CN114060022B - Shale gas productivity prediction method based on multi-scale fault development characteristics - Google Patents
Shale gas productivity prediction method based on multi-scale fault development characteristics Download PDFInfo
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Abstract
The invention discloses a shale gas productivity prediction method based on multi-scale fault development characteristics, which comprises the following steps of: s1: carrying out fault classification on the area to be detected according to the fault development characteristics of the area to be detected; s2: and according to fault classification, predicting the shale gas productivity of the area to be tested. The invention carries out classified research on shale gas storage conditions in a complex structure area, particularly fault distance, a disconnected layer position, fracture period times, fault dip angle and the like of a fault, has important reference value for improving shale gas exploration and development effects, and provides technical support and basis for effective exploration and development of shale gas in a basin margin complex fracture development area.
Description
Technical Field
The invention belongs to the technical field of shale gas development, and particularly relates to a shale gas productivity prediction method based on multi-scale fault development characteristics.
Background
Because the current important shale gas main producing area in China has the characteristics of old times, over-maturity, structural deformation and multiple periods, the shale gas storage conditions in different areas have great difference. On one hand, the existing method considers that the fold and fracture determine the rock deformation and natural crack development degree, thereby controlling the enrichment and capacity of shale gas; on the other hand, the fracture property, scale, combination mode, period and derived structural fracture are considered to be important factors influencing the shale gas layer preservation condition; the fault level and the development degree are also considered to be main reasons for the enrichment preservation and the productivity difference of the shale gas. For complex structural areas with basin edge fracture development, the yield control effect of the multi-scale fault on the shale gas is more obvious, the characterization of fault development characteristics in the areas is developed, the influence of the gas on the productivity is discussed, and the method has important research value and reference significance for improving the exploration and development effects of the shale gas.
Disclosure of Invention
The invention aims to solve the problem of improving the exploration and development of shale gas and provides a shale gas productivity prediction method based on multi-scale fault development characteristics.
The technical scheme of the invention is as follows: a shale gas productivity prediction method based on multi-scale fault development characteristics comprises the following steps:
s1: carrying out fault classification on the area to be detected according to the fault development characteristics of the area to be detected;
s2: and according to fault classification, predicting the shale gas productivity of the area to be tested.
Further, in step S1, the specific method for fault classification of the area to be measured is as follows: fault classification is carried out on the area to be detected by taking fault distance, direction, a disconnected layer position, an extension length and a fault plane dip angle as classification indexes;
the method comprises the following steps of taking an area to be detected with the fault distance larger than 300m as a first-level fault, taking the area to be detected with the fault distance of 200m-300m as a second-level fault, taking the area to be detected with the fault distance of 100m-200m as a third-level fault, taking the area to be detected with the fault distance of 50m-100m as a fourth-level fault, and taking the area to be detected with the fault distance of less than 50m as a fifth-level fault;
dividing the region to be detected into an NE direction fault, an NW direction fault and a near EW direction fault according to the direction;
dividing the area to be detected into a first-level fault, a second-level fault, a third-level fault and a fourth-level fault according to the disconnection layer;
taking the area to be detected with the extension length of 7km-10km as a first-level fault, taking the area to be detected with the extension length of 5km-7km as a second-level fault, taking the area to be detected with the extension length of 3km-5km as a third-level fault, taking the area to be detected with the extension length of 1km-3km as a fourth-level fault, and taking the area to be detected with the extension length of less than 1km as a fifth-level fault;
and taking the area to be detected with the fault plane dip angle smaller than 45 degrees as a first-level fault, taking the area to be detected with the fault plane dip angle of 45-60 degrees as a second-level fault, and taking the area to be detected with the fault plane dip angle larger than 60 degrees as a third-level fault.
Further, in step S2, the specific method for predicting the shale gas capacity according to the fault distance includes: and performing regression analysis on daily average output of the shale gas of all levels of faults and the area to be detected to determine the shale gas productivity.
Further, in step S2, the specific method for predicting the shale gas energy according to the horizon includes: in the first-level fault, the surface of the Hanwu system is disconnected, and shale gas does not exist; in the secondary fault, the secondary fault is disconnected from a quintet group to a two-fold system, the fault distance is 200m as a boundary, the secondary fault is divided into a large fault and a small fault, regression analysis is respectively carried out on the large fault and the small fault, and the shale gas capacity is determined; in the three-level fault, the three-level fault is longitudinally disconnected from the bottom layer of the Han-Wu system to the Longmaxi group, the fault distance is 200m as a boundary, the three-level fault is divided into a large-scale fault and a small-scale fault, regression analysis is respectively carried out on the large-scale fault and the small-scale fault, and the shale gas capacity is determined; in the four-stage fault, the shale gas yield is the largest.
Further, in step S2, the specific method for predicting the shale gas productivity according to the orientation includes: in early EW faults, it does not affect shale gas production; dividing the middle NE direction fault into a large fault and a small fault by taking the fault distance of 200m as a boundary in the middle NE direction fault, respectively carrying out regression analysis on the large fault and the small fault, and determining the distance between the middle NE direction fault and the large fault so as to determine the shale gas capacity; in the later EW fault, the fault distance is 200m as a boundary, the middle NE fault is divided into a large fault and a small fault, regression analysis is respectively carried out on the large fault and the small fault, the distance between the middle NE fault and the large fault is determined, and accordingly shale gas productivity is determined.
Further, in step S2, the specific method for predicting the shale gas capacity according to the fault plane dip angle includes: dividing the fault into a first angle fault, a second angle fault and a third angle fault according to the fault dip angle distribution of the area to be tested, and performing regression analysis according to the fault types of different dip angles and the daily average output of the shale gas to determine the shale gas capacity.
The invention has the beneficial effects that: the invention carries out classified research on shale gas storage conditions in a complex structure area, particularly fault distance, a disconnected layer position, fracture period times, fault dip angle and the like of a fault, has important reference value for improving shale gas exploration and development effects, and provides technical support and basis for effective exploration and development of shale gas in a basin margin complex fracture development area.
Drawings
FIG. 1 is a flow chart of a shale gas productivity prediction method;
FIG. 2 is a view of the position of a Changning shale gas field configuration;
FIG. 3 is a structural diagram of north-west direction measuring lines of Changning construction producing area;
FIG. 4 is a schematic view of north-west direction measurement lines of Changning construction producing area;
FIG. 5 is a fracture layout of the Longmaxi group in Changning construction and production area;
FIG. 6 is a sectional classification chart of Longmaxi group in Changning construction and production area;
FIG. 7 is a sectional view of a Longmaxi group in Changning production area according to fault-distance classification fitting;
FIG. 8 is a sectional classification fitting graph of a Longmaxi group of Changning production area according to a disconnected horizon;
FIG. 9 is a drawing of a Changning Ministry of birk streams according to orientation fault classification fit;
FIG. 10 is a graph of daily average production versus fault run length analysis;
FIG. 11 is a graph of the correlation between daily average yield and fault plane dip.
Detailed Description
The embodiments of the present invention will be further described with reference to the accompanying drawings.
As shown in fig. 1, the invention provides a shale gas productivity prediction method based on multi-scale fault development characteristics, which comprises the following steps:
s1: carrying out fault classification on the area to be detected according to the fault development characteristics of the area to be detected;
s2: and according to fault classification, predicting the shale gas productivity of the area to be tested.
In the embodiment of the present invention, in step S1, the specific method for performing fault classification on the area to be detected includes: fault classification is carried out on the area to be detected by respectively taking the fault distance, the direction, the disconnection position, the extension length and the fault plane dip angle as classification indexes;
the method comprises the following steps of taking an area to be detected with the fault distance larger than 300m as a first-level fault, taking the area to be detected with the fault distance of 200m-300m as a second-level fault, taking the area to be detected with the fault distance of 100m-200m as a third-level fault, taking the area to be detected with the fault distance of 50m-100m as a fourth-level fault, and taking the area to be detected with the fault distance of less than 50m as a fifth-level fault;
dividing the region to be detected into an NE direction fault, an NW direction fault and a near EW direction fault according to the direction;
dividing the area to be detected into a first-level fault, a second-level fault, a third-level fault and a fourth-level fault according to the disconnection layer;
taking the area to be detected with the extension length of 7km-10km as a first-level fault, taking the area to be detected with the extension length of 5km-7km as a second-level fault, taking the area to be detected with the extension length of 3km-5km as a third-level fault, taking the area to be detected with the extension length of 1km-3km as a fourth-level fault, and taking the area to be detected with the extension length of less than 1km as a fifth-level fault;
and taking the area to be detected with the fault plane inclination angle smaller than 45 degrees as a first-level fault, taking the area to be detected with the fault plane inclination angle between 45 degrees and 60 degrees as a second-level fault, and taking the area to be detected with the fault plane inclination angle larger than 60 degrees as a third-level fault.
In the embodiment of the present invention, in step S2, the specific method for predicting the shale gas capacity according to the fault distance includes: and performing regression analysis on daily average output of the shale gas of all levels of faults and the area to be detected to determine the shale gas productivity.
In the embodiment of the present invention, in step S2, the specific method for predicting the shale gas energy according to the horizon includes: in the first-level fault, the surface of the Hanwu system is disconnected, and shale gas does not exist; in the secondary fault, the secondary fault is disconnected from a quintet group to a two-fold system, the fault distance is 200m as a boundary, the secondary fault is divided into a large fault and a small fault, regression analysis is respectively carried out on the large fault and the small fault, and the shale gas capacity is determined; in the three-level fault, the three-level fault is longitudinally disconnected from the bottom layer of the Han-Wu system to the Longmaxi group, the fault distance is 200m as a boundary, the three-level fault is divided into a large-scale fault and a small-scale fault, regression analysis is respectively carried out on the large-scale fault and the small-scale fault, and the shale gas capacity is determined; in the four-stage fault, the shale gas yield is the largest.
In the embodiment of the present invention, in step S2, the specific method for predicting the shale gas production energy according to the orientation includes: in early EW faults, it does not affect shale gas production; dividing the middle NE direction fault into a large fault and a small fault by taking the fault distance of 200m as a boundary in the middle NE direction fault, respectively carrying out regression analysis on the large fault and the small fault, and determining the distance between the middle NE direction fault and the large fault so as to determine the shale gas capacity; in the later EW fault, the fault distance is 200m as a boundary, the middle NE fault is divided into a large fault and a small fault, regression analysis is respectively carried out on the large fault and the small fault, the distance between the middle NE fault and the large fault is determined, and accordingly shale gas productivity is determined.
In the embodiment of the present invention, in step S2, the specific method for predicting shale gas productivity according to the fault plane dip angle includes: dividing the fault into a first angle fault, a second angle fault and a third angle fault according to the fault dip angle distribution of the area to be tested, and performing regression analysis according to the fault types of different dip angles and the daily average output of the shale gas to determine the shale gas capacity.
The present invention will be described with reference to specific examples.
The Changning obstetric area is located at the intersection of the south Sichuan fold belt and the Looshan fold breaking belt, and the main body is located in the building slope. The structure positions of dorsiflexion, hallucination and alpine top structures of east o-Chaning, basalis-canthus and Dazhai, the west of Jia village and xi, and temple, Chinese plaza and Temple of north o lotus. The east is affected by extrusion stress from the structure zone of east China-Xiang Hui West, the west is affected by remote transmission of extrusion stress from Longmen mountain direction, the north is limited by Sichuan basin and Huayi mountain fracture zone, the south is superposed with extrusion and lifting action caused by structure conversion action of purple cloud-Rohdea fracture zone, and the triangle zone is in a multi-stress structure, and has a multi-group complex combined structure.
As shown in FIG. 2, the Changning dorsiflexion structure has an axial direction of NWW Western direction, the nucleus of the dorsiflexion exposes Hanwu system, and the nuclei of Ordovician, Shizishi, Diyi, Sanyi and Jurassic systems expose around the nucleus in turn, the nucleus develops a series of retrograde faults, which mostly dominate NE direction and NNW, and the fault usually crosses Hanwu system. The secondary folds in the anticline develop relatively, the NE wing of the secondary folds is relatively steep, the eastern village nose-shaped structure of the NE trend develops, the eastern oblique end is connected with the anticline and the hallow syncline of the camp mountain, and finally disappears in the near EW direction; the SW wings are gradually and obliquely transited towards the Jianwu, the central Jurassic formation is mainly exposed in the nuclear part of the oblique area, and the two wings are sequentially the lower Jurassic formation and the tri-stacked formation.
As shown in fig. 3-4, the fracture development features of the changning production area are more complex in the longitudinal direction and the plane development features according to the results of the fine interpretation and the structural analysis of the three-dimensional earthquake. The longitudinal upper fault type mainly takes a reverse fault as a main part, and is mainly divided into three types according to the fracture horizon and the scale, wherein one type is a fault disconnected from a Wufeng-Longmaxi group to a binary system, the other type is a fault disconnected from the bottom of a Hanwu system to the Wufeng-Longmaxi group, and the other type is an internal fracture only disconnected from the Wufeng-Longmaxi group; from the aspect of planar distribution, the main development NE-direction and NW-direction fracture systems in the Changning production area are main, the next is a near EW-direction fracture system, a certain regularity is presented from the west to the east by fault development, the west fault is large in scale and is mainly in the NE direction, and the most part is upwards broken to a two-fold system; the fault scale of the middle part is small, the internal fracture of the quintet-Longmaxi group is mainly broken, the fault development of the east N209 well region is complex, except for two on-day fault layers, the trend of other faults comprises an NE direction and an NW direction, the dip angle distribution is different, and the fracture layer is mainly broken from the bottom of a Hanwu system to the quintet-Longmaxi group.
As shown in fig. 5, the extending orientations of most of the longmaxi faults in the longning shale gas production area are unstable, and have composite superposition and transformation phenomena, particularly, part of the faults in the NE direction extend in the NE direction as a whole, but are obviously formed by compounding two or three orientations such as NE and NW (NWW directions), and show structural stress superposition characteristics in different directions at different times; secondly, according to the action mechanism of extrusion stress, the forming time of the NE direction fault is earlier than that of the NW direction, the near EW direction fault is small in scale, the fault is under-developed, the superposition relationship is not obvious, and the forming time is earlier than that of the NE direction. In summary, the formation and evolution of the shale gas production area fault are mainly influenced by three-stage structure movement, wherein an early-stage major marchan structure is extruded from south to north to form an approximate EW fold and fault, a middle stage is extruded from NW-SE direction by the uplift of Qinghai-Tibet plateau to form an NE direction fault which is widely developed in a research area, and a later stage is extruded from NE direction stress generated by the combined action of the uplift of south Jiangnan snow peaks and the uplift of Chuanzhong to form an NW direction fault in the research area finally, so that the current fault system is formed finally.
As shown in fig. 6, the longning-birthplace fault is complex in development, and the longning-birthplace longma fault is classified according to different classification standards according to the broken horizon, the broken distance, the period, the extending length, the dip angle of the fault plane and the like, which are shown in table 1.
TABLE 1
The influence difference of the faults of different scales on the shale gas productivity is large. In order to discuss the influence of the fault on the shale gas productivity in multiple angles, the fault is used forThe research and statistics of 49 horizontal wells with similar production systems in the Changning production area are taken as samples, the daily average yield of each well in one year is counted under the condition that the working systems are the same, the mathematical fitting analysis is carried out by selecting the daily average yield and the distances from the midpoint of a point A (the starting point of a horizontal well section) and the midpoint of a point B (the terminal point of the horizontal well section) of the horizontal well, and the daily average yield is 10 multiplied by 10 4 m 3 And d, as a boundary between high yield and low yield, discussing the influence of the fault under different classification and classification standards on the shale gas productivity.
As shown in fig. 7, the relationship between the five-level fault and the daily average output is respectively counted according to the fault distance, and the shale gas productivity and the fault distance are closely related through comparison. The fault distance of the first-level fault and the second-level fault is large, fault fracture zones and large-scale cracks develop, hydrocarbon is mainly discharged, shale gas is not stored, the well productivity near the first-level fault and the second-level fault is generally poor, and high yield (the daily average yield is more than or equal to 10 multiplied by 10) can be obtained by drilling wells 1.7km away from the first-level fault and 1.3km away from the second-level fault according to the result of regression analysis 4 m 3 D); the fault distance of the third-level fault is relatively small, the destructiveness is relatively weak, and high yield can be obtained for wells which are 0.9km away from the third-level fault; the fault pitches of the four-level fault and the five-level fault are small, the influence on the shale gas storage condition and the productivity is very little, and the high yield can be obtained by 0.4km away from the two types of faults.
The more faults of the disconnected layer positions, the longer the rock mass fracture zone extends in the longitudinal direction, the poor sealing performance is caused, and particularly, the deep fracture that the rock mass fracture zone cuts into the substrate downwards and penetrates the earth surface upwards is not beneficial to the storage of shale gas.
According to the relation between the four-level fault and the daily average yield of the disconnected horizon statistics, the first-level fault disconnects the Hanwu system-earth surface, the shale gas reservoir is completely destroyed within 5km near the fault, and the well drilling is almost not displayed, as shown in figure 8. The second-order fault is disconnected from a new stratum at the upper part in the longitudinal direction, the second-order fault is disconnected from the quincunx group to a two-stacking system, shale gas is enabled to be transported to a conventional reservoir along the fault surface when the butt joint surface of a target layer and other strata is too much in the process that the new stratum is staggered upwards, but the butt joint probability of the shale gas and other strata is weakened along with the reduction of the fault distance, so that the sealing performance of the shale gas is enhanced. Because the fault has large fault distance range, the method is a researchConveniently, the fault is divided into a large fault and a small fault by taking the fault distance of 200m as a boundary to carry out regression analysis respectively, and the result shows that high yield (the daily average yield is more than or equal to 10 multiplied by 10) is obtained in the fault development region of the disconnected quincunx group-binary system 4 m 3 And/d) at least 1km and 0.8km from such large and small faults. The fault of the third-level fault is longitudinally broken to the Longmaxi group due to the fact that the fault mainly occurs at the lower part of the shale gas layer, theoretically, the storage effect on the shale gas is not large when the fault is broken to a new upper stratum, and the fault is divided into a large fault and a small fault by taking the fault distance of 200m as a boundary for regression analysis, and the fact that high yield (the daily average yield is more than or equal to 10 multiplied by 10) is found if the high yield is obtained 4 m 3 D), only requiring at least 1km from such large faults. For the four-level fault developing in the quincunx-Longmaxi group, the wells near the fault are high in yield from the statistical result, and the fact that the internal small fault and associated cracks are favorable for desorption of adsorbed gas and can be used as a migration channel to accelerate enrichment of shale gas without destructiveness.
As shown in fig. 9, the Changning production zone fault can be approximated by an early EW-direction fault, a middle NE-direction fault, and a late NW-direction fault according to azimuth. The development of the near EW to the fault in the early stage is the least, the fault is associated with a small-scale fault when the fold is formed, the fault has small fault distance and is more developed in layers, and from the statistical structure, the fault has no destructive influence on the storage condition, and the fault does not need to be over concerned in the exploration and development process. The NE in the middle stage is widely distributed to faults, the Longmaxi group-two-fold system is broken more, the change of the fault distance range is large, the fault distance is divided into a large fault and a small fault by taking 200m as a boundary to carry out regression analysis respectively, and the result shows that the NE in the middle stage is high in yield (the daily average yield is more than or equal to 10 multiplied by 10) 4 m 3 D), at least 1.1km from such large faults. The late NW fault is divided into small fault and large fault in the same way with the fault distance of 200m, and high yield (daily average yield is more than or equal to 10X 10) 4 m 3 D), at least 1.2km from such large faults. Therefore, the early EW direction fault of the Changning construction production area has certain 'construction' for shale gas productivitySex ", while the scale of development of the NW-direction and NE-direction faults varies, small faults with a fault distance of less than 200m have relatively little effect on the storage conditions of shale gas, and large faults with a fault distance of more than 200m have a certain adverse effect on the storage conditions.
As shown in fig. 10, the fault extension itself has little influence on the sealing performance, the fault with small extension generally only develops in the layer, and has no damage to the storage condition, while the fault with long extension distance generally cuts through more layers, damages the top and bottom plates and even the cover layer condition, and may develop only in the layer, which is related to the fault distance, the inclination angle, the cut-through layer position, and other factors. From the correlation result of different elongation and daily average yield, the correlation between the daily average yield and the elongation is not large, and has no direct relation. The reason is analyzed, the storage condition of the shale gas is closely related to the fault distance, the cut-off position, the orientation and the like of the fault in the longitudinal direction, the fault extension length is not related to the fault distance, the cut-off position and the orientation, even if the fault with the extension length exceeding 5km is adopted, the fault is probably not large, the cut-off position is only cut off to the quincunx group, the upper new stratum is not cut off, and the influence on the storage condition is not large.
As shown in fig. 11, fault plane dip has a significant effect on the seal in the longitudinal direction of the reservoir. The place that the fault plane is steep, the self-sealing nature of shale gas has been destroyed to a certain extent to the high angle fracture of the fault of high angle and associated, is unfavorable for shale gas to preserve, and low inclination fault cuts through still less level generally, and vertical offset is also less, and the fault plane inclination is often the seal ability reinforce by the place that becomes slowly suddenly.
Dividing the fault into a low-angle fault, a medium-angle fault and a high-angle fault according to the distribution condition of the dip angle of the fault in the production area, and performing regression analysis on the fault type of the blind dip angle and the daily average yield respectively, wherein the result shows that if high yield is required (the daily average yield is more than or equal to 10 multiplied by 10) 4 m 3 And/d) at least 1.4km away from the fault of the high-angle fault development area, at least 1km away from the medium-angle fault and 0.4km away from the low-angle fault. It can be seen that low angle faults are more favorable for gas containment, while medium-high angle faults have an adverse effect on storage conditions, especially of high angle faultsThe destructive effect is more remarkable.
In summary, (1) the fault of the Changning production area has complex development characteristics in the longitudinal direction and on the plane. Mainly taking a reverse fault as a main part in the longitudinal direction, wherein the inclination angle is 45-70 degrees, and the fault mainly comprises a Tongtian fault of an east boundary, a fault of a five-peak-LongMa stream group disconnected to a two-fold system, an internal fault of a Hanwu system disconnected to the five-peak-LongMa stream group and a fault of the five-peak-LongMa stream group disconnected from the bottom of a Hanwu system; the main development NE-directional and NW-directional fracture systems on the plane are the main ones, followed by the near EW-directional fracture system, with the EW-directional fault forming the earliest, NE-directional fault stage the second, and NW-directional fault forming the latest.
(2) According to the general development characteristics of the Longmaxi faults in the Changning construction and production area, the classified classification and division research is respectively carried out on the Longmaxi faults according to different classification standards such as a disconnection layer position, a fault distance, an azimuth (period), an extension length, a fault plane dip angle and the like.
(3) The fault of different grades and types has different influence degrees on the shale gas productivity of the Changning construction production area. The fault distance, the disconnection position and orientation (period number), the inclination angle and the like have obvious influence on the shale gas production capacity, the fault distance is larger than 200m, the inclination angle is larger than 60 degrees, the fault which is upwards broken through to a two-fold system or above has the largest influence on the storage condition and the productivity of the shale gas reservoir, and the influence of the fault extension length on the shale gas production capacity is not obvious.
(4) In the exploration and development process of the shale gas in south China, the research on the shale gas storage conditions in a complex structural area is carried out by carrying out classification research on fault distance, a disconnected layer, fracture period times, fault dip angles and the like of faults, and the method has an important reference value for improving the exploration and development effect of the shale gas.
The working principle and the process of the invention are as follows: the fault type and the development characteristics of the area to be tested are systematically analyzed through three-dimensional seismic fine interpretation and structural analysis, and the fault is layered, so that the relation between the fault and the shale gas productivity under different classification and classification standards is determined on the basis.
The invention has the beneficial effects that: the invention is used for researching shale gas storage conditions of complex structural areas, particularly carrying out classification research on fault distance, disconnection positions, fracture periods, fault inclination angles and the like of faults, has important reference value for improving shale gas exploration and development effects, and provides technical support and basis for effective exploration and development of shale gas in basin-edge complex fracture development areas.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (1)
1. A shale gas productivity prediction method based on multi-scale fault development characteristics is characterized by comprising the following steps:
s1: carrying out fault classification on the area to be detected according to the fault development characteristics of the area to be detected;
s2: according to fault classification, shale gas productivity prediction is carried out on the area to be tested;
in step S1, the specific method for performing fault classification on the area to be detected is as follows: fault classification is carried out on the area to be detected by respectively taking the fault distance, the direction, the disconnection position, the extension length and the fault plane dip angle as classification indexes;
the method comprises the following steps of taking an area to be detected with the fault distance larger than 300m as a first-level fault, taking the area to be detected with the fault distance between 200m and 300m as a second-level fault, taking the area to be detected with the fault distance between 100m and 200m as a third-level fault, taking the area to be detected with the fault distance between 50m and 100m as a fourth-level fault, and taking the area to be detected with the fault distance smaller than 50m as a fifth-level fault;
dividing the region to be detected into an NE direction fault, an NW direction fault and a near EW direction fault according to the direction;
dividing the area to be detected into a first-level fault, a second-level fault, a third-level fault and a fourth-level fault according to the disconnection layer;
taking the area to be detected with the extension length of 7km-10km as a first-level fault, taking the area to be detected with the extension length of 5km-7km as a second-level fault, taking the area to be detected with the extension length of 3km-5km as a third-level fault, taking the area to be detected with the extension length of 1km-3km as a fourth-level fault, and taking the area to be detected with the extension length of less than 1km as a fifth-level fault;
taking the area to be detected with the fault plane dip angle smaller than 45 degrees as a first-level fault, taking the area to be detected with the fault plane dip angle of 45-60 degrees as a second-level fault, and taking the area to be detected with the fault plane dip angle larger than 60 degrees as a third-level fault;
in the step S2, the specific method for predicting the shale gas capacity according to the fault distance includes: performing regression analysis on daily average output of the shale gas of all levels of faults and the area to be detected to determine shale gas productivity;
in step S2, the specific method for predicting the shale gas energy according to the disconnected horizon includes: in the first-level fault, the surface of the Hanwu system is disconnected, and shale gas does not exist; in the secondary fault, the secondary fault is disconnected from a quintet group to a two-fold system, the fault distance is 200m as a boundary, the secondary fault is divided into a large fault and a small fault, regression analysis is respectively carried out on the large fault and the small fault, and the shale gas capacity is determined; in the three-level fault, the three-level fault is longitudinally disconnected from the bottom layer of the Han-Wu system to the Longmaxi group, the fault distance is 200m as a boundary, the three-level fault is divided into a large-scale fault and a small-scale fault, regression analysis is respectively carried out on the large-scale fault and the small-scale fault, and the shale gas capacity is determined; in the four-stage fault, the shale gas yield is maximum;
in step S2, the specific method for predicting the shale gas productivity according to the orientation includes: in early EW faults, it does not affect shale gas production; dividing the middle NE direction fault into a large fault and a small fault by taking the fault distance of 200m as a boundary in the middle NE direction fault, respectively carrying out regression analysis on the large fault and the small fault, and determining the distance between the middle NE direction fault and the large fault so as to determine the shale gas capacity; dividing the middle NE direction fault into a large fault and a small fault in the late EW fault by taking the fault distance of 200m as a boundary, respectively carrying out regression analysis on the large fault and the small fault, and determining the distance between the middle NE direction fault and the large fault so as to determine the shale gas capacity;
in the step S2, the specific method for predicting the shale gas capacity according to the fault plane dip angle includes: dividing the fault to be detected into a first angle fault, a second angle fault and a third angle fault according to the fault dip angle distribution of the region to be detected, and performing regression analysis according to the fault types of different dip angles and daily average output of shale gas to determine the shale gas capacity;
in the step S2, according to fault classification, the specific method for predicting shale gas productivity in the area to be tested is as follows: the method comprises the steps of counting daily average yield of each well in one year under the condition that the working system is the same, carrying out regression analysis by taking the daily average yield as a vertical coordinate and taking the distance between a point in each level of fault and an A point or a B point of a horizontal well as a horizontal coordinate, wherein the regression analysis specifically comprises the steps of fitting to obtain a curve of the daily average yield relative to the distance between the point in each level of fault and the A point or the B point of the horizontal well by adopting mathematical fitting analysis, and respectively discussing the influence of the fault on shale gas productivity under different fault grading standards according to indexes of break distance, direction, break horizon, extension length and fault plane dip angle according to the curve obtained by fitting, wherein the A point of the horizontal well is the starting point of the horizontal well section, and the B point is the terminal point of the horizontal well section.
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