A comprehensive evaluation method for the volume fracturing compressibility of shale oil horizontal wells

Abstract

The present invention discloses a method for comprehensive evaluation of the compressibility of shale oil horizontal well volume fracturing, which is specifically as follows: step 1, using the analytic hierarchy process to establish a multi-level evaluation system of factors affecting the compressibility of shale oil reservoirs; step 2, according to the logging interpretation results of the horizontal section of the horizontal well, the geological parameters and rock mechanics parameter sets described in step 1 are obtained, and the maximum and minimum values ​​of each parameter in the geological parameter set and the rock mechanics parameter set are determined; step 3, the threshold of the reservoir section with the best compressibility is determined, and the best compressibility reservoir section is established; step 4, a shale oil reservoir compressibility evaluation model is established, and the comprehensive evaluation factors of different reservoir sections are calculated to quantitatively evaluate the compressibility of the reservoir. The evaluation method of the present invention considers both geological factors and rock mechanics factors to evaluate the compressibility of shale reservoirs, and realizes the quantitative evaluation of the compressibility of shale oil horizontal well volume fracturing.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and natural gas development, and relates to a comprehensive evaluation method for the volume fracturing compressibility of shale oil horizontal wells. Background Art

[0002] China's shale oil technically recoverable resources can reach 145×10 8 t, mainly distributed in large basins such as the Ordos Basin, Junggar Basin, Bohai Bay Basin, and Songliao Basin, with huge development potential. Horizontal well volume fracturing technology has realized the commercial development of shale oil and gas. In 2019, the Qingcheng Oilfield, my country's first 1 billion ton shale oil, was discovered in the Ordos Basin. Changqing Oilfield conducted a large-scale development test of horizontal well volume fracturing and established a national shale oil development demonstration base. Over the years, Changqing Oilfield has learned from the successful experience of shale oil development in North America, based on the characteristics of shale oil in the basin, and has developed long horizontal wells. The advanced energy storage subdivision cutting volume fracturing technology has been developed and widely promoted and applied, which has effectively promoted the efficient development of shale oil in the basin. Reservoir compressibility is the primary key factor to be considered in the optimization design of horizontal well volume fracturing. A large number of microseismic tests in the mine have confirmed that a large amount of resources have not been effectively used. The optimization of fracturing processes with higher production capacity as the goal urgently needs more accurate and reasonable reservoir compressibility evaluation methods to provide effective support.

[0003] However, there are many factors that affect reservoir compressibility and there are complex nonlinear relationships between these factors, which affect the evaluation results to varying degrees. Currently, the main evaluation methods are as follows:

[0004] (1) Name: A method for predicting the complexity of fracture networks formed by shale fracturing, application number: 202010189682.0. This method measures the types and contents of mineral components of shale samples through indoor experiments, calculates the difference between different minerals and evaluates the differences between minerals, and establishes a shale brittleness evaluation model based on mineral composition heterogeneity, thereby evaluating the shale compressibility potential. This method only evaluates shale brittleness from the difference in rock mineral composition, but ignores key rock mechanical parameters. In addition, shale is extremely heterogeneous, and a large number of coring and indoor experiments are limited, so its applicability has certain limitations.

[0005] (2) Name: A method for evaluating shale compressibility, application number: 201811353712.6. This method mainly starts from the influence of mineral brittleness and natural fractures. According to the principle that the better the mineral brittleness, the greater the natural fracture influence factor, the better the rock compressibility, the number of fractures in the rock mechanics triaxial test is used to optimize the mineral compressibility, and then combined with the natural fracture characteristics of the reservoir, the rock compressibility characteristics are described, and the weight coefficients of the mineral compressibility and natural fracture influence factors are calculated, so as to evaluate the rock compressibility. This method only considers the influence of the mineral composition and natural fractures of the reservoir rock on the compressibility, but ignores the key rock mechanics parameters.

[0006] (3) Zhou Lihong et al. Evaluation and application of factors affecting the fracturing properties of continental shale oil rocks - a case study of Kong 2 in Cangdong Depression [J]. China Petroleum Exploration, 2019, 24(5): 670-678. By comprehensively considering the three factors of rock brittleness, natural fractures and geostress, a fracture network index model was established to qualitatively analyze and quantitatively characterize the rock fracturing properties of typical continental shale oil in Kong 2 in Cangdong Depression in Dagang exploration area, and further optimize the horizontal well perforation parameters and fracturing construction parameters. This method also only considers the engineering factors of rock fracturing properties, while ignoring the influence of geological factors.

[0007] The above three representative methods do not consider geological and rock mechanics factors to evaluate the compressibility of shale reservoirs. They ignore the ultimate goal of volume fracturing to maximize production capacity, which is not only to form an effective fracture network swept volume, but also to maximize production capacity. Therefore, it is necessary to consider the geological factors that affect production capacity and the rock mechanics factors of fracture network complexity at the same time. Summary of the invention

[0008] The purpose of the present invention is to provide a comprehensive evaluation method for the volume fracturing compressibility of shale oil horizontal wells, which takes into account geological factors and rock mechanics factors to evaluate the compressibility of shale reservoirs, thereby realizing quantitative evaluation of the volume fracturing compressibility of shale oil horizontal wells.

[0009] The technical solution adopted by the present invention is a comprehensive evaluation method for the volume fracturing compressibility of shale oil horizontal wells, which is specifically implemented according to the following steps:

[0010] Step 1, using the analytic hierarchy process to establish a multi-level evaluation system for factors affecting the compressibility of shale oil reservoirs, wherein the multi-level evaluation system for compressibility factors includes geological parameters of production capacity factors and rock mechanics parameters of fracture network complexity factors;

[0011] Step 2, based on the logging interpretation results of the horizontal section of the horizontal well, the geological parameters and rock mechanics parameter sets described in step 1 are obtained, and the maximum and minimum values ​​of each parameter in the geological parameter set and the rock mechanics parameter set are determined;

[0012] Step 3, determining the threshold of the reservoir section with the best compressibility and establishing the reservoir section with the best compressibility;

[0013] Step 4: Establish a shale oil reservoir compressibility evaluation model, calculate the comprehensive evaluation factors of different reservoir sections, and quantitatively evaluate the reservoir compressibility.

[0014] The present invention is also characterized in that

[0015] In step 1, the geological parameters include: porosity, permeability, oil saturation, and mud content of the horizontal oil layer; the rock mechanics parameters include: brittleness index, horizontal stress difference, and fracture pressure.

[0016] The specific steps of step 3 are as follows:

[0017] Step 3.1, collecting geological parameters, rock mechanical parameters and fluid production profile parameters corresponding to each fracturing stage of the producing horizontal wells in the same layer of the block where the shale oil horizontal well to be evaluated is located;

[0018] Step 3.2, performing correlation analysis on the geological parameters and rock mechanical parameters of each fracturing section of the horizontal well collected in step 3.1 and the daily liquid production ratio of the corresponding fracturing section;

[0019] Step 3.3, determining the thresholds of geological parameters and rock mechanical parameters of the optimal compressibility reservoir section according to the correlation analysis results obtained in step 3.2, wherein the parameter that is positively correlated with the daily liquid production ratio uses the maximum value determined in step 2 as the threshold, and the parameter that is negatively correlated with the daily liquid production ratio uses the minimum value determined in step 2 as the threshold;

[0020] Step 3.4, coupling the threshold value obtained in step 3.3 to a parameter set to obtain the optimal compressible reservoir section, wherein the geological parameters include porosity, permeability, oil saturation, and mud content, and the rock mechanical parameters include brittleness index, horizontal stress difference, and fracture pressure.

[0021] The specific steps of step 4 are as follows:

[0022] Step 4.1, dividing the horizontal oil layer length of the horizontal well to be evaluated into m evaluation units, and the oil layer length of each evaluation unit is l;

[0023] Step 4.2, according to the geological parameter set and rock mechanical parameter set obtained in step 2, obtain the geological parameters and rock mechanical parameters corresponding to the m evaluation units respectively, calculate the average value of the geological parameters corresponding to each evaluation unit as the geological parameters corresponding to the oil layer length l of each evaluation unit, and calculate the average value of the rock mechanical parameters corresponding to each evaluation unit as the rock mechanical parameters corresponding to the oil layer length l of each evaluation unit;

[0024] Step 4.3, establishing a shale oil reservoir compressibility evaluation unit matrix M according to the geological parameters and rock mechanical parameters corresponding to the oil layer length l of each evaluation unit obtained in step 4.2, and taking the optimal compressibility reservoir section geological parameters and rock mechanical parameter thresholds determined in step 3.3 as the evaluation reference series M0;

[0025] Step 4.4, coupling the shale oil reservoir compressibility evaluation unit matrix M obtained in step 4.3 and the evaluation reference series M0 to establish a reservoir compressibility evaluation matrix B;

[0026] Step 4.5, evaluate the element M of the matrix i (j) and the elements in the evaluation reference series are standardized to obtain the reservoir compressibility evaluation standardized matrix B * ;

[0027] Step 4.6: Based on the reservoir compressibility evaluation standardized matrix B obtained in step 4.5 * , calculate the comprehensive evaluation factor of each evaluation unit;

[0028] Step 4.7, the reservoir is divided into compressibility potential according to the comprehensive evaluation factor of each evaluation unit obtained in step 4.6.

[0029] In step 4.1, the expression for the oil layer length l of each evaluation unit is:

[0030]

[0031] In formula (1), l is the length of the oil layer in each evaluation unit, m; m is the number of evaluation units, pieces; L is the length of the oil layer in the horizontal section, m.

[0032] In step 4.3, the expression of the shale oil reservoir compressibility evaluation unit matrix M is:

[0033]

[0034] In formula (2), M i (j) is the evaluation unit matrix element, i = 0, 1, 2, ..., m; j = 1, 2, ..., n; m is the number of evaluation units; n is the number of parameters of the compressibility influencing factors of each evaluation unit;

[0035] The expression for evaluating the reference series M0 is:

[0036] M0=(M0(1),M0(2)…,…,M0(n)) (3)

[0037] In step 4.4, the expression of reservoir compressibility evaluation matrix B is:

[0038]

[0039] The specific steps of step 4.5 are as follows:

[0040] Step 4.5.1, evaluate the unit matrix element M i (j) is standardized and the expression is:

[0041]

[0042] In formula (5), Standardized elements of the unit matrix for shale oil reservoir compressibility evaluation;

[0043] Step 4.5.2: Use formula (5) to standardize all the elements of the shale oil reservoir compressibility evaluation unit matrix to obtain the reservoir compressibility evaluation standardized matrix B: * , the expression is:

[0044]

[0045] In step 4.6, the comprehensive evaluation factor of each evaluation unit is expressed as:

[0046]

[0047] In formula (7): S i is the comprehensive evaluation factor of the evaluation unit, To evaluate the reference series standardized elements, F is the maximum distance between the evaluation unit and the optimal compressible reservoir segment, expressed as:

[0048]

[0049] In step 4.7, the compressibility potential is divided into level I, level II, and level III, where level I>level II>level III;

[0050] Level I is 0.50≤S; Level II is 0.25≤S<0.50; Level III is 0≤S<0.25.

[0051] The beneficial effect of the present invention is that the present invention provides a comprehensive evaluation method for the compressibility of shale oil horizontal well volume fracturing, which couples the geological factors affecting the production capacity factors and the rock mechanics parameters of the complexity of the fracture network, and quantitatively characterizes the reservoir compressibility potential; at the same time, it pursues the maximization of production capacity and the minimization of engineering construction risks, making up for the shortcomings of simply using rock mechanics parameters or mineral components to evaluate the compressibility of the reservoir while ignoring the goal of maximizing production capacity. The evaluation method is simple and feasible, greatly reduces the economic cost, and is also applicable to the evaluation of the compressibility of similar unconventional reservoirs. It has good application prospects and has a good guiding role in fracturing optimization design and on-site construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 It is a multi-level evaluation system diagram of shale oil reservoir compressibility factors in a comprehensive evaluation method for shale oil horizontal well volume fracturing compressibility of the present invention;

[0053] Figure 2 It is a correlation diagram between porosity and daily liquid production ratio in a comprehensive evaluation method for volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0054] Figure 3 It is a correlation diagram between permeability and daily liquid production ratio in a comprehensive evaluation method for volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0055] Figure 4 It is a correlation diagram between oil saturation and daily liquid production ratio in a comprehensive evaluation method for volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0056] Figure 5 It is a correlation diagram between the proportion of mud content and daily liquid production in a comprehensive evaluation method for volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0057] Figure 6 It is a correlation diagram between the brittleness index and the daily liquid production ratio in a comprehensive evaluation method for the volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0058] Figure 7 It is a correlation diagram between horizontal stress difference and daily liquid production ratio in a comprehensive evaluation method for volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0059] Figure 8 It is a correlation diagram between the fracture pressure and the daily liquid production ratio in a comprehensive evaluation method for the volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0060] Fig. 9 It is a comparison diagram of comprehensive evaluation factors of the horizontal well H1 evaluation unit in an embodiment of a method for comprehensive evaluation of volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0061] Fig.10 It is a classification diagram of the compressibility potential of the reservoir where the horizontal well H1 is located in the embodiment of the method for comprehensive evaluation of the compressibility of shale oil horizontal well volume fracturing of the present invention;

[0062] Fig.11 It is a comparison diagram of comprehensive evaluation factors of the horizontal well H3 evaluation unit in the embodiment of the method for comprehensive evaluation of volume fracturing compressibility of shale oil horizontal wells of the present invention;

[0063] Fig.12 It is a classification diagram of the compressibility potential of the reservoir where the horizontal well H3 is located in an embodiment of a method for comprehensive evaluation of the compressibility of shale oil horizontal well volume fracturing of the present invention. DETAILED DESCRIPTION

[0064] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] The present invention provides a method for comprehensively evaluating the volume fracturing compressibility of shale oil horizontal wells, which is specifically implemented according to the following steps:

[0066] Step 1, such as Figure 1 As shown in the figure, a multi-level evaluation system of factors affecting the compressibility of shale oil reservoirs is established by using the hierarchical analysis method, wherein the multi-level evaluation system of compressibility factors includes geological parameters of production capacity factors and rock mechanics parameters of fracture network complexity factors;

[0067] In the embodiment of the present invention, the geological parameters include: porosity, permeability, oil saturation, and shale content of the horizontal oil layer; the rock mechanics parameters include: brittleness index, horizontal stress difference, and fracture pressure;

[0068] Step 2, based on the logging interpretation results of the horizontal section of the horizontal well, the geological parameters and rock mechanics parameter sets described in step 1 are obtained, and the maximum and minimum values ​​of each parameter in the geological parameter set and the rock mechanics parameter set are determined;

[0069] Step 3, determining the threshold of the reservoir section with the best compressibility and establishing the reservoir section with the best compressibility;

[0070] In the embodiment of the present invention, step 3.1, collect geological parameters, rock mechanical parameters and fluid production profile parameters corresponding to each fracturing stage of the producing horizontal wells in the same layer of the block where the shale oil horizontal well to be evaluated is located;

[0071] Among them, geological parameters include: porosity, permeability, oil saturation, and shale content; rock mechanical parameters include: brittleness index, horizontal stress difference, and fracture pressure; and liquid production profile parameters include daily liquid production ratio;

[0072] Step 3.2, performing correlation analysis on the geological parameters and rock mechanical parameters of each fracturing section of the horizontal well collected in step 3.1 and the daily liquid production ratio of the corresponding fracturing section;

[0073] Step 3.3, determining the thresholds of geological parameters and rock mechanical parameters of the optimal compressibility reservoir section according to the correlation analysis results obtained in step 3.2, wherein the parameter that is positively correlated with the daily liquid production ratio uses the maximum value determined in step 2 as the threshold, and the parameter that is negatively correlated with the daily liquid production ratio uses the minimum value determined in step 2 as the threshold;

[0074] Step 3.4, coupling the threshold obtained in step 3.3 to a parameter set to obtain the optimal compressible reservoir segment, wherein the parameters include porosity, permeability, oil saturation, shale content, brittleness index, horizontal stress difference, and fracture pressure;

[0075] Step 4: Establish a shale oil reservoir compressibility evaluation model, calculate the comprehensive evaluation factors of different reservoir sections, and quantitatively evaluate the reservoir compressibility. The larger the comprehensive evaluation factor value, the greater the reservoir compressibility potential;

[0076] In the embodiment of the present invention, in step 4.1, the length of the horizontal oil layer of the horizontal well to be evaluated is divided into m evaluation units, and the length of the oil layer of each evaluation unit is l, and the expression is:

[0077]

[0078] In formula (1), l is the length of the oil layer in each evaluation unit, m; m is the number of evaluation units, pieces; L is the length of the oil layer in the horizontal section, m;

[0079] Step 4.2, according to the geological parameter set and rock mechanical parameter set obtained in step 2, obtain the geological parameters and rock mechanical parameters corresponding to the m evaluation units respectively, calculate the average value of the geological parameters corresponding to each evaluation unit as the geological parameters corresponding to the oil layer length l of each evaluation unit, and calculate the average value of the rock mechanical parameters corresponding to each evaluation unit as the rock mechanical parameters corresponding to the oil layer length l of each evaluation unit;

[0080] Step 4.3, establishing a shale oil reservoir compressibility evaluation unit matrix M according to the geological parameters and rock mechanical parameters corresponding to the oil layer length l of each evaluation unit obtained in step 4.2, and taking the optimal compressibility reservoir section geological parameters and rock mechanical parameter thresholds determined in step 3.3 as the evaluation reference series M0;

[0081] The expression of the shale oil reservoir compressibility evaluation unit matrix M is:

[0082]

[0083] In formula (2), M i (j) is the evaluation unit matrix element, i = 0, 1, 2, ..., m; j = 1, 2, ..., n; m is the number of evaluation units; n is the number of parameters of the compressibility influencing factors of each evaluation unit;

[0084] The expression for evaluating the reference series M0 is:

[0085] M0=(M0(1),M0(2)…,…,M0(n)) (3)

[0086] Step 4.4, coupling the shale oil reservoir compressibility evaluation unit matrix M and the evaluation reference series M0 obtained in step 4.3, establish the reservoir compressibility evaluation matrix B, which is expressed as:

[0087]

[0088] Step 4.5, evaluate the element M of the matrix i (j) and the elements in the evaluation reference series are standardized to obtain the reservoir compressibility evaluation standardized matrix B * ;

[0089] In the embodiment of the present invention, in step 4.5.1, the evaluation unit matrix element M i (j) is standardized and the expression is:

[0090]

[0091] In formula (5), Standardized elements of the unit matrix for shale oil reservoir compressibility evaluation;

[0092] Step 4.5.2: Use formula (5) to standardize all the elements of the shale oil reservoir compressibility evaluation unit matrix to obtain the reservoir compressibility evaluation standardized matrix B: * , the expression is:

[0093]

[0094] Step 4.6: Based on the reservoir compressibility evaluation standardized matrix B obtained in step 4.5 * , calculate the comprehensive evaluation factor of each evaluation unit, the expression is:

[0095]

[0096] In formula (7): S i is the comprehensive evaluation factor of the evaluation unit, F is the maximum distance between the evaluation unit and the optimal compressible reservoir segment;

[0097]

[0098] Step 4.7, the reservoir is divided into the compressibility potential according to the comprehensive evaluation factor of each evaluation unit obtained in step 4.6, specifically: Class I: 0.5≤S; Class II: 0.25≤S<0.50; Class III: 0≤S<0.25, the larger the S value, the greater the compressibility potential, that is, Class I>Class II>Class III, among which fracturing is recommended for Class I and Class II reservoirs, and fracturing is not recommended for Class III reservoirs.

[0099] The shale oil in the basin has the characteristics of low rock brittleness index, low oil layer pressure coefficient and low single well production. The long horizontal well advance energy storage subdivision cutting volume fracturing technology is the key technology for the efficient development of shale oil, and the reservoir compressibility evaluation is the primary consideration for the success of this technology.

[0100] The horizontal well H1 is located in the main shale oil development test area of ​​the basin, with a reservoir depth of 2135m, a completed well depth of 4034m, a horizontal section length of 1680m, a drilling rate of 75.0%, and a horizontal section oil layer length of 1260m. It has strong heterogeneity, which makes the optimization of the horizontal well volume fracturing geological engineering sweet spot and the optimization of perforation parameters face great challenges. The horizontal well H1 is subjected to a comprehensive evaluation of compressibility according to the evaluation method of the present invention, specifically:

[0101] Step 1, using the analytic hierarchy process to establish a multi-level evaluation system for factors affecting the compressibility of shale oil reservoirs, wherein the multi-level evaluation system for compressibility factors includes geological parameters of production capacity factors and rock mechanics parameters of fracture network complexity factors;

[0102] Step 2: Based on the actual evaluation results of the horizontal well H1 logging interpretation, the geological parameters and rock mechanics parameter sets that affect the compressibility of the reservoir in the multi-level evaluation system are obtained, and the maximum and minimum values ​​of each parameter in the geological parameter set and rock mechanics parameter set are determined, as shown in Table 1:

[0103] Table 1 Maximum and minimum values ​​of geological and rock mechanical parameters of the horizontal section of the evaluated horizontal well H1

[0104]

[0105] Step 3.1, collect the geological parameters, rock mechanical parameters and fluid production profile parameters corresponding to each fracturing stage of the producing horizontal well H2 in the same layer of the block where the shale oil horizontal well H1 to be evaluated is located, as shown in Table 2:

[0106] Table 2 Geomechanics and fluid production profile parameters of each fracturing stage of production horizontal well H2

[0107]

[0108] Step 3.2, perform correlation analysis on the geological parameters and rock mechanical parameters of each fracturing section of the horizontal well H2 collected in step 3.1 and the daily liquid production ratio of the corresponding fracturing section, such as Figure 2 , Figure 3 , Figure 4 , Figure 6 As shown in , the porosity, permeability, oil saturation, and brittleness index are positively correlated with the daily liquid production ratio; Figure 5 , Figure 7 , Figure 8As shown, the mud content, horizontal stress difference, and fracture pressure are negatively correlated with the daily liquid production ratio;

[0109] Step 3.3, the porosity, permeability, oil saturation, and brittleness index take the maximum values ​​of the corresponding parameters in step 2 as the optimal compressible reservoir threshold, and the shale content, horizontal stress difference, and fracture pressure take the minimum values ​​of the corresponding parameters in step 2 as the optimal compressible reservoir threshold;

[0110] Step 3.4, based on the optimal compressible reservoir segment threshold determined in step 2 and step 3.3, the optimal compressible reservoir segment is established by coupling geological parameters and rock mechanical parameters, wherein the parameters include porosity, permeability, oil saturation, shale content, brittleness index, horizontal stress difference, and fracture pressure, as shown in Table 3:

[0111] Table 3 Geological and rock mechanical parameters of the optimal compressible reservoir section

[0112]

[0113] Step 4.1, using formula (1), divide the horizontal oil layer length of the reservoir where the horizontal well H1 is located into 252 evaluation units, and the oil layer length of each evaluation unit is 5m;

[0114] Step 4.2, taking the evaluation of 30 continuous evaluation units in the horizontal well H1, the oil layer length is 150m, and the oil layer length of each evaluation unit is 5m as an example to illustrate the practicality of the present invention, as shown in Table 4:

[0115] Table 4 Geological and rock mechanical parameters of the evaluation unit

[0116]

[0117]

[0118] Step 4.3, establish a shale oil reservoir compressibility evaluation unit matrix M according to the geological parameters and rock mechanical parameters corresponding to the oil layer length l of each evaluation unit, and use the optimal compressibility reservoir section geological parameters and rock mechanical parameter thresholds determined in step 3.3 as the evaluation reference series M0;

[0119]

[0120] M0=(14.8,1.24,72.5,4.9,61.7,0.8,42.7)

[0121] Step 4.4, coupling the shale oil reservoir compressibility evaluation unit matrix M obtained in step 4.3 and the evaluation reference series M0 to establish a reservoir compressibility evaluation matrix B;

[0122]

[0123] Step 4.5: Use formula (5) to standardize the elements of the reservoir compressibility evaluation matrix B to obtain the reservoir compressibility evaluation standardized matrix B: * :

[0124] Step 4.6, based on the reservoir compressibility evaluation standardized matrix B * , use formulas (7) and (8) to calculate the comprehensive evaluation factor of each evaluation unit, such as Fig.10 As shown:

[0125] Step 4.7, as shown in Table 5, the comprehensive evaluation factor of each evaluation unit is ranked. The larger the value, the greater the reservoir compressibility potential. At the same time, the reservoir compressibility potential is divided into three levels according to the comprehensive evaluation factor, such as Fig.11 As shown, the order is: Level I (0.50≤S)>Level II (0.25≤S<0.50)>Level III (0≤S<0.25); fracturing is recommended for Level I and Level II, but not for Level III.

[0126] Table 5 Geological and rock mechanical parameters of the evaluation unit

[0127] Evaluation Unit Comprehensive evaluation factor Potential ranking Level classification 1 0.4877 14 II 2 0.4473 15 II 3 0.5749 10 I 4 0.5296 12 I 5 0.1215 28 III 6 0.2990 20 II 7 0.4038 17 II 8 0.4151 16 II 9 0.2417 23 III 10 0.2325 24 III 11 0.1662 26 III 12 0.1742 25 III 13 0.2558 22 II 14 0.3245 19 II 15 0.5013 13 I 16 0.2708 21 II 17 0.0731 29 III 18 0.0000 30 III 19 0.1461 27 III 20 0.3770 18 II 21 0.5569 11 I 22 0.6864 3 I 23 0.6683 5 I 24 0.6578 7 I 25 0.6860 4 I 26 0.6292 8 I 27 0.6650 6 I 28 0.6876 2 I 29 0.6989 1 I 30 0.6250 9 I

[0128] Example Evaluation Horizontal well H3 is located in the main shale oil development test area of ​​the basin, with a reservoir burial depth of 1921m, a completed well depth of 3958m, a horizontal section length of 1036m, a drilling rate of 82.0%, and a horizontal section oil layer length of 850m. It has strong heterogeneity, which makes the horizontal well volume fracturing geological engineering sweet spot optimization and perforation parameter optimization face great challenges. The horizontal well H3 is subjected to a comprehensive evaluation of compressibility according to the evaluation method of the present invention, specifically:

[0129] Step 1, using the analytic hierarchy process to establish a multi-level evaluation system for factors affecting the compressibility of shale oil reservoirs, wherein the multi-level evaluation system for compressibility factors includes geological parameters of production capacity factors and rock mechanics parameters of fracture network complexity factors;

[0130] Step 2: According to the actual evaluation results of the horizontal well H3 logging interpretation, the geological parameters and rock mechanics parameter sets that affect the compressibility of the reservoir in the multi-level evaluation system are obtained, and the maximum and minimum values ​​of each parameter in the geological parameter set and rock mechanics parameter set are determined, as shown in Table 6:

[0131] Table 6 Maximum and minimum values ​​of geological and rock mechanical parameters of the horizontal section of the evaluated horizontal well H3

[0132]

[0133] Step 3.1, collect the geological parameters, rock mechanical parameters and fluid production profile parameters corresponding to each fracturing stage of the producing horizontal well H2 in the same layer of the block where the shale oil horizontal well H3 to be evaluated is located, as shown in Table 2;

[0134] Step 3.2, perform correlation analysis on the geological parameters and rock mechanical parameters of each fracturing section of the horizontal well H2 collected in step 3.1 and the daily liquid production ratio of the corresponding fracturing section, such as Figure 2 , Figure 3 , Figure 4 , Figure 6 As shown in , the porosity, permeability, oil saturation, and brittleness index are positively correlated with the daily liquid production ratio; Figure 5 , Figure 7 , Figure 8 As shown, the mud content, horizontal stress difference, and fracture pressure are negatively correlated with the daily liquid production ratio;

[0135] Step 3.3, the porosity, permeability, oil saturation, and brittleness index take the maximum values ​​of the corresponding parameters in step 2 as the optimal compressible reservoir threshold, and the shale content, horizontal stress difference, and fracture pressure take the minimum values ​​of the corresponding parameters in step 2 as the optimal compressible reservoir threshold;

[0136] Based on the optimal compressible reservoir threshold determined in step 2 and step 3.3, the optimal compressible reservoir segment is established by coupling geological parameters and rock mechanical parameters, where the parameters include porosity, permeability, oil saturation, shale content, brittleness index, horizontal stress difference, and fracture pressure, as shown in Table 7:

[0137] Table 7 Geological and rock mechanical parameters of the optimal compressible reservoir section

[0138]

[0139] Step 4.1, using formula (1), divide the horizontal oil layer length of the reservoir where the horizontal well H3 is located into 170 evaluation units, and the oil layer length of each evaluation unit is 5m;

[0140] Step 4.2, taking the evaluation of horizontal well H3 with 20 continuous evaluation units, an oil layer length of 100m, and an oil layer length of 5m in each evaluation unit as an example, the practicability of the present invention is illustrated, as shown in Table 8:

[0141] Table 8 Geological and rock mechanics parameters of the evaluation unit

[0142]

[0143]

[0144] Step 4.3, establish a shale oil reservoir compressibility evaluation unit matrix M according to the geological parameters and rock mechanical parameters corresponding to the oil layer length l of each evaluation unit, and use the optimal compressibility reservoir section geological parameters and rock mechanical parameter thresholds determined in step 3.3 as the evaluation reference series M0;

[0145] Step 4.4, coupling the shale oil reservoir compressibility evaluation unit matrix M obtained in step 4.3 and the evaluation reference series M0 to establish a reservoir compressibility evaluation matrix B;

[0146] Step 4.5: Use formula (5) to standardize the elements of the reservoir compressibility evaluation matrix B to obtain the reservoir compressibility evaluation standardized matrix B: * :

[0147] Step 4.6, based on the reservoir compressibility evaluation standardized matrix B * , use formulas (7) and (8) to calculate the comprehensive evaluation factor of each evaluation unit, such as Fig.12 As shown:

[0148] Step 4.7, as shown in Table 9, the comprehensive evaluation factor of each evaluation unit is ranked. The larger the value, the greater the reservoir compressibility potential. At the same time, the reservoir compressibility potential is divided into three levels according to the comprehensive evaluation factor, and is ranked as follows: Level I (0.50≤S)>Level II (0.25≤S<0.50)>Level III (0≤S<0.25). Fracturing is recommended for Level I and Level II, and not recommended for Level III.

[0149] Table 9 Geological and rock mechanics parameters of the evaluation unit

[0150]

[0151]

Claims

1. A comprehensive evaluation method for the volume fracturing compressibility of shale oil horizontal wells, characterized in that: Follow the steps below to implement it: Step 1, using the analytic hierarchy process to establish a multi-level evaluation system for factors affecting the compressibility of shale oil reservoirs, wherein the multi-level evaluation system for compressibility factors includes geological parameters of production capacity factors and rock mechanics parameters of fracture network complexity factors; In step 1, the geological parameters include: porosity, permeability, oil saturation, and shale content of the horizontal oil layer; the rock mechanics parameters include: brittleness index, horizontal stress difference, and fracture pressure; Step 2, based on the logging interpretation results of the horizontal section of the horizontal well, the geological parameters and rock mechanics parameter sets described in step 1 are obtained, and the maximum and minimum values ​​of each parameter in the geological parameter set and the rock mechanics parameter set are determined; Step 3, determining the threshold of the reservoir section with the best compressibility and establishing the reservoir section with the best compressibility; The specific steps of step 3 are as follows: Step 3.1, collecting geological parameters, rock mechanical parameters and fluid production profile parameters corresponding to each fracturing stage of the producing horizontal wells in the same layer of the block where the shale oil horizontal well to be evaluated is located; Step 3.2, performing correlation analysis on the geological parameters and rock mechanical parameters of each fracturing section of the horizontal well collected in step 3.1 and the daily liquid production ratio of the corresponding fracturing section; Step 3.3, determining the thresholds of geological parameters and rock mechanical parameters of the optimal compressibility reservoir section according to the correlation analysis results obtained in step 3.2, wherein the parameter that is positively correlated with the daily liquid production ratio uses the maximum value determined in step 2 as the threshold, and the parameter that is negatively correlated with the daily liquid production ratio uses the minimum value determined in step 2 as the threshold; Step 3.4, coupling the threshold obtained in step 3.3 to a parameter set to obtain the optimal compressible reservoir segment, wherein the geological parameters include porosity, permeability, oil saturation, and shale content, and the rock mechanical parameters include brittleness index, horizontal stress difference, and fracture pressure; Step 4, establishing a shale oil reservoir compressibility evaluation model, calculating comprehensive evaluation factors of different reservoir sections, and quantitatively evaluating reservoir compressibility; The specific steps of step 4 are as follows: Step 4.1: Divide the length of the horizontal oil layer of the horizontal well to be evaluated into m evaluation units, and the length of the oil layer in each evaluation unit is ; Step 4.2: Based on the geological parameter set and rock mechanics parameter set obtained in step 2, obtain m The geological parameters and rock mechanical parameters corresponding to each evaluation unit are calculated, and the average value of the geological parameters corresponding to each evaluation unit is taken as the oil layer length of each evaluation unit. Corresponding geological parameters, the average value of the rock mechanical parameters corresponding to each evaluation unit is obtained as the oil layer length of each evaluation unit Corresponding rock mechanical parameters; Step 4.3, the oil layer length of each evaluation unit obtained in step 4.2 Corresponding geological parameters and rock mechanical parameters to establish the shale oil reservoir compressibility evaluation unit matrix The optimal compressibility reservoir geological parameters and rock mechanical parameter thresholds determined in step 3.3 are used as the evaluation reference series ; Step 4.4, coupling step 4.3 to obtain the shale oil reservoir compressibility evaluation unit matrix and Evaluation Reference Series , establish reservoir compressibility evaluation matrix ; Step 4.5, evaluate the matrix elements of the unit The elements in the evaluation reference series are standardized to obtain the reservoir compressibility evaluation standardized matrix ; Step 4.6: Based on the reservoir compressibility evaluation standardized matrix obtained in step 4.5 , calculate the comprehensive evaluation factor of each evaluation unit; Step 4.7, the reservoir is divided into compressibility potential according to the comprehensive evaluation factor of each evaluation unit obtained in step 4.

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2. A method for comprehensive evaluation of the volume fracturing compressibility of shale oil horizontal wells according to claim 1, characterized in that: In step 4.1, the oil layer length of each evaluation unit is The expression is: （1） In formula (1): is the length of the oil layer in each evaluation unit, m; m is the number of evaluation units, ; L is the length of the horizontal oil layer, m.

3. A method for comprehensive evaluation of the volume fracturing compressibility of shale oil horizontal wells according to claim 1, characterized in that: In step 4.3, the shale oil reservoir compressibility evaluation unit matrix The expression is: （2） In formula (2), is the evaluation unit matrix element, ; is the number of evaluation units; The number of parameters of compressibility influencing factors for each evaluation unit; Evaluation reference series The expression is: （3）。 4. A method for comprehensive evaluation of the volume fracturing compressibility of shale oil horizontal wells according to claim 1, characterized in that: In step 4.4, the reservoir compressibility evaluation matrix The expression is:

5. A method for comprehensive evaluation of the volume fracturing compressibility of shale oil horizontal wells according to claim 1, characterized in that: The specific steps of step 4.5 are as follows: Step 4.5.1, Evaluate the cell matrix elements To standardize, the expression is: （5） In formula (5), Standardized elements of the unit matrix for shale oil reservoir compressibility evaluation; Step 4.5.2: Use formula (5) to standardize all the elements of the shale oil reservoir compressibility evaluation unit matrix to obtain the reservoir compressibility evaluation standardized matrix: , the expression is: （6）。 6. A method for comprehensive evaluation of the volume fracturing compressibility of shale oil horizontal wells according to claim 1, characterized in that: In step 4.6, the comprehensive evaluation factor of each evaluation unit is expressed as: （7） In formula (7): is the comprehensive evaluation factor of the evaluation unit, To evaluate the reference series of standardized elements, is the maximum distance between the evaluation unit and the optimal compressible reservoir segment, expressed as: （8）。 7. A method for comprehensive evaluation of the volume fracturing compressibility of shale oil horizontal wells according to claim 1, characterized in that: In step 4.7, the compressibility potential is divided into level I, level II, and level III, where level I>level II>level III; Grade I: 0.50≤ S i ; Level II: 0.25≤ S i <0.50; Grade III: 0≤ S i <0.25.

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