A method for determining sandstone reservoir permeability based on fracture development index

Abstract

The present invention discloses a method for determining the permeability of sandstone reservoirs based on a fracture development index, which relates to the field of oil and gas geological exploration technology. The method comprises the following steps: identifying fracture development characteristics; extracting fracture development parameters; calculating the fracture development index based on conventional well logging data; and establishing a permeability calculation formula based on the fracture development index of conventional well logging data, based on the fracture development index calculation results and conventional well logging porosity calculation results, combined with the analysis results of core experimental data from multiple wells. The present invention can quickly and accurately calculate the permeability of low-porosity and low-permeability sandstone reservoirs, providing basic parameters for reservoir identification, production capacity prediction, and gas reservoir numerical simulation, and improving the permeability evaluation accuracy of complex pore structure reservoirs with simultaneous development of fractures and pores.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas geological exploration, and more specifically to a method for determining the permeability of a sandstone reservoir based on a fracture development index. Background Art

[0002] The permeability of rocks is expressed by the numerical value of permeability. Permeability is the physical foundation of oil (gas) reservoir rocks and is essential data for both oil and gas migration and accumulation and oil (gas) field development. However, well logging calculations of permeability in low-porosity and low-permeability reservoirs have always been a challenge in oil and gas exploration and development. Domestic and foreign scholars have established numerous theoretical models and empirical formulas for permeability and fitted them with conventional logging data, achieving certain application results. However, for reservoirs with complex pore structures where fractures and pores coexist, direct fitting of porosity and permeability from core experimental analysis yields a poor correlation. Consequently, the formation permeability calculated using these fitted formulas is less accurate, hindering reservoir identification, production capacity prediction, and numerical simulation of gas reservoirs.

[0003] To improve the accuracy of permeability evaluation for low-porosity, low-permeability reservoirs, a common approach is to classify and fit different reservoir types. This improves interpretation accuracy to a certain extent, but establishing a standard for reservoir classification is difficult. Inaccurate reservoir classification can sometimes increase permeability calculation errors, with values ​​varying significantly across different oil and gas reservoirs. Therefore, new methods are urgently needed to address these practical issues, improve the accuracy of permeability evaluation for low-porosity, low-permeability reservoirs, and provide fundamental parameters for reservoir identification, productivity prediction, and numerical simulation of gas reservoirs.

[0004] A Chinese patent document with authorization announcement number CN107917865B and authorization announcement date of January 31, 2020 discloses a multi-parameter permeability prediction method for tight sandstone reservoirs, including: (1) determining the geological main controlling factors of permeability in tight sandstone reservoirs, the geological main controlling factors including porosity, grain size and degree of fracture development; (2) establishing a well logging prediction model and a seismic prediction model for porosity and grain size; (3) determining the geological main controlling factors of fracture development; (4) establishing a fracture development index model based on the geological main controlling factors obtained in step (3); (5) establishing a multi-parameter permeability comprehensive prediction model constrained by seismic and geological factors. The advantage of this solution is that it can achieve accurate planar prediction of permeability. However, the above technical solution still analyzes different reservoir types, and errors are prone to occur in the calculation of permeability. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a method for determining the permeability of sandstone reservoirs based on the fracture development index. This method can quantitatively describe the permeability of sandstone reservoirs, quickly and accurately calculate the permeability of sandstone reservoirs, and improve the permeability evaluation accuracy of complex pore structure reservoirs with simultaneous development of fractures and pores, providing basic parameters for reservoir identification, production capacity prediction, and gas reservoir numerical simulation.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A method for determining the permeability of a sandstone reservoir based on a fracture development index comprises the following steps:

[0008] S1. Identification of crack development characteristics;

[0009] Based on the fracture response characteristics of conventional logging data from multiple wells in the study area, combined with the results of electrical imaging fracture interpretation, drilling coring and oil testing, the fracture development of sandstone reservoirs was analyzed by the degree of data anomaly.

[0010] S2, extraction of fracture development parameters;

[0011] Based on the fracture development characteristics, the micro- and low-angle fracture development indices are calculated using neutron acoustic waves and density. The macro- and high-angle fracture development indices are calculated using deep and shallow dual laterals. Finally, the micro- and low-angle fracture development indices are normalized to complete the extraction of fracture development characteristic parameters.

[0012] S3. Calculation of fracture development index based on conventional logging data;

[0013] The calculation of the fracture development index based on conventional well logging data refers to constructing a fracture development index calculation model based on conventional well logging data based on the fracture development parameter extraction results and comprehensively utilizing the micro-fracture and low-angle fracture development indices; and normalizing the fracture development index calculation results based on conventional well logging data;

[0014] S4. Establish a permeability calculation model based on the fracture development index of conventional logging data;

[0015] Combining the analysis results of core test data from multiple wells and the porosity calculation results from conventional logging, a permeability calculation model based on the fracture development index was established based on the fracture development index calculation results of conventional logging data, including:

[0016] The porosity and permeability of the core experimental analysis of the section with sparse fractures in the sandstone reservoir are selected as data points, and a permeability fitting formula for the section with sparse fractures in the sandstone reservoir based on the porosity-permeability relationship is established:

[0017]

[0018] Where: K Φ The permeability is calculated for the section of sandstone reservoir without fractures, in mD; is the porosity, in %; a and K1 are scale factors, dimensionless;

[0019] Then, the coefficients a and K1 are determined by using the established permeability calculation formula for the fracture-undeveloped section of the sandstone reservoir; combined with the fracture development index calculation results of the conventional logging data provided by S3, a sandstone reservoir permeability calculation model based on the fracture development index of conventional logging data is established:

[0020]

[0021] Where: K is the calculated permeability of sandstone reservoir based on the fracture development index, in mD; K2 is the scale factor, dimensionless.

[0022] The identification of fracture development characteristics includes searching for fracture development sections in sandstone reservoirs by using photoelectric absorption cross-section index anomalies, searching for fracture development sections by using wellbore anomalies, searching for fracture development sections by using uranium element anomalies, searching for fine and low-angle fracture development sections by using neutron acoustic wave and density curve anomalies, and searching for high-angle fracture development sections by using deep and shallow dual lateral anomalies.

[0023] The calculation of fine and low-angle fracture development index by neutron acoustic wave and density means that the development of fine and low-angle fractures will lead to abnormal increase of compensated neutron and compensated acoustic wave logging curves and abnormal decrease of compensated density logging curves. Therefore, a fracture development index calculation model can be constructed based on the change rate of logging curves. The compensated neutron (CNL), compensated acoustic wave (AC) and compensated density (DEN) curves of the fracture-undeveloped section of the sandstone reservoir are selected and averaged, and the average value of the cumulative CNL, AC and DEN is calculated:

[0024]

[0025]

[0026]

[0027] n=(DEP end -DEP sta ) / Δsi (4)

[0028] In formulas (1), (2), and (3): are the average values ​​of compensated neutron, compensated acoustic wave and compensated density for the fracture-undeveloped section of porous sandstone reservoir; CNLi is the compensated neutron value at each depth, in PU; ACi is the compensated acoustic wave value at each depth, in us / ft; DENi is the compensated density value at each depth, in g / cm 3 ;DEPend The end depth is in meters; DEP sta is the starting depth, in m; Δsi is the depth sampling interval, in m;

[0029] Secondly, by comparing the measured CNL, AC, and DEN values ​​with the fracture-undeveloped section of the sandstone reservoir, Establish relationships and construct mathematical models for the development index of fine and low-angle cracks:

[0030]

[0031] In formula (5): F c is the development index of fine and low-angle cracks, b1, b2, b3 are fitting coefficients; in addition, when F C The larger the value, the greater the probability of the development of micro cracks and low-angle cracks.

[0032] The deep-shallow dual lateral calculation of the macro high-angle fracture development index refers to the phenomenon of "positive difference" in the deep-shallow dual lateral due to mud invasion at the location where macro high-angle fractures are developed, and the resulting significant decrease in the deep-shallow dual lateral value relative to the section where fractures are not developed in the sandstone reservoir. Therefore, a fracture development index calculation model can be constructed based on the logging curve change rate. The deep lateral resistivity curve of the section where fractures are not developed in the sandstone reservoir is selected, averaged, and the average value of the cumulative deep lateral resistivity curve is calculated:

[0033]

[0034] n=(DEP end -DEP sta ) / Δsi (7)

[0035] In formula (6): RT is the deep lateral resistivity curve value, is the average value of the deep lateral resistivity curve of the section without developed fractures in the sandstone reservoir, in Ω·m; DEP end The end depth is in meters; DEP sta is the starting depth, in m; Δsi is the depth sampling interval, in m;

[0036] Finally, the measured RT and RXO values ​​were compared with the fracture-free section of the sandstone reservoir. Establish relationships and construct a mathematical model of macroscopic high-angle crack development index:

[0037]

[0038] In formula (8): F d is the macro high-angle fracture development index, RXO is the shallow lateral resistivity curve value, f1 and f2 are fitting coefficients; in addition, when F dThe larger the value, the greater the probability of macroscopic high-angle crack development.

[0039] The normalization process of the fine and low-angle crack development index refers to the normalization of the fine and low-angle crack development index F by the data normalization method. c and macroscopic high-angle crack development index F d Perform dimensionless processing respectively:

[0040]

[0041]

[0042] In formulas (9) and (10): F′ c is the normalized fine and low-angle crack development index; F′ d is the normalized macro high-angle crack development index; F c (n), maxF c (n), minF c (n) are respectively the fine and low-angle fracture development index value at a certain depth point in the sandstone reservoir section, the maximum value of the fine and low-angle fracture development index in the sandstone reservoir section, and the minimum value of the fine and low-angle fracture development index in the sandstone reservoir section; F d (n), maxF d (n), minF d (n) are the macro high-angle fracture development index value at a certain depth point in the sandstone reservoir section, the maximum value of the macro high-angle fracture development index in the sandstone reservoir section, and the minimum value of the macro high-angle fracture development index in the sandstone reservoir section.

[0043] The construction of the fracture development index calculation model based on conventional well logging data refers to using the normalized fine and low-angle fracture development indices to construct a fracture development index calculation formula based on conventional well logging data:

[0044]

[0045] In formula (11), W1 and W2 are the sensitivity coefficients of the three porosity curves and resistivity curves to the fracture development index, respectively.

[0046] The normalization processing of the fracture development index based on conventional well logging data refers to the normalization of the fracture development index F based on conventional well logging data by a data normalization method. L Perform dimensionless processing:

[0047]

[0048] In formula (12): F′ L is the normalized fracture development index based on conventional logging data; F L(n), maxF L (n), minF L (n) are the fracture development index value based on conventional logging data at a certain depth point in the sandstone reservoir section, the maximum fracture development index value in the sandstone reservoir section, and the minimum fracture development index value in the sandstone reservoir section. A fracture development index calculation model based on conventional logging data is established by integrating various characteristic parameters to calculate the fracture development index curve F. L , the calculation results are normalized, and the crack development index curve F′ L The closer the curve value is to 1, the higher the possibility or probability of crack development is; the closer the curve value is to 0, the lower the possibility or probability of crack development is.

[0049] The fitting coefficient and sensitivity coefficient are determined based on production experience, and the calibration coefficient is determined by the porosity-permeability relationship of the rock electrical experiment.

[0050] Compared with the prior art, the beneficial technical effects brought about by the present invention are as follows:

[0051] 1. The present invention comprehensively utilizes the fracture development index, conventional logging data, and core experimental data analysis results to establish a permeability calculation model based on the fracture development index. This model can quickly and accurately quantitatively describe the permeability of low-porosity and low-permeability sandstone reservoirs, and improve the permeability evaluation accuracy of complex pore structure reservoirs with simultaneous development of fractures and pores. It can provide accurate basic parameters for reservoir identification, production capacity prediction, and gas reservoir numerical simulation.

[0052] 2. The permeability calculation model based on the fracture development index established in the present invention is very easy to implement through computer programming. It can continuously process well logging data and provide permeability calculation results that vary with depth, providing basic data for oil and gas migration and accumulation and oil (gas) field development. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

[0054] Figure 1 This is the result of identifying high-angle, low-angle and micro-fractures in the fourth section of the Xujiahe Formation in Well YQ104.

[0055] Figure 2 This is the identification result of fracture development characteristics of the fourth member of the Xuzhou Formation in Well YQ104 (3123-3124m);

[0056] Figure 3 This is the electrical imaging fracture identification result map of Well YQ104 (3141-3146m);

[0057] Figure 4 This is the electrical imaging fracture identification result map of Well YQ104 (3146-3150m);

[0058] Figure 5 This is the electrical imaging fracture identification result map of Well YQ104 (3201.5-3205m);

[0059] Figure 6 This is the permeability calculation result of the fourth section of the YQ104 well based on the fracture development index. DETAILED DESCRIPTION

[0060] In order to make the technical solution of the present application clearer, the technical solution of the present application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings.

[0061] This embodiment uses the method of the present invention to calculate the permeability of the sandstone reservoir section of the Xu 4th section of the YQ104 well in the northern Sichuan Basin as an example to illustrate the specific implementation method:

[0062] S1. Identification of crack development characteristics

[0063] The depth and shallowness of the well section 3138.5-3143.2m are significantly lower than those of the surrounding rock, reflecting the development of low-angle fractures in this section. Figure 1 Track 5: The well section 3123.1-3150m and 3193-3202.7m shows that the drilling time is accelerated, reflecting that this section is an abnormal section. Figure 1 Track 6: The wellbore diameters of sections 3115.7-3131.4m, 3142.6-3160m, 3163.5-3195.2m, and 3198.3-3214.5m are enlarged, reflecting that the reservoir fractures in this section are well developed. Figure 1 Track 9: The uranium element in the well section 3114.5-3130.9m, 3140.2-3143.3m, 3146-3151.1m, and 3211-3215.7m increases abnormally, reflecting that the reservoir fractures in this section are well developed. Figure 1 Track 10: The envelope area of ​​the acoustic-neutron porosity overlap method at the well section 3140.3-3146.9 m shows a "spiky" feature, reflecting the development of low-angle fractures in this section. Figure 1 Track 11: The results of the electrical imaging interpretation indicate that multiple fractures of different occurrences are developed at 3123-3124m, 3141-3143m, 3145-3148m, and 3201-3203.5m. Figure 1 12th and Figure 2-Figure 5The results of electrical imaging fracture identification are shown in the figure. The production logging results indicate that the gas production of 1#3121.5-3137.3m, 2#3140.0-3148.7m, 5#3175.2-3178.1m, 7#3190.3-3205.5m, and 8#3222.8-3226.8m is relatively high. Combined with the fact that high-yield layers in this area usually have more developed fractures, it is reflected that the fractures in 1#, 2#, 5#, 7#, and 8# are more developed. Figure 1 No. 13.

[0064] Comprehensive analysis shows that fractures in the Xu4 section of the well are well developed. The fracture development response characteristics reflected by logging curves such as well diameter, uranium element, acoustic-neutron porosity overlap method, and deep-shallow dual lateral difference are basically consistent with the fracture development response characteristics reflected by electrical imaging, production logging and oil testing results.

[0065] S2. Extraction of fracture development parameters

[0066] Neutron acoustic wave and density calculation of fine and low-angle fracture development index: The well section 3110.3-3116.3m was selected as the porous sandstone reservoir fracture-undeveloped section. The calculation formula for the average value of CNL, AC, and DEN in this section is:

[0067]

[0068]

[0069]

[0070] n=(DEP end -DEP sta ) / Δsi (4)

[0071] Through calculation, we can know that the 7.3PU, 59.2us / ft, 2.59g / cm 3 In addition, the fitting coefficients b1, b2, and b3 are set to 0.3, 0.35, and 0.5, respectively. The calculation formula for the fine and low-angle crack development index is:

[0072]

[0073] According to the above formula, the calculation of fine and low-angle crack development index F is completed. c , the calculation results are shown in Figure 6 No. 8.

[0074] Deep and shallow dual lateral calculation of macro high-angle fracture development index: The well section 3110.3-3116.3m is selected as the porous sandstone reservoir fracture-undeveloped section, and the average value of the cumulative deep lateral resistivity curve is calculated as follows:

[0075]

[0076] n=(DEP end -DEP sta ) / Δsi (7)

[0077] Through calculation, we can know that the is 37.34Ω·m. In addition, the fitting coefficients f1 and f2 are 0.45 and 0.65 respectively, and the calculation formula for the macro high-angle crack development index is:

[0078]

[0079] According to the above formula, the macro high-angle crack development index F is calculated. d , the calculation results are shown in Figure 6 No. 10.

[0080] The fine and low angle crack development index F was calculated by data normalization method. c and macroscopic high-angle crack development index F d The dimensionless processing is performed respectively, and the calculation formula is as follows:

[0081]

[0082]

[0083] According to the above formula, the fine and low-angle crack development index F is completed c Normalization F′ c , macro high-angle crack development index F d Normalized processing result, F′ d The calculation results are shown in Figure 6 Tracks 9 and 11.

[0084] S3. Calculation of fracture development index based on conventional logging data

[0085] The sensitivity coefficients W1 and W2 are set to 0.3 and 0.8 respectively, and the fracture development index calculation formula based on conventional logging data is established. The calculation formula is:

[0086]

[0087] Complete the calculation of fracture development index F based on conventional logging data L , the calculation results are shown in Figure 6 No. 12.

[0088] The fracture development index F based on conventional logging data was normalized by data normalization method. L After dimensionless processing, the calculation formula is:

[0089]

[0090] According to the above formula, the fracture development index F is calculated based on conventional logging data. L Normalization processing, F′ L The calculation results are shown in Figure 6 No. 13.

[0091] S4. Establish a permeability calculation model based on the fracture development index of conventional logging data

[0092] The porosity and permeability of the core experimental analysis of the section with sparse fractures in the sandstone reservoir are selected as data points, and the calibration coefficients a and K1 are set as 0.084 and 0.13 respectively. The permeability fitting formula of the section with sparse fractures in the sandstone reservoir based on the porosity-permeability relationship is established:

[0093]

[0094] The calculation results can be seen in Figure 6 No. 14.

[0095] Using scale factors a, K1, F' L , the scale coefficient K2 is taken as 1.2, and a sandstone reservoir permeability calculation model based on the fracture development index of conventional logging data is established. The calculation formula is:

[0096]

[0097] The calculation results can be seen in Figure 6 No. 14.

[0098] The calculation results based on the porosity-permeability relationship fitting formula and the sandstone reservoir permeability calculation results based on the fracture development index of conventional logging data were compared with the core test analysis results. It can be seen that the method of the present invention (the sandstone reservoir permeability calculation results based on the fracture development index of conventional logging data) is more consistent with the core test analysis results, see Figure 6 No. 14.

[0099] The present invention comprehensively utilizes the fracture development index, conventional logging data, and core experimental data analysis results to establish a permeability calculation model based on the fracture development index. This model can quickly and accurately quantitatively describe the permeability of low-porosity and low-permeability sandstone reservoirs, and improve the permeability evaluation accuracy of complex pore structure reservoirs with simultaneously developed fractures and pores.

Claims

1. A method for determining the permeability of a sandstone reservoir based on a fracture development index, characterized in that: The steps are: S1. Identification of crack development characteristics; S2, extraction of fracture development parameters; S3. Calculation of fracture development index based on conventional logging data; S4. Establish a permeability calculation model based on the fracture development index of conventional logging data, including: First, the porosity and permeability of the core experimental analysis of the section of the sandstone reservoir with sparse fractures are selected as data points, and the permeability fitting formula of the section of the sandstone reservoir with sparse fractures is established based on the porosity-permeability relationship: （13） Where: The permeability calculated for the fracture-undeveloped section of the sandstone reservoir, mD; is the porosity, %; a and K1 are scale factors, dimensionless; Then, the calibration coefficients a and K1 are determined by using the established permeability fitting formula for the fracture-undeveloped section of the sandstone reservoir; combined with the fracture development index calculation results based on conventional well logging data provided by S3, a sandstone reservoir permeability calculation model based on the fracture development index of conventional well logging data is established: （14） Where: K is the calculated value of sandstone reservoir permeability based on the fracture development index of conventional logging data, mD; K2 is the scale factor, dimensionless; is the normalized fracture development index based on conventional logging data.

2. The method for determining the permeability of a sandstone reservoir based on a fracture development index according to claim 1, characterized in that: The identification of fracture development characteristics includes searching for fracture development sections in sandstone reservoirs by using photoelectric absorption cross-section index anomalies, searching for fracture development sections by using wellbore anomalies, searching for fracture development sections by using uranium element anomalies, searching for fine and low-angle fracture development sections by using neutron acoustic wave and density curve anomalies, and searching for high-angle fracture development sections by using deep and shallow dual lateral anomalies.

3. The method for determining the permeability of a sandstone reservoir based on a fracture development index according to claim 1, characterized in that: The extraction of crack development parameters includes calculating fine and low-angle crack development indexes, calculating macro high-angle crack development indexes, and normalizing the fine and low- and high-angle crack development indexes.

4. The method for determining the permeability of a sandstone reservoir based on a fracture development index according to claim 3, characterized in that: The calculation of the fine and low-angle fracture development index refers to constructing a fine and low-angle fracture development index calculation model based on the change rate of the well logging curve: First, select the CNL, AC, and DEN curves of the sandstone reservoir fracture-undeveloped section, perform average processing, and calculate the average values ​​of the cumulative CNL, AC, and DEN: （1） （2） （3） （4） In formulas (1), (2) and (3), CNL, AC and DEN are compensation neutron, compensation acoustic wave and compensation density respectively; They are the average values ​​of compensated neutron, compensated acoustic wave and compensated density in the fracture-undeveloped section of porous sandstone reservoir; is the compensated neutron value at each depth; is the compensation sound wave value for each depth; is the compensation density value for each depth; for the end depth; is the starting depth; is the depth sampling interval; Then, the measured CNL, AC, and DEN values ​​were compared with the fracture-undeveloped section of the sandstone reservoir. Establish relationships and construct mathematical models for the development index of fine and low-angle cracks: （5） In formula (5): is the development index of fine and low-angle cracks, and b1, b2, and b3 are fitting coefficients.

5. The method for determining the permeability of a sandstone reservoir based on a fracture development index according to claim 4, characterized in that: The calculation of the macro high-angle fracture development index refers to constructing a macro high-angle fracture development index calculation model based on the change rate of the well logging curve: First, select the deep lateral resistivity curve of the section where the sandstone reservoir fractures are not developed, perform average processing, and calculate the average value of the cumulative deep lateral resistivity curve: （6） （7） In formula (6), RT is the deep lateral resistivity curve value of the sandstone reservoir fracture-undeveloped section, is the average value of the deep lateral resistivity curve of the section with no developed fractures in the sandstone reservoir; Then, the measured RT and RXO values ​​were compared with the fracture-undeveloped section of the sandstone reservoir. Establish relationships and construct a mathematical model of macroscopic high-angle crack development index: （8） In formula (8): is the macro high-angle fracture development index, RXO is the shallow lateral resistivity curve value, and f1 and f2 are fitting coefficients.

6. The method for determining the permeability of a sandstone reservoir based on a fracture development index according to claim 5, characterized in that: The normalization processing of fine and low angle crack development index refers to the normalization of fine and low angle crack development index by data normalization method. and macroscopic high-angle crack development index Perform dimensionless processing respectively: （9） （10） In formulas (9) and (10): is the normalized fine and low-angle crack development index; is the normalized macroscopic high-angle crack development index; 、 They are respectively the fine and low-angle fracture development index value at a certain depth point in the sandstone reservoir section, the maximum value of the fine and low-angle fracture development index in the sandstone reservoir section, and the minimum value of the fine and low-angle fracture development index in the sandstone reservoir section; 、 They are respectively the macro high-angle fracture development index value at a certain depth point in the sandstone reservoir section, the maximum value of the macro high-angle fracture development index in the sandstone reservoir section, and the minimum value of the macro high-angle fracture development index in the sandstone reservoir section.

7. The method for determining the permeability of a sandstone reservoir based on a fracture development index according to claim 6, characterized in that: The calculation of the fracture development index based on conventional well logging data includes constructing a fracture development index calculation model based on conventional well logging data and normalizing the fracture development index based on conventional well logging data.

8. The method for determining sandstone reservoir permeability based on fracture development index according to claim 7, characterized in that: The construction of the fracture development index calculation model based on conventional well logging data refers to using the normalized fine and low-angle fracture development indices to construct a fracture development index calculation formula based on conventional well logging data: （11） In formula (11), W1 and W2 are the sensitivity coefficients of the three porosity curves and resistivity curves to the fracture development index, respectively.

9. The method for determining sandstone reservoir permeability based on fracture development index according to claim 7, characterized in that: The normalization processing of the fracture development index based on conventional well logging data refers to the normalization of the fracture development index based on conventional well logging data by a data normalization method. Perform dimensionless processing: （12） In formula (12): is the normalized fracture development index based on conventional logging data; 、 They are respectively the fracture development index value of a certain depth point in the sandstone reservoir section based on conventional logging data, the maximum fracture development index value of the sandstone reservoir section based on conventional logging data, and the minimum fracture development index value of the sandstone reservoir section based on conventional logging data.

10. The method for determining sandstone reservoir permeability based on fracture development index according to claim 8, characterized in that: The fitting coefficient and sensitivity coefficient are determined based on production experience, and the calibration coefficient is determined by the porosity-permeability relationship of the rock electrical experiment.

Images