Method for determining permeability of sandstone reservoir based on fracture development index

Abstract

The invention discloses a method for determining the permeability of a sandstone reservoir based on a fracture development index, and relates to the technical field of oil and gas geological exploration. Fracture development parameters are extracted; calculating a fracture development index based on conventional logging information; and based on a fracture development index calculation result and a conventional logging porosity calculation result, a permeability calculation formula of the fracture development index based on conventional logging information is established in combination with a multi-well core experiment data analysis result. According to the method, the permeability of the low-porosity and low-permeability sandstone reservoir can be rapidly and accurately calculated, basic parameters are provided for reservoir identification, productivity prediction, gas reservoir numerical simulation and the like, and the permeability evaluation precision of the complex pore structure reservoir with cracks and pores developed at the same time is improved.

Description

Technical Field

[0001] The 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 property basis of oil (gas) reservoir rocks. It is basic data for oil and gas migration and accumulation, as well as oil (gas) field development. Well logging calculation of permeability of low-porosity and low-permeability reservoirs has always been a difficult point in oil and gas exploration and development. Domestic and foreign scholars have established many theoretical models and empirical formulas for permeability, and fitted them with conventional logging data, achieving certain application results. However, for complex pore structure reservoirs with both fractures and pores, the direct fitting of porosity and permeability from core experimental analysis has a poor correlation. Therefore, the accuracy of formation permeability obtained by the fitting formula is poor, which makes reservoir identification, production capacity prediction, and gas reservoir numerical simulation difficult to carry out.

[0003] In order to improve the permeability evaluation accuracy of low-porosity and low-permeability reservoirs, the usual practice is to classify and fit based on different reservoir types, which improves the interpretation accuracy to a certain extent. However, it is difficult to establish the standard for reservoir type classification. Sometimes, inaccurate reservoir type classification will increase the permeability calculation error, and its value varies greatly in different oil (gas) layers. Therefore, it is urgent to find new methods to solve these practical problems, improve the permeability evaluation accuracy of low-porosity and low-permeability reservoirs, and provide basic parameters for reservoir identification, production capacity prediction, and gas reservoir numerical simulation.

[0004] A Chinese patent document with an authorization announcement number of CN107917865B and an authorization announcement date of January 31, 2020 discloses a multi-parameter permeability prediction method for tight sandstone reservoirs, including: (1) determining the main geological control factors of permeability in tight sandstone reservoirs, the main geological control 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 main geological control factors of fracture development; (4) establishing a fracture development index model based on the geological control 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 is still based on the analysis of different reservoir types, and errors are prone to occur in the calculation of permeability. Summary of the invention

[0005] In order 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. By adopting this method, the permeability of sandstone reservoirs can be quantitatively described, the permeability of sandstone reservoirs can be calculated quickly and accurately, and the permeability evaluation accuracy of reservoirs with complex pore structures where fractures and pores are developed simultaneously can be improved, thereby providing basic parameters for reservoir identification, production capacity prediction and numerical simulation of gas reservoirs.

[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] According to the fracture response characteristics of conventional logging data of 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 crack development situation identified by crack development characteristics, the micro- and low-angle crack development index is calculated using neutron acoustic waves and density; the macroscopic high-angle crack development index is calculated using deep and shallow dual laterals; finally, the micro- and low- and high-angle crack development indexes are normalized to complete the extraction of crack 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 by comprehensively utilizing the fracture development index of micro fractures and low-height angle fractures based on the fracture development parameter extraction results; 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 is 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 sandstone reservoir fracture-undeveloped section are selected as data points, and the permeability fitting formula of the sandstone reservoir fracture-undeveloped section based on the porosity-permeability relationship is established:

[0017]

[0018] Where: K Φ The permeability is calculated for the section of sandstone reservoir without fracture development, 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 value of sandstone reservoir permeability based on the fracture development index, in mD; K2 is the scale factor, dimensionless.

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

[0023] The neutron acoustic wave and density calculation of the fine and low-angle fracture development index means that the fine and low-angle fracture development section will cause the compensated neutron and compensated acoustic wave logging curves to increase abnormally, and the compensated density logging curve to decrease abnormally. Therefore, a fracture development index calculation model can be constructed based on the logging curve change rate, and the compensated neutron (CNL), compensated acoustic wave (AC) and compensated density (DEN) curves of the sandstone reservoir fracture undeveloped section are selected for average processing, and the average values ​​of the accumulated CNL, AC and DEN are calculated:

[0024]

[0025]

[0026]

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

[0028] In formula (1), (2) and (3): are the average values ​​of compensated neutron, compensated acoustic wave and compensated density of the porous sandstone reservoir with undeveloped fractures; 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 is the end depth, in meters; DEP sta is the starting depth, in m; Δsi is the depth sampling interval, in m;

[0029] Secondly, the measured CNL, AC, and DEN values ​​were compared with the fracture-free section of the sandstone reservoir. Establish relationships and construct mathematical models of fine and low-angle crack development indexes:

[0030]

[0031] In formula (5): F c is the development index of fine and low-angle cracks, b1, b2, and 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 macro high-angle fracture development site, and the deep-shallow dual lateral value is greatly reduced relative to the sandstone reservoir fracture undeveloped section. Therefore, a fracture development index calculation model can be constructed based on the logging curve change rate, and the deep lateral resistivity curve of the sandstone reservoir fracture undeveloped section is selected for average processing, 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, DEP is the average value of the deep lateral resistivity curve of the section without fracture development in the sandstone reservoir, in Ω·m; end is the end depth, 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 macroscopic 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 cracks developing.

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

[0040]

[0041]

[0042] In formula (9) and (10): F′ c is the normalized fine and low-angle crack development index; F′ d is the normalized macroscopic 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 respectively the value of the macroscopic high-angle fracture development index at a certain depth point in the sandstone reservoir section, the maximum value of the macroscopic high-angle fracture development index in the sandstone reservoir section, and the minimum value of the macroscopic 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 index 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 curve 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 based on various characteristic parameters to calculate the fracture development index curve F L , the calculation results are normalized, and the fracture development index curve F′ L The closer the curve value is to 1, the higher the possibility or probability of fracture development; the closer the curve value is to 0, the lower the possibility or probability of fracture development.

[0049] The fitting coefficient and the 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 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, which 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, and 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 by computer programming, can continuously process well logging data, and provide permeability calculation results that vary with depth, thus 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, low angle and micro fractures in the fourth section of the YQ104 well;

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

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

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

[0058] Figure 5 This is the result of electrical imaging fracture identification in 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 fourth 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 lower than the surrounding rock in both sides and the difference is obvious, reflecting the development of low-angle fractures in this section. Figure 1 Track 5: The well section 3123.1-3150m, 3193-3202.7m logging 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 more developed. Figure 1 Track 9: The abnormal increase of uranium elements in the well sections 3114.5-3130.9m, 3140.2-3143.3m, 3146-3151.1m, and 3211-3215.7m reflects that the reservoir fractures in this section are relatively developed. Figure 1 Track 10: The envelope area of ​​the acoustic-neutron porosity overlap method at the well section 3140.3-3146.9m shows a "spiky" feature, reflecting the development of low-angle fractures in this section. Figure 1 Track 11: The results of electrical imaging interpretation indicate that there are multiple fractures of different occurrences at 3123-3124m, 3141-3143m, 3145-3148m, and 3201-3203.5m. Figure 1 No. 12 and Figure 2-Figure 5The result of electrical imaging fracture identification; 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 characteristics of high-yield layers in this area, which usually have more developed fractures, it reflects that the fractures in 1#, 2#, 5#, 7#, and 8# are more developed. Figure 1 No. 13.

[0064] Comprehensive analysis shows that the fractures in the fourth section of the well are relatively developed. The fracture development response characteristics reflected by logging curves such as wellbore diameter, uranium element, acoustic-neutron porosity overlap method, and deep and shallow dual lateral differences 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 is 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 know that the 7.3PU, 59.2us / ft, 2.59g / cm 3 In addition, the fitting coefficients b1, b2, and b3 are taken as 0.3, 0.35, and 0.5 respectively, and the calculation formula of 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 know that the is 37.34Ω·m; in addition, the fitting coefficients f1 and f2 are taken as 0.45 and 0.65 respectively, and the calculation formula of the macro high-angle crack development index is:

[0078]

[0079] According to the above formula, the macro high-angle crack development index calculation F is completed d , the calculation results are shown in Figure 6 Question 10.

[0080] The fine and low-angle crack development index F was calculated by data normalization method. c and the 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 , macroscopic 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 calculation formula of the fracture development index 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 Track 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, 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 sandstone reservoir fracture sparse section are selected as data points, and the calibration coefficients a and K1 are taken as 0.084 and 0.13 respectively. The permeability fitting formula of the sandstone reservoir fracture sparse section based on the porosity-permeability relationship is established:

[0093]

[0094] The calculation results can be seen in Figure 6 Track 14.

[0095] Using scale factors a, K1, F′ L , the calibration 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 Track 14.

[0098] The calculation results based on the porosity-permeability relationship fitting formula and the calculation results of sandstone reservoir permeability based on the fracture development index of conventional logging data were compared with the core experimental analysis results. It can be seen that the method of the present invention (the calculation results of sandstone reservoir permeability based on the fracture development index of conventional logging data) is more consistent with the core experimental analysis results, see Figure 6 Track 14.

[0099] The present invention comprehensively utilizes the fracture development index, conventional logging data, and core experiment data analysis results to establish a permeability calculation model based on the fracture development index, which 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 sandstone reservoir fracture-undeveloped section are selected as data points, and the permeability fitting formula of the sandstone reservoir fracture-undeveloped section based on the porosity-permeability relationship is established: Where: K Φ The permeability calculated for the fracture-less 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: 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.

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 finding fracture development sections in sandstone reservoirs through photoelectric absorption cross-section index anomalies, finding fracture development sections through wellbore anomalies, finding fracture development sections through uranium element anomalies, finding fine and low-angle fracture development sections through neutron acoustic wave and density curve anomalies, and finding high-angle fracture development sections through 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 fracture development parameters includes calculating fine and low-angle fracture development indexes, calculating macroscopic high-angle fracture development indexes, and normalizing fine and low- and high-angle fracture 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 logging curve: First, select the CNL, AC and DEN curves of the sandstone reservoir fracture sparse section, perform average processing, and calculate the average values ​​of the cumulative CNL, AC and DEN: n=(DEP end -DEP sta ) / Δsi (4) In formulas (1), (2) and (3), CNL, AC and DEN are compensation neutron, compensation acoustic wave and compensation density respectively; are the average values ​​of compensated neutron, compensated acoustic wave and compensated density in the porous sandstone reservoir with undeveloped fractures; CNLi is the compensated neutron value at each depth; ACi is the compensated acoustic wave value at each depth; DENi is the compensated density value at each depth; DEP end DEP is the end depth. sta is the starting depth; Δsi is the depth sampling interval; Then, the measured CNL, AC, and DEN values ​​were compared with the fracture-free section of the sandstone reservoir. Establish relationships and construct mathematical models of fine and low-angle crack development indexes: In formula (5): F c 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 3, characterized in that: The calculation of the macroscopic high-angle fracture development index refers to constructing a macroscopic high-angle fracture development index calculation model based on the change rate of the 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: n=(DEP end -DEP sta ) / Δsi (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 without fracture development in the sandstone reservoir; Then, 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: In formula (8): F d 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 1, characterized in that: The normalization processing of the fine and low-angle crack development index refers to the normalization of the fine and low-angle crack development index F by a data normalization method. c and the macroscopic high-angle crack development index F d Perform dimensionless processing respectively: In formula (9) and (10): F′ c is the normalized fine and low-angle crack development index; F′ d is the normalized macroscopic high-angle crack development index; F c (n), maxF c (n), min F 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), min F d (n) are respectively the value of the macroscopic high-angle fracture development index at a certain depth point in the sandstone reservoir section, the maximum value of the macroscopic high-angle fracture development index in the sandstone reservoir section, and the minimum value of the macroscopic 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 1, 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 the permeability of a sandstone reservoir based on a 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 index to construct a fracture development index calculation formula based on conventional well logging data: In formula (11), W1 and W2 are the sensitivity coefficients of the three porosity curves and resistivity curve to the fracture development index, respectively.

9. The method for determining the permeability of a sandstone reservoir based on a 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 F based on conventional well logging data by a data normalization method. L Perform dimensionless processing: 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 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. A method for determining sandstone reservoir permeability based on fracture development index according to any one of claims 4, 5 and 7, characterized in that: The fitting coefficient and the sensitivity coefficient are determined based on production experience, and the calibration coefficient is determined by the porosity-permeability relationship of the rock electrical experiment.

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