CN112324412A - Method for forming complex seam net through volume fracturing - Google Patents
Method for forming complex seam net through volume fracturing Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/70—Compositions for forming crevices or fractures characterised by their form or by the form of their components, e.g. foams
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/80—Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/261—Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking the formation
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
Abstract
The invention belongs to the technical field of volume fracturing, and particularly relates to a method for forming a complex fracture network by volume fracturing. The method comprises the following steps: 1) carrying out uneven perforation in the horizontal well, wherein the uneven perforation is that the number of perforations of two adjacent clusters of perforations in a perforation section is different, and two adjacent clusters of perforations form main cracks with corresponding number difference after uneven perforation; 2) pumping liquid carbon dioxide into the main fracture formed in the step 1), and fracturing the stratum and extending the fracture; 3) pumping the sand mullion into the stratum and supporting the cracks formed in the step 2). According to the method, different numbers of main cracks are generated in different clusters during perforation by utilizing the nonuniformity of the perforation, pressure difference exists among the main cracks, secondary cracks can be formed under the action of the pressure difference among the clusters, and the secondary cracks can communicate with the adjacent main cracks. The fracturing fluid can enter the secondary fractures through the main fractures, and the generated fractures are supported by the subsequent propping agents, so that the complexity of the fractures is improved.
Description
Technical Field
The invention relates to the technical field of volume fracturing of low-permeability and unconventional reservoirs, in particular to a method for forming a complex fracture network by volume fracturing.
Background
Due to the characteristics of low porosity and low permeability of low permeability and unconventional reservoirs, a complex seam network is formed in the reservoirs by adopting a volume fracturing technology to obtain a good development effect. The complex fracture network is characterized in that a relation between a difference value of two horizontal main stresses of a reservoir and a fracture extension net pressure is utilized, when the extension net pressure of the fracture is larger than the difference value of the two horizontal main stresses or critical pressure required by a natural fracture of the reservoir, a secondary fracture is formed in the lateral direction of the main fracture, a plurality of secondary fractures and microcracks are finally extended and communicated along the wall surface of the main fracture, and a vertically and horizontally staggered three-dimensional complex network-shaped fracture system is formed in a stratum, so that the seepage distance of oil gas in a matrix in any direction to the fracture is shortest, the integral permeability of the reservoir is greatly improved, and the productivity and the ultimate recovery ratio of a low-permeability unconventional reservoir oil-gas well are improved.
The volume fracturing technology can form a complex fracture network with a plurality of mutually interwoven fractures in a reservoir, and the volume fracturing technology is used for enabling natural fractures to continuously expand and brittle rocks to generate shear slip in the fracturing process to form the complex fracture network with the natural fractures and artificial fractures criss-cross mutually, so that the modification volume of the reservoir is increased, and the permeability of the reservoir and the final recovery ratio of an oil field are improved.
At present, the common horizontal well volume fracturing technologies at home and abroad mainly comprise horizontal well staged fracturing, repeated fracturing, synchronous fracturing and the like.
The staged fracturing of the horizontal well is to separate the well shaft by using a packer or other chemical materials, fracture one well section at a time in the horizontal well shaft, then fracture the well section by section, wherein each fracturing section also comprises a plurality of perforation clusters, and under ideal conditions, a plurality of cracks generated by each perforation cluster are converged into one crack at a short distance from the well shaft, and finally enough cracks are pressed. However, in the process of volume fracturing transformation, the horizontal casing pipe is subjected to complex mechanical behaviors such as shearing, sliding and dislocation and changes of stress fields, so that the casing pipe is deformed and fails.
Repeated fracturing refers to fracturing twice or more times in the same well. As production is carried out, the fracture flow conductivity of the first pressed open is seriously reduced due to the influence of factors such as proppant breaking, stratum particle blocking, fracture closure and the like, so that the yield is reduced and even stagnated. Repeated fracturing is effective in treating hypotonic, natural fracture development, layered and heterogeneous formations, but the success of repeated fracturing is closely related to the success of fracture diversion, which has uncertainty.
Synchronous fracturing is to fracture two or more parallel horizontal wells simultaneously, and a fracture network in a certain range is generated by the interaction of the opposite extension of transverse fractures at the tips of the fractures. The more the number of wells synchronously fractured is, the better the stress interference effect is, and the more complex fracture network is easily generated. Synchronous fracturing has obvious yield increase in a short period of the shale gas well, small influence on the working area environment, high completion speed and fracturing cost saving, but the synchronous fracturing requires that the tips of the cracks between wells are close to each other and cannot completely communicate the two cracks. Therefore, the optimization of the fracture length and the optimization of the well spacing of the synchronous fracturing well are particularly important, and no related theoretical support exists at present.
Therefore, the existing volume fracturing technologies at home and abroad respectively have advantages and disadvantages and application range, and have the characteristic of complex construction process, so that the complex fracture network in the stratum cannot be simply, conveniently and economically obtained to improve the recovery ratio of the unconventional reservoir stratum.
Disclosure of Invention
The invention aims to provide a method for forming a complex fracture network by volume fracturing, which aims to solve the problems that the existing volume fracturing method is complex in fracturing process, high in fracture uncertainty and incapable of simply and conveniently obtaining the complex fracture network of a stratum.
In order to achieve the purpose, the technical scheme of the method for forming the complex seam net by volume fracturing is as follows:
a method of forming a complex fracture network by volume fracturing, comprising the steps of:
1) carrying out uneven perforation in the horizontal well, wherein the uneven perforation is that the number of perforations of two adjacent clusters of perforations in a perforation section is different, and two adjacent clusters of perforations form main cracks with corresponding number difference after uneven perforation;
2) pumping liquid carbon dioxide into the main fracture formed in the step 1), and fracturing the stratum and extending the fracture;
3) pumping the sand mullion into the stratum and supporting the cracks formed in the step 2).
The method for forming the complex fracture network by volume fracturing utilizes the nonuniformity of the perforation to generate different numbers of main fractures in different clusters during perforation, and the clusters with more perforations in the same section have more generated main fractures, small friction in the fractures and more liquid carbon dioxide fracturing fluid entering amount; the clusters with few perforations generate few main cracks, the friction in the cracks is large, and the entering amount of liquid carbon dioxide fracturing fluid is small, so that the generated main cracks have stress interference among the cracks, namely, pressure difference exists among the cracks, secondary cracks can be formed under the action of the pressure difference among the clusters, and the secondary cracks can communicate with the adjacent main cracks. The fracturing fluid can enter the secondary fractures through the main fractures, and the generated fractures can be propped by the subsequent propping agents, so that the complexity of the fractures is improved. In addition, under the action of differential pressure, the fractured secondary fractures can spontaneously extend, and can communicate with a plurality of secondary fractures, microcracks and natural fractures to form a criss-cross three-dimensional complex reticular fracture system in the stratum, so that the seepage capacity of the reservoir is greatly improved.
In the step 1), in two adjacent clusters of perforation, the ratio of the number of the one cluster with more perforation number to the number of the one cluster with less perforation number is 1.2-4: 1. The cluster distance between two adjacent clusters of perforation is 10-30 meters. Non-uniform perforations, preferably having the above parameters, may create significant pressure imbalances between the fractures during the fracturing process, thereby creating stress disturbances between the fractures.
In the step 2), the pumping discharge capacity of the liquid carbon dioxide is 4-8m3And/min. The adoption of liquid carbon dioxide fracturing has good energizing effect, and the flow-back is fast and thorough after the fracturing; and CO2The viscosity is low, the penetrability is strong, can communicate the microcrack in the reservoir, can reduce rock fracture pressure simultaneously, is favorable to forming complicated crack.
In the step 3), the sand mixing fluid consists of a propping agent and slickwater fracturing fluid, and the sand ratio is 10-20%. Preferably, the proppant consists of 70-140 meshes of silt and 40-70 meshes of ceramsite.
To further improve the complexity of the seam net of the stratum, preferably, the method for forming the complex seam net by the above volume fracturing further comprises the following steps:
step 4): pumping a temporary plugging diverter into the stratum to plug the cracks, and continuously pumping fracturing fluid to make cracks;
step 5): the proppant is pumped into the formation.
In the step 4), liquid carbon dioxide fracturing fluid is continuously pumped in after temporary plugging to form cracks, so that the cracks can be diverted to form complex cracks. The fracturing fluid can be liquid carbon dioxide or slickwater.
Further preferably, the step 5) of pumping the proppant into the formation comprises injecting the proppant with different particle sizes and different sand ratios into the formation in the form of slugs. More preferably, the slugs include a preceding proppant slug, which is smaller in particle size and sand ratio, and a following proppant slug, which is larger in particle size and sand ratio. The proppant is injected in a slug mode, so that the migration distance of the proppant and the propping degree of the branch fracture can be improved, and the flow conductivity of a complex fracture system is improved. After the fracturing is carried out by combining the uneven perforation and the liquid carbon dioxide, a plurality of secondary fractures are formed, the secondary fractures can be supported by injecting the fracturing blender containing the propping agent in a slug type manner, a complex reticular fracture system is formed, and the seepage capability of a reservoir stratum is greatly improved.
Drawings
FIG. 1 is a schematic diagram of a horizontal well section of a heterogeneous perforation combined with liquid carbon dioxide fracturing in example 1 of the present invention;
FIG. 2 is a schematic illustration of heterogeneous perforation combined with liquid carbon dioxide fracturing to form a complex network of fissures in a formation in accordance with example 1 of the present invention;
FIG. 3 is a diagram of a rock sample before fracturing in a conventional fracturing manner in a comparative experiment;
FIG. 4 is a diagram of a rock sample fractured in a conventional fracturing manner in a comparative experiment;
FIG. 5 is a graph of a sample of rock before fracturing using the fracturing method of the example in a comparative experiment;
FIG. 6 is a diagram of a rock sample fracture after fracturing using the fracturing method of the example in a comparative experiment;
FIG. 7 is a graph of a fracture of a rock sample after fracturing using the fracturing method of the examples in a comparative experiment;
FIG. 8 is a detail view of a rock sample after fracturing using the fracturing method of the example in a comparative experiment;
in the figure, 1-horizontal well perforation section, 2-main fracture, 3-secondary fracture, 4-liquid carbon dioxide fracturing fluid flowing direction, and 5-natural fracture and microfracture in the stratum.
Detailed Description
The following examples are provided to further illustrate the practice of the invention.
In the following examples, the viscosity of the slickwater fracturing fluid is 5 to 8 mPas.
First, the volume fracturing of the invention forms a complex fracture network
Example 1
The method for forming the complex seam net by volume fracturing comprises the following steps:
1) and measuring stratum basic parameters such as the ground stress parameter of the reservoir, the rock physical property parameter, the microscopic pore characteristic, the reservoir sensitivity and the like, and designing a non-uniform perforation scheme.
In this embodiment, three clusters are perforated in a horizontal perforation interval with a cluster spacing of 15 meters. Only 15 holes were shot in the first cluster and 36 holes were shot in the second cluster; in the third shower 20 holes were punched.
2) Pumping liquid carbon dioxide into stratum in horizontal well with uneven perforation, wherein the discharge capacity is 6m3Min, the pumping amount of liquid carbon dioxide in the whole process is 300m3And fracturing to form a fracture. In other implementation cases, the liquid carbon dioxide pump displacement and the pump injection amount can be determined according to the formation small-scale fracturing test result and in combination with the fracturing optimization design result.
3) Pumping the sand mullion into the stratum and supporting the cracks formed in the step 2).
The sand mixing fluid consists of a propping agent and slickwater fracturing fluid, and the sand ratio is 15%. The proppant is prepared from 70-140 meshes of powder ceramic and 40-70 meshes of ceramsite according to the volume ratio of 3: 1. The injection amount of the mixed sand liquid is 600m3. In other implementation cases, the composition and injection amount of the mixed sand liquid can be determined according to the fracture form and the number obtained from the formation small fracturing test result and the subsequent fracturing optimization design result.
4) And determining the form of the formation fracture according to the ground stress parameters and the monitoring of the artificial fracture, and applying a temporary plugging diversion agent to plug the fracture.
In this example, the formation fractures are 3 main fractures formed along the perforation direction, a plurality of secondary fractures are formed after carbon dioxide injection, and the temporary plugging agent is injected by liquid carbon dioxide (the volume ratio of the liquid carbon dioxide to the temporary plugging agent is 10: 1, and the total injection amount is 150 m)3) The bridge plug is formed in the existing crack and continues to be 6m3Permin displacement injection 150m3And liquid carbon dioxide is used, so that more secondary cracks are formed in the fracturing fluid, and the complexity of the cracks is improved.
In other example scenarios, the injection amount of the temporary plugging working fluid and the subsequent fracture-creating fracturing fluid is determined according to the geostress parameters and the morphology of the formation fracture monitored for the artificial fracture. When more secondary cracks are formed, more temporary plugging working fluid and subsequent crack-forming fracturing fluid are pumped.
5) The proppant slug continues to be pumped into the formation, propping the fracture.
According to the fracturing optimization design, slickwater with the viscosity of 7mPa & s is injected with a propping agent, and the propping agent slug comprises two parts: one is 70/140 meshes of powder ceramic and 40/70 meshes of ceramsite 60m3The proportion is 6:4, the sand ratio is 10 percent, and the aim is to support the microcracks formed by temporary plugging steering; the other section of the filter is 40/70-mesh ceramsite proppant 60m3The sand ratio is 15 percent so as to support the cracks with larger sizes; slug injection can improve fracture complexity and conductivity.
6) And injecting a displacing liquid to displace the proppant slug in place.
In the above volume fracturing process, uneven perforation is combined with liquid carbon dioxide fracturing schematic diagram as shown in fig. 1, and in a horizontal well perforation section 1, the unevenness of perforation causes different numbers of main fractures 2 to be generated in different clusters. In the flowing direction 4 of the liquid carbon dioxide fracturing fluid, more main cracks are generated for clusters with more perforations in the same section, the friction in the cracks is small, and the entering amount of the liquid carbon dioxide fracturing fluid is large; the clusters with few perforations generate few main cracks, the friction in the cracks is large, and the entering amount of liquid carbon dioxide fracturing fluid is small, so that the generated cracks have stress interference among the cracks, namely, pressure difference exists among the cracks, secondary cracks 3 can be formed under the action of the pressure difference among the clusters and are supported by subsequent propping agents, and the complexity of the cracks is improved.
A schematic illustration of the formation of a complex network of seams in a formation is shown in conjunction with fig. 2. After uneven perforation fracturing and liquid carbon dioxide pumping, because pressure difference exists between main fractures formed by perforation or between artificial fractures and natural fractures, a plurality of secondary fractures are generated among the fractures under the action of the pressure difference, slick water fracturing fluid containing propping agents is injected in a slug type manner to support the secondary fractures, and the fractured secondary fractures can spontaneously extend under the action of the pressure difference to communicate the main fractures or the plurality of secondary fractures, the natural fractures and the microcracks 5 in the stratum, so that a complex reticular fracture system is formed, and the permeability of a reservoir stratum is greatly improved.
Example 2
The method for forming the complex seam net by volume fracturing of the embodiment only differs from the embodiment 1 in that:
in the step 1), the uneven perforation scheme related according to the basic parameters of the stratum is as follows: 5 clusters of perforations are arranged in the horizontal perforation well section, and the distance between clusters is 10 meters. Only 20 holes were punched in the first cluster and 40 holes were punched in the second cluster; the third cluster has 30 holes, the fourth cluster has only 10 holes, and the fifth cluster has 36 holes.
In the step 2), the discharge capacity of the liquid carbon dioxide is 8m3And/min, fracturing to form cracks. The pumping amount of the liquid carbon dioxide is 400m3。
In the step 4), slickwater with viscosity of 7 mPas is used for carrying the temporary plugging agent to be injected into the stratum to form bridge plugging in the existing cracks, and the thickness of the temporary plugging agent is continued to be 6m3Permin displacement injection 200m3And water is slick, so that more secondary cracks are formed by fracturing hydraulic fracture, and the complexity of the cracks is improved.
In the step 5), slickwater with viscosity of 7 mPas is injected with a propping agent, and the propping agent slug comprises two components: one is 70/140 meshes of powder ceramic and 40/70 meshes of ceramsite 80m3The proportion is 8:2, and the sand ratio is 10%; the other section of the filter is 30/50-mesh ceramsite proppant 40m3The sand ratio was 15%.
In other embodiments of the method of forming a complex slotted web by volume fracturing of the present invention, only steps 1) -3) may be performed to obtain a slotted web having a degree of complexity.
Second, Experimental example
The experimental example simulates the fracturing effect of conventional fracturing and the fracturing mode of the example.
And (3) applying a true triaxial simulation fracturing experimental device, adopting a cement sample with the size of 300 multiplied by 300mm, fracturing different perforated rock samples of a horizontal section in a conventional fracturing mode and the fracturing mode of the embodiment respectively, recording pressure change, and scanning fracture forms. The pre-and post-fractured rock sample plots for the conventional fracturing mode are shown in fig. 3 and 4, and the pre-and post-fractured rock sample plots for the fracturing mode of the example are shown in fig. 5-8.
The conventional fracturing mode adopts continuous and uniform hole distribution and slickwater fracturing fluid, three clusters of perforation are adopted, and each cluster of perforation has 3 holes. The method of example 1 is simulated by adopting uneven perforation and liquid carbon dioxide fracturing, and three clusters of perforations are formed, the number of each cluster of perforations is determined according to the proportion of each cluster of perforations in example 1, the number of the first cluster of perforations is 2, 5 holes are formed in the second cluster of perforations, and 3 holes are formed in the third cluster of perforations. The experimental ground stress is approximated by the true ground stress, overburden pressure (not shown), maximum horizontal principal stress (σ)H) Minimum horizontal principal stress (σ)h) 40MPa, 15MPa and 10MPa respectively.
According to the figures 3 and 4, under the reservoir stress condition and the test condition, after the rock sample adopting the conventional fracturing mode is fractured, the fracture form is a simple straight fracture which is perpendicular to the direction of the minimum horizontal main stress, the brittleness is not strong, and the fracture pressure is 25 MPa. And the crack is slightly deflected in the process of expanding, which is caused by slight difference of the mechanical properties of the natural rock core and the cement sample.
As can be seen from fig. 5-8, under reservoir stress and test conditions, more complex fractures were formed, with the vertical minimum horizontal principal stress direction fractures formed overall, but also extended in the maximum horizontal principal stress direction and passed through the liquid CO2After fracturing, the physical and mechanical properties of the rock sample are greatly changed, the rock sample develops in a flaky mode, brittleness is strengthened, cracks are continuously formed in the fracturing process, large new cracks can be generated due to the brittleness strengthening, the cracks generate large steering, and the crack forms are complex.
The physical model experiment results show that a criss-cross three-dimensional complex reticular seam system is easier to form in the stratum by adopting the fracturing mode of the embodiment, so that the permeability of the reservoir is greatly improved.
Claims (9)
1. A method of forming a complex fracture network by volume fracturing, comprising the steps of:
1) carrying out uneven perforation in the horizontal well, wherein the uneven perforation is that the number of perforations of two adjacent clusters of perforations in a perforation section is different, and two adjacent clusters of perforations form main cracks with corresponding number difference after uneven perforation;
2) pumping liquid carbon dioxide into the main fracture formed in the step 1), and fracturing the stratum and extending the fracture;
3) pumping the sand mullion into the stratum and supporting the cracks formed in the step 2).
2. The method for forming a complex fracture network by volume fracturing according to claim 1, wherein in step 1), the ratio of the number of the one cluster with the larger number of the perforations to the number of the one cluster with the smaller number of the perforations in two adjacent clusters of the perforations is 1.2-4: 1.
3. The method for forming a complex network of fractures by volume fracturing as claimed in claim 1, wherein in step 2), the cluster spacing between two adjacent clusters of perforations is 10-30 meters.
4. The method for forming a complex fracture network by volume fracturing according to any one of claims 1 to 3, wherein in the step 2), the pumping displacement of liquid carbon dioxide is 4 to 8m3/min。
5. The method for forming a complex slotted net by volume fracturing as claimed in claim 1, wherein in step 3), the fracturing fluid consists of proppant and slickwater fracturing fluid, and the sand ratio is 10-20%.
6. The method for forming a complex fracture network by volume fracturing as claimed in claim 5, wherein said proppant is composed of powder ceramic of 70-140 mesh and ceramsite of 40-70 mesh.
7. The method of volume fracturing to form a complex fracture network of any one of claims 1 to 3, further comprising:
step 4): pumping a temporary plugging diverter into the stratum to plug the cracks, and continuously pumping fracturing fluid to make cracks;
step 5): the proppant is pumped into the formation.
8. The method for forming a complex fracture network by volume fracturing according to claim 7, wherein in step 5), the pumping proppant into the formation comprises injecting proppant of different particle sizes and different sand ratios into the formation in the form of slugs.
9. The method of volume fracturing to form a complex fracture network of claim 8, wherein the slugs comprise a preceding proppant slug, which is smaller in size and sand ratio, and a following proppant slug, which is larger in size and sand ratio.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112814641A (en) * | 2021-03-19 | 2021-05-18 | 中国石油天然气集团有限公司 | Fracturing method of reservoir |
| CN113029898A (en) * | 2021-02-22 | 2021-06-25 | 西南石油大学 | Device and method for testing dynamic flow conductivity of crack and gas supply capacity of bedrock |
| CN114526046A (en) * | 2022-03-04 | 2022-05-24 | 西南石油大学 | Construction method of complex fracturing network system under simulated formation condition |
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| CN114526046B (en) * | 2022-03-04 | 2023-08-15 | 西南石油大学 | Construction method of complex fracture network system under simulated stratum condition |
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