in the entire well section through inherent theoretical formulas, regional empirical formulas, or machine intelligence algorithms. Regional empirical formulas, such as those proposed by Schmoker, Fertl, and Hu Huiting, use natural gamma, density, uranium curves, and rock sample data to establish empirical formulas for specific study areas. Due to regional limitations, these formulas are difficult to promote. Although machine intelligence algorithms have high calculation accuracy, they rely more on sample data and lack theoretical basis, making them difficult to adjust according to actual conditions. The more commonly used theoretical formula is the ΔLogR method proposed by Passey et al. in 1990. 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 transit time of the non-source rock section, us / ft; LOM is the organic matter maturity index, dimensionless; K is the scale factor of resistivity and porosity, dimensionless; TOC is the organic carbon content, %; ΔLogR is the difference coefficient between acoustic wave and resistivity at the baseline.

[0009] The application background of the ΔLogR method is that the simple structure is constructed, the reservoir is mainly formed in a reducing environment, the shale is distributed stably, the continuous thickness is large, the clay content is low, and the marine sedimentary environment is relatively homogeneous and integrated. Compared with marine shale gas, the transgressive facies shale gas in large basins such as Ordos and Sichuan accounts for 25% of the total shale gas resources in China, and has not been developed on a large scale. The reason is that the transgressive facies shale is mainly formed in tidal flat, lagoon, marsh, delta and other sedimentary environments, and is affected by sedimentary environment changes, so that the shale thickness and distribution are unstable, the clay content is high, the lithology is various and changes fast in the vertical direction, and is often associated with coal seams. A small amount of organic carbon is derived from marine plankton, and most of it is derived from terrestrial plants, resulting in a large difference in organic carbon content. The direct use of the ΔLogR method has a large error, and there is no accurate and effective method for evaluating the organic carbon of transgressive facies shale. SUMMARY

[0010] The purpose of the present application is to provide an evaluation method for the organic carbon content of coal measure source rock, which solves the problem of no accurate and effective method for evaluating the organic carbon of transgressive facies shale.

[0011] The present application is realized by the following technical solutions:

[0012] The present application discloses an evaluation method for the organic carbon content of coal measure source rock, comprising the following steps:

[0013] S1, obtaining the organic carbon experimental data and mineral component experimental data of the same batch of rock samples of the target zone target layer;

[0014] Obtaining the natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curves of the target zone target layer at each sampling point;

[0015] S2, obtaining the sedimentary environment indicating curve at each sampling point by using the uranium and thorium curves;

[0016] S3, calibrating the organic carbon experimental data obtained in S1 with the uranium curve at each sampling point, and homing the core depth to obtain the homed and corrected rock sample depth data and the logging curve data corresponding to the homed and corrected rock sample depth data;

[0017] S4, determining the non-hydrocarbon source rock section of the target zone target layer by using the organic carbon experimental data obtained in S1, the acoustic wave curve and the resistivity curve at each sampling point, and the homed and corrected rock sample depth data obtained in S3;

[0018] S5, calculating the acoustic wave and resistivity calibration proportionality coefficient of the non-hydrocarbon source rock section of the target zone target layer according to the resistivity curve and the acoustic wave curve at each sampling point obtained in S1;

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

[0020] Establish a true resistivity calculation model for the target layer in the target area based on the final clay content calculation formula;

[0021] S7, improving ΔLogR based on the acoustic wave and resistivity scale coefficients 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] Place the organic carbon experimental data and the uranium curve in the same curve channel, 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] Using the depth data of the rock sample after the correction as the standard, the natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curve data of the same depth point are obtained;

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

[0032] Furthermore, S5 is specifically as follows: using the non-source rock section determined in S4, an acoustic wave-resistivity cross-plot is established for each sampling point in the non-source rock section, and a relationship between the two is obtained 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 acoustic wave and the resistivity scale is K = -a.

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

[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 energy spectrum 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 ray 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 ray curve value of pure mudstone in the target layer; GR_index is a dimensionless process variable.

[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 lithologic 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] Furthermore, 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 between 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 coefficient of the acoustic wave and resistivity.

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

[0057]

[0058] ORID is the organic carbon origin indicator factor curve, dimensionless; Vsh min is the minimum value of clay content; Vsh 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] This invention provides a method for evaluating the organic carbon content of coal-bearing source rocks. This method determines the acoustic and resistivity conversion coefficients of shale reservoirs by using core calibration acoustic waves and resistivity curve envelopes. Based on the definite true resistivity of the formation, it further considers the influence of sedimentary environmental indicators and differences in organic carbon sources on organic carbon content, constructs environmental impact factors, and forms a new method and calculation model for evaluating organic carbon in transitional shale. 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 not only reflects the sedimentary changes and reservoir characteristics of marine-continental transitional shale, but also fills the gap in organic carbon calculation methods for this type of shale. The calculation results provide a solid data foundation for the selection of favorable areas and resource assessment of marine-continental transitional shale, and the model method has excellent application 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 This is a schematic diagram of core depth positioning provided by an embodiment of the present invention;

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

[0070] Figure 4 This is a relationship diagram of the acoustic wave and resistivity ratio scaling coefficients for determining non-source rock sections 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 It is an organic carbon content calculation model provided by an embodiment of the present invention;

[0073] Figure 7 This 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 solutions and advantages of the present invention more clear, the following is a further detailed description 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 intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0075] The components described and illustrated in the drawings and embodiments of the present invention may be arranged and designed in a variety of different 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. All other embodiments derived by those skilled in the art based on the drawings and embodiments of the present invention without inventive effort shall fall 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 apparatus 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 apparatus.

[0077] The purpose of the present invention is to establish a sedimentary environment indicator curve using logging data. Taking into account the high clay content and strong lithofacies heterogeneity of the marine-continental transitional shale reservoir, the acoustic wave and resistivity conversion coefficients and the true resistivity of the marine-continental transitional shale reservoir are re-determined, and an improved ΔLogR calculation method is obtained. Combined with the sedimentary environment indicators and the differences in organic carbon sources, an evaluation method for the organic carbon content of coal-bearing source rocks is ultimately constructed. This solves the problem that marine-continental transitional shale is affected by sedimentary changes, has large differences in organic carbon content, and has led to inaccurate quantitative calculations. This provides technical support for the optimization of sweet spots and favorable areas and resource assessment of marine-continental transitional shale.

[0078] The features and performance of the present invention are further described in detail below with reference to 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: Conduct organic carbon and mineral composition experiments on rock samples from Formation A in Study Area X according to the procedures specified in the Technical Specification for Shale Gas Well Logging Evaluation (Q / SY 16847-2020) to obtain experimental data on the organic carbon and clay content of the rock samples. Use conventional methods to obtain natural gamma ray, uranium, and thorium curves for each sampling point from the natural gamma ray spectrum logging data, and obtain acoustic wave, density, neutron, and deep induction resistivity curves for each sampling point from the conventional logging data.

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

[0082] RTHU=TH / U (1)

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

[0084] Step 3: Calibrate the organic carbon experimental data obtained in step 1 with the uranium curve of each sampling point, and perform resetting on the core depth to obtain the resetting-corrected rock sample depth data and its corresponding logging curve data;

[0085] Specifically, the organic carbon experimental data and the uranium curve are placed in the same curve channel, 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 at 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 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 relocation 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 scales, 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 section determined in step 4, a cross-plot of acoustic wave and resistivity at each sampling point in the non-source rock section is established to obtain the relationship between the two, as shown in the following example: 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 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 core placement obtained in step 3, a relationship between the two is 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 energy spectrum 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 ray 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 ray curve value of pure mudstone in the target layer, API; Vsh_GR is the clay content calculated by natural gamma ray, 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, 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 final clay content calculation formula (9) is obtained by using the average weighted method:

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

[0116] Where: Vsh is the final calculated clay content, 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 between 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 coefficient of the acoustic wave and resistivity.

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

[0122]

[0123] Where: ORID is the organic carbon origin indicator curve, dimensionless; Vsh min is the minimum value of clay content; Vsh 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 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 the figure below: 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 and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the 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 by 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 composition experimental data of the same batch of rock samples in the target layer of the target area; Obtain natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curves of target layers in target areas at each sampling point; S2. Using the uranium and thorium curves, obtain the sedimentary environment indicator curve for each sampling point; S3. Calibrate the organic carbon experimental data obtained in S1 with the uranium curve of each sampling point, reposition the core depth, and obtain the repositioned and corrected rock sample depth data and the corresponding logging curve data under the repositioned and corrected rock sample depth data; S4. Determine the non-source rock section of the target layer in the target area 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 relocation correction obtained in S3; S5. Calculate the acoustic wave and resistivity scale ratio coefficient of the non-source rock section of the target layer in the target area based on the resistivity curve and acoustic wave curve of each sampling point obtained in S1; S6. Establish a final clay content calculation formula based on the natural gamma, thorium, neutron and density curves obtained in S1; Establish a true resistivity calculation model for the target layer in the target area based on the final clay content calculation formula; S7, improving ΔLogR based on the acoustic wave and resistivity scale coefficients 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, wherein: 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, wherein: S3 specifically includes the following processes: Place the organic carbon experimental data and the uranium curve in the same curve channel, 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; Using the depth data of the rock sample after the correction as the standard, the natural gamma, uranium, thorium, acoustic wave, density, neutron and resistivity curve data of the same depth point are obtained; 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, wherein: S5 specifically involves: using the non-source rock segment determined in S4, establishing an acoustic wave-resistivity cross-plot for each sampling point in the non-source rock segment, and obtaining 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 acoustic 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, wherein: 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, wherein: The calculation formula of clay content calculated by energy spectrum 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, wherein: The formula for calculating the clay content by natural gamma ray 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 ray curve value of pure mudstone in the target layer; GR_index is a dimensionless process variable.

8. The method for evaluating the organic carbon content of coal-bearing source rocks according to claim 5, wherein: 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 lithologic 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, wherein: 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 between 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 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, wherein: 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 value of 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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