Comprehensive sweet spot evaluation method for muddy shale oil geological engineering

Abstract

The present invention relates to the technical field of shale oil and gas extraction, and in particular to a method for evaluating a comprehensive sweet spot in muddy shale oil geology and engineering. The method comprises step S1, sampling and analysis; step S2, determining a first-level thickness fracture height evaluation value based on the analysis results; and step S3, determining a second-level comprehensive sweet spot evaluation value in geology and engineering corresponding to each target exploration area based on the first-level thickness fracture height evaluation value. The present invention determines the importance of favorable exploration areas in each target exploration area based on the characteristic value of the target layer interval, normalizes the parameters of the geological and engineering main controlling factors in the target exploration area to eliminate the influence of different parameter dimensions, thereby enhancing the comparability between the parameters, and quantifies the weight coefficients of the main controlling factors and establishes a comprehensive sweet spot evaluation formula for geology and engineering to more accurately guide exploration strategies, thereby providing comprehensive and accurate technical support for the exploration and development of shale oil.

Description

Technical Field

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

[0002] In geological exploration, "sweet spots" refer to areas within a reservoir that possess high-quality geology and are amenable to efficient volumetric fracturing. Engineering "sweet spots" primarily refer to areas of the reservoir that exhibit excellent fracturability and are prone to forming a network of fractures. Gulong shale oil, a typical muddy shale, has achieved significant production breakthroughs through the adoption of volumetric fracturing technology, leading to the initial development of a "four-property" evaluation standard for Gulong shale oil reservoirs. However, each evaluation standard is relatively independent, often relying on empirical experience to select the sweet spot. This results in significant variations in production results under identical geological and fracturing process conditions. This is primarily due to two factors: first, the unique fracture formation mechanism of the Gulong shale creates limitations in the adaptability of existing fracturability evaluation methods; second, the manual layer and section selection process relies primarily on empirical experience, failing to integrate the selection of geological and engineering sweet spots, resulting in a lack of systematic and scientific approach.

[0003] Patent publication CN117474368A discloses a shale oil dual-sweet spot characterization method based on adaptive weighted fusion. The method comprises the following steps: S1. Optimization of shale oil sweet spot evaluation parameters based on entropy analysis; 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 an adaptive algorithm; and S5. As can be seen, existing geological sweet spots are primarily used to evaluate the overall oil content of a layer or well section, often serving as a guiding tool for geological well and layer selection. However, these evaluation methods do not clearly define the impact of various geological parameters on engineering stimulation, resulting in inaccurate application in actual fracturing layer and section selection. While there are a wide variety of existing fracturability evaluation methods, they often face limitations in practical application, such as the difficulty in obtaining evaluation parameters in the field. Furthermore, the contribution weights of sweet spot influencing factors are typically calculated using mathematical or statistical methods. This approach ignores the physical meaning of some parameters, resulting in significant discrepancies between application and actual field conditions. Furthermore, a comprehensive geo-engineering sweet spot evaluation method for muddy shale oil has yet to be found. Therefore, to meet the needs of muddy shale oil exploration and development, there is an urgent need to develop a comprehensive sweet spot evaluation method that can quantitatively assess the geo-engineering impact weight of muddy shale oil, accurately identify "targets," and provide technical support for precise 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 to conduct a preliminary evaluation of the potential of the exploration area. Based on the results of the preliminary evaluation, areas with greater potential are accurately selected and sweet spot evaluation is prioritized.

[0005] To achieve the above objectives, the present invention provides a comprehensive sweet spot evaluation method for 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 proportion of the favorable area 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 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 the target layer segment characteristic value;

[0010] generating a first-level thickness and fracture height evaluation value according to the analysis results, and determining the importance of a favorable exploration area in each target exploration area according to the first-level thickness and 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 target exploration area is determined in descending order of importance of the favorable exploration area.

[0014] Furthermore, calculating the layer characteristic value according to the layer thickness characteristics 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 thickness uniformity of the target exploration area;

[0017] When determining that the thickness of the target exploration area is uneven, comparing the first standard area ratio with the favorable area ratio 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 ratio in combination with the second standard area ratio 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 determined to have uniform thickness. The initial layer segment characteristic value is calculated based on the total thickness of the area, the continuous thickness, the thickness of the intermediate single-layer sandstone, the sandstone ratio, and the predicted fracture height. 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 based on the real-time total thickness value corresponding to each sampling point;

[0023] 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 where the simulated total thickness difference is 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 ratio in combination with the second standard area ratio 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 that of the first standard area, the initial layer characteristic value is calculated based on the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height of the target layer, and the proportion of favorable areas is determined based on 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 comprehensive sweet spot evaluation value of engineering.

[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 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] Furthermore, the geological engineering comprehensive sweet spot evaluation value corresponding to any target exploration area is determined based on the main controlling factors, including:

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

[0034] A geological engineering comprehensive sweet spot evaluation formula is established based on the normalized results, 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 evaluation value of geological engineering sweet spot, 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 electrical resistance, N1 is the weight coefficient corresponding to the brittleness index, N2 is the weight coefficient corresponding to the in-situ 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 geological engineering comprehensive sweet spot evaluation value, including:

[0039] Calculating the weight coefficient of each geological main controlling factor parameter based on the geological model, and calculating the weight coefficient of each engineering main controlling factor parameter based on 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 evaluation value of geological engineering sweet spot, 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.

[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 thickness of the region, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio and predicted fracture height, including:

[0045] Obtain the total thickness, continuous thickness, intermediate single-layer sandstone thickness, and sandstone ratio at each sampling point, and calculate their average values ​​respectively. Obtain the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height of the target layer to calculate the initial layer 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 lamellae cementation 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 is 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 correlating 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 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. The geological and engineering comprehensive sweet spot evaluation value of the target exploration area is obtained according to the priority of the importance of the favorable exploration area, which can guide the exploration strategy more accurately. By quantifying the impact 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 controlling factors in the target exploration area are normalized to eliminate the influence of different parameter dimensions, thereby enhancing the comparability between the parameters. This data processing method improves the exploration accuracy. By quantifying the weight coefficients of the main controlling factors and establishing a geological and engineering comprehensive sweet spot evaluation formula, the target layer characteristic values ​​are calculated by associating the layer thickness characteristics and 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 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 mud 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.

[0050] Furthermore, by subdividing the target exploration area and calculating the average total thickness of each simulated exploration module, the geological changes and heterogeneity within the area can be more accurately assessed. Areas with larger thickness variations 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 thickness uniformity, when the thickness of the target exploration area is determined to be uniform, the characteristic value of the target layer segment is directly calculated based on the detected thickness data. When the thickness of the target exploration area is determined to be non-uniform, the degree of thickness non-uniformity is analyzed to adaptively correct the evaluation value more finely, so as to preliminarily predict the evaluation value of the target exploration area more accurately, and quickly identify areas suitable for further development, avoiding misidentification of areas with non-uniform thickness. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0053] Figure 2 This is a schematic diagram of a process for calculating layer segment characteristic values ​​according to layer segment thickness characteristics 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 These are the comprehensive sweet spot evaluation results and tracer monitoring fitting results of the four wells in the embodiment of the present invention. 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 merely used to explain the present invention and are not intended 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 scope of protection 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 accompanying drawings. This is only 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] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0060] See also Figure 1 As shown, it is a flow chart of a method for evaluating a comprehensive sweet spot in geo-engineering of muddy shale oil according to an embodiment of the present invention. The present invention provides a method for evaluating a comprehensive sweet spot in geo-engineering of muddy shale oil, including:

[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 proportion of the favorable area 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 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 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 a 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 target exploration area in descending order of importance of the favorable exploration area;

[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] In this embodiment, the selection of the target exploration area is related to the equipment conditions and environmental safety. It is necessary to ensure that the sampling points can meet the installation requirements of the instruments and equipment, and to avoid areas with environmental risks, such as landslides, floods, etc. 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. It is also possible to select key areas based on geological characteristics, oil and gas potential, and other indicators, and 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 correlating the layer thickness characteristics and the fracture height prediction value. That is, the importance of the exploration favorable area of ​​each target exploration area is determined according to the target layer characteristic value for 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 values ​​are used to initially determine the fracture height expansion capacity of the target exploration area, so as to obtain the geological and engineering comprehensive sweet spot evaluation value of the target exploration area based on the priority of the favorable exploration area, more accurately guide the exploration strategy, and form a comprehensive sweet spot evaluation formula by quantifying the impact 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 controlling factors in the target exploration area are normalized to eliminate the influence of different parameter dimensions and enhance the comparability between the parameters. This data processing method improves the exploration accuracy. By quantifying the weight coefficients of the main controlling factors and establishing a geological and engineering comprehensive sweet spot evaluation formula, the target layer characteristic values ​​are calculated by correlating the layer thickness characteristics and fracture height prediction values ​​to more accurately guide the exploration strategy, providing comprehensive and accurate technical support for shale oil exploration and development.

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

[0072] Specifically, the calculation of layer characteristic values ​​based on 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 thickness uniformity of the target exploration area;

[0075] When determining that the thickness of the target exploration area is uneven, comparing the first standard area ratio with the favorable area ratio 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 ratio in combination with the second standard area ratio 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 mud 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, calculating 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 thicknesses 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 all 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 assess the geological changes and heterogeneity within the area. Areas with large thickness variations 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 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 thickness uniformity 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 determined to have uniform thickness. The initial layer segment characteristic value is calculated based on the total thickness of the area, the continuous thickness, the thickness of the intermediate single-layer sandstone, the sandstone ratio, and the predicted fracture height. 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 based on the real-time total thickness value corresponding to each sampling point;

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

[0087] The standard total thickness difference set in this embodiment represents the deviation value of the allowed 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 thickness uniformity, when the thickness of the target exploration area is determined to be uniform, the characteristic value of the target layer segment is directly calculated based on the detected thickness data. When the thickness of the target exploration area is determined to be non-uniform, the degree of thickness non-uniformity is analyzed to adaptively correct the evaluation value more finely, 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 non-uniform 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 ratio in combination with the second standard area ratio 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 that of the first standard area, the initial layer characteristic value is calculated based on the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height of the target layer, and the proportion of favorable areas is determined based on 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 comprehensive sweet spot evaluation value of engineering.

[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 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 set to 20%, and the second standard area ratio represents a larger thickness uniformity, generally set between 70% and 80%, and 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 is highly uneven. 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 oilfields.

[0099] Specifically, the determination and normalization of the main geological and engineering controlling factors include:

[0100] Determine the main geological controlling factors: TOC, S1, gas logging, GR and resistivity;

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

[0102] Total organic carbon, referred to as TOC, 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 indicates that the rock contains more mobile hydrocarbons, and represents better reservoir quality and higher mining value.

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

[0105] GR is the abbreviation of Gamma-Ray well 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 the rock, and characterize the concentration of radioactive elements in the rock. A high GR value usually indicates that the rock contains more organic matter, indicating a higher oil and gas generation potential.

[0106] Resistivity characterizes the degree to which rock hinders the flow of electric current. By measuring the resistance of rock to electric current, the resistance value is obtained 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 indicates high oil and gas saturation, that is, the presence of oil and gas sandstone layers at the corresponding sampling point. Low resistivity indicates the presence of water-saturated rock 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, the higher the brittleness of the rock and the higher its mining value.

[0107] The in-situ stress difference represents the difference between the maximum and minimum horizontal principal stresses in the reservoir. A larger in-situ stress difference indicates a better fracturing effect, as it is easier to form a fracture network in the reservoir, thereby increasing 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 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; 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 expansion.

[0115] The tension-compression ratio is the ratio of tensile strength to compressive strength, which is used to correct the brittleness of shale. 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 correlation. Among them, TOC, S1, gas testing, GR, brittleness index, ground stress difference, and nuclear magnetic macropores are positively correlated main control factors; electrical 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, and 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] Based on 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 contributions of various parameters to production results, the normalized results of the 10 main control factors were integrated according to the positive and negative correlation relationships of their contributions to production capacity, and the comprehensive geological engineering sweet spot evaluation formula was obtained as follows:

[0122]

[0123] Where, F1 is the comprehensive evaluation value of geological engineering sweet spot, 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 large hole 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 electrical resistance, N1 is the weight coefficient corresponding to the brittleness index, N2 is the weight coefficient corresponding to the in-situ 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, by varying a single variable within each geological parameter, the weight coefficients of the primary geological factors affecting production were determined based on the degree of impact of that parameter on production results. The results were then compared with tracer production capacity monitoring results. After multiple rounds of calculations, the weight coefficients of the geological parameters' impact on production capacity were ultimately determined. Based on the calculations, the contribution weights of each factor were determined: M1 = 10.2%, M2 = 10.2%, M3 = 9.3%, M4 = 10.8%, and M5 = 13.2%. M1 represents the TOC contribution weight, M2 represents the S1 contribution weight, M3 represents the gas logging contribution weight, M4 represents the GR contribution weight, and M5 represents the resistivity contribution weight.

[0125] Through numerical simulation, by varying a single variable within each engineering parameter, the weight coefficients of the engineering's primary controlling factors on production were determined based on the degree of impact of that parameter on the fracture stimulation volume. The results were then compared with tracer production monitoring results. After multiple rounds of calculations, the weight coefficients of the engineering parameters' impact on production capacity were ultimately determined. Based on the calculations, the contribution weights of each factor were determined as follows: N1 = 10%, N2 = 8%, N3 = 13%, N4 = 10.3%, and N5 = 5%. N1 represents the brittleness index contribution weight, N2 represents the in-situ stress difference contribution weight, N3 represents the nuclear magnetic macropore contribution weight, N4 represents the toughness difference ratio contribution weight, and N5 represents the tension-compression ratio contribution weight.

[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] Calculating the weight coefficient of each geological main controlling factor parameter based on the geological model, and calculating the weight coefficient of each engineering main controlling factor parameter based on 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 evaluation value of geological engineering sweet spot, 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 large hole value (>8ms), G KC is the normalized result of toughness difference ratio, G LY is the normalized result of the 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 interval characteristic values ​​are calculated based on the regional total thickness, continuous thickness, intermediate single-layer sandstone thickness and sandstone ratio, including:

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

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

[0135] Where Fc is the initial layer characteristic value, TH is the total thickness of the target layer, 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 cementation strength, δ is the formation pressure, E is the elastic modulus of shale, and k5 is the weight of the predicted fracture height, k5 = 0.4. Total thickness (TH) represents the total thickness of the shale layer, which affects reserves and fluid flow capacity.

[0136] Continuous thickness (CH): It affects the effect of the fracturing process and reflects 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 lamellae bonding strength is MPa. The elastic modulus of shale indicates its deformation capacity under stress and is obtained through experiments.

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

[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 geological and engineering comprehensive sweet spot evaluation results were compared with the tracer production 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 production capacity were finally obtained. That is, the results calculated under the shale oil sweet spot area evaluation value formula conditions have a good correlation with the tracer monitoring results of each section.

[0143] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0144] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A comprehensive sweet spot evaluation method for muddy shale oil geological engineering, characterized by: 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 proportion of the favorable area 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 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 the target layer segment characteristic value; generating a first-level thickness and fracture height evaluation value according to the analysis results, and determining the importance of a favorable exploration area in each target exploration area according to the first-level thickness and 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 target exploration area is determined in descending order of importance of the favorable exploration area.

2. The method for comprehensive sweet spot evaluation of muddy shale oil geological engineering according to claim 1, characterized in that: Calculating the layer characteristic values ​​based on the 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 thickness uniformity of the target exploration area; When determining that the thickness of the target exploration area is uneven, comparing the first standard area ratio with the favorable area ratio 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 ratio in combination with the second standard area ratio 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 comprehensive sweet spot evaluation of muddy shale oil geological engineering according to claim 2, characterized in that: The analysis of the thickness uniformity 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 determined to have uniform thickness. The initial layer segment characteristic value is calculated based on the total thickness of the area, the continuous thickness, the thickness of the intermediate single-layer sandstone, the sandstone ratio, and the predicted fracture height. 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 based on the real-time total thickness value corresponding to each sampling point; 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 where the simulated total thickness difference is greater than the standard total thickness difference.

4. The method for comprehensive sweet spot evaluation 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 ratio in combination with the second standard area ratio 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 that of the first standard area, the initial layer characteristic value is calculated based on the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height of the target layer, and the proportion of favorable areas is determined based on 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 comprehensive sweet spot evaluation value of engineering.

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 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 controlling factor parameters to obtain normalized results, wherein the main controlling factor parameters include geological main controlling factor parameters and engineering main controlling factor parameters; A geological engineering comprehensive sweet spot evaluation formula is established based on the normalized results, 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 comprehensive sweet spot evaluation 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 evaluation value of geological engineering sweet spot, 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 electrical resistance, N1 is the weight coefficient corresponding to the brittleness index, N2 is the weight coefficient corresponding to the in-situ 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 comprehensive sweet spot evaluation 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 geological engineering sweet spot evaluation value, including: Calculating the weight coefficient of each geological main controlling factor parameter based on the geological model, and calculating the weight coefficient of each engineering main controlling factor parameter based on the engineering model; The comprehensive sweet spot evaluation value of geological engineering is calculated according to the weight coefficient, wherein: F1 is the comprehensive evaluation value of geological engineering sweet spot, 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.

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

10. The method for comprehensive evaluation of sweet spots in muddy shale oil geological engineering according to claim 4, characterized in that: The initial interval characteristic values ​​are calculated based on the total thickness of the region, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height, including: Obtain the total thickness, continuous thickness, intermediate single-layer sandstone thickness, and sandstone ratio at each sampling point, and calculate their average values ​​respectively. Obtain the total thickness, continuous thickness, intermediate single-layer sandstone thickness, sandstone ratio, and predicted fracture height of the target layer to calculate the initial layer 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 lamellae cementation strength, δ is the formation pressure, E is the elastic modulus of shale, and k5 is the weight of the predicted fracture height.

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