A method and device for optimizing the fractal dimension of pore surfaces in organic-rich shale

Abstract

The present application discloses a method and device for optimizing the fractal dimension of the pore surface of organic-rich shale, which relates to the field of fractal geometry. The method calculates the adsorption volume interval of the gas at equilibrium pressure by using the initial surface fractal dimension and the monolayer adsorption volume on the particle. The relative pressure interval is determined based on the adsorption volume interval, and the ln(V) and ln(ln(P)) in the relative pressure interval are plotted. O / P)) image, obtain the slope of the image, and calculate the modified surface fractal dimension according to the second formula. Determine whether the change between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold. If it is less than the threshold, output the modified surface fractal dimension to obtain the optimized surface fractal dimension. If it is greater than the threshold, iterate until it is less than the threshold. This application introduces an iterative approach to make the optimized surface fractal dimension more accurate, avoiding misjudgment of the reservoir adsorption and seepage capacity during the exploration and development of source rock natural gas.

Description

Technical Field

[0001] The present application relates to the technical field of fractal geometry, and in particular to a method for optimizing the fractal dimension of the pore surface of organic-rich shale. Background Art

[0002] Whether conventional or unconventional, hydrocarbon fluids are stored within the pore and fracture systems of reservoirs. Therefore, characterizing the reservoir's pore structure is a crucial step in oil and gas exploration and development. Porosity in unconventional reservoirs is typically studied using methods such as small-angle scattering (SAS), scanning electron microscopy (SEM), gas adsorption, computed tomography (CT), and nuclear magnetic resonance (NMR). However, SAS testing yields poor results on large rock samples; SEM requires good sample conductivity and can only visualize localized pores; CT scanning is complex and expensive; and NMR cannot study smaller pore structures and is affected by paramagnetic compounds. Gas adsorption tests not only objectively characterize the pore structure of shale but are also relatively convenient and inexpensive. Consequently, gas adsorption experiments are widely used to study the pore structure of unconventional reservoirs.

[0003] In order to quantify the pore structure parameters, Brunauer, Emmett and Teller proposed the multi-molecular layer adsorption equation, namely the BET equation, based on the Langmuir equation to calculate the specific surface area of ​​shale. Inspired by the Kelvin equation, Barrett et al. derived a method to determine the pore size distribution, namely the BJH method. In the early 20th century, scholars introduced the density functional theory (DFT) method based on the principles of statistical mechanics to characterize the microporous structure. These methods are still in use today, but considering the complexity and variability of shale structure, scholars have introduced the surface fractal dimension (D S ) to characterize the complexity of the pores.

[0004] Mandelbrot defines a dimension D for fractal objects that is larger than the topological dimension but smaller than the dimension of Euclidean space. Therefore D S Between 2 and 3, D S The closer the value is to 2, the smoother the surface, and the closer it is to 3, the rougher the surface. The surface fractal dimension of solid particles can be determined through various experimental methods, such as small-angle X-ray scattering, neutron scattering, mercury intrusion, and gas adsorption.

[0005] Liu and Nie's research found that the complexity of coal pore surfaces significantly affects their methane adsorption capacity. As the surface fractal dimension increases, the rougher the surface, the more adsorption sites for methane are created. This increases the Langmuir's volume of methane adsorption and decreases the Langmuir's pressure, making the coal surface more receptive to methane. Studies on shale have shown that higher surface fractal dimensions indicate more complex pore structures and pore surface roughness, which complicates gas diffusion and percolation within the shale. While higher surface fractal dimensions imply greater methane adsorption capacity, they also imply a more complex reservoir pore structure, which inhibits gas desorption and results in lower gas flow capacity. To resolve this conflict, it is necessary to more accurately characterize reservoir pore complexity, construct models that explain the impact of pore structure on adsorption and percolation, and implement appropriate stimulation treatments during development to form a pore-fracture network. Therefore, a more accurate fractal dimension calculation method is needed to characterize pore surface roughness.

[0006] Currently, there are three methods for calculating the fractal dimension based on low-pressure adsorption: the first involves sorting adsorbate particles into different sizes and conducting adsorption experiments on each particle using the same adsorbent. The fractal dimension is calculated based on the particle radius and the adsorption capacity of the adsorbent monolayer; the second involves conducting adsorption experiments on the adsorbate particles using adsorbents of different molecular diameters and calculating the fractal dimension based on the adsorbent molecular diameter and the measured adsorbate surface area; and the third involves conducting adsorption experiments on the adsorbate particles using a single adsorbent and calculating the fractal dimension using a modified Frenkel-Halsey-Hill (FHH) theory. Because both the first and second methods require multiple adsorption experiments and are more cumbersome to perform, and the second method may not be able to characterize finer structures on the particle surface when using adsorbent molecules with larger cross-sectional areas, the third method is currently the most commonly used method for calculating the fractal dimension based on adsorption experiments. Using nitrogen as the adsorbent, this method requires only a single test and is calculated based on the adsorption curve.

[0007] However, the relative pressure range selected for calculations must be controlled after nitrogen molecules have completed filling the micropores and before capillary condensation occurs, with the ideal nitrogen molecular layer on the adsorbent surface being 1-2 layers. However, determining the pressure at which capillary condensation begins is not easy. Some researchers use a P / Po ratio of 0.45 or 0.5 as a dividing line, or divide the image into two segments based on fitting, calculate the fractal dimension of each segment separately, and then determine whether the two calculated values ​​are reasonable. Values ​​falling within the interval [2, 3] are considered reasonable. Other researchers use full-segment curve fitting to calculate the surface fractal dimension. However, these segmentation methods are subject to human error, can lead to misjudgment of the reservoir's adsorption and seepage capacity, and lack clear physical meaning. Summary of the Invention

[0008] To this end, the present application provides a method and device for optimizing the surface fractal dimension of organic-rich shale pores to solve the problem that the surface fractal dimension calculation method in the prior art has errors, which may lead to misjudgment of the adsorption and seepage capacity of the reservoir.

[0009] In order to achieve the above objectives, this application provides the following technical solutions:

[0010] In a first aspect, a method for optimizing the fractal dimension of the pore surface of organic-rich shale comprises:

[0011] Input the initial surface fractal dimension and the monolayer adsorption volume on the particle;

[0012] Calculate the adsorption volume interval of the gas at equilibrium pressure according to the first formula;

[0013] The first formula is: V = V m *n^(3-D S ), where V is the adsorption volume of the gas at equilibrium pressure, V m is the monolayer adsorption volume on the particle, 1.0±0.5≤n≤2.0±0.5, D S is the surface fractal dimension;

[0014] determining a relative pressure interval according to the adsorption volume interval;

[0015] Plot ln(V) and ln(ln(P O / P)), where P is the equilibrium pressure, P O is the saturation pressure of the gas at a given temperature;

[0016] Obtaining the slope of the image, and calculating the corrected surface fractal dimension according to a second formula;

[0017] The second formula is: D S =3+αA, where A is the slope of the image and α is the coefficient;

[0018] determining whether a difference between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold;

[0019] If it is less than the threshold, the corrected surface fractal dimension is output to obtain the optimized surface fractal dimension;

[0020] If it is greater than the threshold, iterate until it is less than the threshold;

[0021] The pore surface roughness of organic-rich shale is determined based on the optimized surface fractal dimension.

[0022] Furthermore, the coefficient α is obtained after judging the adsorption mechanism according to the third formula;

[0023] The third formula is: δ=3(1+A)-2, when δ<0, α is 1, and when δ≥0, α is 3.

[0024] Furthermore, the calculation process of the initial surface fractal dimension is specifically as follows:

[0025] The rock sample to be tested is crushed into 40-60 mesh, and a low-pressure nitrogen adsorption test is performed to obtain low-pressure nitrogen adsorption data within the relative pressure range;

[0026] According to the low pressure nitrogen adsorption data, ln(V) and ln(ln(P O / P)) and draw the image;

[0027] Calculating the thickness of the nitrogen adsorption layer, and calculating the relative pressure range corresponding to the nitrogen adsorption layer according to the fourth formula;

[0028] The fourth formula is: t=0.88*(P / P O )^2+6.45*(P / P O )+2.98, where t is the thickness of the nitrogen adsorption layer;

[0029] Calculate the slope of ln(V) and ln(ln(Po / P)) within the relative pressure range corresponding to the nitrogen adsorption layer according to the fifth formula;

[0030] The fifth formula is: ln(V / V m )=C+A(ln(ln(P O / P)));

[0031] The initial surface fractal dimension is calculated according to the second formula.

[0032] Furthermore, in the low-pressure nitrogen adsorption test, there are no less than 40 measuring points on the adsorption curve.

[0033] Furthermore, the low-pressure nitrogen adsorption data is low-pressure nitrogen adsorption data in a relative pressure range of 0.005 to 0.998.

[0034] Furthermore, the thickness of the nitrogen adsorption layer is the thickness of 1-2 layers of nitrogen molecule adsorption layers.

[0035] Furthermore, the thickness of the nitrogen adsorption layer is calculated based on hexagonal closest packing.

[0036] In a second aspect, a device for optimizing the fractal dimension of the pore surface of organic-rich shale comprises:

[0037] A data input module for inputting the initial surface fractal dimension and the monolayer adsorption volume on the particles;

[0038] an adsorption volume calculation module, configured to calculate the adsorption volume interval of the gas at equilibrium pressure according to a first formula;

[0039] The first formula is: V = V m *n^(3-D S ), where V is the adsorption volume of the gas at equilibrium pressure, V m is the monolayer adsorption volume on the particle, 1.0±0.5≤n≤2.0±0.5, D S is the surface fractal dimension;

[0040] A relative pressure determination module, configured to determine a relative pressure interval according to the adsorption volume interval;

[0041] An image drawing module is used to draw ln(V) and ln(ln(P O / P)), where P is the equilibrium pressure, P O is the saturation pressure of the gas at a given temperature;

[0042] a correction module, configured to obtain the slope of the image and calculate the corrected surface fractal dimension according to a second formula;

[0043] The second formula is: D S =3+αA, where A is the slope of the image and α is the coefficient;

[0044] A first judging module is used to judge whether the difference between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold;

[0045] If it is less than the threshold, the corrected surface fractal dimension is output to obtain the optimized surface fractal dimension;

[0046] If it is greater than the threshold, iterate until it is less than the threshold;

[0047] The second judgment module is used to judge the pore surface roughness of the organic-rich shale according to the optimized surface fractal dimension.

[0048] In a third aspect, a computer device includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the steps of a method for optimizing the fractal dimension of the pore surface of organic-rich shale.

[0049] In a fourth aspect, a computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for optimizing the fractal dimension of the pore surface of organic-rich shale.

[0050] Compared with the prior art, this application has at least the following beneficial effects:

[0051] The present application provides a method and device for optimizing the fractal dimension of the pore surface of organic-rich shale. By inputting the initial surface fractal dimension and the monolayer adsorption volume on the particle, according to the formula V=V m *n^(3-D S ) calculate the adsorption volume range of the gas at equilibrium pressure; determine the relative pressure range based on the adsorption volume range; plot ln(V) and ln(ln(P O / P)) image, obtain the image slope, and calculate the modified surface fractal dimension according to the second formula; determine whether the change between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold; if less than the threshold, output the modified surface fractal dimension to obtain the optimized surface fractal dimension; if greater than the threshold, iterate until less than the threshold. This application introduces an iterative approach, making the optimized surface fractal dimension more accurate and avoiding misjudgment of reservoir adsorption and seepage capacity during source rock natural gas exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] To more intuitively illustrate the prior art and the present application, several exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be considered as limiting conditions for implementing the present application; for example, based on the technical concepts disclosed in the present application and the exemplary drawings, those skilled in the art are capable of easily making routine adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components).

[0053] Figure 1 A flow chart of a method for optimizing the fractal dimension of pore surfaces in organic-rich shale provided in this application;

[0054] Figure 2 An iterative flow chart of an optimization method for the fractal dimension of the pore surface of organic-rich shale provided in this application;

[0055] Figure 3 The nitrogen isotherm adsorption curve provided in the examples of this application;

[0056] Figure 4 A relationship diagram between ln(V) and ln(ln(Po / P)) is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0057] The present application will be further described below in detail through specific embodiments in conjunction with the accompanying drawings.

[0058] In the description of this application: unless otherwise specified, the meaning of "plurality" is two or more. The terms "first", "second", "third", etc. in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (for example, they should not be understood as emphasizing the importance or order, etc.). Expressions such as "including", "comprising", "having", etc. also mean "not limited to" (certain units, components, materials, steps, etc.).

[0059] Terms such as "upper," "lower," "left," "right," and "center" used in this application are generally intended to facilitate intuitive understanding when compared with the accompanying drawings and are not intended to be absolute limitations on positional relationships in actual products. Changes to these relative positional relationships are considered within the scope of this application without departing from the technical concepts disclosed herein.

[0060] See also Figure 1 and Figure 2 The present application provides a method for optimizing the fractal dimension of the pore surface of organic-rich shale, comprising:

[0061] S1: Input the initial surface fractal dimension and the monolayer adsorption volume on the particle;

[0062] S2: Calculate the adsorption volume range of the gas at equilibrium pressure according to the first formula;

[0063] The first formula is: V = V m *n^(3-D S ), where V is the adsorption volume of the gas at equilibrium pressure P, V m is the monolayer adsorption volume on the particle, 1.0±0.5≤n≤2.0±0.5, D S is the surface fractal dimension;

[0064] S3: Determine the relative pressure range based on the adsorption volume range;

[0065] Specifically, the relative pressure value corresponding to the adsorption volume can be directly obtained through low-pressure nitrogen adsorption testing.

[0066] S4: Plot ln(V) and ln(ln(P O / P)), where P is the equilibrium pressure, P O is the saturation pressure of the gas at a given temperature;

[0067] S5: obtaining the slope of the image and calculating the corrected surface fractal dimension according to the second formula;

[0068] The second formula is: D S=3+αA, where A is the slope of the image and the coefficient α is related to the gas adsorption mechanism. The third formula can be used to determine the adsorption mechanism.

[0069] The third formula is: δ=3(1+A)-2. When δ<0, it means that surface tension (or capillary condensation) is dominant, and α is 1. When δ≥0, van der Waals force is dominant, and α is 3.

[0070] S6: determining whether a difference between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold;

[0071] Specifically, the threshold is set to 0.01.

[0072] S7: If it is greater than the threshold, repeat the above steps;

[0073] If the difference between the modified surface fractal dimension and the initial surface fractal dimension is greater than 0.01, the above steps are repeated;

[0074] S8: If it is less than the threshold, the corrected surface fractal dimension is output to obtain the optimized surface fractal dimension;

[0075] If the difference between the modified surface fractal dimension and the initial surface fractal dimension is less than 0.01, the modified surface fractal dimension is output to obtain the optimized surface fractal dimension.

[0076] S9: Determine the pore surface roughness of the organic-rich shale based on the optimized surface fractal dimension. More specifically, the initial surface fractal dimension in step S1 is calculated by the following steps:

[0077] S101: crushing the rock sample to be tested into 40-60 mesh, and performing a low-pressure nitrogen adsorption test to obtain low-pressure nitrogen adsorption data within a relative pressure range;

[0078] Specifically, low-pressure nitrogen adsorption data within the relative pressure range (P / Po) of 0.005-0.998 are obtained.

[0079] S102: Calculate ln(V) and ln(ln(Po / P)) based on the low-pressure nitrogen adsorption data and draw a graph;

[0080] S103: Calculating the thickness of the nitrogen adsorption layer, and calculating the relative pressure range corresponding to the nitrogen adsorption layer according to the fourth formula;

[0081] The fourth formula is: t = 0.88*(P / P O )^2+6.45*(P / P O )+2.98, where t is the thickness of the nitrogen adsorption layer;

[0082] Preferably, the thickness of the nitrogen adsorption layer is roughly calculated based on the thickness of 1-2 nitrogen molecules adsorption layers (about 0.354-0.679 nm) according to hexagonal closest packing.

[0083] S104: Calculating the slope of ln(V) and ln(ln(Po / P)) in the relative pressure range corresponding to the nitrogen adsorption layer according to the fifth formula;

[0084] The fifth formula is: ln(V / Vm)=C+A(ln(ln(Po / P))), where V is the volume of gas adsorbed at equilibrium pressure P, V m is the monolayer adsorption volume on the particle, Po is the saturation pressure of the gas at a given temperature, C is the pre-exponential factor, A is the slope of the graph, and is affected by D S And adsorption mechanism control, please refer to the third formula for details.

[0085] S105: Calculate the initial surface fractal dimension according to the second formula.

[0086] More specifically, the monolayer adsorption volume on the particle in step S1 is calculated according to the sixth formula;

[0087] The sixth formula is:

[0088]

[0089] The following describes a method for optimizing the fractal dimension of the pore surface of organic-rich shale provided by the present application in conjunction with a specific embodiment.

[0090] The samples provided in this example were collected from the Shanxi Formation of the Balougou section in Baode County, on the eastern edge of the Ordos Basin. They are typical marine-continental transitional shale. The basic organic geochemical and inorganic mineral composition information of the samples is shown in Table 1.

[0091] Table 1: Basic geological and geochemical information of shale samples

[0092]

[0093] Note: TOC is total organic carbon content, Ro is vitrinite reflectance.

[0094] 1. Calculate the initial surface fractal dimension;

[0095] Step 1: Crush and grind the shale samples, select the 40-60 mesh shale samples for low-pressure nitrogen adsorption, and obtain the isothermal adsorption curve with relative pressure (P / Po) between 0.005 and 0.998. Figure 3 ;

[0096] Step 2: Calculate ln(V) and ln(ln(Po / P)) based on the low-pressure nitrogen adsorption data, plot the graph, and obtain Figure 4 ;

[0097] Step 3: According to the thickness of 1-2 layers of nitrogen molecules adsorption layer (approximately ), using the fourth formula, it is calculated that the relative pressure range corresponding to 1-2 nitrogen adsorption layers is approximately 0.086-0.550;

[0098] Step 4: Based on the pressure range obtained in step 3, calculate the A value using the fifth formula. m ) is a constant, so the slope of the relationship graph between ln(V) and ln(ln(Po / P)) for the corresponding relative pressure range can be directly calculated, and A = -0.425 is obtained;

[0099] Step 5: Calculate the surface fractal dimension D S Previously, the third formula was used to judge the adsorption mechanism and it was found that δ<0, in which case α is taken as 1;

[0100] Step 6: After step 5, the initial D is calculated. S =2.575; Based on the corresponding relative pressure range, the sixth formula is used to calculate the monolayer adsorption volume on the particle, i.e. V m =0.344cm 3 / g.

[0101] 2. Using the optimization method of the organic-rich shale pore surface fractal dimension provided in this application to optimize the final D S =2.648.

[0102] The present application provides an optimization method for the fractal dimension of the pore surface of organic-rich shale, which introduces an iterative concept, making the optimized surface fractal dimension more accurate and avoiding misjudgment of the adsorption and seepage capacity of the reservoir during the exploration and development of source rock natural gas.

[0103] The present application also provides a device for optimizing the fractal dimension of the pore surface of organic-rich shale, comprising:

[0104] A data input module for inputting the initial surface fractal dimension and the monolayer adsorption volume on the particles;

[0105] an adsorption volume calculation module, configured to calculate the adsorption volume interval of the gas at equilibrium pressure according to a first formula;

[0106] The first formula is: V = V m *n^(3-D S ), where V is the adsorption volume of the gas at equilibrium pressure, V mis the monolayer adsorption volume on the particle, 1.0±0.5≤n≤2.0±0.5, D S is the surface fractal dimension;

[0107] A relative pressure determination module, used for determining a relative pressure interval according to an adsorption volume interval;

[0108] Image drawing module, used to draw ln(V) and ln(ln(P O / P)), where P is the equilibrium pressure, P O is the saturation pressure of the gas at a given temperature;

[0109] a correction module, configured to obtain the slope of the image and calculate the corrected surface fractal dimension according to a second formula;

[0110] The second formula is: D S =3+αA, where A is the slope of the image and α is the coefficient;

[0111] A first judging module is used to judge whether the difference between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold;

[0112] If it is less than the threshold, the corrected surface fractal dimension is output to obtain the optimized surface fractal dimension;

[0113] If it is greater than the threshold, iterate until it is less than the threshold;

[0114] The second judgment module is used to judge the pore surface roughness of the organic-rich shale according to the optimized surface fractal dimension.

[0115] The specific definition of an optimization device for the fractal dimension of the pore surface of an organic-rich shale can be found in the above definition of an optimization method for the fractal dimension of the pore surface of an organic-rich shale, which will not be repeated here.

[0116] The present application also provides a computer device including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the steps of a method for optimizing the fractal dimension of the pore surface of organic-rich shale.

[0117] The present application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a method for optimizing the fractal dimension of the pore surface of organic-rich shale.

[0118] The technical features of the above embodiments can be combined arbitrarily (as long as there is no contradiction in the combination of these technical features). In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described; these embodiments that are not explicitly written should also be considered to be within the scope of this specification.

[0119] The present application has been described in a relatively specific and detailed manner through general explanations and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations may be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present application, the technical solutions obtained by such conventional adjustments or further innovations also fall within the scope of protection of the claims of the present application.

Claims

1. A method for optimizing the fractal dimension of the pore surface of organic-rich shale, characterized in that: include: Input the initial surface fractal dimension and the monolayer adsorption volume on the particle; Calculate the adsorption volume interval of the gas at equilibrium pressure according to the first formula; The first formula is: V = V m *n^(3-D S ), where V is the adsorption volume of the gas at equilibrium pressure, V m is the monolayer adsorption volume on the particle, 1.0±0.5≤n≤2.0±0.5, D S is the surface fractal dimension; determining a relative pressure interval according to the adsorption volume interval; Plot ln(V) and ln(ln(P O / P)), where P is the equilibrium pressure, P O is the saturation pressure of the gas at a given temperature; Obtaining the slope of the image, and calculating the corrected surface fractal dimension according to a second formula; The second formula is: D S =3+αA, where A is the slope of the image and α is the coefficient; the coefficient α is obtained by judging the adsorption mechanism according to the third formula; The third formula is: δ=3(1+A)-2, when δ<0, α is 1, when δ≥0, α is 3; determining whether a difference between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold; If it is less than the threshold, the corrected surface fractal dimension is output to obtain the optimized surface fractal dimension; If it is greater than the threshold, iterate until it is less than the threshold; The pore surface roughness of organic-rich shale is determined based on the optimized surface fractal dimension; The calculation process of the initial surface fractal dimension is specifically as follows: The rock sample to be tested is crushed into 40-60 mesh, and a low-pressure nitrogen adsorption test is performed to obtain low-pressure nitrogen adsorption data within the relative pressure range; According to the low pressure nitrogen adsorption data, ln(V) and ln(ln(P O / P)) and draw the image; Calculating the thickness of the nitrogen adsorption layer, and calculating the relative pressure range corresponding to the nitrogen adsorption layer according to the fourth formula; The fourth formula is: t = 0.88*(P / P O )^2+6.45*(P / P O )+2.98, where t is the thickness of the nitrogen adsorption layer; Calculate the slope of ln(V) and ln(ln(Po / P)) within the relative pressure range corresponding to the nitrogen adsorption layer according to the fifth formula; The fifth formula is: ln(V / V m )=C+A(ln(ln(P O / P))) ; The initial surface fractal dimension is calculated according to the second formula.

2. The method for optimizing the fractal dimension of the pore surface of organic-rich shale according to claim 1, characterized in that: In the low-pressure nitrogen adsorption test, there are no less than 40 measuring points on the adsorption curve.

3. The method for optimizing the fractal dimension of the pore surface of organic-rich shale according to claim 1, characterized in that: The low-pressure nitrogen adsorption data is low-pressure nitrogen adsorption data in a relative pressure range of 0.005 to 0.

998.

4. The method for optimizing the fractal dimension of the pore surface of organic-rich shale according to claim 1, characterized in that: The thickness of the nitrogen adsorption layer is the thickness of 1-2 layers of nitrogen molecule adsorption layers.

5. The method for optimizing the fractal dimension of the pore surface of organic-rich shale according to claim 1, characterized in that: The thickness of the nitrogen adsorption layer is calculated based on hexagonal closest packing.

6. An optimization device for the fractal dimension of the pore surface of organic-rich shale, characterized in that: include: A data input module for inputting the initial surface fractal dimension and the monolayer adsorption volume on the particles; an adsorption volume calculation module, configured to calculate the adsorption volume interval of the gas at equilibrium pressure according to a first formula; The first formula is: V = V m *n^(3-D S ), where V is the adsorption volume of the gas at equilibrium pressure, V m is the monolayer adsorption volume on the particle, 1.0±0.5≤n≤2.0±0.5, D S is the surface fractal dimension; A relative pressure determination module, configured to determine a relative pressure interval according to the adsorption volume interval; Image drawing module, used to draw ln(V) and ln(ln(P O / P)), where P is the equilibrium pressure, P O is the saturation pressure of the gas at a given temperature; a correction module, configured to obtain the slope of the image and calculate the corrected surface fractal dimension according to a second formula; The second formula is: D S =3+αA, where A is the slope of the image and α is the coefficient; the coefficient α is obtained by judging the adsorption mechanism according to the third formula; The third formula is: δ=3(1+A)-2, when δ<0, α is 1, when δ≥0, α is 3; A first judging module is used to judge whether the difference between the modified surface fractal dimension and the initial surface fractal dimension is greater than a threshold; If it is less than the threshold, the corrected surface fractal dimension is output to obtain the optimized surface fractal dimension; If it is greater than the threshold, iterate until it is less than the threshold; The second judgment module is used to judge the pore surface roughness of the organic-rich shale according to the optimized surface fractal dimension; The calculation process of the initial surface fractal dimension is specifically as follows: The rock sample to be tested is crushed into 40-60 mesh, and a low-pressure nitrogen adsorption test is performed to obtain low-pressure nitrogen adsorption data within the relative pressure range; According to the low pressure nitrogen adsorption data, ln(V) and ln(ln(P O / P)) and draw the image; Calculating the thickness of the nitrogen adsorption layer, and calculating the relative pressure range corresponding to the nitrogen adsorption layer according to the fourth formula; The fourth formula is: t = 0.88*(P / P O )^2+6.45*(P / P O )+2.98, where t is the thickness of the nitrogen adsorption layer; Calculate the slope of ln(V) and ln(ln(Po / P)) within the relative pressure range corresponding to the nitrogen adsorption layer according to the fifth formula; The fifth formula is: ln(V / V m )=C+A(ln(ln(P O / P))) ; The initial surface fractal dimension is calculated according to the second formula.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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