CN112096362B

CN112096362B - Unconventional reservoir multi-cluster perforation competition cracking and expansion simulation method and device

Info

Publication number: CN112096362B
Application number: CN202011031263.0A
Authority: CN
Inventors: 曾凡辉; 郭建春; 张宇; 张蔷
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2020-09-27
Filing date: 2020-09-27
Publication date: 2021-10-22
Anticipated expiration: 2040-09-27
Also published as: CA3113764A1; CN112096362A

Abstract

The invention provides a method and a device for unconventional reservoir multi-cluster perforation competition cracking and expansion simulation, wherein the method comprises the following steps: generating a well circumferential stress prediction model according to the in-situ stress, the well bore induced stress and the well bore track; generating a seepage-stress fracture initiation pressure prediction model according to the well circumferential stress prediction model based on the percolation characteristics in the fracturing fluid injection process; and generating a multi-cluster perforation competition initiation and expansion model according to the well-periphery stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the initial initiation perforation cluster and the induced stress generated by the pressure change of the formation fluid based on the physical properties of the reservoir around the well, the stress heterogeneity of the ground around the well and the perforation pressure. The invention can better improve the fracturing transformation effect of unconventional reservoir stages and multiple clusters.

Description

Unconventional reservoir multi-cluster perforation competition cracking and expansion simulation method and device

Technical Field

The invention relates to the technical field of exploration and development of oil and gas fields, in particular to the technical field of development of unconventional oil and gas fields, and particularly relates to a method and a device for competitive fracture initiation and expansion simulation of unconventional reservoirs with multiple cluster jet holes.

Background

Unconventional oil and gas resources have larger energy occupation ratio and have huge exploration and development potential. Unconventional oil and gas resources will become important strategy successors of the conventional oil and gas resources in the future, and heterogeneity is the fundamental characteristic of the unconventional reservoir. The staged multi-cluster fracturing of the horizontal well is used as a key technology for the efficient development of unconventional oil gas, and the volumetric fracturing modification of a reservoir is realized through staged multi-cluster perforation fracturing acidizing modification. The precondition for effective reconstruction of volume fracturing is that each perforation cluster can be fractured and effectively extended. However, field tests and theoretical researches show that all perforation clusters can not crack and effectively extend due to the difference of ground stress, reservoir heterogeneity and the like and the shielding effect caused by stress shadow, so that the fracture acidizing effect of unconventional oil and gas reservoirs is limited.

In the prior art, research on a multi-cluster perforation and multi-fracture propagation model assumes that all perforation clusters are initiated at the same time to form fractures and propagate, and the influence factors and mechanisms of multi-fracture competitive propagation are intensively researched. In the actual fracture acidizing process, not all the perforation cluster fractures can be initiated at the same time. Therefore, the current research does not fully consider the influence of the ground stress, the reservoir heterogeneity, the induced stress of the fracture of the initial perforating cluster on the initiation of the subsequent perforating cluster and the initiation sequence; and the research on the multi-cluster perforation and the competitive fracture of the heterogeneous reservoir as a whole is not carried out. The law of competitive initiation and expansion of multiple cluster perforation of a heterogeneous reservoir is not clearly known, and the fracturing modification effect of multiple clusters of horizontal wells of unconventional reservoirs is restricted.

Disclosure of Invention

Aiming at the problems in the prior art, the unconventional reservoir multi-cluster perforation competition initiation and expansion simulation method and device provided by the invention comprehensively consider the influences of the shielding effect caused by the ground stress difference, reservoir heterogeneity and stress shadow on the initiation and expansion of the perforation clusters of the unconventional reservoir, and establish and solve a model on the basis of the influences, so that the fracturing modification effect of the unconventional reservoir multi-cluster subsection is better improved.

In order to solve the technical problems, the invention provides the following technical scheme:

in a first aspect, the invention provides a method for simulating competitive fracture initiation and expansion of unconventional reservoirs through multiple cluster jet holes, which comprises the following steps:

generating a well circumferential stress prediction model according to the in-situ stress, the well bore induced stress and the well bore track;

generating a seepage-stress fracture initiation pressure prediction model according to the well circumferential stress prediction model based on the percolation characteristics in the fracturing fluid injection process;

and generating a multi-cluster perforation competition initiation and expansion model according to the well-periphery stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the initial initiation perforation cluster and the induced stress generated by the pressure change of the formation fluid based on the physical properties of the reservoir around the well, the stress heterogeneity of the ground around the well and the perforation pressure.

In one embodiment, the generating a seepage-stress fracture initiation pressure prediction model according to the well-to-well stress prediction model based on the percolation characteristics in the injection process of the fracturing fluid comprises:

generating a fracture initiation pressure prediction model according to the well circumferential stress prediction model, the induced stress of the in-situ stress, the induced stress of the casing cement sheath and the stress field of the perforation hole;

and generating the seepage-stress crack initiation pressure prediction model according to the rock water absorption induced pore elastic coefficient and the crack initiation pressure prediction model by using a maximum tensile stress method.

In one embodiment, the generating a multi-cluster perforation competition initiation and propagation model according to the well-surrounding stress prediction model, the pressure prediction model, the dynamic flow allocation during multi-fracture initiation, the dynamic flow allocation during multi-fracture propagation, the fracture induced stress generated by the extension of a pre-initiated perforation cluster, and the induced stress generated by the pressure change of formation fluid based on the well-surrounding reservoir physical properties, the well-surrounding geostress heterogeneity and the perforation pressure comprises:

generating a perforation cluster crack expansion model according to the perforation cluster crack expansion stress field and the crack friction resistance;

and generating the multi-cluster-jet competitive cracking and expanding model according to the perforation cluster crack expanding model and the multi-cluster-jet competitive cracking and expanding physical model.

In one embodiment, the generating the multi-cluster-perforation competition fracture initiation and propagation model according to the perforation cluster fracture propagation model and the multi-cluster-perforation competition fracture initiation and propagation physical model includes:

generating a competition expansion model according to the hydraulic fracture expansion stress field, the hydraulic fracture friction resistance and the multi-fracture flow distribution model;

and generating the multi-cluster perforation competition crack initiation and expansion model according to the competition expansion model.

In one embodiment, the step of generating the multi-fracture flow distribution model comprises:

establishing a multi-fracture initiation flow distribution model corresponding to the injection to the initiation stage according to the flow and the pressure injected to the initiation stage;

establishing a multi-fracture expansion flow distribution model corresponding to the stages from initiation to expansion according to the flow and the pressure from the initiation to the expansion;

and generating the multi-fracture flow distribution model according to the multi-fracture initiation flow distribution model and the multi-fracture expansion flow distribution model.

In one embodiment, the step of generating the multiple-cluster-hole competition fracture initiation and expansion physical model comprises:

and generating a physical model of competitive initiation and expansion of the multiple clusters of perforation holes according to the characteristics of the initiation process of the single fracture, the flow distribution characteristics of the multiple fractures, the extension characteristics of the fracture of the initial initiation perforation cluster, the induced stress generated by the extension of the initial initiation perforation cluster to form the fracture and the induced stress generated by the pressure change of the formation fluid.

In a second aspect, the present invention provides an unconventional reservoir multi-cluster-hole competition fracture initiation and extension simulation apparatus, which includes:

the well circumferential stress prediction unit is used for generating a well circumferential stress prediction model according to the in-situ stress, the well bore induced stress and the well bore track;

the fracture initiation pressure prediction unit is used for generating a seepage-stress fracture initiation pressure prediction model according to the well peripheral stress prediction model based on the percolation characteristics in the injection process of the fracturing fluid;

and the multi-cluster model generation unit is used for generating a multi-cluster perforation competition initiation and expansion model according to the well circumferential stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the pre-initiated perforation cluster and the induced stress generated by the pressure change of the formation fluid based on the physical properties of the reservoir around the well, the stress heterogeneity around the well and the perforation pressure.

In one embodiment, the fracture initiation pressure prediction unit comprises:

the prediction model generation module is used for generating a fracture initiation pressure prediction model according to the well circumferential stress prediction model, the induced stress of the in-situ stress, the induced stress of the casing cement sheath and the stress field of the perforation hole;

and the fracture pressure prediction module is used for generating the seepage-stress fracture pressure prediction model according to the rock water absorption induced pore elastic coefficient and the fracture pressure prediction model by using a maximum tensile stress method.

In one embodiment, the multi-cluster model generation unit includes:

the expansion model generation module is used for generating a perforation cluster crack expansion model according to the perforation cluster crack expansion stress field and the crack friction resistance;

and the multi-cluster model generation module is used for generating the multi-cluster perforation competition cracking and expanding model according to the perforation cluster crack expanding model and the multi-cluster perforation competition cracking and expanding physical model.

In one embodiment, the multi-cluster model generation module comprises:

the competition expansion model generation module is used for generating a competition expansion model according to the hydraulic fracture expansion stress field, the hydraulic fracture friction and the multi-fracture flow distribution model;

and the multi-cluster model generation submodule is used for generating the multi-cluster perforation competition cracking and expanding model according to the competition expanding model.

In one embodiment, the unconventional reservoir multi-cluster-hole competition fracture initiation and extension simulation device further comprises: a flow distribution model generation unit configured to generate the multi-fracture flow distribution model, the flow distribution model generation unit including:

the flow model of the initiation stage is used for establishing a multi-crack initiation flow distribution model corresponding to the injection to the initiation stage according to the flow and the pressure injected to the initiation stage;

the expansion stage flow model is used for establishing a multi-fracture expansion flow distribution model corresponding to the fracture initiation to expansion stage according to the flow and the pressure from the fracture initiation to the expansion stage;

and the flow distribution model generation module is used for generating the multi-fracture flow distribution model according to the multi-fracture initiation flow distribution model and the multi-fracture expansion flow distribution model.

In one embodiment, the unconventional reservoir multi-cluster-hole competition fracture initiation and extension simulation device further comprises: and the physical model generating unit is specifically used for generating the multi-cluster-perforation competition initiation and expansion physical model according to the single-fracture initiation process characteristic, the multi-fracture flow distribution characteristic, the extension characteristic of the fracture of the first initiation perforation cluster, the induced stress generated by the extension of the first initiation perforation cluster to form the fracture and the induced stress generated by the change of the formation fluid pressure.

In a third aspect, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor implements the steps of the unconventional reservoir multiple-shower competitive fracture initiation and extension simulation method when executing the program.

In a fourth aspect, the present invention provides a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the unconventional reservoir multi-cluster-hole competitive fracture initiation and propagation simulation method.

From the above description, the unconventional reservoir multi-cluster-jet competitive fracture initiation and extension simulation method and device provided by the embodiment of the invention firstly generate a well-periphery stress prediction model according to the in-situ stress, the well-bore induced stress and the well-bore trajectory; then, based on the percolation characteristics in the injection process of the fracturing fluid, generating a seepage-stress crack initiation pressure prediction model according to the well-periphery stress prediction model; and finally, based on the physical properties of the reservoir around the well, the heterogeneity of the geostress around the well and the pressure of the perforation holes, generating a multi-cluster perforation competition initiation and expansion model according to a well-around stress prediction model, a pressure prediction model, the dynamic flow distribution in the multi-fracture initiation process, the dynamic flow distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the initiation perforation cluster and the induced stress generated by the pressure change of the formation fluid. The method comprehensively considers the influences of the shielding effect caused by the ground stress difference, the reservoir heterogeneity and the stress shadow on the cracking and the expansion of the perforation clusters of the unconventional reservoir, and establishes and solves the model on the basis of the influences, so that the fracturing transformation effect of the unconventional reservoir in the segmented and multi-cluster mode is better improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic flow chart of a unconventional reservoir multi-cluster-hole competitive fracture initiation and propagation simulation method according to an embodiment of the present invention;

FIG. 2 is a flow chart illustrating step 200 according to an embodiment of the present invention;

FIG. 3 is a flow chart illustrating step 300 according to an embodiment of the present invention;

FIG. 4 is a flowchart illustrating step 302 according to an embodiment of the present invention;

FIG. 5 is a flow chart illustrating step 500 according to an embodiment of the present invention;

FIG. 6 is a flowchart illustrating a step 600 according to an embodiment of the present invention;

FIG. 7 is a schematic flow chart of an unconventional reservoir multi-cluster-hole competitive fracture initiation and propagation simulation method according to an embodiment of the present invention;

FIG. 8 is a diagram illustrating an unconventional reservoir multi-cluster-hole competitive fracture initiation and propagation physical model in an embodiment of the present invention;

FIG. 9 is a graph of Young's modulus versus moisture content for a specific example application of the present invention;

FIG. 10 is a graph showing the distribution of different permeability combinations of competitive crack initiation and propagation trajectories (0.5 μ D-0.5 μ D-0.5 μ D) in an embodiment of the present invention;

FIG. 11 is a graph showing the distribution of different permeability combinations of competitive crack initiation and propagation trajectories (0.1 μ D-0.9 μ D-0.5 μ D) in an embodiment of the present invention;

FIG. 12 is a graph showing the distribution of different permeability combinations of competitive crack initiation and propagation trajectories (0.1 μ D-0.5 μ D-0.9 μ D) in an embodiment of the present invention;

FIG. 13 is a graph showing the combined competitive fracture initiation and propagation pressure distributions for different permeabilities (0.5 μ D-0.5 μ D-0.5 μ D-bottom hole pressure and newly calculated fracture initiation pressure (0-3600 s)) in an exemplary embodiment of the present invention;

FIG. 14 is a graph showing the combined competitive fracture initiation and propagation pressure distributions at different permeabilities (0.5 μ D-0.5 μ D-0.5 μ D-bottom hole pressure and newly calculated fracture initiation pressure (0-2 s)) in an exemplary embodiment of the present invention;

FIG. 15 is a graph showing the distribution of different permeability combinations of competitive initiation and propagation pressure (0.1 μ D-0.9 μ D-0.5 μ D-bottom hole pressure and newly calculated initiation pressure (0-3600 s)) in an example embodiment of the present invention;

FIG. 16 is a graph showing the distribution of different permeability combinations of competitive initiation and propagation pressures (0.1 μ D-0.9 μ D-0.5 μ D-bottom hole pressure and newly calculated initiation pressure (0-30 s)) in an example embodiment of the present invention;

FIG. 17 is a graph showing the distribution of different permeability combinations of competitive initiation and propagation pressure (0.1 μ D-0.5 μ D-0.9 μ D-bottom hole pressure and newly calculated initiation pressure (0-3600 s)) in an example embodiment of the present invention;

FIG. 18 is a graph showing the distribution of different permeability combinations of competitive initiation and propagation pressures (0.1 μ D-0.5 μ D-0.9 μ D-bottom hole pressure and newly calculated initiation pressure (0-30 s)) in an example embodiment of the present invention;

FIG. 19 is a schematic diagram of different permeability combinations competing for crack initiation and spread displacement distributions (0.5 μ D-0.5 μ D-0.5 μ D-displacement distribution (0-3600 s)) in an embodiment of the present invention;

FIG. 20 is a schematic diagram of different permeability combinations competing for crack initiation and spread displacement distributions (0.1 μ D-0.9 μ D-0.5 μ D-displacement distribution (0-3600 s)) in an embodiment of the present invention;

FIG. 21 is a schematic diagram of different permeability combinations competing for crack initiation and spread displacement distributions (0.1 μ D-0.9 μ D-0.5 μ D-displacement distribution (0-30 s)) in an embodiment of the present invention;

FIG. 22 is a schematic diagram of different permeability combinations competing for crack initiation and spread displacement distributions (0.1 μ D-0.5 μ D-0.9 μ D-displacement distribution (0-120 s)) in an embodiment of the present invention;

FIG. 23 is a graph showing the distribution of different permeability combinations competing for crack initiation and spread displacement (0.1 μ D-0.5 μ D-0.9 μ D-displacement distribution (0-2 s)) in an embodiment of the present invention;

FIG. 24 is a schematic diagram of the distribution of different cluster spacing competitive crack initiation and propagation trajectories in an exemplary embodiment of the present invention (cluster spacing 10 m);

FIG. 25 is a schematic diagram of the distribution of competing crack initiation and propagation trajectories with different cluster spacings (cluster spacing of 5m) in an exemplary embodiment of the present invention;

FIG. 26 is a diagram illustrating pressure distribution of different cluster spacing competing fracture initiation and propagation for each cluster in a specific application example of the present invention (cluster spacing 10 m);

FIG. 27 is a diagram illustrating pressure distribution of different cluster spacing competing fracture initiation and propagation for each cluster in an exemplary embodiment of the present invention (cluster spacing of 5 m);

FIG. 28 is a schematic diagram of the distribution of the displacement of different cluster spacing competing fracture initiation and propagation clusters (cluster spacing 10m) in a specific application example of the present invention;

FIG. 29 is a schematic diagram of the distribution of the displacement of different cluster spacing competing fracture initiation and propagation clusters (cluster spacing 5m) in a specific application example of the present invention;

FIG. 30 is a schematic diagram showing the distribution of the trajectories of the fractures competing for initiation and propagation of the clusters combined with the diameter of the perforations (the combination of the diameters of the perforations ranges from 10mm to 10mm) in the embodiment of the invention;

FIG. 31 is a schematic diagram showing the distribution of the trajectories of the fractures competing for initiation and propagation of the clusters combined with the diameter of the perforations (the diameter of the perforations combined 6mm-10mm-14mm) in an embodiment of the present invention;

FIG. 32 is a graph showing pressure distribution (10mm-10mm-10mm) of different combinations of hole diameters competing for initiation and propagation of clusters of fractures in an example embodiment of the present invention;

FIG. 33 is a graph showing pressure distribution (6mm-10mm-14mm) of different combinations of hole diameters competing for initiation and propagation of clusters of fractures in an example embodiment of the present invention;

FIG. 34 is a graph (10mm-10mm-10mm) showing the displacement distribution of different combinations of perforation diameters competing for initiation and propagation of each cluster of fractures in an example embodiment of the present invention;

FIG. 35 is a graph (6mm-10mm-14mm) showing the displacement distribution of different combinations of perforation diameters competing for initiation and propagation of each cluster of fractures in an example embodiment of the present invention;

FIG. 36 is a schematic diagram of the distribution of different fracture fluid viscosity competition initiation and propagation clusters of fractures (5 mPa. multidot.s) in the embodiment of the invention

FIG. 37 is a schematic diagram showing the distribution of different fracture fluid viscosity competition initiation and propagation clusters of fractures (25 mPa. multidot.s) in the embodiment of the invention

FIG. 38 is a graphical representation of the pressure distribution (5 mPa. multidot.s-bottom hole pressure and newly calculated fracture initiation pressure) of different viscosity competing initiated and propagated clusters of fractures in an embodiment of the invention;

FIG. 39 is a partial enlarged schematic view of the pressure distribution of different viscosity competing fracture initiation and propagation clusters in an embodiment of the invention (5 mPa. multidot.s-bottom hole pressure and newly calculated fracture initiation pressure);

FIG. 40 is a graphical representation of the pressure distribution (25mPa s-bottom hole pressure and newly calculated fracture initiation pressure) of clusters of fractures competitively initiated and propagated by different viscosities in an embodiment of the invention;

FIG. 41 is a partial enlarged schematic view of the pressure distribution of different viscosity competing fracture initiation and propagation clusters in an example embodiment of the present invention (25 mPa. multidot.s-bottom hole pressure and newly calculated fracture initiation pressure);

FIG. 42 is a schematic diagram of the trajectory distribution of different construction displacement competitive initiation and propagation clusters of cracks in the concrete application example of the invention (5 m)³/min)；

FIG. 43 shows different displacement competitive crack initiation for different applications of the present inventionDistribution diagram of crack tracks of each cluster of expansion (8 m)³/min)；

FIG. 44 is a schematic diagram of pressure distribution of different construction displacement competitive initiation and propagation clusters of fractures in a specific application example of the present invention (5 m)³Min-bottom hole pressure and newly calculated fracture initiation pressure);

FIG. 45 is a partial enlarged view (5 m) of pressure distribution of different displacement competitive fracture initiation and expansion clusters in the embodiment of the invention³Min-bottom hole pressure and newly calculated fracture initiation pressure);

FIG. 46 is a pressure distribution diagram of different construction displacement competitive initiation and propagation clusters of fractures in a specific application example of the invention (8 m)³Min-bottom hole pressure and newly calculated fracture initiation pressure);

FIG. 47 is a partial enlarged view (8 m) of pressure distribution of different displacement competitive fracture initiation and expansion clusters in the embodiment of the present invention³Min-bottom hole pressure and newly calculated fracture initiation pressure);

FIG. 48 is a schematic diagram of the distribution of different displacement volumes of cracks in different groups (the displacement volume of construction is 5m) for competitive initiation and propagation in the embodiment of the invention³Min-displacement distribution (0-120 s));

FIG. 49 is a schematic diagram of the distribution of different displacement volumes of cracks in different groups (the displacement volume of construction is 5m) for competitive initiation and propagation in the embodiment of the invention³Min-displacement distribution (0-2 s));

FIG. 50 is a schematic diagram of the distribution of different construction displacement competing crack initiation and propagation clusters of cracks in the concrete application example of the present invention (construction displacement 8m)³Min-displacement distribution (0-120 s));

FIG. 51 is a schematic diagram of the distribution of different construction displacement competing crack initiation and propagation clusters of cracks in the concrete application example of the present invention (construction displacement 8m)³Min-displacement distribution (0-2 s));

FIG. 52 is a first schematic structural diagram of a unconventional reservoir multi-cluster perforation competition fracture initiation and propagation simulation apparatus according to an embodiment of the present invention;

FIG. 53 is a schematic diagram of a fracture initiation pressure prediction unit according to an embodiment of the present invention;

FIG. 54 is a schematic structural diagram of a multi-cluster model generation unit in an embodiment of the present invention;

FIG. 55 is a block diagram of a multi-cluster model generation module in an embodiment of the invention;

FIG. 56 is a schematic structural diagram of a unconventional reservoir multi-cluster-hole competitive fracture initiation and propagation simulation apparatus according to an embodiment of the present invention;

fig. 57 is a schematic structural diagram of a flow distribution model generation unit in the embodiment of the present invention;

FIG. 58 is a third schematic structural diagram of a unconventional reservoir multi-cluster-hole competitive fracture initiation and propagation simulation apparatus in an embodiment of the present invention;

fig. 59 is a schematic structural diagram of an electronic device in an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

It should be noted that the terms "comprises" and "comprising," and any variations thereof, in the description and claims of this application and the above-described drawings, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

The embodiment of the invention provides a specific implementation mode of a unconventional reservoir multi-cluster perforation competition cracking and extension simulation method, and referring to fig. 1, the method specifically comprises the following steps:

step 100: and generating a well circumferential stress prediction model according to the in-situ stress, the well bore induced stress and the well bore track.

It will be appreciated that perforations are typically in a stressed state under compression, which is primarily subject to overburden pressure and formation stresses. When the rock debris in a compacted state is removed, the bore hole wall surface is supported by the liquid column pressure. However, the fluid column pressure is often not perfectly matched to the in situ stress conditions, and therefore, a redistribution of stresses may occur. The redistribution stress field may be obtained from the perforation stress in situ, borehole induced stress and casing cement sheath induced stress.

Step 200: and generating a seepage-stress fracture initiation pressure prediction model according to the well circumferential stress prediction model based on the percolation characteristics in the fracturing fluid injection process.

Assuming the rock is permeable and saturated with fracturing fluid, the fluid is slightly compressible, ignoring capillary forces and other fluid invasion. Upon initiation of wellbore injection, the pore pressure around the wellbore of each perforation cluster increases as fracturing fluid flows from each perforation cluster through the rock pores. The stress field distribution of the rock around the shaft can be obtained according to a two-dimensional radial flow stress diffusion equation.

Step 300: and generating a multi-cluster perforation competition initiation and expansion model according to the well-periphery stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the initial initiation perforation cluster and the induced stress generated by the pressure change of the formation fluid based on the physical properties of the reservoir around the well, the stress heterogeneity of the ground around the well and the perforation pressure.

On the basis of the

steps

100 and 200, according to the physical properties of the reservoir, the ground stress heterogeneity, the intraocular pressure drop of the perforation hole and the like, an unconventional reservoir seepage flow-stress initiation pressure prediction model is combined, flow dynamic distribution, initial initiation perforation cluster extension and fracture induced stress in the multi-fracture initiation and extension process are coupled, a horizontal well multi-cluster perforation competition initiation and extension model is established, main control factors influencing fracture extension and initiation are analyzed, and the fracturing and acidizing effects of the reservoir are improved.

From the above description, the unconventional reservoir multi-cluster-jet competitive fracture initiation and extension simulation method provided by the embodiment of the invention includes the steps of firstly generating a well-periphery stress prediction model according to in-situ stress, well-bore induced stress and well-bore trajectory; then, based on the percolation characteristics in the injection process of the fracturing fluid, generating a seepage-stress crack initiation pressure prediction model according to the well-periphery stress prediction model; and finally, based on the physical properties of the reservoir around the well, the heterogeneity of the geostress around the well and the pressure of the perforation holes, generating a multi-cluster perforation competition initiation and expansion model according to a well-around stress prediction model, a pressure prediction model, the dynamic flow distribution in the multi-fracture initiation process, the dynamic flow distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the initiation perforation cluster and the induced stress generated by the pressure change of the formation fluid. The method comprehensively considers the influences of the shielding effect caused by the ground stress difference, the reservoir heterogeneity and the stress shadow on the cracking and the expansion of the perforation clusters of the unconventional reservoir, and establishes and solves the model on the basis of the influences, so that the fracturing transformation effect of the unconventional reservoir in the segmented and multi-cluster mode is better improved.

In one embodiment, referring to fig. 2, step 200 further comprises:

step 201: generating a fracture initiation pressure prediction model according to the well circumferential stress prediction model, the induced stress of the in-situ stress, the induced stress of the casing cement sheath and the stress field of the perforation hole;

step 202: and generating the seepage-stress crack initiation pressure prediction model according to the rock water absorption induced pore elastic coefficient and the crack initiation pressure prediction model by using a maximum tensile stress method.

In step 201 and step 202, considering the in-situ stress of the unconventional reservoir, the induced stress of a perforation hole and the like, establishing a fracture initiation pressure prediction model of the unconventional reservoir under the influence of injection, fluid disturbance and the like of a comprehensive horizontal wellbore; combining the change of the elastic coefficient of the hole caused by rock water absorption, the mechanical property of the rock under the disturbance of working fluid and the percolation characteristic in the injection process of fracturing fluid to obtain the stress distribution around the perforation hole; based on the maximum tensile stress theory, a seepage-stress crack initiation pressure prediction model under the unconventional reservoir complex working condition is established.

In one embodiment, referring to fig. 3, step 300 further comprises:

step 301: generating a perforation cluster crack expansion model according to the perforation cluster crack expansion stress field and the crack friction resistance;

specifically, a perforation cluster fracture propagation model is established based on reservoir physical properties, a perforation cluster stress field, hydraulic fracture friction resistance and the like by coupling an in-situ stress field and induced stress generated by formation fluid pressure change.

Step 302: and generating the multi-cluster-jet competitive cracking and expanding model according to the perforation cluster crack expanding model and the multi-cluster-jet competitive cracking and expanding physical model.

Specifically, an unconventional reservoir seepage-stress initiation pressure prediction model and a perforation cluster fracture expansion model are combined, and a heterogeneous reservoir segmented multi-cluster competitive initiation-expansion model is established based on reservoir physical properties, geostress heterogeneity, perforation hole intraocular pressure drop and the like and by coupling flow dynamic distribution, hydraulic fracture friction, first initiation perforation cluster extension and fracture induced stress in the multi-fracture initiation and expansion process.

In one embodiment, referring to fig. 4, step 302 further comprises:

step 3021: generating a competition expansion model according to the hydraulic fracture expansion stress field, the hydraulic fracture friction resistance and the multi-fracture flow distribution model;

step 3021, when implemented, specifically includes: considering the hydraulic fracture perforation friction resistance, the fracture extension friction resistance, the dynamic fracture width, the dynamic fracture length, the fracturing fluid loss and the hydraulic fracture stress field influence of the superposition of the induced stress and the in-situ stress, the flow distribution and the fracture initiation-extension coupling flow distribution are carried out in the injection-fracture initiation stage based on the flow conservation and pressure balance criterion, and a competition extension model is established.

Step 3022: and generating the multi-cluster perforation competition crack initiation and expansion model according to the competition expansion model.

In one embodiment, referring to fig. 5, generating the multi-fracture flow distribution model comprises the steps of:

step 501: establishing a multi-fracture initiation flow distribution model corresponding to the injection to the initiation stage according to the flow and the pressure injected to the initiation stage;

step 502: establishing a multi-fracture expansion flow distribution model corresponding to the stages from initiation to expansion according to the flow and the pressure from the initiation to the expansion;

step 503: and generating the multi-fracture flow distribution model according to the multi-fracture initiation flow distribution model and the multi-fracture expansion flow distribution model.

As can be seen from the background art, in the prior art, the influence of the induced stress of the fracture of the first initiated perforation cluster on the initiation of the subsequent perforation cluster and the initiation sequence is not considered, and the flow distribution is divided into the following two stages through steps 501 to 503: 1 injecting the mixture into a crack initiation stage; 2 to the expansion phase. In the stage from injection to crack initiation, flow distribution is carried out by adopting an orifice flow balance equation and a crack initiation pressure balance equation; and in the stage from the crack initiation to the expansion, flow distribution is carried out by adopting an orifice flow balance equation and an expansion stage pressure balance equation.

In one embodiment, referring to fig. 6, the step of generating the multiple-cluster-hole competition fracture initiation and propagation physical model includes:

step 601: and generating a physical model of competitive initiation and expansion of the multiple clusters of perforation holes according to the characteristics of the initiation process of the single fracture, the flow distribution characteristics of the multiple fractures, the extension characteristics of the fracture of the initial initiation perforation cluster, the induced stress generated by the extension of the initial initiation perforation cluster to form the fracture and the induced stress generated by the pressure change of the formation fluid.

It can be understood that the unconventional reservoir multi-cluster-hole competitive fracture initiation and expansion is a very complex physical process, and is interfered by a plurality of influencing factors, and the following processes are mainly coupled in the process of establishing a multi-cluster-hole competitive fracture initiation and expansion physical model: a single crack initiation process; dynamic allocation of multi-crack flow; initiating the extension of the perforation cluster cracks; the initial fracture perforation cluster extends to form induced stress generated by the fracture.

From the above description, the unconventional reservoir multi-cluster-perforation competitive fracture initiation and extension simulation method provided by the embodiment of the invention establishes a horizontal well circumferential stress prediction model in which the influences of rock mechanics, casing/cement sheath mechanics characteristics, fluid disturbance and the like are comprehensively considered in a flowing manner on the premise that the factors such as in-situ stress, well induced stress, horizontal well track and the like are comprehensively considered; comprehensively considering rock mechanics and percolation characteristics of fracturing fluid in the injection process, and establishing a seepage-stress fracture initiation pressure prediction model based on a maximum tensile stress theory by combining a well circumferential stress dynamic prediction model.

In order to further illustrate the scheme, the invention provides a specific application example of the unconventional reservoir multi-cluster-hole competitive fracture and extension simulation method by taking the unconventional reservoir horizontal well multi-cluster-hole competitive fracture and extension process as an example, and the specific application example specifically comprises the following contents, and refer to fig. 7.

S1: and establishing a physical model of multi-cluster-jet hole competition crack initiation and expansion.

FIG. 8 is a schematic diagram of a unconventional reservoir horizontal well multi-cluster perforation competition fracture initiation and expansion physical model, wherein the physical model is numbered according to the sequence that fracture initiation pressure is increased from small to large, and n perforation clusters are totally initiated to form n fractures. The segmented multi-cluster fracturing construction displacement of the horizontal well is Q, and the fluid pressure of a shaft is p when each perforation cluster crack expands to the jth segment_w(j) (ii) a The flow rate distributed to each perforation cluster under the construction flow rate is q_1,j,…,q_i,j,…,q_n,j(ii) a Pressure in each crack is p due to crack propagation_1,j,…,p_i,j,…,p_n,j(ii) a Each perforation cluster has a pressure drop of p_pf1,j,…,p_pfi,j,…,p_pfn,j。

In the initial stage of fracturing, along with the continuous injection of fracturing fluid, the flow dynamic change of each perforation cluster causes different fracture initiation pressures; when the bottom hole pressure is gradually increased to the minimum fracture initiation pressure of each perforation cluster, the fracture of each perforation cluster is expanded; similarly, the un-fractured perforation clusters are dynamically distributed according to the flow rate to cause new fracture initiation pressure, the fracture of each perforation cluster expands when the bottom hole pressure is gradually increased to the minimum fracture initiation pressure of each perforation cluster, and the like until the construction is finished. Therefore, to build a physical model and conduct further research, the following basic assumptions were made:

(1) the compressive stress is positive and the tensile stress is negative;

(2) the fracture section is a homogeneous and isotropic elastomer, and the fracture section is an elliptical fracture;

(3) the chemical action of the fracturing fluid after the action with reservoir rock is not considered;

(4) only one fracture is created for one perforation cluster.

S2: and establishing a fracturing fluid injection dynamic boundary effect fracture initiation pressure prediction model.

Specifically, the unconventional reservoir fracture initiation pressure prediction model under the influence of horizontal wellbore injection, fluid disturbance and the like is established by considering the in-situ stress of the unconventional reservoir, the induced stress of a perforation hole and the like; combining the change of the elastic coefficient of the hole caused by rock water absorption, the mechanical property of the rock under the disturbance of working fluid and the percolation characteristic in the injection process of fracturing fluid to obtain the stress distribution around the perforation hole; based on the maximum tensile stress theory, a seepage-stress crack initiation pressure prediction model under the unconventional reservoir complex working condition is established. Further, step S2 further includes:

s21: and determining the cracking stress field distribution of the perforation holes.

The stress of the perforation hole is subjected to the combined action of the in-situ stress induced stress and the casing cement sheath induced stress, and a redistribution stress field can be obtained.

(1) In situ stress induced stress

In the formula:

respectively generating radial stress, circumferential stress and axial stress along the well hole direction of a shaft section by in-situ stress induction, wherein the stress is MPa; sigma_H、σ_hRespectively the horizontal maximum principal stress and the horizontal minimum principal stress, MPa; χ, ψ are azimuth and well angle, rad;

is the shear stress component, MPa, in a three-dimensional coordinate system; sigma_vIs the vertical stress, MPa.

(2) Induced stress of casing cement sheath

In the formula:

the radial stress, the circumferential stress and the axial stress along the direction of a hole of a shaft section are considered when a casing cement sheath is considered, and the stress is MPa; r_wIs the wellbore radius, m; r is the radial distance, m; TF is the conductivity coefficient;

the shear stress around the cross section of the shaft is considered when the casing cement sheath is taken into account, and the pressure is MPa; θ is the perforation phase angle, rad.

Wherein, the conductivity coefficient TF of the pressure in the borehole to the stratum rock is represented as:

in the formula: v. of_cIs the cannula poisson's ratio; e_cYoung's modulus of the sleeve, MPa; r_o、R_iIs the outer and inner diameter, m, of the cannula, respectively.

(3) Stress field of perforation hole

The stress distribution of the horizontal well perforation hole of the unconventional reservoir comprises radial stress, circumferential stress, axial stress along the direction of the hole and shear stress of the interface of the perforation hole:

in the formula: sigma_rp、σ_θp、σ_zpRadial stress, circumferential stress and axial stress along the direction of the perforation hole are respectively the radial stress and the circumferential stress of the perforation hole interface, and the axial stress is MPa; p (r)_w) Is the bottom hole pressure, MPa; alpha is the hole elasticity coefficient and is dimensionless; v is the poisson's ratio, dimensionless; r (t) is the activation radius at time t at the perforation, m; r is_wIs the perforation radius, m; p (r) is the pore pressure at location r in the perforated formation, MPa at time t; theta^*Is σ_zpThe angle, rad, rotated at the section after projection onto the perforation hole section;

is the shear stress component, MPa, in a three-dimensional coordinate system; p is a radical of_eIs the formation pressure, MPa; tau is_θzpThe shear stress around the perforation hole is MPa.

S22: and establishing a pressure diffusion equation.

It is here assumed that the rock is permeable and saturated with fracturing fluid, the fluid is slightly compressible, ignoring capillary forces and other fluid invasion. Upon initiation of wellbore injection, the pore pressure around the wellbore of each perforation cluster increases as fracturing fluid flows from each perforation cluster through the rock pores. The stress field distribution of rocks around the wellbore can be obtained according to a two-dimensional radial flow stress diffusion equation, specifically:

in the formula: k is the permeability of the rock corresponding to the perforation hole, mum²(ii) a Phi is rock porosity, dimensionless; μ is the fluid viscosity, mPas; c is the overall compressibility, MPa^-1(ii) a t is the injection time, s.

Pressure boundary and initial conditions:

p(r)＝p_p，t＝0 (6)

p(r)→p_p，r→∞ (8)

in the formula: q is the displacement of orifice injection, m³/min；N_pThe number of perforation holes is two; l is_pIs the perforation depth, m.

And (3) solving the formula (5) by combining the initial condition formula (6) and the boundary condition formulas (7) and (8), wherein the rock pore pressure equation is simplified by a method proposed by Polubarinova-Kochina, and then the pore pressure distribution of an activation region in the liquid injection process is solved, namely:

ei refers to the power exponent, which is expressed as:

s23: and determining a crack initiation criterion.

It will be appreciated that tensile failure is commonly used to predict fracture initiation pressure, assuming that when the maximum principal stress component at any point on the wellbore wall reaches rock tensile strength, the perforation is initiated, and the corresponding three principal stresses are as follows:

σ₁＝σ_rp (11)

as can be seen by comparing the equations (11) to (13), σ₃Indicating the maximum tensile stress (negative) at the wall of the hole. The effective maximum tensile stress is reduced when the hole modulus is considered:

when considering the effect of fluid percolation, this can lead to increased pore pressure in unconventional reservoirs. Therefore, the effective strength σ of unconventional reservoirs_fIs σ in the formation₃A function of pore pressure distribution; meanwhile, after unconventional reservoir rock absorbs water, the Young modulus of the formation rock is changed, and the elastic coefficient of rock pores is further influenced. The pore elastic coefficient α is defined as:

in the formula K_maIs the rock skeleton bulk modulus, MPa.

In order to obtain the relation between the Young modulus and the water content, a shale water absorption experiment is carried out. The experimental temperature was 25 ℃ and the pressure was 1 atm. Firstly, the prepared standard rock sample with the thickness of 25mm multiplied by 50mm is dried in a drying oven for 24 hours, and then weighed, and the weight m of the dried rock sample is recorded₀(ii) a Completely immersing the rock sample in slickwater fracturing fluid (fresh water, 0.1% of resistance reducing agent, 0.1% of anti-swelling agent and 1% of cleanup additive), taking out a rock sample every 6 hours to measure the mass m of the rock sample, carrying out a triaxial compression test (confining pressure 40MPa) after the measurement to obtain the Young modulus and the Poisson ratio, and obtaining the water content omega (m-m) according to omega₀)/m₀X 100% calculation. Table 1 shows the young's modulus data obtained from the triaxial experiment after the shale rock sample absorbs water. The results show thatThe Young's modulus decreases with increasing water content and the Poisson's ratio does not change much.

TABLE 1 Young's modulus and Poisson's ratio changes after shale water absorption

To further clarify the relationship between Young's modulus and moisture content, a curve was prepared showing the change in Young's modulus with moisture content, as shown in FIG. 9.

Fitting the relationship between the Young modulus E and the water content omega to obtain:

E＝-2272.6ω+33152 (16)

the water content near the perforation during fracturing can be defined as the ratio of the mass of the injected fracturing fluid to the mass of the rock within the range of the radius of stimulation over a certain period of time. When the rock is not saturated with water, the water content is a function of the injection amount; when the rock absorbs water to reach saturation, the water content does not change, namely:

where rho_sIn terms of fracturing fluid density, kg/m³；ρ_rIs the density of the rock skeleton in kg/m³；

The volume balance during fluid injection also follows that the injected volume of the frac well per unit time is equal to the change in the elastic fluid compression in the disturbance zone. The average pressure of the activation region is then:

the maximum tensile stress criterion is used to determine the fracture initiation pressure:

σ_f≤-σ_t (19)

in the formula: sigma_tIs the tensile strength of rock, MPa.

The direction of fracture initiation, not along the wellbore axis but along the direction of the fracture initiation angle γ, can be determined by using the moire circle:

in the formula: gamma is the fracture initiation angle, rad.

S3: and establishing a perforation cluster crack propagation model.

Specifically, a perforation cluster fracture propagation model is established based on reservoir physical properties, a perforation cluster stress field, hydraulic fracture friction resistance and the like by coupling an in-situ stress field and induced stress generated by formation fluid pressure change. Further, step S3 further includes the following steps:

s31: and establishing a perforation cluster crack propagation stress field.

It will be appreciated that the hydraulic fracture propagation stress field distribution is a superposition of fracture induced stress, induced stress due to changes in formation fluid pressure, and in situ stress, and that the normal and shear stress components in the x and y coordinates are:

in the formula: sigma_x，σ_y，τ_xyIs the normal and shear stress components in x and y coordinates, MPa; sigma_H，σ_hIs the maximum and minimum horizontal principal stresses, MPa;

corresponding crack is expanded to the j section of induced stress, MPa, under x and y coordinates; sigma_xx，σ_yyIs the induced stress, MPa, produced by the change in formation fluid pressure.

(1) Crack induced stress

Wherein

And

the expression is as follows:

in the formula: g is shear modulus, MPa, G ═ E/2/(1-v);

x_j、y_jthe coordinates of the center of the crack extending to the jth section; x is the number of_k、y_kTo expand the center coordinates of the k-th segment in the fracture.

In the formula:

representing an intermediate variable; a is_kThe extension crack is dispersed into the half length m of the kth unit in j units; alpha is alpha_j,kAnd (4) the included angle between the central coordinate of the crack unit from the crack to the jth section and the connecting line of the kth section of the crack to be expanded and the horizontal direction, namely rad.

Constant displacement discontinuity values on boundary cells

Can induce normal stress into corresponding gap net pressure p according to initial value condition_netAnd taking the corresponding coordinates of any two discrete units m, k (m is more than or equal to 1 and k is more than or equal to j)

And

and (4) obtaining.

Namely:

wherein:

in the formula L_f,jM to expand the crack length; h_fM is the crack height.

From the matrix equation (25), the inverse can be solved

(2) Induced stress from changes in formation fluid pressure

In the formula: α is the Biot porous elastic coefficient, dimensionless; p is a radical of_pIs the current formation pressure, MPa; p is a radical of_eIs the original formation pressure, MPa.

S32: determining hydraulic fracture friction resistance

(1) Friction resistance for perforation hole

The perforation friction resistance can influence the pressure distribution of the fracturing fluid in the fracturing construction, and further influence the initiation process of a plurality of clusters of cracksThe distribution of flow, which ultimately affects the fracture initiation pressure and the construction pressure, is an important parameter in the implementation process of hydraulic fracturing. Based on Bernoulli equation, friction resistance p of fracture perforation_pfThe calculation formula of (a) is as follows:

in the formula: rho_sIs the fracturing fluid density, kg/m³；d_pThe diameter of perforation cluster holes of the horizontal well is m; c_dThe flow coefficient of the horizontal well perforation is zero dimension.

(2) Crack extension friction resistance

The pressure drop of the fracturing fluid in the fracture can be approximately treated according to the laminar flow between the infinite parallel plates, and the extension friction resistance (delta p) of the horizontal well fracture extending to the j section_f,j) The calculation formula is as follows:

in the formula: n is the fracturing fluid flow index, dimensionless; Δ L_f,jThe length of a horizontal well crack extending to a jth section crack is m; w is a_f,jThe average width m of the horizontal well crack when the horizontal well crack expands to the jth section; kf is the consistency coefficient of the fracturing fluid with power law type fluid in the fracture, Pa.sⁿ(ii) a K is the laboratory-determined fracturing fluid viscosity coefficient, Pa · sⁿ。

Wherein the width w of the slit_f,jComprises the following steps:

in the formula: k_ICIs the I-type fracture toughness of rock, MPa.m^1/2；L_f,jIs the total length of the horizontal well fracture when the horizontal well fracture is expanded to the j sectionThe ratio of degrees, m,

ΔL_f,jthe fracture propagation length m when the horizontal well fracture propagates to the jth section.

Thus, the total pressure drop Δ p in the fracture when the horizontal well fracture propagates to the j-th section_fComprises the following steps:

wherein, the total time required for the extension is:

in the formula: c is the fluid loss coefficient, m/min^0.5。

S33: fracture propagation criteria are determined.

After the cracks of the perforation clusters are initiated at the perforation holes, the connection near the well wall can be regarded as a type I and type II composite fracture problem, and in the problem, the stress field near the tips of the cracks can be K_I、K_IIAnd the propagation direction of the crack can be calculated. Based on the theory of linear elastic fracture mechanics, K is obtained_I、K_IIExpression of type intensity factor:

in the formula: k_IIs a type I strength factor, MPa.m^1/2；K_IIIs type II intensity factor, MPa.m^1/2；p_netIs the net pressure, MPa, generated by the infinitesimal section x; sigma₁₁、σ₃₃Is the maximum principal stress and the minimum principal stress, MPa; s calculationDistance from point to crack center (s ═ L)_f,j) M; β is a fracture propagation direction angle, and β ═ γ, rad, at the initial time.

Wherein the maximum positive stress and the minimum positive stress sigma₁₁、σ₃₃The calculation formula is as follows:

maximum circumferential stress theory holds that when the circumferential stress σ is_βWhen a certain value is reached, the crack breaks and propagates in the direction of maximum circumferential stress. Based on the fracture mechanics theory, solving a polar coordinate expression of the circumferential stress at the crack tip:

the ultimate hoop stress when the crack fails is:

in the formula: sigma_βcIs the ultimate hoop stress, MPa; k_IcIs the fracture toughness of rock, MPa.m^1/2。

United type (38) (3-170) and formula (39) (3-171) when sigma is_β≥σ_βcWhen, the crack propagates, i.e.:

at this point, an equivalent intensity factor is defined:

in the formula: k_eIs the equivalent strength factor, MPa.m^1/2。

Therefore, the criterion for describing the maximum circumferential stress by using the equivalent strength factor is as follows:

K_e-K_Ic≥0 (42)

and (3) calculating a first derivative of the left side (3-170) of the formula (42), wherein the first derivative is 0, and meanwhile, ensuring that the second derivative is less than 0, and obtaining the extending direction angle beta of the perforation crack as follows:

s4: and establishing a heterogeneous reservoir segmented multi-cluster competitive fracture initiation-expansion model.

Step S4 further includes:

s41: and establishing a competition expansion model.

Considering the hydraulic fracture perforation friction resistance, the fracture extension friction resistance, the dynamic fracture width, the dynamic fracture length, the fracturing fluid loss and the hydraulic fracture stress field influence of the superposition of the induced stress and the in-situ stress, the flow distribution and the fracture initiation-extension coupling flow distribution are carried out in the injection-fracture initiation stage based on the flow conservation and pressure balance criterion, and a competition extension model is established.

Specifically, it is first necessary to determine the hydraulic fracture propagation stress field distribution. The hydraulic fracture propagation stress field is the superposition of multiple fracture induced stress, induced stress generated by formation fluid pressure change and in-situ stress, and the multiple fracture induced stress is superposed on the basis of a perforation cluster propagation stress field formula (21) to obtain the components of normal stress and shear stress under x and y coordinates as follows:

in the formula: sigma_mx，σ_my，τ_mxyMultiple cracks generate normal stress and shear stress components under x and y coordinates, and the components are MPa; sigma_H，σ_hIs maximum waterFlat principal stress and minimum horizontal principal stress, MPa;

the induced stress (MPa) is calculated and obtained from the ith perforation cluster parameter under x and y coordinates according to a formula (22) and is expanded to the jth section.

And then determining the friction resistance of the hydraulic fracture, which specifically comprises the following aspects:

(1) friction resistance for perforation hole

The perforation friction resistance can influence the pressure distribution of fracturing fluid in fracturing construction, further seriously influences the flow distribution in the process of initiating a plurality of clusters of cracks, and finally influences the initiation pressure and the construction pressure, and is an important parameter in the implementation process of hydraulic fracturing. Based on Bernoulli equation, friction resistance p of fracture perforation_pfi,jThe calculation formula of (a) is as follows:

in the formula: q. q.s_i,jThe flow rate m when the ith perforation cluster crack of the horizontal well expands to the jth section³/min；d_p,iThe diameter of the hole of the ith perforation cluster of the horizontal well is m.

(2) Crack extension friction resistance

The pressure drop of the fracturing fluid in the fracture can be approximately treated according to the laminar flow between infinite parallel plates, and the fracture of the ith perforation cluster of the horizontal well is expanded to the jth extension friction resistance (delta p)_fi,j) The calculation formula is as follows:

in the formula: Δ L_fi,jThe length m from the crack i of the horizontal well to the jth section; w is a_fi,jThe average crack width m is calculated according to a formula (31) when the horizontal well crack i extends to the jth section; q. q.s_i,jIs the fracture flow, m, of the horizontal well when the fracture i propagates to the j section³/min。

Then, the total pressure drop in the horizontal well fracture i when the fracture i extends to the jth section is as follows:

in the formula: Δ p_i,jThe total friction resistance pressure drop of the fracture is MPa when the fracture i of the horizontal well expands to the jth section.

And when the initial fracture is expanded to the j section, the expansion step length of the initial fracture is always delta L in the time period t (j) -t (j-1).

The total time required for expansion is:

in the formula: q. q.s_f1The corresponding flow of the initial crack, m³/min。

And the expansion crack length of the non-initial fracture in the time period t (j) -t (j-1) is as follows:

in the formula: Δ L_fi,jIs the length, m, of the horizontal well fracture i extending to the jth section.

And then, determining that the multi-cluster perforation competition initiation and expansion of the flow distribution horizontal well firstly needs to solve the problem of multi-fracture flow dynamic distribution. In the injection-cracking stage, flow distribution is carried out by adopting an eyelet flow balance equation and a pressure balance equation in the cracking stage; and in the crack initiation-expansion stage, flow distribution is carried out by adopting an orifice flow balance equation and an expansion stage pressure balance equation. The flow distribution in the injection-cracking stage mainly comprises the following aspects:

(1) injection-initiation stage flow balance

In the injection-crack initiation stage, the construction discharge capacity is Q, the total flow is divided into clusters of holes, but the cracks are not expanded, and the discharge capacity of each cluster is Q_i,0The total displacement of fluid is equal to the sum of the displacements per cluster of all fractures, i.e.:

in the formula: q is the construction displacement of fracturing fluid injection, m³/min。

(2) Injection-initiation stage pressure equalization

The fluid pressure balance criteria in the horizontal wellbore were established using the horizontal wellbore in fig. 1 (O target) as a reference point based on Kirchoff's second law. The pressure at the O-target is equal to the sum of the fluid pressure at the entrance of each cluster of fractures and the friction of the perforation holes. When the horizontal well has n perforation clusters and each perforation cluster is not expanded, n pressure balance equations exist:

p_1,0＝…＝p_n,0＝p_i,0＝p_pfi,0+p_i(r_w,i) (i＝1,2,…,n) (51)

in the formula: p is a radical of_i,0The wellbore fluid pressure of a horizontal well fracture i is MPa; p is a radical of_pfi,0The friction resistance of an eyelet when a horizontal well crack i is not expanded is MPa; p is a radical of_i(r_w,i) Is the hole r calculated by the formula (9) when the horizontal well crack i is not expanded_w,iThe fluid pressure, MPa.

Therefore, by combining equations (50) and (51), the flow rate and pressure of each perforation cluster can be solved.

Crack initiation-propagation coupled flow distribution

(1) Crack-propagation stage flow balancing

A physical model of unconventional reservoir horizontal well multi-cluster perforation competition fracture initiation and expansion flow dynamic allocation is shown in fig. 8. Based on the Kirchoff first law, when the staged multi-cluster fracturing of the horizontal well is carried out, the total discharge capacity of a fracturing pump is Q, the total flow is divided into clusters, the discharge capacity of the ith perforation cluster of the horizontal well expanded to the jth section is Q_i,jThe total displacement of fluid is equal to the sum of the displacements per cluster of all fractures, i.e.:

(2) pressure balance in initiation-propagation stage

The fluid pressure balance criteria in the horizontal wellbore were established using the horizontal wellbore in fig. 1 (O target) as a reference point based on Kirchoff's second law. The pressure at the O-target is equal to the sum of the fluid pressure at the entrance of each cluster of fractures and the friction at the perforation. When the horizontal well has n perforation clusters, and each perforation cluster extends to the j section, n pressure balance equations exist:

p_i,j＝Δp_i,j+p_pfi,j+σ_βy,i,j (i＝1,2,…,n) (53)

in the formula: p is a radical of_i,jThe fluid pressure when the horizontal well crack i expands to the jth section is MPa; Δ p_i,jThe friction pressure of the fluid is MPa when the horizontal well crack i expands to the jth section; sigma_βy,i,jThe circumferential stress of the fracture end is MPa when the horizontal well fracture i extends to the jth section.

The circumferential stress of the fracture end when the fracture i of the horizontal well perforation cluster expands to the jth section is as follows:

according to the pressure balance principle, the wellbore pressure corresponding to each cluster of fractures is equal, namely:

p_w(j)＝p_1,j＝…＝p_i,j＝…＝p_n,j (i＝1,2,…,n) (55)

in the formula: p is a radical of_w(j) Is the wellbore fluid pressure, MPa, from all the propagating fractures to the j-th section;

therefore, by combining equations (52) and (55), the flow rate and pressure for each perforation cluster can be solved.

S42: and establishing a competitive fracture initiation-expansion coupling model.

The unconventional reservoir horizontal well mostly adopts a segmented multi-cluster fracturing mode to fully utilize the reservoir, but due to the influence of ground stress and reservoir heterogeneity, not all perforation clusters can simultaneously initiate fractures, and the perforation cluster which is initiated first enters an extension stage. Real-time control over crack initiation and extension sequence is achieved by means of crack extension pressure and eyelet friction resistance, multi-cluster perforation competition initiation and expansion of unconventional reservoir horizontal wells are achieved, and then hydraulic fracture complexity is improved.

In the initial stage of fracturing, along with the continuous injection of fracturing fluid, the bottom hole pressure gradually rises; calculating the size of the crack initiation pressure of each cluster based on the early-stage flow dynamic distribution model, and calculating the crack initiation pressure (p) of each cluster₁(r_w,1),…,p₂(r_w,2),…,p_n(r_w,n) Sorting (p) in order from smaller to larger_fr1(j),p_fr2(j)…,p_frn(j) Suppose that the fracture initiation pressure of the 1 st perforation cluster of the horizontal well is the maximum, the fracture initiation pressure of the 2 nd perforation cluster is the second, and so on, when the bottom hole pressure reaches the fracture initiation pressure of the 1 st perforation cluster first; the bottom hole pressure at this time satisfies:

p_frn(j)＞…＞p_fr2(j)＞p_i,j＞p_fr1(j) (56)

in the formula: p is a radical of_fr1(j) The fracture initiation pressure of the 1 st perforation cluster is MPa when the sequenced fractures expand to the jth section; p is a radical of_fr2(j) The fracture initiation pressure of the 2 nd perforation cluster from the sequenced fractures to the jth section is MPa; p is a radical of_frn(j) The fracture initiation pressure of the n-th perforation cluster after sequencing is MPa.

After the cracks of the sequenced 2 nd perforation cluster are initiated, continuously injecting fracturing fluid, and simultaneously extending the cracks generated by the sequenced 2 nd perforation cluster and the sequenced 1 st perforation cluster; the fracturing fluid injected at the moment enters the stratum through the perforations of the sequenced 2 nd perforation cluster, and in the fracture extension process of the sequenced 2 nd perforation cluster, the bottom hole pressure is the fluid pressure at the entrance of each fracture, so that the extension of the sequenced 2 nd perforation cluster is ensured, and the bottom hole pressure is always lower than the initiation pressure of the sequenced 3 rd perforation cluster, namely:

p_frn(j)＞…＞p_fr3(j)＞p_i,j (57)

after the crack generated by the 2 nd perforation cluster extends for a period of time, judging the magnitude relation between the bottom hole pressure and the cracking pressure of the 3 rd perforation cluster in real time; when the bottom hole pressure is further larger than the fracture pressure of the 3 rd perforation cluster, the 3 rd perforation cluster is fractured, namely:

p_frn(j)＞…＞p_i,j＞p_fr3(j) (58)

subsequently, the 3 rd perforation cluster generates cracks to start extending, and the crack initiation extending process of the 2 nd perforation cluster is repeated. And finally, the sum of perforation friction generated by the extension of the 1 st perforation cluster, the 2 nd perforation cluster and the 3 rd perforation cluster, on-way friction in crack extension and circumferential stress at the end part of the extended crack further improves the bottom hole pressure to enable the bottom hole pressure to reach the cracking pressure of the 4 th perforation cluster, so that the 4 th perforation cluster is cracked, and by analogy, the competitive cracking of a plurality of clusters of cracks is finally realized.

S43: and (5) crack propagation criterion.

After a plurality of clusters of cracks are initiated at the perforation hole, the connection near the well wall can be regarded as a type I and type II composite fracture problem, and in the problem, the stress field near the crack tip can be K_I、K_IIAnd the propagation direction of the crack can be calculated. Based on the linear elastic fracture mechanics theory, substituting formula (36) and formula (37) according to formula (44) and corresponding fracture parameters, and substituting formula (34) and formula (35) to obtain K_Ii,j、K_IIi,jExpression of type intensity factor:

in the formula: k_Ii,jIs the I-type strength factor, MPa.m, calculated according to the formula (34) when the ith cluster perforation crack expands to the jth section^1/2；K_IIi,jIs a type II intensity factor, MPa.m, calculated according to a formula (35) when the ith cluster perforation crack expands to the jth section^1/2；p_neti,jThe net pressure, MPa, calculated according to the formula (34) when the ith shower jet hole crack expands to the jth section; sigma_11i,j、σ_33i,jThe maximum principal stress and the minimum principal stress are calculated according to a formula (36) and a formula (37) when the ith shower perforation crack expands to the jth section, and are MPa; s_i,jIth clusterCalculating the distance(s) from the point to the center of the fracture when the perforation fracture propagates to the j section_i,j＝L_fi,j)，m；β_i,jAnd (3) when the ith cluster perforation crack expands to the jth section, the corresponding crack parameter is the crack extension direction angle, rad, according to the formula (43).

S5: and solving the model.

Likewise, the solution is performed in stages according to the time of the fracturing fluid entering the formation:

s51: injection-initiation phase.

Assuming that the horizontal well has n clusters of perforation holes, the construction displacement Q is constant, and the construction displacement Q is divided into the perforation holes according to a flow balance equation and a pressure balance equation. At the moment, the displacement of each cluster is q_i,0The construction displacement is equal to the sum of the displacements of all perforation clusters

Suppose the aperture flow of the 1 st shower is q_1,0。

(1) First, assuming a fracture initiation time t, based on a 1 st shower perforation pore pressure p₁(r) distribution (equation 9), calculating the perforation position (r)_w,1) Fluid pressure p₁(r_w,1) And reducing the pore pressure to the original formation pressure p_eRadius of activation (R) corresponding to a 1% difference₁(t))；

(2) Then substituting the activation radius and the fluid pressure at the perforation into a formula (4) to obtain the normal stress and the shear stress (sigma) of the perforation interface at the 1 st position_rp,1、σ_θp,1、σ_zp,1And τ_θzp,1) And calculating the mean pressure of the activation region using equation (18)

Substituting the positive stress and the shear stress of the 1 st perforation hole interface into the formulas (11) to (13) to obtain three main stresses (sigma) corresponding to the perforation holes₁、σ₂And σ₃)；

(3) Then calculating the hole elasticity coefficient (alpha) considering the water content change by using the formulas (15), (16) and (17); using the maximum tensile stress (sigma) at the wall of the eye₃) The pore elastic coefficient (alpha) and the radius of agitation (R)₁(t)) into equation (14) to obtain the effective maximum tensile stress (sigma)_f) And substituting the formula (20) to calculate the crack initiation angle (gamma)₁) According to the tensile strength criterion σ of perforation initiation_f≤-σ_tAnd (4) judging, if the tensile strength criterion is not met, changing the cracking time t, and repeating the steps (1) to (3) until the tensile strength criterion of the eyelet cracking is met. At the corresponding perforation (r)_w,1) Fluid pressure p₁(r_w,1) I.e. the fracture initiation pressure.

(4) Substituting the aperture flow of the 1 st shower of perforation into a formula (45) to calculate the friction resistance (p) of the fracture perforation_pf1,0) And then substituting the 1 st cluster perforation hole cracking pressure calculated in the step (3) into a formula (51) to calculate the shaft fluid pressure (p) of the 1 st cluster perforation hole of the horizontal well_1,0) (ii) a Then, p can be known according to the pressure balance equation_1,0＝p_2,0Thus, assume that the 2 nd shower orifice flow is Q_2,0According to the solution p_1,0Repeating the steps (1) to (3) to obtain the wellbore fluid pressure (p) of the 2 nd cluster perforation of the horizontal well_2,0) If (p)_2,0-p_1,0) Completing the calculation when the accuracy is less than a certain value, otherwise changing the aperture flow (Q) of the 2 nd shower aperture_2,0) Up to (p)_2,0-p_1,0) Less than a certain accuracy range. By analogy, the displacement (Q) of each cluster is obtained_i,0) And corresponding fracture initiation pressure (p)_i(r_w,i) And wellbore fluid pressure (p)_i,0)。

(5) If the difference between the sum of the displacement of each cluster and the construction displacement

If the accuracy requirement is not met, changing the aperture flow of the 1 st shower to q_1,0Repeating the steps (1) to (4) until

Certain precision is met; at this time, the displacement (q) per cluster is obtained_i,0) And corresponding fracture initiation pressure (p)_i(r_w,i) And wellbore fluid pressure (p)_i,0)。

S52: a crack initiation-propagation phase.

The fracture initiation pressure (p) obtained according to the injection-fracture initiation phase at each time of the fracture initiation-propagation phase₁(r_w,1),…,p₂(r_w,2),…,p_n(r_w,n) Sorting from small to large according to the size of the crack ((p)_fr1(j),p_fr2(j)…,p_frn(j) ))). Likewise, the construction displacement Q is constant, which is divided into clusters of holes according to the flow balance and pressure balance equations. Taking the initial fracture initiation step length delta L, dividing the time t (j) required by the completion of the injection of all fracturing fluid into j time periods, and dividing each time interval [ t (j) -t (j-1) ]]Correspondingly injecting a section of liquid into the crack, wherein the first initiated crack is turned to the forward extending length delta L, but the first initiated crack extending length is delta L_fi,j. The first initiated fracture length is j Δ L and the non-first initiated fracture length is

At the moment, the displacement of each cluster is q_i,jThe construction displacement is equal to the sum of the displacements of all perforation clusters

Assuming that the flow rate of perforation hole for the crack propagation of the first initiated perforation cluster is q_1,j；

1) When j is 1:

(1) since it has not yet propagated at the previous moment, the first crack initiation induced stress (

And

) 0, only the induced stress due to the formation fluid pressure change is superimposed on the in situ stress, so the extended stress field normal stress (σ) is calculated according to equation (44)_mxAnd σ_my) And a shear stress component (τ)_mxy)；

(2) Will expand the stress field normal stress (σ)_mxAnd σ_my) And a shear stress component (τ)_mxy) Substituting equations (36) and (37) to obtain the maximum positive stress sumMinimum positive stress sigma₁₁And σ₃₃Then substituting the formula into the formulas (59) and (60) to obtain the type I and type II intensity factors K_I1,1And K_II1,1(ii) a Then the type I and type II intensity factors K_I1,1And K_II1,1Substituting the formula (43) to obtain the extending direction angle beta of the 1 st shower perforation crack extending to the jth section_1,j；

(3) Then substituting the normal stress and the shear stress component of the expansion stress field into a formula (54) to obtain the circumferential stress (sigma) of the fracture end when the 1 st perforation cluster of the horizontal well expands to the 1 st section_βy,1,1) (ii) a Perforation flow q for initial crack propagation_1,1Substituting Q into equations (45) and (31) to obtain the perforation friction (p) of the 1 st perforation cluster crack_pf1,1) Average crack width (w) of the 1 st stage when crack 1 propagates to the 1 st stage_f1,1) Then the average width and the aperture flow q are calculated_1,1Substituting the step length (Δ L) into equation (46) to obtain the previous 1 st stage friction resistance (Δ p) when the crack 1 extends to the 1 st stage_f1,1) (ii) a Then substituting the value into the formula (47) to obtain delta p_1,1。

(4) Substituting the flow and step length of the perforation hole which is firstly initiated and expanded into a formula (48) to obtain the expansion time t (1) according to the initiation angle (gamma) of the initial point₁) And the step length (Delta L) is used to obtain x₁₁And y₁₁Coordinates; at the moment, other holes are not cracked and expanded; will sigma_βy,1,1、p_pf1,1And Δ p_1,1Substituting the formula (53) to obtain the fluid pressure (p) when the horizontal well crack 1 extends to the 1 st section_1,1)。

2) When j is 2:

firstly p is put in_1,1And the ordered fracture initiation pressure p_fr2Making a comparison if p_1,1＜p_fr2(j) Then, according to the solution idea of 1), crack 1 continues to expand to obtain p_1,1(ii) a If p is_1,1＞p_fr2(j) Then crack 2 begins to propagate.

(1) Q to be assumed_1,jSubstituting the formula (26) to obtain the net pressure p in each cluster of cracks_net1,jThen inducing normal stress according to the initial condition

Taking the coordinate average value corresponding to any two discrete units m, k (m is more than or equal to 1 and k is more than or equal to j) for the net pressure in the seam

And

substituting the obtained value into formula (25), and obtaining the discontinuity value of the constant displacement on the boundary unit of each perforation cluster crack through matrix transformation

(1≤k≤j)。

(2) Then x is put₁₁And y₁₁Coordinate and constant displacement discontinuity value

Substituting the formula (22) to obtain the crack-induced stress (

And

and

) (ii) a Superposing the induced stress generated by the corresponding induced stress of the two initiated fracture units and the formation fluid pressure change and the in-situ stress, and calculating the induced stress (sigma) generated by the formation fluid pressure change according to a formula (27)_xx、σ_yy) Substitution into equation (44) to obtain the extended stress field normal stress (σ)_mxAnd σ_my) And a shear stress component (τ)_mxy)；

(3) Correspondingly expanding the normal stress (sigma) of the stress field of the two cracked units_mxAnd σ_my) And a shear stress component (τ)_mxy) The maximum positive stress and the minimum positive stress sigma are obtained by substituting the equations (36) and (37) respectively₁₁And σ₃₃Then substituting the formula into the formulas (59) and (60) to obtain the type I and type II intensity factors K_I1,jAnd K_II1,j(ii) a Then the I type,Type II intensity factor K_IAnd K_IISubstituting the formula (43) to obtain the extending direction angle beta of the perforation crack extending to the j section_1,jAnd beta_2,jCorrespondingly, x is determined from the starting point and the step length (Delta L)₁₂And y₁₂Coordinates, from start point and step length (Δ L)_f2,j) Finding x₂₂And y₂₂Coordinates;

(4) suppose q_2,jThen substituting the normal stress and the shear stress component of the expansion stress field into a formula (54) to obtain the circumferential stress (sigma) of the fracture end when the horizontal well

perforation cluster fractures

1 and 2 expand to the jth section_βy,1,j、σ_βy,2,j) (ii) a Flow q of two initiated and expanded perforation holes_1,j、q_2,jSubstituting into equations (45) and (31) to obtain two fracture perforation friction resistances (p)_pf1,j、p_pf2,j) Average crack widths (w) of the 1 st and 2 nd stages when the crack 1 propagates to the 1 st stage_f1,1、w_f1,j) And the average width (w) of the crack of the 2 nd stage when the crack 2 spreads to the 2 nd stage_f2,j) Then the average width, the aperture flow and the step length are respectively substituted into a formula (46) to obtain the friction resistance (delta p) of each previous section when the two cracks are expanded to the jth section_f1,1、Δp_f1,jAnd Δ p_f2,j) (ii) a Then substituting each section of friction resistance into a formula (47) to obtain delta p_1,jAnd Δ p_2,j。

(5) Substituting the flow and step length of the perforation hole with crack initiation and expansion into a formula (48) to obtain expansion time t (j), wherein other holes do not crack and expand; will sigma_βy,1,j、p_pf1,j、Δp_1,jAnd σ_βy,2,j、p_pf2,j、Δp_2,jSubstituting the formula (53) to obtain the horizontal well fluid pressure (p)_1,jAnd p_2,j). According to the pressure balance equation, if (p)_1,j-p_2,j) If the precision requirement is not met, changing Q_2,jRepeating (4) to (5) until (p)_1,j-p_2,j) The accuracy requirement is met.

(6) If (q)_1,j+q_2,j-Q) does not meet the accuracy requirement, then Q is changed_1,jRepeating (1) to (6) until (q)_1,j+q_2,j-Q) meets the accuracy requirement.

3) And the like until the time t (j) required by the injection of all the fracturing fluid is finished.

The specific application example also provides a calculation example carried out according to the method, and based on the established unconventional reservoir horizontal well multi-cluster perforation competition initiation and expansion model, three clusters are selected for each section of perforation as an example, and multi-cluster fracture competition initiation and expansion rule analysis is carried out. It should be noted that the multi-cluster fracture propagation models established by most scholars in the past all assume that clusters are fractured simultaneously, and neglect that due to reservoir heterogeneity, ground stress difference and perforation pressure drop, perforation clusters are not fractured simultaneously, that is, each cluster has a certain fracture initiation sequence. Therefore, the patent respectively arranges 3 different permeability areas near the three perforation clusters to describe the physical heterogeneity, and the specific parameters are shown in table 2. The basic parameters used in this patent are the data in Table 2, unless otherwise specified.

TABLE 2 unconventional reservoir well multi-fracture competition initiation and propagation model calculation basic parameter table

Heterogeneous physical properties: the physical heterogeneity mainly influences the dynamic flow distribution in the model calculation process, and the influence of the physical heterogeneity of the reservoir on the competition cracking and expansion of the multiple cluster jet holes is further analyzed from the perspective of permeability distribution. Because the permeability near the three perforation clusters is different, three different combinations of three permeability areas, namely 0.1 mu D-0.5 mu D-0.9 mu D, 0.1 mu D-0.9 mu D-0.5 mu D and 0.5 mu D-0.1 mu D-0.9 mu D, are respectively selected. Wherein "0.1. mu.D-0.5. mu.D-0.9. mu.D" represents that the first cluster, the second cluster and the third cluster have permeabilities of 0.1. mu.D, 0.5. mu.D and 0.9. mu.D, respectively, and the remaining 2 combinations are similar.

(1) Different permeability combination competition crack initiation and propagation trajectories

FIGS. 10-12 are calculated results of competitive crack initiation and propagation trajectory distributions for different permeability combinations, showing simultaneous crack initiation of clusters at permeability combinations of 0.5 μ D-0.5 μ D-0.5 μ D; the cracking sequence under the permeability combination of 0.1 mu D-0.9 mu D-0.5 mu D for non-simultaneous cracking is respectively the 2 nd cluster-the 1 st cluster, wherein the 3 rd cluster is not cracked; the non-simultaneous crack initiation has a permeability of 0.1-0.5-0.9. mu.D, and the crack initiation sequence is 3 rd cluster-1 st cluster-2 nd cluster. Meanwhile, the expansion joint length of the permeability combination of 0.1 mu D-0.9 mu D-0.5 mu D for non-simultaneous cracking is found to be larger than that of the permeability combination of 0.5 mu D-0.5 mu D for simultaneous cracking. The method means that for the perforation of the reservoir with large permeability distribution difference, the situation that the permeability of the middle part is large and the permeability of the two sides is low is avoided, so that each cluster can compete for initiation and expansion non-simultaneously.

(2) The different permeability combinations compete for the initiation and the expansion of the initiation pressure and the bottom hole pressure of each cluster of cracks.

FIGS. 13 to 18 are calculated results of different permeability pressure distributions, which show that clusters crack simultaneously at 0.2s (crack initiation pressure 79.8MPa) at a combination of permeability of 0.5. mu.D-0.5. mu.D; and the non-simultaneous fracture initiation has a permeability combination of 0.1 muD to 0.9 muD to 0.5 muD, with the fracture initiation sequence, time and pressure being cluster 2 (0.9s, 79.7MPa) to cluster 1 (27.0s, 70.8MPa), respectively, with cluster 3 not fractured; the non-simultaneous crack initiation has the crack initiation sequence of the 3 rd cluster (0.5s, 80.3MPa) -the 1 st cluster (25.2s, 71.0MPa) -the 2 nd cluster (103.9s, 68.9MPa) under the permeability combination of 0.1 muD-0.5 muD-0.9 muD.

(3) Different permeability combinations compete for crack initiation and displacement expansion.

FIGS. 19-23 are calculations of different permeability displacement profiles, showing that for the permeability combinations of 0.5 μ D-0.5 μ D-0.5 μ D, the same permeability for each cluster results in a displacement of 1.67m for each cluster³Min; for permeability combinations of 0.1 μ D-0.9 μ D-0.5 μ D, cluster 2 initiation at 0.9s resulted in cluster 2 displacement from 5.3X 10^-3m³Min was changed to 4.2m³At 27.0 s/min, the 1 st cluster cracks, so that the 1 st cluster displacement is from 2.4X 10^-5m³Min was changed to 3.5m³And/min. For permeability combinations of 0.1 μ D-0.5 μ D-0.9 μ D, cluster 3 at 0.5s initiated so that cluster 3 displaced from 4.8m³Min was changed to 5.0m³At 25.2s, the 1 st cluster is cracked, so that the 1 st cluster displacement is from 2.5 multiplied by 10^-5m³Min was changed to 3.5m³At 103.9 s/min, the 2 nd cluster cracks, so that the 2 nd cluster displacement is from 5.6 multiplied by 10^-5m³Min was changed to 3.0m³/min。

Perforation parameters: on the basis of analyzing formation parameters and construction parameters, the influence of perforation parameters on the competitive fracture initiation and expansion of the multiple clusters of perforation holes is further developed. Therefore, the influence of perforation parameters on competitive crack initiation and expansion is analyzed by selecting the perforation cluster spacing and the perforation diameter.

The cluster spacing: the calculation example analyzes the influence of perforation parameters on competitive crack initiation and propagation by selecting the cluster spacing of 10m and 5m under the permeability combination of 0.1 mu D-0.5 mu D-0.9 mu D.

(1) Different cluster pitches compete for crack initiation and trajectory expansion.

Fig. 24 and fig. 25 show the competitive crack initiation and propagation trajectory distribution with different cluster pitches, and it can be seen that the 1 st, 2 nd and 3 rd cluster slit lengths with a cluster pitch of 5m are 100.1m, 98.1m and 101.0m, respectively; and a tuft spacing of 10m the tuft length of the 1 st, 2 nd and 3 rd tufts is 100.1m, 98.2 and 101.1m, respectively. It can be seen that the larger the cluster spacing, the greater the crack length developed and the smaller the induced stress, and overall, the cluster spacing had no significant effect on crack length development.

(2) Different cluster intervals compete for the initiation and the expansion of the initiation pressure and the bottom hole pressure of each cluster of cracks.

Fig. 26 and 27 show different cluster spacing competition initiation and expansion of each cluster fracture pressure distribution, and it can be seen that the cluster spacing is 5m, each cluster initiation sequence, initiation pressure and time, 3 rd cluster (0.5s, 80.3MPa) -1 st cluster (25.1s, 71.2MPa) -2 nd cluster (103.5s, 69.1 MPa); and the cluster spacing is 10m, and the cluster initiation sequence, initiation pressure and time are 3 rd cluster (0.5s, 80.3MPa) -1 st cluster (25.2s, 71.0MPa) -2 nd cluster (103.9s, 68.9 MPa). It can be seen that the cluster spacing only affects the post-initiation perforation clusters without affecting the initial initiation, and that the induced stresses are smaller due to the larger cluster spacing, resulting in lower initiation pressures. Meaning that the size of the cluster spacing can be adjusted to reduce the burst pressure so that each cluster can initiate crack propagation.

(3) Different cluster pitches compete for initiating and expanding the discharge of each cluster of cracks.

FIG. 28 and FIG. 29 are calculated results of different cluster spacing competing for initiation and propagation of each cluster of fracture displacement distribution, which shows that for a cluster spacing of 10m, each cluster of fracture displacement distribution is consistent with the analysis of FIG. 22; for 5m, 0.5s cluster 3 initiated so that cluster 3 displacement was from 4.8m³Min was changed to 5.0m³At 25.1s, the 1 st cluster cracks, so that the 1 st cluster displacement is from 2.5 multiplied by 10^- ⁵m³Min was changed to 3.5m³At 103.5 s/min, the 2 nd cluster cracks, so that the 2 nd cluster displacement is from 5.6 multiplied by 10^-5m³Min was changed to 3.0m³/min。

Eyelet diameter: two different combinations of three perforation diameters, namely 10mm-10mm-10m and 6mm-10mm-14mm, were selected for this calculation example. Wherein "10 mm-10mm-10 mm" means that the aperture diameters of cluster 1, cluster 2 and cluster 3 are 10mm, 10mm and 10mm, respectively, and the other combinations are similar.

(1) Different hole diameter combinations compete for initiation and propagation of each cluster of fracture trajectories.

Fig. 30 and fig. 31 show the combined competitive initiation and propagation of the crack trajectory distribution of each cluster with different hole diameters, and it can be seen that three clusters with the same hole diameter can initiate and propagate the same trajectory at the same time in 0.2s, and the propagation crack length is 93.8 m; and the combination of 6mm-10mm-14mm with different perforation diameters leads to three clusters of non-simultaneous initiation, the initiation sequence of each cluster, initiation pressure, crack length and time are 1 st cluster (1.7s, 80.3MPa, 92.6m) -2 nd cluster (101.7s, 71.4MPa, 102.5m) -3 rd cluster (800.3s, 68.8MPa, 94.0m), the non-uniform perforation diameter leads to the non-simultaneous initiation of each cluster, and the crack length of the non-simultaneous initiation expansion is longer than the crack length of the simultaneous initiation expansion. In addition, the 3 rd cluster crack initiation time is much longer than the other clusters. On one hand, the cluster can be well initiated and expanded by avoiding the large diameter of the two sides and the small middle of the perforation of the reservoir stratum with large distribution difference of the perforation diameters, and on the other hand, the cluster of cracks can be initiated and expanded by improving the perforation diameter of the cluster of cracks, so that the oil-gas flow area is enlarged.

(2) Different hole diameters are combined to compete for the initiation and the expansion of the initiation pressure and the bottom hole pressure of each cluster of cracks.

Fig. 32 and 33 show that different perforation diameters compete for the pressure distribution of the initiation and expansion clusters of cracks in combination, and it can be seen that three clusters with the same perforation diameter can initiate and expand the same track at the same time in 0.2s, and the length of the expansion crack is 93.8 m; the combination of 6mm-10mm-14mm with different perforation diameters leads to three clusters of non-simultaneous initiation, the initiation sequence of each cluster, initiation pressure, seam length and time are 1 st cluster (1.7s, 80.3MPa, 92.6m) -2 nd cluster (101.7s, 71.4MPa, 102.5m) -3 rd cluster (800.3s, 68.8MPa, 94.0m), and the non-uniform perforation diameters lead to the non-simultaneous initiation of each cluster; in addition, the 3 rd cluster crack initiation time is much longer than the other clusters. On one hand, for the reservoir perforation with larger distribution difference of the perforation diameters, the cluster can be well initiated and expanded by avoiding the large diameter at two sides and the small diameter at the middle.

(3) Different hole diameter combinations compete for crack initiation and propagation of each cluster of crack displacement.

The calculation results of different perforation diameter combination competition initiation and expansion clusters of fracture displacement distribution are shown in FIG. 34 and FIG. 35, and the perforation diameter 10mm-10mm-10mm combination displacement is kept at 1.67m³The/min remained unchanged. The combination of the perforation diameters of 6mm-10mm-14mm is higher at the beginning because of higher permeability, the higher the flow rate is, so that the displacement of the corresponding perforation clusters of 0.1 mu D, 0.5 mu D and 0.9 mu D is increased step by step. Along with the time, the displacement of the new initiation perforation cluster is suddenly increased and then gradually reduced, and the displacement of the rest 2 clusters is correspondingly reduced and then increased. Specifically, for the combination of perforation diameter 6mm-10mm-14mm, the 1 st cluster cracks at 1.7s, so that the 1 st cluster displacement is from 1.5 multiplied by 10^-4m³Min was changed to 3.9m³At/min, 101.7s the 2 nd cluster is cracked so that the 2 nd cluster displacement is from 6X 10^-5m³Min was changed to 3.5m³At/min, 800.3s cluster 3 cracks making cluster 3 move from 5.6X 10^-5m³Min was changed to 3.7m³/min。

Construction parameters are as follows: the calculation example mainly analyzes two construction parameters, namely the viscosity and the construction displacement of the fracturing fluid in the shale hydraulic fracturing process, and influences on the competitive fracture initiation and expansion of the multiple cluster jet holes.

The viscosity of the fracturing fluid is an important construction parameter in the hydraulic fracturing process of the shale. The method analyzes the influence of different fracturing fluid viscosities of 5mPa · s and 25mPa · s on competitive cracking and expansion of the shale multiple-cluster perforation respectively.

(1) Different fracturing fluid viscosities compete for initiation and propagation of each cluster of fracture tracks.

Fig. 36 and 37 show that different fracturing fluid viscosities compete for crack initiation and propagation of each cluster of fracture track distribution, and it can be seen that the fracturing fluid viscosities of 5mPa · s and 25mPa · s can initiate crack propagation. Wherein the three clusters with the viscosity of 5 mPas have the crack initiation sequence and the seam length of 3 rd cluster (100.1m) -1 st cluster (98.2m) -2 nd cluster (101.1m), and the three clusters with the viscosity of 25 mPas have the crack initiation sequence and the seam length of 3 rd cluster (100.8m) -1 st cluster (99.8m) -2 nd cluster (98.3 m).

(2) Different viscosities compete for the initiation and the expansion of the initiation pressure and the bottom hole pressure of each cluster of cracks.

FIGS. 38-41 show the different viscosity competing initiation and propagation clusters fracture pressure profiles, and it can be seen that three clusters initiated non-simultaneously at 5 mPa.s, cluster initiation sequence, initiation pressure and time cluster 3 (0.5s, 80.3MPa) -cluster 1 (25.2s, 71.0MPa) -cluster 2 (103.9s, 68.9 MPa); and three clusters crack non-simultaneously at 25 mPas, and the cracking sequence, the cracking pressure and the cracking time of each cluster are 3 rd cluster (2.26s, 79.7MPa) -1 st cluster (27.6s, 71.1MPa) -2 nd cluster (102.6s, 70.0 MPa). The higher the viscosity, the more difficult the fracturing fluid fails to percolate into the formation and the time to initiate the fracture of each cluster becomes longer.

The construction discharge capacity is an important construction parameter in the shale hydraulic fracturing process, and 5m is selected in the method³Min and 8m³And analyzing the influence of construction discharge capacity on the competition crack initiation and expansion of the multiple shower holes.

(1) Different construction discharge capacities compete for crack initiation and crack track distribution of each cluster.

FIG. 42 and FIG. 43 show the trajectory distribution of each cluster of cracks of different construction displacement competitive initiation and propagation, and it can be seen that 5m³The length of the three clusters of expansion seams is respectively the 1 st cluster (100.1m), the 2 nd cluster (98.2m) and the 3 rd cluster (101.1 m); and 8m³The length of the three clusters of expansion gaps is respectively the 1 st cluster (161.3m), the 2 nd cluster (163.7m) and the 3 rd cluster (165.3m), and the larger the displacement is, the larger the net pressure is, so that the longer the crack expansion gap is, and the longer each cluster of crack expansion gap is.

(2) Different construction discharge capacity compete for the initiation and the expansion of the initiation pressure and the bottom hole pressure of each cluster of cracks.

FIGS. 44 to 47 show the pressure distribution of each cluster of cracks in competition initiation and expansion of different construction displacement, and 5m can be seen³Three clusters crack non-simultaneously at/min, the order of cracking of each cluster, cracking pressure and time cluster 3 (0.5s, 80.3MPa) -cluster 1 (25.2s, 71.0MPa) -cluster 2 (103.9s, 68.9 MPa); and 8m³Three clusters crack non-simultaneously at/min, the order of cracking of each cluster, the cracking pressure and the time from cluster 3 (0.5s, 80.1MPa) to cluster 2 (7.6s, 80.0MPa) to cluster 1 (26.6s, 73.1 MPa). This is because the larger the displacement, the larger the net pressure, resulting in a significant reduction in fracture initiation time.

(3) Different construction discharge capacities compete for crack initiation and expansion of the discharge capacity distribution of each cluster of cracks.

FIGS. 48 to 51 show different construction displacement competing crack initiation and propagation clusters of crack displacement distributions, and it can be seen that 5m³Three clusters are not simultaneously cracked at/min, the cracking sequence of each cluster is 3 rd cluster (0.5s) -1 st cluster (25.2s) -2 nd cluster (103.9s), and the corresponding row quantity is changed from 3.8m of the 3 rd cluster³Min was changed to 5.0m³Min, cluster 1 from 2.5X 10^-5m³Min was changed to 3.5m³Min, cluster 2 from 5.7X 10^-5m³Min was changed to 3.0m³Min; and 8m³Three clusters are not simultaneously cracked at/min, the cracking sequence of each cluster and the time are 3 rd cluster (0.5s) -2 nd cluster (7.6s) -1 st cluster (26.6s), and the corresponding row quantity is changed from 7.7m of the 3 rd cluster³Min was changed to 7.9m³Min, cluster 2 from 2.7X 10^-4m³Min was changed to 5.6m³Min, cluster 2 from 2.5X 10^-5m³Min was changed to 4.3m³/min。

The specific application example comprehensively considers the influence factors such as the in-situ stress of the unconventional reservoir, the borehole induced stress, the borehole trajectory of the horizontal shaft and the like, and establishes a cracking pressure prediction model of the unconventional reservoir under the influence of comprehensive horizontal cylinder injection, fluid disturbance and the like; combining the change of the elastic coefficient of the hole caused by rock water absorption, the mechanical property of the rock under the disturbance of working fluid and the percolation characteristic in the injection process of fracturing fluid to obtain the stress distribution around the perforation hole; based on the maximum tensile stress theory, a seepage-stress fracture initiation pressure prediction model under the unconventional reservoir complex working condition is established, and the influence of formation parameters, construction parameters and perforation parameters on the fracture initiation pressure is further analyzed. Secondly, coupling multi-crack flow dynamic distribution, crack initiation perforation cluster extension and crack induction stress by combining an established seepage-stress crack initiation pressure prediction model based on reservoir physical properties, ground stress, perforation hole intraocular pressure drop and the like, and establishing a horizontal shaft multi-cluster perforation competition crack initiation and expansion model; and further analyzing influence rules and factors of multi-cluster-jet-hole competitive cracking and expanding.

Based on the same inventive concept, the embodiment of the present application further provides an unconventional reservoir multi-cluster-hole competition fracture initiation and expansion simulation apparatus, which can be used to implement the method described in the above embodiment, as described in the following embodiments. Because the problem solving principle of the unconventional reservoir multi-cluster-jet competitive fracturing and expansion simulation device is similar to the unconventional reservoir multi-cluster-jet competitive fracturing and expansion simulation method, the implementation of the unconventional reservoir multi-cluster-jet competitive fracturing and expansion simulation device can be implemented by referring to the implementation of the unconventional reservoir multi-cluster-jet competitive fracturing and expansion simulation method, and repeated parts are not repeated. As used hereinafter, the term "unit" or "module" may be a combination of software and/or hardware that implements a predetermined function. While the system described in the embodiments below is preferably implemented in software, implementations in hardware, or a combination of software and hardware are also possible and contemplated.

The embodiment of the invention provides a specific implementation mode of an unconventional reservoir multi-cluster-jet competitive fracture and extension simulation device capable of realizing an unconventional reservoir multi-cluster-jet competitive fracture and extension simulation method, and referring to fig. 52, the unconventional reservoir multi-cluster-jet competitive fracture and extension simulation device specifically comprises the following contents:

the well circumferential stress prediction unit 10 is used for generating a well circumferential stress prediction model according to the in-situ stress, the borehole induced stress and the borehole trajectory;

the fracture initiation pressure prediction unit 20 is used for generating a seepage-stress fracture initiation pressure prediction model according to the well circumferential stress prediction model based on the percolation characteristics in the injection process of the fracturing fluid;

and the multi-cluster model generation unit 30 is configured to generate a multi-cluster perforation competition initiation and propagation model according to the well circumferential stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture propagation process, the fracture induced stress generated by the extension of the pre-initiated perforation cluster, and the induced stress generated by the pressure change of the formation fluid, based on the well circumferential reservoir physical properties, the well circumferential geostress heterogeneity and the perforation pressure.

In one embodiment, referring to fig. 53, the fracture initiation pressure prediction unit 20 includes:

a prediction model generation module 201, configured to generate a fracture initiation pressure prediction model according to the well circumferential stress prediction model, the induced stress of the in-situ stress, the induced stress of the casing cement sheath, and the stress field of the perforation hole;

and the fracture initiation pressure prediction module 202 is configured to generate the seepage-stress fracture initiation pressure prediction model according to the pore elastic coefficient caused by rock water absorption and the fracture initiation pressure prediction model by using a maximum tensile stress method.

In one embodiment, referring to fig. 54, the multi-cluster model generation unit 30 includes:

the expansion model generation module 301 is used for generating a perforation cluster fracture expansion model according to the perforation cluster fracture expansion stress field and the fracture friction resistance;

a multi-cluster model generating module 302, configured to generate a multi-cluster perforation competition fracture initiation and propagation model according to the perforation cluster fracture propagation model and the multi-cluster perforation competition fracture initiation and propagation physical model.

In one embodiment, referring to fig. 55, the multi-cluster model generation module 302 includes:

a competition expansion model generation module 3021, configured to generate a competition expansion model according to the hydraulic fracture expansion stress field, the hydraulic fracture friction resistance, and the multi-fracture flow distribution model;

a multi-cluster model generation submodule 3022, configured to generate the multi-cluster perforation competition cracking and expanding model according to the competition expanding model.

In one embodiment, referring to fig. 56, the unconventional reservoir multi-cluster perforation competition fracture initiation and propagation simulation apparatus further includes: a flow distribution model generating unit 40 configured to generate the multi-fracture flow distribution model, referring to fig. 57, where the flow distribution model generating unit 40 includes:

the flow model 401 of the initiation stage is used for establishing a multi-fracture initiation flow distribution model corresponding to the injection to initiation stage according to the flow and the pressure injected to the initiation stage;

the expansion stage flow model 402 is used for establishing a multi-fracture expansion flow distribution model corresponding to the fracture initiation to expansion stage according to the flow rate and pressure from the fracture initiation to the expansion stage;

a flow distribution model generating module 403, configured to generate the multi-fracture flow distribution model according to the multi-fracture initiation flow distribution model and the multi-fracture propagation flow distribution model.

In one embodiment, referring to fig. 58, the unconventional reservoir multi-cluster perforation competition fracture initiation and propagation simulation apparatus further includes: and the physical model generating unit 50 is used for generating the multi-cluster-perforation competition initiation and propagation physical model, and the physical model generating unit is specifically used for generating the multi-cluster-perforation competition initiation and propagation physical model according to the single-fracture initiation process characteristics, the multi-fracture flow distribution characteristics, the extension characteristics of the fractures of the first initiation perforation cluster, the induced stress generated by the fractures formed by the extension of the first initiation perforation cluster and the induced stress generated by the change of the formation fluid pressure.

As can be seen from the above description, in the unconventional reservoir multi-cluster-perforation competitive fracture initiation and expansion simulation device provided by the embodiment of the present invention, firstly, a gradient data volume is generated according to an elevation data volume of an ancient karst landform; generating a section curvature data volume according to the elevation data volume; then, generating a valley data volume according to the elevation data volume; and finally, classifying the karst ancient landforms of the target work area according to the gradient data volume, the section curvature data volume and the valley data volume. According to the method, a more reasonable and fine dividing result of the paleo-karst landform can be obtained, and based on the dividing result, the reservoir development characteristics and the gas well yield difference of different micro-landform units can be analyzed, so that guidance is provided for reservoir prediction and well position deployment.

The apparatuses, modules or units illustrated in the above embodiments may be implemented by a computer chip or an entity, or implemented by a product with certain functions. A typical implementation device is an electronic device, which may be, for example, a personal computer, a laptop computer, a cellular telephone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

In a typical example, the electronic device specifically includes a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the computer program, the method implements the steps of the front-end framework-based dynamic pointing method, including:

step 100: generating a well circumferential stress prediction model according to the in-situ stress, the well bore induced stress and the well bore track;

step 200: generating a seepage-stress fracture initiation pressure prediction model according to the well circumferential stress prediction model based on the percolation characteristics in the fracturing fluid injection process;

Referring now to FIG. 59, shown is a schematic diagram of an electronic device 600 suitable for use in implementing embodiments of the present application.

As shown in fig. 59, the electronic apparatus 600 includes a Central Processing Unit (CPU)601 that can perform various appropriate works and processes according to a program stored in a Read Only Memory (ROM)602 or a program loaded from a storage section 608 into a Random Access Memory (RAM)) 603. In the RAM603, various programs and data necessary for the operation of the system 600 are also stored. The CPU601, ROM602, and RAM603 are connected to each other via a bus 604. An input/output (I/O) interface 605 is also connected to bus 604.

The following components are connected to the I/O interface 605: an input portion 606 including a keyboard, a mouse, and the like; an output portion 607 including a display such as a Cathode Ray Tube (CRT), a Liquid Crystal Display (LCD), and the like, and a speaker; a storage section 608 including a hard disk and the like; and a communication section 609 including a network interface card such as a LAN card, a modem, or the like. The communication section 609 performs communication processing via a network such as the internet. The driver 610 is also connected to the I/O interface 605 as needed. A removable medium 611 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, or the like is mounted on the drive 610 as necessary, so that a computer program read out therefrom is mounted as necessary on the storage section 608.

In particular, according to an embodiment of the present invention, the processes described above with reference to the flowcharts may be implemented as computer software programs. For example, an embodiment of the present invention includes a computer-readable storage medium having a computer program stored thereon, which when executed by a processor implements the front-end framework-based dynamic point-burying method described above.

In such an embodiment, the computer program may be downloaded and installed from a network through the communication section 609, and/or installed from the removable medium 611.

Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.

For convenience of description, the above devices are described as being divided into various units by function, and are described separately. Of course, the functionality of the units may be implemented in one or more software and/or hardware when implementing the present application.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A unconventional reservoir multi-cluster perforation competition cracking and expanding simulation method is characterized by comprising the following steps:

generating a multi-cluster perforation competition initiation and expansion model according to the well-periphery stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the initial initiation perforation cluster and the induced stress generated by the pressure change of the formation fluid based on the physical properties of the reservoir around the well, the stress heterogeneity of the ground around the well and the perforation pressure;

the generating of the seepage-stress fracture initiation pressure prediction model according to the well circumferential stress prediction model based on the percolation characteristics in the fracturing fluid injection process comprises the following steps:

determining the cracking stress field distribution of the perforation holes;

establishing a pressure diffusion equation;

determining a crack initiation criterion;

the establishing of the pressure diffusion equation comprises:

it is required here that assuming that the rock is permeable and saturated with fracturing fluid, the fluid is slightly compressible, and neglecting the invasion of capillary force and other fluids, when the well bore is initially charged, as the fracturing fluid flows from each perforation cluster through the rock pore space, the pore pressure around the well bore of each perforation cluster is increased, and the stress field distribution of the rock around the well bore can be obtained according to a two-dimensional radial flow stress diffusion equation, specifically:

in the formula: k is the permeability of the rock corresponding to the perforation hole, mum²(ii) a Phi is rock porosity, dimensionless; μ is the fluid viscosity, mPas; c is the overall compressibility, MPa^-1(ii) a t is the injection time, s;

pressure boundary and initial conditions:

p(r)＝p_p，t＝0 (6)

p(r)→p_p，r→∞ (8)

in the formula: q is the displacement of orifice injection, m³/min；N_pThe number of perforation holes is two; l is_pIs the perforation depth, m;

ei refers to the power exponent, which is expressed as:

the method for generating the multi-cluster perforation competition initiation and propagation model according to the well-surrounding stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture propagation process, the fracture induced stress generated by the extension of the initial initiation perforation cluster and the induced stress generated by the pressure change of the formation fluid based on the well-surrounding reservoir physical properties, the well-surrounding ground stress heterogeneity and the perforation pressure comprises the following steps:

generating a multi-cluster-jet competitive cracking and expanding model according to the perforation cluster crack expanding model and the multi-cluster-jet competitive cracking and expanding physical model;

the step of generating the multi-cluster-hole competition fracture initiation and expansion physical model comprises the following steps:

2. The simulation method of claim 1, wherein the generating a seepage-stress fracture initiation pressure prediction model from the periwell stress prediction model based on the percolation characteristics during the injection of the fracturing fluid comprises:

3. The simulation method of claim 2, wherein the generating the multi-cluster perforation competition initiation and propagation model from the perforation cluster fracture propagation model and a multi-cluster perforation competition initiation and propagation physical model comprises:

4. The simulation method of claim 3, wherein the step of generating the multi-fracture flow distribution model comprises:

5. An unconventional reservoir multi-cluster perforation competition cracking and expansion simulation device is characterized by comprising:

the multi-cluster model generation unit is used for generating a multi-cluster perforation competition initiation and expansion model according to the well peripheral stress prediction model, the pressure prediction model, the flow dynamic distribution in the multi-fracture initiation process, the flow dynamic distribution in the multi-fracture expansion process, the fracture induced stress generated by the extension of the pre-initiated perforation cluster and the induced stress generated by the pressure change of formation fluid based on the well peripheral reservoir physical properties, the well peripheral geostress heterogeneity and the perforation pressure;

determining the cracking stress field distribution of the perforation holes;

establishing a pressure diffusion equation;

determining a crack initiation criterion;

the establishing of the pressure diffusion equation comprises:

pressure boundary and initial conditions:

p(r)＝p_p，t＝0 (6)

p(r)→p_p，r→∞ (8)

ei refers to the power exponent, which is expressed as:

the multi-cluster model generation unit includes:

the multi-cluster model generation module is used for generating a multi-cluster perforation competition initiation and expansion model according to the perforation cluster crack expansion model and the multi-cluster perforation competition initiation and expansion physical model;

unconventional reservoir multi-cluster perforation competition cracking and expansion simulation device, further comprising: and the physical model generating unit is specifically used for generating the multi-cluster-perforation competition initiation and expansion physical model according to the single-fracture initiation process characteristic, the multi-fracture flow distribution characteristic, the extension characteristic of the fracture of the first initiation perforation cluster, the induced stress generated by the extension of the first initiation perforation cluster to form the fracture and the induced stress generated by the change of the formation fluid pressure.

6. The simulation device of claim 5, wherein the fracture initiation pressure prediction unit comprises:

7. The simulation apparatus of claim 6, wherein the multi-cluster model generation module comprises:

8. The simulation apparatus of claim 7, further comprising: a flow distribution model generation unit configured to generate the multi-fracture flow distribution model, the flow distribution model generation unit including:

9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor when executing the program implements the steps of the unconventional reservoir multiple-cluster-perforation competition starting and propagation simulation method of any one of claims 1 to 4.

10. A computer readable storage medium having stored thereon a computer program, wherein the computer program when executed by a processor implements the steps of the unconventional reservoir multiple-cluster-hole competition fracturing and propagation simulation method of any one of claims 1 to 4.