Comprehensive dessert evaluation method for mud pattern type shale oil geological engineering

Abstract

The invention relates to the technical field of shale oil and gas exploitation, in particular to a comprehensive dessert evaluation method for mud pattern type shale oil geological engineering. The method comprises the following steps: S1, sampling and analyzing; s2, determining a first level thickness seam height evaluation value according to an analysis result; and S3, determining a second-level geological engineering comprehensive sweet point evaluation value corresponding to each target exploration area based on the first-level thickness seam height evaluation value. According to the method, the exploration favorable area importance degree of each target exploration area is determined according to the target layer segment characteristic value, and the influence of different parameter dimensions is eliminated by performing normalization processing on the geological and engineering main control factor parameters of the target exploration area, so that the comparability among the parameters is enhanced, and the accuracy of the exploration is improved. By quantifying the weight coefficient of the main control factor and establishing the geological engineering comprehensive dessert evaluation formula, the exploration strategy is guided more accurately, and comprehensive and accurate technical support is provided for exploration and development of shale oil.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil and gas exploitation, and in particular to a method for evaluating a comprehensive sweet spot in muddy shale oil geological engineering. Background Art

[0002] In the field of geological exploration, "sweet spots" refer to areas in the reservoir that have high-quality geological qualities and are conducive to efficient fracturing volume transformation. The so-called engineering "sweet spots" mainly refer to areas where the reservoir has good fracturing characteristics and is easy to form a fracturing network. Gulong shale oil is a typical muddy shale oil. After adopting volume fracturing technology, it has achieved a significant breakthrough in production and has initially formed the "four properties" evaluation standard for Gulong shale oil reservoirs; however, each part of the evaluation standard is relatively independent, and usually relies on experience to select sweet spots, which leads to large differences in production results under the same geological and fracturing process conditions. There are two main reasons for this: First, the fracture mechanism of Gulong shale is unique, and the existing fracturing evaluation methods have certain limitations in adaptability; second, the process of artificial layer and section selection mainly relies on experience, and the selection of geological and engineering sweet spots has not been organically combined, lacking systematicity and scientificity.

[0003] The patent document with the publication number CN117474368A discloses a shale oil double sweet spot characterization method based on adaptive weighted fusion, which includes the following steps in sequence: S1. Optimization of shale oil sweet spot evaluation parameters based on entropy analysis method; S2. Quantitative characterization of shale oil geological sweet spot evaluation parameters; S3. Quantitative characterization of shale oil engineering sweet spot evaluation parameters; S4. Weighted fusion of shale oil sweet spot evaluation parameters based on adaptive algorithm; S5 effect test; It can be seen that the existing geological sweet spots are mainly used to evaluate the overall oil content of the layer or well section, and are usually used as a guiding tool for geological well selection and layer selection. However, these evaluation methods do not clearly define the influence of various geological parameters on engineering transformation, resulting in the inability to accurately apply them to actual fracturing layer selection and segment selection. Although there are many types of existing compressibility evaluation methods, there are often some restrictions in actual applications, such as the difficulty of obtaining evaluation parameters on site. On the other hand, the contribution weights of sweet spot influencing factors are usually solved by mathematical or statistical methods. This method ignores the physical meaning of some parameters, resulting in a large difference between the application and the actual situation on site. In addition, a comprehensive sweet spot evaluation method for geoengineering of muddy shale oil has not yet been found. Therefore, in order to meet the needs of exploration and development of muddy shale oil, it is urgent to form a comprehensive sweet spot evaluation method that can quantitatively evaluate the geoengineering impact weight of muddy shale oil, so as to accurately identify the "target" and provide technical support for accurate and efficient transformation. Summary of the invention

[0004] To this end, the present invention provides a comprehensive sweet spot evaluation method for muddy shale oil geological engineering, which is used to overcome the problem of low efficiency of sweet spot evaluation in the prior art due to the lack of initial determination of evaluation values ​​due to the lack of associated area thickness characteristics and fracture height characteristics, so as to make a preliminary assessment of the potential of the exploration area, thereby accurately selecting areas with greater potential based on the results of the preliminary assessment and giving priority to sweet spot evaluation.

[0005] To achieve the above object, the present invention provides a method for evaluating comprehensive sweet spots in muddy shale oil geological engineering, comprising:

[0006] Sampling is performed at each sampling point set in the target exploration area to obtain the layer thickness characteristics corresponding to each sampling point, so as to analyze the thickness distribution of the target exploration area and calculate the target layer characteristic value according to the layer thickness characteristics;

[0007] The thickness distribution includes uneven thickness in the target exploration area and uniform thickness in the target exploration area;

[0008] When the thickness of the target exploration area is uneven, the favorable area ratio is calculated according to the real-time total thickness value corresponding to each sampling point, and the favorable area ratio is determined according to the first standard area ratio and the second standard area ratio, so as to determine the target layer section characteristic value of the target exploration area based on the initial layer section characteristic value;

[0009] When the favorable area ratio is less than or equal to the first standard area ratio, the output target layer segment characteristic value is zero; when the favorable area ratio is greater than the first standard area ratio and less than the second standard area ratio, the initial layer segment characteristic value is corrected to the target layer segment characteristic value;

[0010] Generating a first-level thickness fracture height evaluation value according to the analysis result, and determining the importance of the favorable exploration area of ​​each target exploration area according to the first-level thickness fracture height evaluation value;

[0011] Determine the second-level geological engineering comprehensive sweet spot evaluation value corresponding to each target exploration area based on the first-level thickness and fracture height evaluation value;

[0012] Among them, the first-level thickness and fracture height evaluation value is the calculated target layer characteristic value, and the second-level geological engineering comprehensive sweet spot evaluation value is the calculated geological engineering comprehensive sweet spot evaluation value;

[0013] The geological engineering comprehensive sweet spot evaluation value corresponding to each of the target exploration areas is determined in descending order of importance of the favorable exploration areas.

[0014] Further, calculating the layer segment characteristic value according to the layer segment thickness characteristic includes:

[0015] Obtain the real-time total thickness value corresponding to each sampling point in the target exploration area to calculate the maximum total thickness difference in the target exploration area;

[0016] Determining the maximum total thickness difference according to the standard total thickness difference to analyze the uniformity of the thickness of the target exploration area;

[0017] When determining that the thickness of the target exploration area is uneven, comparing the first standard area proportion with the favorable area proportion to obtain a comparison result;

[0018] Determine whether to output the initial layer segment characteristic value as zero according to the comparison result, or determine the favorable area proportion in combination with the second standard area proportion to obtain the target layer segment characteristic value;

[0019] Among them, the proportion of the first standard area is smaller than that of the second standard area.

[0020] Furthermore, analyzing the uniformity of the thickness of the target exploration area includes:

[0021] If the maximum total thickness difference is less than or equal to the standard total thickness difference, the target exploration area is judged to have uniform thickness, and the initial layer segment characteristic value is calculated according to the total thickness of the area, the continuous thickness, the thickness of the middle single-layer sandstone, the sandstone ratio and the predicted fracture height, and the initial layer segment characteristic value is output as the target layer segment characteristic value;

[0022] If the maximum total thickness difference is greater than the standard total thickness difference, it is determined that the thickness of the target exploration area is uneven, and the proportion of the favorable area is calculated according to the real-time total thickness value corresponding to each sampling point;

[0023] The favorable area ratio is the percentage of difference sampling points to the total number of sampling points, and the difference sampling points are sampling points corresponding to the simulated total thickness difference being greater than the standard total thickness difference.

[0024] Further, according to the comparison result, it is determined whether to output the initial layer segment characteristic value as zero, or to determine the favorable area proportion in combination with the second standard area proportion, so as to obtain the target layer segment characteristic value, including:

[0025] When the proportion of favorable areas is less than or equal to the proportion of the first standard area, the output target layer segment characteristic value is zero;

[0026] When the proportion of favorable areas is greater than the proportion of the first standard area, the initial layer characteristic value is calculated according to the total thickness, continuous thickness, middle single-layer sandstone thickness, sandstone ratio and predicted fracture height of the target layer, and the proportion of favorable areas is determined according to the proportion of the second standard area;

[0027] Among them, F1'=F1×[1-(Qb1-Qs) / Qb1], Qs is the proportion of favorable areas, Qb1 is the proportion of the first standard area, F1 is the comprehensive sweet spot evaluation value of geological engineering, and F1' is the modified engineering comprehensive sweet spot evaluation value.

[0028] Further, determining the favorable area ratio according to the second standard area ratio includes:

[0029] When the proportion of the favorable area is greater than the proportion of the second standard area, the initial layer segment characteristic value is not corrected, and the initial layer segment characteristic value is output as the target layer segment characteristic value;

[0030] When the proportion of the favorable area is greater than the proportion of the first standard area and less than the proportion of the second standard area, the initial layer segment characteristic value is corrected to obtain the target layer segment characteristic value;

[0031] Among them, F2=Fc×[1-(Qb2-Qs) / Qb2], Qs is the proportion of favorable areas, Qb2 is the proportion of the second standard area, F2 is the characteristic value of the target layer segment, and Fc is the characteristic value of the initial layer segment.

[0032] Further, the geological engineering comprehensive sweet spot evaluation value corresponding to any of the target exploration areas is determined based on the main control factors, including:

[0033] Normalizing the main control factor parameters to obtain normalized results, wherein the main control factor parameters include geological main control factor parameters and engineering main control factor parameters;

[0034] A geological engineering comprehensive sweet spot evaluation formula is established based on the normalized result, and the weight coefficients of the main control factor parameters are quantified to obtain a geological engineering comprehensive sweet spot evaluation value.

[0035] Furthermore, the geological engineering comprehensive sweet spot evaluation formula is:

[0036]

[0037] Among them, F1 is the comprehensive sweet spot evaluation value of geological engineering, D TOC is the normalized result of TOC value, D S1 is the normalized result of S1 value, D C1 is the normalized result of gas measurement value, D GR is the normalized result of GR value, D DZ is the normalized result of the resistance value, G B is the normalized result of the brittleness index value, G SC is the normalized result of the in-situ stress difference, GFFV is the normalized result of the nuclear magnetic macropore value, G KC is the normalized result of toughness difference ratio, G LYis the normalized result of the tension-compression ratio, M1 is the weight coefficient corresponding to TOC, M2 is the weight coefficient corresponding to S1, M3 is the weight coefficient corresponding to gas logging, M4 is the weight coefficient corresponding to GR, M5 is the weight coefficient corresponding to resistance, N1 is the weight coefficient corresponding to the brittleness index, N2 is the weight coefficient corresponding to the ground stress difference, N3 is the weight coefficient corresponding to the nuclear magnetic macropore, N4 is the weight coefficient corresponding to the toughness difference ratio, and N5 is the weight coefficient corresponding to the tension-compression ratio.

[0038] Furthermore, the weight coefficients of the main control factor parameters are quantified to obtain the comprehensive sweet spot evaluation value of geological engineering, including:

[0039] Calculate the weight coefficient of each geological main controlling factor parameter according to the geological model, and calculate the weight coefficient of each engineering main controlling factor parameter according to the engineering model;

[0040] The comprehensive sweet spot evaluation value of geological engineering is calculated according to the weight coefficient, wherein:

[0041]

[0042] F1 is the comprehensive sweet spot evaluation value of geological engineering, D TOC is the normalized result of TOC value, D S1 is the normalized result of S1 value, D C1 is the normalized result of gas measurement value, D GR is the normalized result of GR value, D DZ is the normalized result of the resistance value, G B is the normalized result of the brittleness index value, G SC is the normalized result of the in-situ stress difference, GFFV is the normalized result of the nuclear magnetic macropore value, G KC is the normalized result of toughness difference ratio, G LY is the normalized result of tension-compression ratio.

[0043] Furthermore, the weight coefficients include weight coefficients of geological main controlling factor parameters and weight coefficients of engineering main controlling factor parameters.

[0044] Furthermore, the initial layer characteristic values ​​are calculated based on the total regional thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height, including:

[0045] The total thickness, continuous thickness, intermediate single-layer sandstone thickness and sandstone ratio at each sampling point are obtained, and their average values ​​are calculated respectively to obtain the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio and predicted fracture height of the target layer segment to calculate the initial layer segment characteristic value:

[0046] Fc=k1×TH+k2×CH+k3×(1-SH / Smax)+k4×(1-SPR)+0.5×SH, SH=K×δ / E;

[0047] Among them, Fc is the characteristic value of the initial layer segment, TH is the total thickness of the target layer segment, k1 is the weight of the total thickness, CH is the continuous thickness, k2 is the weight of the continuous thickness, SH is the thickness of the intermediate single-layer sandstone, k3 is the weight of the thickness of the intermediate single-layer sandstone, Smax is the maximum allowable thickness of the intermediate single-layer sandstone, SPR is the sandstone ratio, k4 is the weight of the sandstone ratio, SH is the predicted fracture height, K is the lamella fracture bonding strength, δ is the formation pressure, E is the elastic modulus of shale, and k5 is the weight of the predicted fracture height.

[0048] Compared with the prior art, the beneficial effect of the present invention lies in that, by dividing the target exploration area into regular grids, a sampling point is set in each grid, and the sampling spacing can be adaptively selected and adjusted according to factors such as geological characteristics, resource distribution and exploration cost. Key areas can also be selected according to geological characteristics, oil and gas potential and other indicators to increase the density of sampling points in key areas. It is only necessary to ensure that detailed data is obtained, and each target exploration area is preliminarily evaluated by associating layer thickness characteristics and fracture height prediction values, that is, the importance of the exploration favorable area of ​​each target exploration area is determined according to the target layer characteristic value, so as to preliminarily evaluate the value. The higher the calculated target layer characteristic value, the stronger the fracture height expansion ability of the target exploration area. Therefore, the fracture height expansion ability of the target exploration area is initially judged according to the target layer characteristic value. According to the priority of the importance of the favorable exploration area, the comprehensive sweet spot evaluation value of the target exploration area is obtained to guide the exploration strategy more accurately. By quantifying the influence of parameters on oil and gas production, a comprehensive sweet spot evaluation formula is formed. Since accurate sweet spot area evaluation can significantly improve mining efficiency and increase shale oil production, the parameters of the geological and engineering main control factors in the target exploration area are normalized to eliminate the influence of different parameter dimensions, so that the comparability between the parameters is enhanced. This data processing method improves the accuracy of exploration. By quantifying the weight coefficients of the main control factors and establishing a comprehensive sweet spot evaluation formula for geological engineering, the characteristic values ​​of the target layer segment are calculated by associating the layer segment thickness characteristics and the fracture height prediction values ​​to more accurately guide the exploration strategy, providing comprehensive and accurate technical support for the exploration and development of shale oil.

[0049] Furthermore, when the total thickness at any randomly selected sampling point is greater than 30 m, the target exploration area is determined with the sampling point as the center, and sampling is performed by setting multiple sampling points in the target exploration area to detect the real-time total thickness value of each sampling point, so as to analyze the thickness uniformity of the target exploration area through simple calculations, so that the total thickness condition ensures that the overall volume of the shale section can support large-scale mining, and when the regional thickness is uneven, the sweet spot evaluation formula is optimized according to the uniformity of the regional thickness to improve the development efficiency of shale oil.

[0050] Furthermore, by subdividing the target exploration area and calculating the average total thickness of each simulated exploration module, the geological changes and heterogeneity in the area can be more accurately evaluated. Areas with large thickness changes indicate more complex geological conditions. Therefore, based on the analysis results of regional thickness, the sweet spot evaluation formula is continuously optimized to achieve flexible response to complex geological conditions.

[0051] Furthermore, by collecting data and analyzing the thickness uniformity, when it is determined that the thickness of the target exploration area is uniform, the characteristic value of the target layer segment is directly calculated based on the detected thickness data; when it is determined that the thickness of the target exploration area is uneven, the evaluation value is adaptively corrected more finely by analyzing the degree of thickness unevenness, so as to preliminarily predict the evaluation value of the target exploration area more accurately, and quickly identify areas suitable for further development to avoid misidentification of areas with uneven thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a schematic diagram of the process of the comprehensive sweet spot evaluation method for muddy shale oil geological engineering according to an embodiment of the present invention;

[0053] Figure 2 It is a schematic diagram of a process of calculating a layer segment characteristic value according to a layer segment thickness characteristic according to an embodiment of the present invention;

[0054] Figure 3 A logical decision diagram for calculating the evaluation value of a shale oil sweet spot area according to an embodiment of the present invention;

[0055] Figure 4 The comprehensive sweet spot evaluation results and tracer monitoring fitting results of the four wells in the embodiment of the present invention are shown. DETAILED DESCRIPTION

[0056] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with 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.

[0057] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0058] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0059] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] See also Figure 1 As shown, it is a schematic diagram of the process of the comprehensive sweet spot evaluation method for muddy shale oil geological engineering according to an embodiment of the present invention. The present invention provides a comprehensive sweet spot evaluation method for muddy shale oil geological engineering, comprising:

[0061] Step S1, sampling is performed at each sampling point set in the target exploration area to obtain the layer thickness characteristics corresponding to each sampling point, so as to analyze the thickness distribution of the target exploration area and calculate the target layer characteristic value according to the layer thickness characteristics;

[0062] The thickness distribution includes uneven thickness in the target exploration area and uniform thickness in the target exploration area;

[0063] When the thickness of the target exploration area is uneven, the favorable area ratio is calculated according to the real-time total thickness value corresponding to each sampling point, and the favorable area ratio is determined according to the first standard area ratio and the second standard area ratio, so as to determine the target layer section characteristic value of the target exploration area based on the initial layer section characteristic value;

[0064] When the favorable area ratio is less than or equal to the first standard area ratio, the output target layer segment characteristic value is zero; when the favorable area ratio is greater than the first standard area ratio and less than the second standard area ratio, the initial layer segment characteristic value is corrected to the target layer segment characteristic value;

[0065] Step S2, generating a first-level thickness fracture height evaluation value according to the analysis result, and determining the importance of the favorable exploration area of ​​each target exploration area according to the first-level thickness fracture height evaluation value;

[0066] Step S3, determining the second-level geological engineering comprehensive sweet spot evaluation value corresponding to each target exploration area based on the first-level thickness and fracture height evaluation value;

[0067] Among them, the first-level thickness and fracture height evaluation value is the calculated target layer characteristic value, and the second-level geological engineering comprehensive sweet spot evaluation value is the calculated geological engineering comprehensive sweet spot evaluation value;

[0068] Determine the geological engineering comprehensive sweet spot evaluation value corresponding to each of the target exploration areas in descending order of importance of the favorable exploration areas;

[0069] Among them, the geological engineering comprehensive sweet spot evaluation value corresponding to any of the target exploration areas is determined based on the main controlling factors; the importance of the favorable exploration area is the value corresponding to the characteristic value of the target layer segment.

[0070] The selection of the target exploration area in this embodiment is related to equipment conditions and environmental safety. It is necessary to ensure that the sampling points can meet the installation requirements of instruments and equipment, and to select areas that avoid environmental risks, such as landslides, floods and other impact areas. By dividing the target exploration area into regular grids, a sampling point is set in each grid. The sampling spacing can be adapted and adjusted according to factors such as geological characteristics, resource distribution, and exploration costs. Key areas can also be selected according to geological characteristics, oil and gas potential and other indicators to increase the density of sampling points in key areas. It is only necessary to ensure that detailed data is obtained, and each target exploration area is pre-evaluated by associating layer thickness characteristics and fracture height prediction values, that is, the importance of the exploration favorable area of ​​each target exploration area is determined according to the target layer characteristic value, so as to make a preliminary evaluation. The higher the calculated target layer characteristic value, the stronger the fracture height expansion ability of the target exploration area. Therefore, according to the target The layer characteristic value initially determines the fracture height expansion capacity of the target exploration area, so as to obtain the geological engineering comprehensive sweet spot evaluation value of the target exploration area according to the priority of the importance of the favorable exploration area, guide the exploration strategy more accurately, and form a comprehensive sweet spot evaluation formula by quantifying the influence of parameters on oil and gas production. Since accurate sweet spot area evaluation can significantly improve mining efficiency and increase shale oil production, the parameters of the geological and engineering main control factors in the target exploration area are normalized to eliminate the influence of different parameter dimensions, so that the comparability between the parameters is enhanced. This data processing method improves the exploration accuracy. By quantifying the weight coefficients of the main control factors and establishing a geological engineering comprehensive sweet spot evaluation formula, the target layer characteristic value is calculated by associating the layer thickness characteristics and the fracture height prediction value to more accurately guide the exploration strategy, providing comprehensive and accurate technical support for the exploration and development of shale oil.

[0071] See also Figure 2 As shown, it is a schematic diagram of a process of calculating a layer segment characteristic value according to a layer segment thickness characteristic according to an embodiment of the present invention;

[0072] Specifically, the calculation of layer characteristic values ​​according to layer thickness characteristics includes:

[0073] Step S301, obtaining the real-time total thickness value corresponding to each sampling point in the target exploration area to calculate the maximum total thickness difference in the target exploration area;

[0074] Step S302, determining the maximum total thickness difference according to the standard total thickness difference to analyze the uniformity of the thickness of the target exploration area;

[0075] When determining that the thickness of the target exploration area is uneven, comparing the first standard area proportion with the favorable area proportion to obtain a comparison result;

[0076] Step S303, determining whether to output the initial layer segment characteristic value as zero according to the comparison result, or determining the favorable area proportion in combination with the second standard area proportion to obtain the target layer segment characteristic value;

[0077] Among them, the proportion of the first standard area is smaller than that of the second standard area.

[0078] In this implementation, when the total thickness at any randomly selected sampling point is greater than 30m, the target exploration area is determined with the sampling point as the center. Multiple sampling points are set in the target exploration area for sampling to detect the real-time total thickness value of each sampling point. The thickness uniformity of the target exploration area is analyzed through simple calculations, so that the total thickness condition ensures that the overall volume of the shale section can support large-scale mining. When the regional thickness is uneven, the sweet spot evaluation formula is optimized according to the uniformity of the regional thickness to improve the development efficiency of shale oil.

[0079] Specifically, the calculation of the maximum total thickness difference within the target exploration area includes:

[0080] Use vertical lines to divide the target exploration area into several simulated exploration modules, calculate the average total thickness of each simulated exploration module and record it as the simulated total thickness, calculate the quotient of the sum of the simulated total thickness and the number of simulated exploration modules to obtain the regional total thickness value of the target exploration area, subtract the regional total thickness value from each simulated total thickness to obtain several simulated total thickness differences, take the absolute value of each simulated total thickness difference, and obtain the largest value among the absolute values ​​as the maximum total thickness difference.

[0081] In this embodiment, the target exploration area is subdivided and the average total thickness of each simulated exploration module is calculated to more accurately evaluate the geological changes and heterogeneity in the area. Areas with large thickness changes indicate more complex geological conditions. Therefore, based on the analysis results of regional thickness, the sweet spot evaluation formula is continuously optimized to achieve flexible response to complex geological conditions.

[0082] See also Figure 3 As shown, it is a logical decision diagram for calculating the evaluation value of the shale oil sweet spot area according to an embodiment of the present invention;

[0083] Specifically, the analysis of the uniformity of thickness of the target exploration area includes:

[0084] If the maximum total thickness difference is less than or equal to the standard total thickness difference, the target exploration area is judged to have uniform thickness, and the initial layer segment characteristic value is calculated according to the total thickness of the area, the continuous thickness, the thickness of the middle single-layer sandstone, the sandstone ratio and the predicted fracture height, and the initial layer segment characteristic value is output as the target layer segment characteristic value;

[0085] If the maximum total thickness difference is greater than the standard total thickness difference, it is determined that the thickness of the target exploration area is uneven, and the proportion of the favorable area is calculated according to the real-time total thickness value corresponding to each sampling point;

[0086] The favorable area ratio is the percentage of the difference sampling points to the total number of sampling points, and the difference sampling points are sampling points corresponding to the simulated total thickness difference being greater than the standard total thickness difference;

[0087] The standard total thickness difference set in this embodiment represents the deviation value of the allowable thickness fluctuation, which is set between 1m and 3m and is adjusted according to different geological conditions and exploration targets;

[0088] By collecting data and analyzing the thickness uniformity, when it is determined that the thickness of the target exploration area is uniform, the characteristic value of the target layer segment is directly calculated based on the detected thickness data; when it is determined that the thickness of the target exploration area is uneven, the evaluation value is adaptively corrected more finely by analyzing the degree of thickness unevenness, so as to preliminarily predict the evaluation value of the target exploration area more accurately, and quickly identify areas suitable for further development to avoid misidentification of areas with uneven thickness.

[0089] Specifically, according to the comparison result, it is determined whether to output the initial layer segment characteristic value as zero, or to determine the favorable area proportion in combination with the second standard area proportion, so as to obtain the target layer segment characteristic value, including:

[0090] When the proportion of favorable areas is less than or equal to the proportion of the first standard area, the output target layer segment characteristic value is zero;

[0091] When the proportion of favorable areas is greater than the proportion of the first standard area, the initial layer characteristic value is calculated according to the total thickness, continuous thickness, middle single-layer sandstone thickness, sandstone ratio and predicted fracture height of the target layer, and the proportion of favorable areas is determined according to the proportion of the second standard area;

[0092] Among them, F1'=F1×[1-(Qb1-Qs) / Qb1], Qs is the proportion of favorable areas, Qb1 is the proportion of the first standard area, F1 is the comprehensive sweet spot evaluation value of geological engineering, and F1' is the modified engineering comprehensive sweet spot evaluation value.

[0093] Specifically, judging the favorable area ratio according to the second standard area ratio includes:

[0094] When the proportion of the favorable area is greater than the proportion of the second standard area, the initial layer segment characteristic value is not corrected, and the initial layer segment characteristic value is output as the target layer segment characteristic value;

[0095] When the proportion of the favorable area is greater than the proportion of the first standard area and less than the proportion of the second standard area, the initial layer segment characteristic value is corrected to obtain the target layer segment characteristic value;

[0096] Among them, F2=Fc×[1-(Qb2-Qs) / Qb2], Qs is the proportion of favorable areas, Qb2 is the proportion of the second standard area, F2 is the characteristic value of the target layer segment, and Fc is the characteristic value of the initial layer segment.

[0097] The first standard area ratio set in this embodiment represents a smaller thickness uniformity, generally, it is set to 20%, and the second standard area ratio represents a larger thickness uniformity, generally, it is set between 70%-80%, and it is selected and adjusted according to the operational requirements of the target exploration area.

[0098] When it is determined that the proportion of favorable areas is less than or equal to the proportion of the first standard area, it indicates that the regional thickness unevenness is very high. The real-time geological engineering comprehensive sweet spot evaluation is dynamically adjusted according to the degree of deviation between the proportion of favorable areas and the proportion of the first standard area. When it is determined that the proportion of favorable areas is greater than the proportion of the first standard area and less than the proportion of the second standard area, it indicates that the target exploration area is in an intermediate state. At this time, the initial layer segment characteristic value needs to be corrected to more accurately reflect the sweet spot evaluation value of the area. When it is determined that the proportion of favorable areas is greater than the proportion of the second standard area, it indicates that the area has good development potential. Therefore, there is no need to correct the initial layer segment characteristic value, and the target layer segment characteristic value is directly output. This not only can timely identify areas without development potential, but also ensure the scientificity and effectiveness of the sweet spot evaluation of leaf oilfields.

[0099] Specifically, the main geological and engineering control factors are determined and normalized, including:

[0100] Determine the main geological control factors: TOC, S1, gas logging, GR and electrical resistance;

[0101] Determine the main controlling factors of the project: brittleness index, ground stress difference, nuclear magnetic resonance macropores, toughness difference ratio, and tension-compression ratio.

[0102] Total organic carbon is referred to as TOC, which reflects the abundance of organic matter in the shale layer. A high TOC value means that the rock contains more organic matter, which can generate oil and gas.

[0103] The S1 value refers to the content of mobile hydrocarbons in the rock. A high S1 value means that the rock contains more mobile hydrocarbons, and represents better reservoir quality and higher mining value.

[0104] Gas testing represents the gas content and gas mobility in the shale layer. The gas testing value is the total gas concentration of hydrocarbon gases such as methane, ethane, and propane. A high gas testing value means that the rock contains more movable hydrocarbons, and represents better reservoir quality and higher mining value.

[0105] GR is the abbreviation of Gamma-Ray logging curve. The GR value is obtained by measuring the intensity of gamma rays naturally emitted in the formation. It is used to identify lithology and determine the mineral composition of rocks, and characterize the concentration of radioactive elements in rocks. A high GR value usually indicates that the rock contains more organic matter, indicating a higher potential for oil and gas generation.

[0106] Resistance characterizes the degree of rock's resistance to the flow of electric current. The resistance value is obtained by measuring the resistance of the rock to the electric current to evaluate the reservoir characteristics and oil and gas content of the reservoir. High porosity and high fluid saturation usually lead to lower resistivity. Higher resistivity represents high oil and gas saturation, that is, there is a sandstone layer containing oil and gas at the corresponding sampling point. Low resistivity indicates the presence of water-saturated rocks or areas lacking oil and gas. The brittleness index is the ratio of the uniaxial compressive strength to the tensile strength of the rock. The larger this ratio is, the higher the brittleness of the rock is and the higher its mining value is.

[0107] The geostress difference represents the difference between the maximum and minimum horizontal principal stresses in the reservoir. The larger the geostress difference, the better the fracturing effect, because in this case it is easier to form a fracture network in the reservoir, thereby improving the flow efficiency and production of oil and gas;

[0108] NMR macropores refer to the NMR macropore evaluation value obtained by analyzing the larger pores in the rock detected by the nuclear magnetic resonance (NMR) technology. The calculation formula of the NMR macropore evaluation value is:

[0109] PV = α × Φ + β × pore size distribution index;

[0110] Wherein, PV is the nuclear magnetic macropore evaluation value, α and β are weight coefficients, α = 0.6, β = 0.4, the pore size distribution index is the average pore size, which reflects the parameters of the pore size distribution characteristics and is obtained by analyzing the T2 spectrum data, and Φ is the porosity;

[0111] Porosity is the ratio of the pore volume to the total volume in the rock. It is calculated using NMR logging data. The porosity calculation formula is:

[0112]

[0113] Where Φ is the porosity, f(T2) is the T2 spectrum distribution, T2 is the relaxation time, and Vs is the rock skeleton volume;

[0114] The toughness difference ratio is the ratio of longitudinal to transverse fracture toughness and is an indicator for evaluating the degree of crack height extension.

[0115] The tension-compression ratio is the ratio of tensile strength to compressive strength, which is used to correct the brittleness of shale, and its value is inversely proportional to the degree of brittleness.

[0116] Taking into full consideration the contribution of the 10 main control factors to production, they are divided according to positive and negative correlations. Among them, TOC, S1, gas testing, GR, brittleness index, geostress difference, and nuclear magnetic macropores are positively correlated main control factors; resistance, toughness difference ratio, and tension-compression ratio are negatively correlated main control factors. In order to reduce the impact of dimensional units on data calculation results, the 10 selected parameters are normalized according to the positive and negative correlation of their contribution to production capacity. The normalization formula is as follows:

[0117] Xz=(X-Xmin) / (Xmax-Xmin);

[0118] Yz=(Ymax-Y) / (Ymax-Ymin);

[0119] Among them, Xz is the normalized result of the positive correlation parameter, and the value range of Xz is between 0 and 1. Yz is the normalized result of the negative correlation parameter, and the value range of Yz is between 0 and 1. X is the actual value of the positive correlation parameter, Xmax is the maximum value of the positive correlation parameter, Xmin is the minimum value of the positive correlation parameter, Y is the actual value of the negative correlation parameter, Ymax is the maximum value of the negative correlation parameter, and Ymin is the minimum value of the negative correlation parameter.

[0120] According to the positive and negative correlation of geological and engineering parameters on production capacity, a comprehensive geological and engineering sweet spot evaluation formula is established, including:

[0121] In order to fully reflect the differences in the contribution of each parameter to the production results, the normalized results of the 10 main control factors are integrated according to the positive and negative correlation relationship of their contribution to production capacity, and the comprehensive sweet spot evaluation formula for geological engineering is obtained as follows:

[0122]

[0123] Where F1 is the comprehensive sweet spot evaluation value of geological engineering, D TOC is the normalized result of TOC value, D S1 is the normalized result of S1 value, D C1 is the normalized result of gas measurement value, D GR is the normalized result of GR value, D DZ is the normalized result of the resistance value, G B is the normalized result of the brittleness index value, G SC is the normalized result of the in-situ stress difference, GFFV is the normalized result of the nuclear magnetic macropore value (>8ms), G KC is the normalized result of toughness difference ratio, G LYis the normalized result of the tension-compression ratio, M1 is the weight coefficient corresponding to TOC, M2 is the weight coefficient corresponding to S1, M3 is the weight coefficient corresponding to gas logging, M4 is the weight coefficient corresponding to GR, M5 is the weight coefficient corresponding to resistance, N1 is the weight coefficient corresponding to the brittleness index, N2 is the weight coefficient corresponding to the ground stress difference, N3 is the weight coefficient corresponding to the nuclear magnetic macropore, N4 is the weight coefficient corresponding to the toughness difference ratio, and N5 is the weight coefficient corresponding to the tension-compression ratio.

[0124] Specifically, through geological modeling, a single variable in each geological parameter is changed, and the weight coefficient of the influence of the geological main control factor on the output is determined according to the degree of influence of the parameter on the production effect, and the result is compared with the tracer capacity monitoring result. After multiple rounds of calculation, the weight coefficient of the influence of geological parameters on the capacity is finally obtained. According to the calculation results, the contribution weight of each factor is clarified: M1 = 10.2%, M2 = 10.2%, M3 = 9.3%, M4 = 10.8%, M5 = 13.2%. Among them, M1 is the contribution weight of TOC, M2 is the contribution weight of S1, M3 is the contribution weight of gas measurement, M4 is the contribution weight of GR, and M5 is the contribution weight of resistance.

[0125] Through numerical simulation, a single variable in each engineering parameter is changed. According to the degree of influence of the parameter on the fracture transformation volume, the weight coefficient of the main control factor of the project on the production is determined, and the result is compared with the tracer capacity monitoring result. After multiple rounds of calculation, the weight coefficient of the influence of the engineering parameter on the capacity is finally obtained. According to the calculation results, the contribution weight of each factor is clarified: N1 = 10%, N2 = 8%, N3 = 13%, N4 = 10.3%, N5 = 5%. Among them, N1 is the contribution weight of the brittleness index, N2 is the contribution weight of the ground stress difference, N3 is the contribution weight of the nuclear magnetic macropore, N4 is the contribution weight of the toughness difference ratio, and N5 is the contribution weight of the tension-compression ratio.

[0126] Specifically, the weight coefficients of the main control factor parameters are quantified to obtain the comprehensive sweet spot evaluation value of geological engineering, including:

[0127] Calculate the weight coefficient of each geological main controlling factor parameter according to the geological model, and calculate the weight coefficient of each engineering main controlling factor parameter according to the engineering model;

[0128] The comprehensive sweet spot evaluation value of geological engineering is calculated according to the weight coefficient, wherein:

[0129]

[0130] F1 is the comprehensive sweet spot evaluation value of geological engineering, D TOC is the normalized result of TOC value, D S1 is the normalized result of S1 value, D C1 is the normalized result of gas measurement value, DGR is the normalized result of GR value, D DZ is the normalized result of the resistance value, G B is the normalized result of the brittleness index value, G SC is the normalized result of the in-situ stress difference, GFFV is the normalized result of the nuclear magnetic macropore value (>8ms), G KC is the normalized result of toughness difference ratio, G LY is the normalized result of tension-compression ratio.

[0131] Specifically, the weight coefficients include weight coefficients of geological main controlling factor parameters and weight coefficients of engineering main controlling factor parameters.

[0132] Specifically, the initial layer characteristic values ​​are calculated based on the total regional thickness, continuous thickness, intermediate single-layer sandstone thickness and sandstone ratio, including:

[0133] The total thickness, continuous thickness, intermediate single-layer sandstone thickness and sandstone ratio at each sampling point are obtained, and their average values ​​are calculated respectively to obtain the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio and predicted fracture height of the target layer segment to calculate the initial layer segment characteristic value:

[0134] Fc=k1×TH+k2×CH+k3×(1-SH / Smax)+k4×(1-SPR)+0.5×SH, SH=K×δ / E;

[0135] Among them, Fc is the characteristic value of the initial layer segment, TH is the total thickness of the target layer segment, k1 is the weight of the total thickness, k1=0.1, CH is the continuous thickness, k2 is the weight of the continuous thickness, k2=0.2, SH is the thickness of the intermediate single-layer sandstone, k3 is the weight of the intermediate single-layer sandstone thickness, k3=0.2, Smax is the maximum allowable thickness of the intermediate single-layer sandstone, Smax is 2m, SPR is the sandstone ratio, k4 is the weight of the sandstone ratio, k4=0.1, SH is the predicted fracture height, K is the lamella fracture bonding strength, δ is the formation pressure, E is the elastic modulus of shale, k5 is the weight of the predicted fracture height, k5=0.4. Among them, total thickness (TH): represents the total thickness of the mud shale layer, which affects the reserves and fluid flow capacity.

[0136] Continuous thickness (CH): It will affect the effect of the fracturing process and reflect the effectiveness of the layer.

[0137] Intermediate single-layer sandstone thickness (SH): Too thick sandstone may affect the fracturing effect.

[0138] Sandstone ratio within 10m (SPR): affects the permeability of shale and the distribution of overall resources.

[0139] The unit of shaling strength is MPa. The elastic modulus of shale indicates its deformation capacity under stress and is obtained through experiments.

[0140] See also Figure 4 As shown, it is the comprehensive sweet spot evaluation results of four wells in the embodiment of the present invention and the tracer monitoring fitting results;

[0141] The shale oil sweet spot area evaluation value obtained by the sweet spot evaluation method of this embodiment is the geological engineering comprehensive sweet spot evaluation result;

[0142] like Figure 4 As shown in the figure, the comprehensive geological and engineering sweet spot evaluation results are compared with the tracer capacity test results. After multiple rounds of adjustment of the contribution weights of each parameter, the weight coefficients of the influence of geological and engineering parameters on capacity are finally obtained. That is, the results calculated under the shale oil sweet spot area evaluation value formula are well correlated with the tracer monitoring results of each section.

[0143] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0144] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A comprehensive sweet spot evaluation method for muddy shale oil geological engineering, characterized in that: include, Sampling is performed at each sampling point set in the target exploration area to obtain the layer thickness characteristics corresponding to each sampling point, so as to analyze the thickness distribution of the target exploration area and calculate the target layer characteristic value according to the layer thickness characteristics; The thickness distribution includes uneven thickness in the target exploration area and uniform thickness in the target exploration area; When the thickness of the target exploration area is uneven, the favorable area ratio is calculated according to the real-time total thickness value corresponding to each sampling point, and the favorable area ratio is determined according to the first standard area ratio and the second standard area ratio, so as to determine the target layer section characteristic value of the target exploration area based on the initial layer section characteristic value; When the favorable area ratio is less than or equal to the first standard area ratio, the output target layer segment characteristic value is zero; when the favorable area ratio is greater than the first standard area ratio and less than the second standard area ratio, the initial layer segment characteristic value is corrected to the target layer segment characteristic value; Generating a first-level thickness fracture height evaluation value according to the analysis result, and determining the importance of the favorable exploration area of ​​each target exploration area according to the first-level thickness fracture height evaluation value; Determine the second-level geological engineering comprehensive sweet spot evaluation value corresponding to each target exploration area based on the first-level thickness and fracture height evaluation value; Among them, the first-level thickness and fracture height evaluation value is the calculated target layer characteristic value, and the second-level geological engineering comprehensive sweet spot evaluation value is the calculated geological engineering comprehensive sweet spot evaluation value; The geological engineering comprehensive sweet spot evaluation value corresponding to each of the target exploration areas is determined in descending order of importance of the favorable exploration areas.

2. The method for evaluating the comprehensive sweet spot of muddy shale oil geological engineering according to claim 1, characterized in that: The calculation of layer characteristic values ​​based on layer thickness characteristics includes: Obtain the real-time total thickness value corresponding to each sampling point in the target exploration area to calculate the maximum total thickness difference in the target exploration area; Determining the maximum total thickness difference according to the standard total thickness difference to analyze the uniformity of the thickness of the target exploration area; When determining that the thickness of the target exploration area is uneven, comparing the first standard area proportion with the favorable area proportion to obtain a comparison result; Determine whether to output the initial layer segment characteristic value as zero according to the comparison result, or determine the favorable area proportion in combination with the second standard area proportion to obtain the target layer segment characteristic value; Among them, the proportion of the first standard area is smaller than that of the second standard area.

3. The method for evaluating the comprehensive sweet spot of muddy shale oil geological engineering according to claim 2, characterized in that: The analysis of the uniformity of thickness of the target exploration area includes: If the maximum total thickness difference is less than or equal to the standard total thickness difference, the target exploration area is judged to have uniform thickness, and the initial layer segment characteristic value is calculated according to the total thickness of the area, the continuous thickness, the thickness of the middle single-layer sandstone, the sandstone ratio and the predicted fracture height, and the initial layer segment characteristic value is output as the target layer segment characteristic value; If the maximum total thickness difference is greater than the standard total thickness difference, it is determined that the thickness of the target exploration area is uneven, and the proportion of the favorable area is calculated according to the real-time total thickness value corresponding to each sampling point; The favorable area ratio is the percentage of difference sampling points to the total number of sampling points, and the difference sampling points are sampling points corresponding to the simulated total thickness difference being greater than the standard total thickness difference.

4. The method for evaluating the comprehensive sweet spot of muddy shale oil geological engineering according to claim 3, characterized in that: Determine whether to output the initial layer segment characteristic value as zero according to the comparison result, or determine the favorable area proportion in combination with the second standard area proportion, so as to obtain the target layer segment characteristic value, including: When the proportion of favorable areas is less than or equal to the proportion of the first standard area, the output target layer segment characteristic value is zero; When the proportion of favorable areas is greater than the proportion of the first standard area, the initial layer characteristic value is calculated according to the total thickness, continuous thickness, middle single-layer sandstone thickness, sandstone ratio and predicted fracture height of the target layer, and the proportion of favorable areas is determined according to the proportion of the second standard area; Among them, F1'=F1×[1-(Qb1-Qs) / Qb1], Qs is the proportion of favorable areas, Qb1 is the proportion of the first standard area, F1 is the comprehensive sweet spot evaluation value of geological engineering, and F1' is the modified engineering comprehensive sweet spot evaluation value.

5. The method for comprehensive sweet spot evaluation of muddy shale oil geological engineering according to claim 4, characterized in that: The determination of the favorable area ratio according to the second standard area ratio includes: When the proportion of the favorable area is greater than the proportion of the second standard area, the initial layer segment characteristic value is not corrected, and the initial layer segment characteristic value is output as the target layer segment characteristic value; When the proportion of the favorable area is greater than the proportion of the first standard area and less than the proportion of the second standard area, the initial layer segment characteristic value is corrected to obtain the target layer segment characteristic value; Among them, F2=Fc×[1-(Qb2-Qs) / Qb2], Qs is the proportion of favorable areas, Qb2 is the proportion of the second standard area, F2 is the characteristic value of the target layer segment, and Fc is the characteristic value of the initial layer segment.

6. The method for comprehensive sweet spot evaluation of muddy shale oil geological engineering according to claim 1, characterized in that: Determining the geological engineering comprehensive sweet spot evaluation value corresponding to any target exploration area based on the main controlling factors includes: Normalizing the main control factor parameters to obtain normalized results, wherein the main control factor parameters include geological main control factor parameters and engineering main control factor parameters; A geological engineering comprehensive sweet spot evaluation formula is established based on the normalized result, and the weight coefficients of the main control factor parameters are quantified to obtain a geological engineering comprehensive sweet spot evaluation value.

7. The method for evaluating the comprehensive sweet spot of muddy shale oil geological engineering according to claim 6, characterized in that: The geological engineering comprehensive sweet spot evaluation formula is: Among them, F1 is the comprehensive sweet spot evaluation value of geological engineering, D TOC is the normalized result of TOC value, D S1 is the normalized result of S1 value, D C1 is the normalized result of gas measurement value, D GR is the normalized result of GR value, D DZ is the normalized result of the resistance value, G B is the normalized result of the brittleness index value, G SC is the normalized result of the in-situ stress difference, GFFV is the normalized result of the nuclear magnetic macropore value, G KC is the normalized result of toughness difference ratio, G LY is the normalized result of the tension-compression ratio, M1 is the weight coefficient corresponding to TOC, M2 is the weight coefficient corresponding to S1, M3 is the weight coefficient corresponding to gas logging, M4 is the weight coefficient corresponding to GR, M5 is the weight coefficient corresponding to resistance, N1 is the weight coefficient corresponding to the brittleness index, N2 is the weight coefficient corresponding to the ground stress difference, N3 is the weight coefficient corresponding to the nuclear magnetic macropore, N4 is the weight coefficient corresponding to the toughness difference ratio, and N5 is the weight coefficient corresponding to the tension-compression ratio.

8. The method for evaluating the comprehensive sweet spot of muddy shale oil geological engineering according to claim 7, characterized in that: Quantify the weight coefficients of the main control factor parameters to obtain the comprehensive sweet spot evaluation value of geological engineering, including: Calculate the weight coefficient of each geological main controlling factor parameter according to the geological model, and calculate the weight coefficient of each engineering main controlling factor parameter according to the engineering model; The comprehensive sweet spot evaluation value of geological engineering is calculated according to the weight coefficient, wherein: F1 is the comprehensive sweet spot evaluation value of geological engineering, D TOC is the normalized result of TOC value, D S1 is the normalized result of S1 value, D C1 is the normalized result of gas measurement value, D GR is the normalized result of GR value, D DZ is the normalized result of the resistance value, G B is the normalized result of the brittleness index value, G SC is the normalized result of the in-situ stress difference, GFFV is the normalized result of the nuclear magnetic macropore value, G KC is the normalized result of toughness difference ratio, G LY is the normalized result of tension-compression ratio.

9. The method for evaluating the comprehensive sweet spot of muddy shale oil geological engineering according to claim 8, characterized in that: The weight coefficients include the weight coefficients of geological main controlling factor parameters and the weight coefficients of engineering main controlling factor parameters.

10. The method for comprehensive sweet spot evaluation of muddy shale oil geological engineering according to claim 4, characterized in that: The initial layer characteristic values ​​calculated based on the total regional thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height include: The total thickness, continuous thickness, intermediate single-layer sandstone thickness and sandstone ratio at each sampling point are obtained, and their average values ​​are calculated respectively to obtain the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio and predicted fracture height of the target layer segment to calculate the initial layer segment characteristic value: Fc=k1×TH+k2×CH+k3×(1-SH / Smax)+k4×(1-SPR)+0.5×SH, SH=K×δ / E; Among them, Fc is the characteristic value of the initial layer segment, TH is the total thickness of the target layer segment, k1 is the weight of the total thickness, CH is the continuous thickness, k2 is the weight of the continuous thickness, SH is the thickness of the intermediate single-layer sandstone, k3 is the weight of the thickness of the intermediate single-layer sandstone, Smax is the maximum allowable thickness of the intermediate single-layer sandstone, SPR is the sandstone ratio, k4 is the weight of the sandstone ratio, SH is the predicted fracture height, K is the lamella fracture bonding strength, δ is the formation pressure, E is the elastic modulus of shale, and k5 is the weight of the predicted fracture height.

Images