A comprehensive prediction and evaluation method for fractures in thin interbedded tight oil and gas mixed rock reservoirs

Abstract

The present invention belongs to the technical field of comprehensive evaluation of reservoir fractures, and discloses a method for comprehensive prediction and evaluation of fractures in thin interbedded tight oil and gas mixed rock reservoirs. Based on the causes of rock fracture, rock formations with similar lithology and physical properties are regarded as separate fracture units, and it is found that the fracture development index is negatively correlated with the thickness of the rock formation, so a lithology thickness evaluation factor (YXHD) is constructed; there are differences in the intensity of fracture formation in different structural areas, so corresponding structural deformation intensity factors (SFD) can be established for different structural areas; finally, considering the distribution of structural principal stress, the law of fracture development near the fault, and the fracture effect area, a fracture fracture intensity factor (FFD) is proposed. Combining three fracture development evaluation indicators, a comprehensive fracture evaluation model is established, and numerical simulation calculations are performed after trend constraints are imposed on the grid of the fracture prediction indicators, forming a comprehensive prediction technology for thin interbedded tight oil reservoir fractures based on the coordinated characterization of internal and external causes of rock fractures, and the prediction results are consistent with the well profile fracture identification rate of 88%.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive evaluation of reservoir fractures, and in particular relates to a comprehensive prediction and evaluation method for thin interbedded tight oil-gas mixed rock reservoir fractures. Background Art

[0002] Fracture prediction of limestone, shale and sandstone composite tight oil and gas reservoirs under mixed sedimentary background is a hot topic in current oil and gas exploration research. Mixed sedimentary rocks are usually formed in delta front-lake sedimentary background, with the characteristics of fine-grained sedimentation, diverse lithology, frequent thin-layer interaction and strong heterogeneity. The geological causes of reservoir fracture development caused by mixed deposition of multiple lithologies are complex. At present, the comprehensive evaluation technology of reservoir fractures at home and abroad is mainly aimed at single lithology, and no comprehensive fracture prediction and evaluation method based on thin interbedded tight oil and gas mixed sedimentary rock reservoir has been formed. Moreover, it is difficult to accurately characterize the natural fractures developed in mixed sedimentary rock reservoirs through a single evaluation index. Summary of the invention

[0003] The purpose of the present invention is to solve the defects of the above-mentioned prior art and provide a method for comprehensive prediction and evaluation of fractures in thin interbedded dense oil and gas mixed rock reservoirs.

[0004] The present invention adopts the following technical solution:

[0005] A method for comprehensive prediction and evaluation of fractures in thin interbedded tight oil and gas mixed rock reservoirs, comprising the following steps:

[0006] (1) A rock layer with the same or similar lithology and physical properties can be regarded as a separate fracture unit. The fracture development index is negatively correlated with the increase of rock layer thickness, so the lithology thickness evaluation factor (YXHD) is constructed;

[0007] (2) There are differences in the intensity of crack formation in different tectonic zones under the same tectonic deformation intensity (when the value of the main tectonic curvature is the same), so the corresponding tectonic deformation intensity factor (SFD) can be established for different tectonic zones;

[0008] (3) Considering the distribution of tectonic principal stress, the development law of fractures near the fault, and the fracture effect zone, a comprehensive parameter, namely the fracture rupture factor (FFD), is proposed;

[0009] (4) Based on the three fracture development evaluation indicators and starting from the core mechanism of rock fracture, a comprehensive fracture evaluation model is established. Trend constraints are imposed on the grid of fracture prediction indicators. The three indicators after constraints are numerically simulated and calculated according to the work area, ultimately achieving reservoir fracture prediction.

[0010] Furthermore, in step (1), since the lithology of the tight oil and gas mixed rock reservoir is complex, the main lithologies are limestone, shale and sandstone, and the degree of development of fractures in each lithology is different, the thickness of the rock layer is considered by distinguishing the lithology, and the lithology thickness evaluation factors of the three lithology systems are established. The specific evaluation factor expressions are as follows:

[0011]

[0012] Where: YXHD is the evaluation factor of lithology thickness; a1, a2, a3 represent the relative development rate of fractures in limestone, shale and sandstone respectively (the lithology is distinguished based on the statistical results of fracture identification of core and well logging, a1+a2+a3=1);

[0013] —Represented as the comprehensive parameters of lithology thickness after normalization of the ratio of mechanical layer number to thickness of evaluation layer for limestone, shale and sandstone, respectively.

[0014] Furthermore, the step (1) further includes: based on the ratio of the number of single rock layers with similar lithology in a single well to the total thickness of the rock layers, a rock layer thickness inverse index (J) is introduced to reflect the severity of the lithology change. The lithology thickness evaluation factors (YXHD) of the three lithology systems can also be expressed by the following formula:

[0015] YXHD=a1J1+a2J2+a3J3

[0016] Where: J1, J2 and J3 are the inverse indices of the thickness of the limestone, shale and sandstone layers in the evaluation layer, respectively.

[0017] Furthermore, in step (2), based on the relationship between the principal curvature value (SC) of different structural zones and the relative density of fractures, corresponding structural deformation intensity factors can be established for different structural zones.

[0018] Furthermore, the step (3) is as follows: according to the fault morphology, the fault can be divided into three types, namely, isolated straight faults, intersecting faults and faults with convex curvature. The rock fracture laws in different fault effect concentration areas are different. In order to consider the distribution of structural principal stress, the law of crack development near the fault and the fault effect area, a comprehensive parameter (FFD) is proposed. The specific calculation formula is:

[0019] FFD=(S1,S2,S2)*『(A1,A2,A3,A4)*FD+(A1,A2,A3,A4)*STR』

[0020] Where: FFD is the fracture strength factor; A1, A2, A3, A4 are the correction factors of different structural zones, S1, S2, S3 are the tuning factors of different effect zones, which are determined by the statistics of the relative density of single well fractures in different fault effect zones, and FD is the density of fractures associated with the fault zone.

[0021] Furthermore, the step (4) is: constructing two core fracture elements, element one is expressed as lithology thickness evaluation factor*structural deformation intensity factor; element two is expressed as lithology thickness evaluation factor*fracture fracture intensity factor, calculating the lithology thickness evaluation factor, structural deformation intensity factor and fracture fracture intensity factor of each well, and establishing a comprehensive fracture evaluation model by constructing the core fracture elements and using the multivariate linear regression relationship between the relative density of well point fractures and the core fracture elements:

[0022] Relative density of fractures = 0.123 + 2.826 * YXHD * FFD + 1.337 * SFD * YXHD

[0023] The structural deformation intensity factor relies on the simulation of the main structural curvature, and different correction values ​​are assigned according to the structural division to realize the spatial constraint relationship of the structural deformation intensity factor; the lithology thickness evaluation factor is constructed using the well point value on the well point, and is constrained in the plane space using the rock layer thickness inverse index J and the page-to-ground ratio.

[0024] Furthermore, in step (4), the three constrained indicators are divided into 60×100m grids according to the work area, the continuous space is discretized, and the prediction model is numerically simulated by random sampling and verification, and finally the fracture prediction of different layers in the study area is realized.

[0025] Beneficial effects of the present invention:

[0026] Based on the causes of internal and external rock fractures, the present invention constructs three fracture development evaluation indicators. Starting from the core mechanism of rock fracture, a comprehensive fracture evaluation model is established to realize the fracture prediction of different layers in the study area. The prediction results are consistent with the fracture development of the well profile by 88%.

[0027] The present invention realizes the comprehensive evaluation technology of fractures in mixed rock reservoirs. The comprehensive evaluation results of fractures are highly reliable and accurate, overcoming the inaccuracy caused by the traditional single lithology fracture evaluation method. The comprehensive evaluation of fractures in mixed rock reservoirs is the basis for the production and development of oil and gas fields. The more accurate the fracture prediction results are, the higher the recovery rate of the oil and gas fields will be. The comprehensive fracture prediction map established by three fracture development evaluation indicators is an indispensable part of the comprehensive evaluation of reservoirs, and also lays a geological foundation for the subsequent dynamic development of production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the present invention.

[0029] Figure 2 : It is a relationship diagram between the rock formation thickness inverse index (J) and the fracture development index in the study area provided by an embodiment of the present invention, wherein (a) is the relationship between the rock formation thickness inverse index and the fracture development index of the first section; (b) is the relationship between the rock formation thickness inverse index and the fracture development index of the second section; (c) is the relationship between the rock formation thickness inverse index and the fracture development index of the third section; (d) is the relationship between the rock formation thickness inverse index and the fracture development index of the Da'anzhai section.

[0030] Figure 3 This is the relationship between the principal curvature value (SC) of the structure in different structural areas and the relative density of fractures provided by the embodiment of the present invention.

[0031] Figure 4 It is a plane distribution diagram of the fracture rupture intensity factor of the study area provided by an embodiment of the present invention.

[0032] Figure 5 1 is a graph showing the relationship between the inverse index of rock layer thickness and the page-to-ground ratio provided by the embodiment of the present invention. (a) is a graph showing the relationship between the inverse index of the thickness of the first section and the page-to-ground ratio; (b) is a graph showing the relationship between the inverse index of the thickness of the second section and the page-to-ground ratio; (c) is a graph showing the relationship between the inverse index of the thickness of the third section and the page-to-ground ratio; (d) is a graph showing the relationship between the inverse index of the thickness of the Daanzhai section and the page-to-ground ratio.

[0033] Figure 6 It is a comprehensive prediction map of cracks in the Da'anzhai section provided by the embodiment of the present invention. Among them, (a) is a comprehensive prediction map of cracks in the first section; (b) is a comprehensive prediction map of cracks in the second section; (c) is a comprehensive prediction map of cracks in the third section.

[0034] FIG. 7( a ) is a graph showing the relationship between the relative density of the predicted fractures in the first section and the fracture development index identified in a single well provided by an embodiment of the present invention;

[0035] FIG. 7( b ) is a graph showing the relationship between the relative density of fractures predicted in the second segment and the fracture development index identified in a single well provided by an embodiment of the present invention;

[0036] FIG. 7( c ) is a graph showing the relationship between the relative density of the predicted fractures in the third segment and the fracture development index identified in a single well, provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] like Figure 1 As shown, the embodiment of the present invention provides a method for comprehensive prediction and evaluation of fractures in thin interbedded tight oil and gas mixed rock reservoirs, comprising the following steps:

[0039] In the first step, a rock layer with the same or similar lithology and physical properties can be regarded as a separate fracture unit. The fracture development index is negatively correlated with the increase of rock layer thickness, so the lithology thickness evaluation factor (YXHD) is constructed.

[0040] In the second step, the crack formation intensity in different tectonic areas is different under the same tectonic deformation intensity (when the value of the main tectonic curvature is the same), so the corresponding tectonic deformation intensity factor (SFD) can be established for different tectonic areas;

[0041] The third step is to propose a comprehensive parameter, namely the fracture rupture factor (FFD), by considering the distribution of structural principal stress, the law of fracture development near the fault, and the fracture effect zone;

[0042] The fourth step is to integrate the three fracture development evaluation indicators, start from the core mechanism of rock fracture, establish a comprehensive fracture evaluation model, impose trend constraints on the grid of fracture prediction indicators, perform numerical simulation calculations on the three constrained indicators according to the work area, and finally realize reservoir fracture prediction.

[0043] (1) Lithology thickness evaluation factor (YXHD): A rock layer with the same or similar lithology and physical properties is regarded as a separate fracture unit. The fracture development index and layer thickness of each rock layer in the Da'anzhai section are statistically analyzed and it is found that the fracture development index is negatively correlated with the increase of rock layer thickness. Since the main lithologies in the study area are limestone, shale and sandstone, the degree of fracture development of each lithology is different. Therefore, when considering the thickness of the rock layer, the lithology is distinguished to achieve the lithology thickness evaluation factor of the three lithology systems. The specific evaluation factor expression is as follows.

[0044]

[0045] Where: YXHD is the evaluation factor of lithology thickness; a1, a2, a3 represent the relative development rate of fractures in limestone, mudstone and sandstone respectively (the lithology is determined by the statistics of fracture identification results of core and logging, a1+a2+a3=1);

[0046] —Represented as the comprehensive parameters of lithology thickness after normalization of the ratio of mechanical layer number to thickness of evaluation layer for limestone, shale and sandstone, respectively.

[0047] It also includes the introduction of the rock thickness reverse index (J) based on the ratio of the number of single rock layers with similar lithology in a single well to the total thickness of the rock layer, which can reflect the severity of the lithology change. By statistically analyzing the relationship between the rock thickness reverse index and the fracture development index of each well, it can be seen that as the rock thickness reverse index increases, the more severe the lithology change is, the higher the degree of fracture development is (e.g. Figure 2 shown).

[0048] Since the study area is large and the structure is complex, the relationship between the rock thickness inverse index and the fracture development index in different structural areas is fitted separately. The function equation of the fracture development index (y) and the rock thickness inverse index (J) in each structural area is:

[0049] Daanzhai Section 1:

[0050] Fenggu-Gaomiao structure: y=0.2913*J 0.9414 ; Fuxing structure: y=0.5104*ln(J)+0.3036; Hexinchang-Shiquanchang structure: y=0.172*J+0.1105; Zhongjiang-Huilong structure: y=0.3891*ln(J)+0.3342.

[0051] Daanzhai Section 2:

[0052] Fenggu-Gaomiao structure: y=0.2954*J 1.2553 ; Fuxing structure: y = 0.6951*ln(J)+0.3851; Hexinchang-Shiquanchang structure: y = 0.1613*e 0.6149*J ; Zhongjiang-Huilong structure: y=0.7009*ln(J)+0.3821.

[0053] Daanzhai Section 3:

[0054] Fenggu-Gaomiao structure: y=0.4764*J 0.6049 ; Fuxing structure: y = 0.0473*e 2.3875*J ; Hexinchang-Shiquanchang structure: y=0.1501*e 0.8309*J ; Zhongjiang-Huilong structure: y=0.032*e 2.4714*J .

[0055] The main lithologies of the Da'anzhai section are limestone, shale and sandstone. The degree of development of fractures in each lithology is different. Therefore, when considering the thickness of the rock layer, it is achieved by distinguishing the lithology. The present invention establishes the lithology thickness evaluation factor (YXHD) of the three lithology systems. The specific evaluation factor expression is as follows:

[0056] YXHD=a1J1+a2J2+a3J3

[0057] a1, a2, a3—represent the relative development rate of fractures in limestone, shale and sandstone respectively (the lithology is determined by the statistics of fracture identification results of core and well logging, a1+a2+a3=1);

[0058] J1, J2, J3—respectively, the thickness inverse indexes of limestone, shale, and sandstone layers in the evaluation layer.

[0059] (2) Structural deformation intensity factor (SFD): The structure of the study area is complex. Based on the relationship between the principal curvature value (SC) and the relative density of fractures in different structural areas (e.g. Figure 3 As shown), the present invention establishes corresponding structural deformation intensity factors according to different structural areas.

[0060] Fuxing structure: SFD = 0.3419 * SC + 0.3066 (N = 2, R 2 =1.0000)

[0061] Fenggu-Gaomiao structure: SFD = 0.4042SC 0.2925 (N=12, R 2 =0.4521)

[0062] Hexing Field-Shiquan Field Structure: SFD = 0.0549*exp(4.5747*SC)(N = 7, R 2 =0.8498)

[0063] Structure near Zhongjiang-Huilong: SFD = 0.1123*exp(6.2072*SC)(N = 6, R 2 =0.5553)

[0064] (3) Fault fracture factor (FFD): According to the fault morphology, it can be divided into three types, namely isolated straight faults, intersecting faults and faults with convex curvature. The rock fracture laws in different fault effect concentration areas are different. The faults in the study area are mainly isolated straight faults and intersecting faults. The effect areas near these faults are stress concentration areas during the generation, development and movement of faults. The rocks here are very easy to break and the cracks are generally well developed.

[0065] The present invention is a comprehensive parameter that takes into account the distribution of structural principal stress, the law of crack development near the fault, and the fracture effect zone. The specific calculation formula is:

[0066] FFD=(S1,S2,S2)*『(A1,A2,A3,A4)*FD+(A1,A2,A3,A4)*STR』

[0067] Where: FFD is the fracture strength factor;

[0068] A1, A2, A3, and A4 are correction factors for different structural zones, respectively, which are determined by the statistics of the relative density of fractures in single wells in different structural zones. A1 is the correction factor for the Fuxing structural zone, and its value is 0.365 this time; A2 is the correction factor for the Fenggu-Gaomiao structural zone, and its value is 0.286 this time; A3 is the correction factor for the Hexingchang-Shiquanchang structural zone, and its value is 0.312 this time; A4 is the correction factor for the Zhongjiang-Huilong structural zone, and its value is 0.348 this time.

[0069] S1, S2, and S3 represent the tuning factors of different effect zones, respectively, which are determined by the statistics of the relative density of single-well fractures in different fault effect zones. S1 is the tuning factor of the terminal effect zone, and its value is 0.365 this time; S2 is the tuning factor of the fault effect zone in the multi-fault intersection transition zone, and its value is 0.378 this time; S3 is the tuning factor of the fault bulge effect zone, and its value is 0.251 this time.

[0070] FD is the density of fractures associated with the fault zone, and the FD expression is: FD = -0.1272*L + 0.4547 (R = 0.827), where L is the normal distance to the adjacent fault.

[0071] STR is the distribution of principal structural stress within 2.5 km of the fault-controlled area.

[0072] According to the above judgment principle, the fracture strength distribution of the study area was established (such as Figure 4 shown).

[0073] (4) Establish a comprehensive evaluation model for fractures: According to the causal relationship of fracture formation, and based on a variety of mathematical simulations or statistical algorithm attempts, the present invention reconstructs two core fracture elements. The first element is expressed as the lithology thickness evaluation factor * structural deformation intensity factor; the second element is expressed as the lithology thickness evaluation factor * fracture fracture intensity factor. Sixteen wells in the study area were randomly selected to calculate the lithology thickness evaluation factor, structural deformation intensity factor and fracture fracture intensity factor of each well. Through the construction of core fracture elements, a comprehensive fracture evaluation model was established using the multivariate linear regression relationship between the relative density of well point fractures and the core fracture elements:

[0074] Relative density of fractures = 0.123 + 2.826 * YXHD * FFD + 1.337 * SFD * YXHD

[0075] The structural deformation intensity factor is simulated by the principal curvature of the structure. Different correction values ​​are assigned according to the structural division to achieve the spatial constraint relationship of the structural deformation intensity factor. The lithology thickness evaluation factor is constructed using the well point value at the well point, and is constrained in the plane space using the rock layer thickness inverse index (J) and the shale-to-stratum ratio (the ratio of the shale thickness to the formation thickness in the Da'anzhai section). This constraint relationship is based on phase control. From the perspective of single well analysis, the thicker the shale is, the more the limestone and mud shale appear as thin interlayers (such as Figure 5 shown.)

[0076] The constraint relationship expression between the inverse index of rock layer thickness and the page-to-ground ratio established in each layer section of the present invention is as follows:

[0077] Large section: J = 2.5719*x 1.0994 (R 2 =0.3844)

[0078] Second stage: J = 2.5974*x 0.8216 (R 2 =0.2660)

[0079] Big three sections: J = 2.9763*x 0.8676 (R 2 =0.3004)

[0080] The lithology thickness evaluation factor can be used to calculate the page-to-land ratio distribution based on the lithology distribution obtained by geophysical inversion, and then the lithology thickness evaluation factor grid trend constraint is performed, and the well points are corrected with the actual well point calculation values.

[0081] The present invention divides the lithology thickness evaluation factor, fracture rupture intensity factor and structural deformation intensity factor after trend constraint into 60×100m equal grids according to the work area morphology, and discretizes the continuous space. Then, numerical simulation calculation is performed through random sampling and verification according to the established prediction model, and the fracture prediction of different layers in the study area is realized, such as Figure 6 As shown, the distribution of fractures from the third section to the first section.

[0082] From the comprehensive prediction results of fractures, it can be seen that the density of fracture development gradually decreases from the third section of Da'anzhai to the first section of Da'anzhai, and fractures are relatively developed in the fault structure area, the local structure area of ​​Zhongjiang-Huilong, the Fenggu structure area and the Fuxing area. From the fracture prediction results, the fracture density predicted in each layer section is consistent with the fracture density identified by a single well. The predicted values ​​and single well values ​​of the simulation well and the verification well are basically near the 45-degree line. The prediction results of the present invention are reliable (as shown in Figure 7 (a), Figure 7 (b), and Figure 7 (c)).

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A comprehensive prediction and evaluation method for fractures in thin interbedded tight oil and gas mixed rock reservoirs, characterized in that: The following steps are involved: In the first step, a rock layer with the same or similar lithology and physical properties is regarded as a separate fracture unit. The fracture development index is negatively correlated with the increase of rock layer thickness, so the lithology thickness evaluation factor YXHD is constructed; Since the lithology of tight oil and gas mixed rock reservoirs is complex, including limestone, shale and sandstone, and the degree of fracture development of each lithology is different, the thickness of the rock layer is considered by distinguishing the lithology, and the lithology thickness evaluation factor of the three lithology systems is established. The expression of the lithology thickness evaluation factor is as follows: Where: YXHD is the evaluation factor of lithology thickness; a1, a2, a3 represent the relative development rate of fractures in limestone, shale and sandstone respectively; the lithology is distinguished based on the statistical results of fracture identification of core and well logging, where a1+a2+a3=1; —Represented as the comprehensive parameters of lithological thickness after normalization of the ratio of mechanical layers of limestone, shale and sandstone to the thickness of the evaluation layer; Based on the ratio of the number of single rock layers with similar lithology in a single well to the total thickness of the rock layer, the rock layer thickness inverse index J is introduced to reflect the severity of the lithology change. The lithology thickness evaluation factor YXHD of the three lithology systems can be expressed by the following formula: YXHD=a1J1+a2J2+a3J3 Where: J1, J2 and J3 are the inverse indices of the thickness of the limestone, shale and sandstone layers in the evaluation layer, respectively; The second step is that the crack formation intensity in different tectonic areas is different under the same tectonic deformation intensity, so the corresponding tectonic deformation intensity factor SFD is established in different tectonic areas; Based on the relationship between the principal curvature value SC and the relative density of fractures in different structural areas, the corresponding structural deformation intensity factor is established according to different structural areas; The third step is to consider the distribution of structural principal stress, the law of fracture development near the fault, and the fracture effect zone, and propose a comprehensive parameter, namely the fracture rupture strength factor FFD; According to the fault morphology, there are three types, namely isolated straight faults, intersecting faults and faults with convex curvature. The rock fracture laws in different fault effect concentration areas are different. In order to consider the distribution of structural principal stress, the law of crack development near the fault and the fault effect area, a comprehensive parameter FFD is proposed. The specific calculation formula is: FFD=(S1,S2,S2)*『(A1,A2,A3,A4)*FD+(A1,A2,A3,A4)*STR』 Where: FFD is the fracture strength factor; A1, A2, A3, A4 are the correction factors of different structural areas, S1, S2, S3 are the tuning factors of different effect areas, which are determined by the statistics of the relative density of single well fractures in different fault effect areas, FD is the density of fractures associated with the fault zone, and STR is the distribution of the main structural stress within 2.5 km of the fault-controlled area; The fourth step is to comprehensively consider the three fracture development indicators, namely, the lithology thickness evaluation factor YXHD, the structural deformation intensity factor SFD, and the fracture rupture intensity factor, and establish a fracture comprehensive evaluation model based on the core mechanism of rock fracture. The trend of the grid of fracture prediction indicators is constrained, and the three constrained indicators are numerically simulated and calculated according to the work area, so as to finally realize reservoir fracture prediction. Two core fracture factors were constructed. The first factor was expressed as lithology thickness evaluation factor * structural deformation intensity factor; the second factor was expressed as lithology thickness evaluation factor * fracture fracture intensity factor. The lithology thickness evaluation factor, structural deformation intensity factor and fracture fracture intensity factor of each well were calculated. Through the construction of core fracture factors, a comprehensive fracture evaluation model was established using the multivariate linear regression relationship between the relative density of well point fractures and the core fracture factors: Relative density of fractures = 0.123 + 2.826 * YXHD * FFD + 1.337 * SFD * YXHD The structural deformation intensity factor relies on the simulation of the main structural curvature, and different correction values ​​are assigned according to the structural division to realize the spatial constraint relationship of the structural deformation intensity factor; the lithology thickness evaluation factor is constructed using the well point value on the well point, and is constrained in the plane space using the rock layer thickness inverse index J and the page-to-ground ratio.

2. The method according to claim 1, characterized in that The three constrained indicators are divided into equal grids of 60×100m according to the work area, and the continuous space is discretized. The prediction model is numerically simulated through random sampling and verification, and finally the fracture prediction of different layers in the study area is realized.

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