Simulation method for the opening and expansion of each cluster in multi-cluster flow-limiting perforation fracturing within the evaluation section

Abstract

The present invention relates to the technical field of oil and gas well production enhancement and transformation, and in particular to a simulation method for the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing in an evaluation section, comprising: establishing a method for calculating the number of openings and the porosity; establishing a calculation model for fracturing fluid distribution in multiple clusters of fractures in a wellbore; establishing a fluid-solid coupling model for the initiation and expansion of multiple clusters of fractures, and applying a Picard iteration method and an implicit pressure-explicit saturation method for coupling solution; obtaining the number of openings in each cluster and the characteristics of fracture initiation and expansion through calculation using a simulation program, so as to judge the number of openings in each cluster and the opening status of each cluster of fractures; the present invention solves the problem of whether multiple clusters in the middle section of flow-limiting perforation fracturing are effectively opened and transformed through simulation calculation, and while providing technical guidance for the efficient exploration and development of tight oil and gas reservoirs, improves the practicality and stability of the on-site construction diagnosis process technology for well completion using flow-limiting perforation fracturing.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas well production enhancement and transformation, and in particular to a simulation method for the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section. Background Art

[0002] Currently, fracturing of tight oil and gas reservoirs is often completed using multi-cluster perforation within the casing cementing section, and cluster-based flow-limiting perforation is often used during stimulation. During intra-segment multi-cluster fracturing, due to significant differences in reservoir lithology, stress values, physical properties, and other geological conditions at different perforation cluster locations, perforation clusters cannot effectively initiate and propagate fractures. The actual number of activated clusters is lower than the expected design, resulting in some intervals being unable to be effectively stimulated and failing to achieve the designed stimulation effect. A rapid, effective, and practical simulation method for evaluating the initiation and propagation of multi-cluster fractures within a segment is urgently needed.

[0003] Chinese Patent Authorization Publication No. CN112836446B discloses a method for optimizing clustered flow control perforation layout for tight reservoir horizontal wells. This invention discloses a method for optimizing clustered flow control perforation layout for tight reservoir horizontal wells, including the following steps: S1: Acquiring basic rock mechanics parameters, minimum horizontal in-situ stress parameters, and fracturing engineering parameters; S2: Establishing a fracture propagation model for multi-cluster fracture propagation, simulating the fracture morphology of uniformly distributed multi-cluster fractures; S3: Simulating the induced stress field distribution under multi-cluster fracture propagation morphology and quantitatively characterizing the uniformity of multi-cluster fracture propagation; S4: Establishing the intra-segment pressure and flow distribution relationship for multiple clusters and an optimization model for clustered flow control perforation layout under non-abrasive conditions; S5: Designing the clustered flow control perforation layout under perforation abrasion conditions; and S6: Verifying the fracture propagation effect of the optimized clustered flow control perforation layout. This invention effectively avoids the generation of ineffective perforation clusters and improves the perforation cluster efficiency of multi-cluster fractured wells. It is of great significance for the scientific design of optimized clustered flow control perforation layout for tight oil and gas reservoirs and the efficient and economic development of tight reservoirs.

[0004] There is also a Chinese patent authorization announcement number: CN112417644B discloses a horizontal well multi-stage multi-cluster extreme flow limiting fracturing process design method. This invention is in the field of horizontal well fracturing technology, specifically a horizontal well multi-stage multi-cluster extreme flow limiting fracturing process design method, including the following steps: (1) data collection; (2) cluster spacing design; (3) single-stage cluster number design; (4) single-stage hole number design; (5) phase angle design; (6) construction displacement and scale design; (7) sand addition method design. This invention can solve the problems existing in existing fracturing processes, such as low number of effective cracks, small gas leakage area, inability to achieve uniform transformation, poor proppant laying effect, and relatively high single-well construction cost. The present invention adopts the "sub-segment dense clustering + extreme flow limiting + high-intensity sand adding" fracturing process. On the basis of not increasing the average construction cost, it effectively increases the gas leakage area, improves production capacity, and improves the efficiency of perforation clusters in multiple cluster sections, achieving uniform transformation of multiple cluster cracks; by optimizing the sand adding method and optimizing the well entry material, it greatly improves the proppant laying effect, and improves the effective crack quality and transformation strength.

[0005] However, the above methods have the following problems: Research on intra-segment multi-cluster flow-limiting perforation fracturing has mainly focused on optimization design, and no research has been conducted on whether each cluster in intra-segment multi-cluster flow-limiting perforation fracturing should be opened. During intra-segment multi-cluster fracturing construction, some layers cannot be effectively transformed, and the designed transformation effect cannot be achieved. Downhole television monitoring is expensive and time-consuming, and requires downhole operations with gas well pressure, which affects the gas testing and production of the construction well. Summary of the Invention

[0006] To this end, the present invention provides a simulation method for evaluating the opening and expansion of each cluster of intra-segment multi-cluster flow-limiting perforation fracturing, so as to overcome the problems that in the prior art, research on intra-segment multi-cluster flow-limiting perforation fracturing is mainly based on optimization design, and no research is conducted on whether each cluster of intra-segment multi-cluster flow-limiting perforation fracturing is opened. During the intra-segment multi-cluster fracturing construction, some layers cannot be effectively transformed and the designed transformation effect cannot be achieved. The downhole television monitoring is expensive and has a long cycle, and the gas well needs to be operated under pressure, which affects the gas testing and production of the construction well.

[0007] To achieve the above objectives, the present invention provides a simulation method for evaluating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within a section, comprising:

[0008] The influence of pore friction on the porosity and the friction along the fracturing fluid under different completion string conditions were studied. Combined with the pre-fracturing test data, a calculation method for the number of openings and the porosity was established.

[0009] The liquid volume conservation equation and pressure balance equation are combined to establish a calculation model for fracturing fluid distribution in multiple fracture clusters within the wellbore.

[0010] According to the rock mechanics failure and multi-cluster crack propagation criteria, a fluid-solid coupling model of multi-cluster crack initiation and propagation was established using the finite element and discrete element coupling method, and the Picard iteration method and the implicit pressure explicit saturation method were coupled to solve the problem.

[0011] A simulation program for the opening and expansion of each cluster in intra-segment multi-cluster flow-limiting perforation fracturing was developed. Based on the input parameters, the simulation program calculated the number of openings in each cluster and the characteristics of fracture initiation and expansion. This was used to determine the number of openings in each cluster and the opening of each fracture cluster, guiding the optimization design of fracturing and reservoir construction and reconstruction.

[0012] The input parameters include reservoir parameters, wellbore parameters, perforation parameters, and test fracturing parameters. Furthermore, targeted experiments were conducted to measure the perforation rate and frictional resistance of fluids flowing through perforations of different diameters. A relationship was established between the frictional resistance and flow rate of different fluids flowing through perforations of different diameters. The large amount of measured data was plotted into a curve to establish a relationship between the perforation rate and frictional resistance of fluids flowing through perforations of different diameters at different displacement rates.

[0013] Furthermore, based on the established relationship diagram, combined with different fluids, perforation hole diameters, and different string types, the corresponding pore friction and single hole displacement can be obtained. Combined with the pre-pressure test data, the number of test openings and the porosity can be calculated.

[0014] The pre-pressure test data includes the maximum displacement tested, the pressure under the maximum displacement tested, and the pump stop pressure.

[0015] Furthermore, the flow distribution of each cluster of fracturing fluid satisfies the liquid volume conservation equation and the pressure balance equation. The two equations are combined to establish a nonlinear equation group with the flow rate of each cluster of fracturing fluid and the reference point pressure as unknown quantities. Through the iterative solution of the Newton method, the fluid volume of the flow distribution of each cluster of fracturing fluid can be calculated. The fluid volume of the flow distribution of each cluster of fracturing fluid can be used to judge the uniformity of the initiation and expansion of multiple clusters of cracks, and the initiation and expansion of the multiple clusters of cracks can be further calculated.

[0016] Furthermore, the Mohr-Coulomb failure criterion and the maximum tensile stress criterion are used to determine whether the rock block undergoes shear failure or tensile failure.

[0017] Furthermore, when the principal stress under maximum pressure is greater than the tensile strength of the rock, the rock block undergoes tensile failure, generating tensile cracks, and the shear amount of the tensile cracks is zero;

[0018] When the shear stress under the maximum pressure is greater than the sum of the cohesion and the friction, the rock block undergoes shear failure, generating shear cracks, and the normal displacement of the shear cracks is zero.

[0019] Furthermore, according to the flow distribution of each cluster of fracturing fluid, the liquid flow equation of each cluster of fracturing fluid can be established by the law of conservation of mass and momentum;

[0020] Wherein, each cluster of fracturing fluid is regarded as an incompressible Newtonian fluid.

[0021] Furthermore, the discrete element theory is applied to discretize the fractured reservoir into several matrix block units. A control volume unit exists between the mutually contacting matrix block units. In the control volume unit, the Barton-Bandis implicit contact force is introduced as the traction force to obtain the matrix block deformation equation.

[0022] In the control volume, the effects of inertial force and rigid body force on rock deformation are ignored.

[0023] Furthermore, the flow of each cluster of fracturing fluid is related to the deformation of the matrix block unit;

[0024] The change in fluid pressure on the boundary surface of the matrix block unit affects the deformation of the matrix block unit, thereby causing a change in the crack width. The change in the crack width causes a change in the flow rate of each cluster of fracturing fluid, ultimately affecting the distribution of fluid pressure of each cluster of fracturing fluid in the crack.

[0025] Furthermore, the correlation between the flow of each cluster of fracturing fluid and the deformation of the matrix block unit adopts a fluid-solid coupling model, and each control equation is solved by coupling the Picard iteration method and the implicit pressure explicit saturation method. The coupled iteration of the fluid pressure field of each cluster of fracturing fluid and the deformation of the matrix block unit is calculated, and the pressure convergence of all nodes is used as the judgment condition.

[0026] Furthermore, a fluid-solid coupling model of multi-cluster fracture initiation and expansion is established according to the coupling method, an information file for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within a segment is formed, the input parameters are set, and a simulation program for the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within a segment is compiled.

[0027] Furthermore, a simulation program for the opening and expansion of each cluster of perforation fracturing based on the multi-cluster flow limiting method within the segment is used to calculate the actual number of openings in each cluster and the characteristics of crack initiation and expansion, which are used to determine the number of perforation openings and the opening status of each cluster of cracks, and guide fracturing optimization design and reservoir construction and transformation.

[0028] Compared with the existing technology, the beneficial effect of the present invention lies in that it is based on the multi-cluster flow-limiting perforation completion technology within the section, with the goal of uniformly transforming multiple clusters of fractures. By establishing a method for calculating the number of perforation openings for flow-limiting fracturing, it provides technical guidance for the efficient exploration and development of tight oil and gas reservoirs, while improving the practicality and stability of the on-site construction diagnosis process technology of flow-limiting perforation fracturing completion.

[0029] Furthermore, by using the calculation model of multi-cluster fluid distribution in the wellbore and the discrete element mechanics model of multi-cluster fracture initiation and expansion, through simulation calculations, the problem of whether the multi-cluster in the middle section of the flow-limiting perforation fracturing is effectively opened and transformed is solved, while further improving the practicality and stability of the on-site construction diagnostic process technology of the flow-limiting perforation fracturing completion. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of a simulation method for the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section of the present invention;

[0031] Figure 2 This is embodiment 5 of the present invention 1 / 2 Relationship diagram of friction resistance along the casing with a hole diameter of 10.2 mm and different fracturing fluids;

[0032] Figure 3 This is a relationship diagram between single hole friction and single hole displacement at different hole diameters according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0034] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0035] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0036] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0037] See also Figure 1As shown, it is a flow chart of a simulation method for evaluating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within a segment according to the present invention. A simulation method for evaluating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within a segment comprises:

[0038] Step S1, studying the pore friction that affects the porosity and the friction along the fracturing fluid under different completion string conditions, and establishing a calculation method for the number of openings and the porosity based on pre-fracturing test data;

[0039] Step S2, combining the liquid volume conservation equation and the pressure balance equation to establish a calculation model for fracturing fluid distribution in multiple clusters of fractures in the wellbore;

[0040] Step S3, based on the rock mechanics failure and multi-cluster crack propagation criteria, a finite element and discrete element coupling method is used to establish a fluid-solid coupling model for the initiation and propagation of multi-cluster cracks, and the Picard iteration method and the implicit pressure explicit saturation method are coupled to solve the problem;

[0041] Step S4: Develop a simulation program for the opening and expansion of each cluster of intra-segment multi-cluster flow-limiting perforation fracturing. Based on the input parameters, the simulation program calculates the number of openings in each cluster and the characteristics of fracture initiation and expansion. This is used to determine the number of openings in each cluster and the opening of each cluster, guiding the optimal design of fracturing and reservoir reconstruction.

[0042] The input parameters include reservoir parameters, wellbore parameters, perforation parameters and test fracturing parameters.

[0043] Specifically, in step S1, the single-hole displacement and single-hole friction resistance of the fluid flowing through the perforation at different perforation diameters are measured through targeted experiments, and a relationship between the change in friction resistance and flow rate when different fluids flow through perforations with different diameters is established. The large amount of measured data is plotted into a curve, and a relationship diagram between the single-hole displacement and single-hole friction resistance of the fluid flowing through the perforation at different displacement rates is established.

[0044] See also Figure 2 As shown, it is embodiment 5 of the present invention 1 / 2 The relationship diagram of the friction resistance of different fracturing fluids along the perforation diameter of 10.2mm; the friction resistance of different fluids flowing through the casing of different perforation diameters at different displacements was measured in the laboratory, and a large amount of measured data was plotted into a curve. The relationship between the perforation parameters, pumping parameters and fluid type and the friction resistance along the way was fitted, and a relationship diagram of the displacement of different fluids flowing through the perforation and the friction resistance along the way was established.

[0045] See also Figure 3As shown, it is a relationship diagram between single-hole friction resistance and single-hole displacement at different apertures according to an embodiment of the present invention; the single-hole displacement and single-hole friction resistance of fluid flowing through the hole at different perforation diameters are measured through laboratory targeted experiments, and a relationship between the change of friction resistance and flow rate when different fluids flow through blastholes with different perforation diameters is established. A large amount of measured data is plotted into a curve, and a relationship diagram between single-hole displacement and single-hole friction resistance of fluid flowing through the hole at different displacement rates is established.

[0046] Specifically, in step S1, based on the established relationship diagram, combined with different fluids, perforation hole diameters, and different string types, the corresponding hole friction and single hole displacement can be obtained. Combined with the pre-pressure test data, the number of test openings and the porosity are calculated.

[0047] Among them, the pre-pressure test data includes the test maximum displacement, the test pressure under the maximum displacement and the pump stop pressure.

[0048] Number of test openings = Q test / Q i ;

[0049] Test opening ratio = number of openings / designed number of holes × 100;

[0050] Where: Q test -Tested maximum displacement, m 3 / min;

[0051] Q i - Single hole displacement of the i-th hole, m 3 / min.

[0052] Specifically, in step S2, the flow distribution of each cluster of fracturing fluid satisfies the liquid volume conservation equation and the pressure balance equation. The two equations are combined to establish a nonlinear equation group with the flow rate of each cluster of fracturing fluid and the reference point pressure as unknown quantities. Through the iterative solution of the Newton method, the fluid volume of the flow distribution of each cluster of fracturing fluid can be calculated. The fluid volume of the flow distribution of each cluster of fracturing fluid can be used to judge the uniformity of the initiation and expansion of multiple clusters of cracks, and further calculate the initiation and expansion of multiple clusters of cracks.

[0053]

[0054]

[0055] Where: q 总 -Total fluid flow during fracturing, m 3 / min;

[0056] q i - Fluid flow rate entering the i-th crack, m 3 / min;

[0057] n-total number of crack clusters, dimensionless;

[0058] P a -Reference point pressure, MPa;

[0059] ΔP bi - Closure pressure (minimum principal stress) of layer i, MPa;

[0060] ΔP ei - Effective fracturing pressure (fracture resistance) of the i-th layer wellbore, MPa;

[0061] ΔP kfi - hole friction of the i-th layer perforation, MPa;

[0062] ΔP hk -The hydrostatic pressure between the i-th layer and the i-1-th layer, MPa;

[0063] ΔP fdk - Friction resistance along the path between the i-th layer and the i-1-th layer, MPa;

[0064] Among them, the relationship between borehole friction resistance, along-the-line friction resistance and pump displacement is obtained by fitting the experimental results.

[0065] Specifically, in step S3, the Mohr-Coulomb failure criterion and the maximum tensile stress criterion are used to determine whether the rock block has undergone shear failure or tensile failure.

[0066] Specifically, in step S3, when the principal stress under maximum pressure is greater than the tensile strength of the rock, the rock block undergoes tensile failure, generating tensile cracks, and the shear amount of the tensile cracks is zero;

[0067] When the shear stress under maximum pressure is greater than the sum of cohesion and friction, the rock block undergoes shear failure, resulting in shear cracks, and the normal displacement of the shear cracks is zero.

[0068] -σ1>σ T ;

[0069]

[0070] Where: σ1-maximum compressive principal stress, MPa;

[0071] σ T -Tensile strength, MPa;

[0072] τ-shear stress on the rupture wall, MPa;

[0073] τ0-cohesion, MPa;

[0074] φ-internal friction angle, MPa;

[0075] σ n-Effective compressive stress normal to the seam surface, MPa.

[0076] Specifically, in step S3, according to the flow distribution of each cluster of fracturing fluid, the liquid flow equation of each cluster of fracturing fluid can be established by the law of conservation of mass and momentum;

[0077] Among them, each cluster of fracturing fluid is regarded as an incompressible Newtonian fluid.

[0078]

[0079] Where: q-volume flow rate, m 3 / s;

[0080] w-dynamic crack width, m;

[0081] μ-fracturing fluid viscosity, mPa·s;

[0082] p-fluid pressure, MPa;

[0083] s-coordinate of any point in the crack, m;

[0084] t-time, s;

[0085] q L -Fracturing fluid loss, m 3 / s;

[0086] Q i -Pumping rate of the i-th fracture cluster, m 3 / s;

[0087] δ() - velocity matrix.

[0088] Specifically, in step S3, the discrete element theory is applied to discretize the fractured reservoir into several matrix block units. A control volume unit exists between the mutually contacting matrix block units. Within the control volume unit, the Barton-Bandis implicit contact force is introduced as the traction force to obtain the matrix block deformation equation;

[0089] In the control volume, the effects of inertial force and rigid body force on rock deformation are ignored.

[0090] Matrix block deformation equation:

[0091]

[0092] Where:

[0093] η - the first Lame coefficient in the strain-stress relationship;

[0094] λ - the second Lame coefficient in the strain-stress relationship;

[0095] n - normal unit vector;

[0096] t-tangential unit vector;

[0097] r - control volume unit radius, mm;

[0098] u n - rock normal displacement, m;

[0099] u t - rock tangential displacement, m;

[0100] σ o - stress tensor of the rock, MPa;

[0101] α-Biot coefficient;

[0102] Γ b -The area of ​​the contact surface between the matrix and the crack, m2;

[0103] p f -Fracturing fluid pressure, MPa.

[0104] Specifically, in step S3, the fracturing fluid flow of each cluster is correlated with the deformation of the matrix block unit;

[0105] The change of fluid pressure on the boundary surface of the matrix block unit affects the deformation of the matrix block unit, which in turn causes the change of fracture width. The change of fracture width causes the flow rate of each cluster of fracturing fluid to change, and ultimately affects the distribution of fluid pressure of each cluster of fracturing fluid in the fracture.

[0106] Specifically, in step S3, the correlation between the flow of each cluster of fracturing fluid and the deformation of the matrix block unit adopts the fluid-solid coupling model, and each control equation is solved by the Picard iteration method and the implicit pressure saturation method. The coupled iteration of the fluid pressure field of each cluster of fracturing fluid and the deformation of the matrix block unit is calculated, and the pressure convergence of all nodes is used as the judgment condition.

[0107]

[0108] Where: p-fluid pressure, MPa;

[0109] w-crack width, mm;

[0110] u-displacement, mm;

[0111] p k+1 / 2 -Pressure trial solution of the k+1th iteration step, MPa;

[0112] w k - crack width at the kth iteration, mm;

[0113] t k- the time step of the k-th iteration, s;

[0114] p k -pressure at the kth iteration step, MPa;

[0115] α-is the empirical coefficient.

[0116] p k+1 -pressure at the k+1th iteration step, MPa;

[0117] u k+1 - displacement of the k+1th iteration step, mm;

[0118] w k+1 - crack width at the k+1th iteration, mm;

[0119] A-global stiffness matrix;

[0120] ξ-empirical coefficient;

[0121] F-correction function.

[0122] Specifically, in step S4, a fluid-solid coupling model for the initiation and expansion of multiple clusters of fractures is established according to the coupling method, an information file for simulating the initiation and expansion of each cluster of the intra-segment multiple cluster flow-limiting perforation fracturing is generated, input parameters are set, and a simulation program for the initiation and expansion of each cluster of the intra-segment multiple cluster flow-limiting perforation fracturing is compiled.

[0123] Specifically, in step S4, a simulation program for the opening and expansion of each cluster of perforation fracturing based on the intra-segment multi-cluster flow limiting method is used to calculate the actual number of openings in each cluster and the characteristics of crack initiation and expansion, which are used to determine the number of perforation openings and the opening status of each cluster of cracks, and to guide the fracturing optimization design and reservoir construction and transformation.

[0124] In one embodiment, a simulation method for the opening and expansion of each cluster of multi-cluster flow-restricted perforation fracturing within an evaluation section was applied to the fracturing field application of the DS23-Ping 1 well in the deep gas layer of the northern Songliao Basin. The numerical simulation parameters of the multi-cluster flow-restricted perforation fracturing of the DS23-Ping 1 well were input into the simulation program, and Tables 1 and 2 were obtained.

[0125] Among them, Table 1 is the horizontal stress difference table; Table 2 is the perforation depth table;

[0126] The input parameters include reservoir parameters, wellbore parameters, perforation parameters and test fracturing parameters.

[0127] Table 1 Horizontal stress difference table

[0128]

[0129]

[0130]

[0131] Table 2 Perforation depth table

[0132]

[0133] Running the simulation program, we get the numerical simulation results of the first stage multi-cluster perforation fracturing of the flow limiting method in DS23-Ping 1 well. The simulation calculation shows that the friction resistance along the DS23-Ping 1 well is 15.4MPa, the friction resistance of the pores and fractures is 23.7MPa, and the single hole displacement is 0.55m 3 / min, with 26 holes opened and an opening rate of 81.2%. The simulation of fracture propagation during the multi-cluster perforation test clearly shows that all three fracture clusters initiated normally. Downhole television monitoring of the multi-cluster perforation fracturing process in Well DS23-Ping 1 demonstrated that all three fracture clusters initiated and propagated normally, consistent with the downhole television monitoring and the fracture propagation simulation during the multi-cluster perforation test.

[0134] Specifically, based on the intra-segment multi-cluster flow-limiting perforation completion technology, with the goal of uniformly transforming multiple clusters of fractures, by establishing a flow-limiting fracturing perforation number calculation method, while providing technical guidance for the efficient exploration and development of tight oil and gas reservoirs, it also improves the practicality and stability of the flow-limiting perforation fracturing completion field construction diagnostic process technology.

[0135] Specifically, by utilizing the calculation model of multi-cluster fluid distribution in the wellbore and the discrete element mechanics model of multi-cluster fracture initiation and expansion, through simulation calculations, the problem of whether the multi-cluster in the middle section of the flow-limiting perforation fracturing is effectively opened and transformed is solved. At the same time, the practicality and stability of the on-site construction diagnostic process technology of the flow-limiting perforation fracturing completion is further improved.

[0136] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0137] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A simulation method for evaluating the opening and expansion of each cluster in a multi-cluster flow-limiting perforation fracturing within a segment, characterized by: include: The influence of pore friction on the porosity and the friction along the fracturing fluid under different completion string conditions were studied. Combined with the pre-fracturing test data, a calculation method for the number of openings and the porosity was established. The liquid volume conservation equation and pressure balance equation are combined to establish a calculation model for fracturing fluid distribution in multiple fracture clusters within the wellbore. According to the rock mechanics failure and multi-cluster crack propagation criteria, a fluid-solid coupling model of multi-cluster crack initiation and propagation was established using the finite element and discrete element coupling method, and the Picard iteration method and the implicit pressure explicit saturation method were coupled to solve the problem. A simulation program for the opening and expansion of each cluster in intra-segment multi-cluster flow-limiting perforation fracturing was developed. Based on the input parameters, the simulation program calculated the number of openings in each cluster and the characteristics of fracture initiation and expansion. This was used to determine the number of openings in each cluster and the opening of each fracture cluster, guiding the optimization design of fracturing and reservoir construction and reconstruction. The input parameters include reservoir parameters, wellbore parameters, perforation parameters and test fracturing parameters.

2. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 1, characterized in that: Through targeted experiments, the single-hole displacement and single-hole friction resistance of fluid flowing through holes with different perforation diameters were measured, and the relationship between the friction resistance and flow rate of different fluids flowing through holes with different diameters was established. The large amount of measured data was plotted into a curve, and a relationship diagram between the single-hole displacement and single-hole friction resistance of fluid flowing through holes with different displacement rates was established.

3. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 2, characterized in that: Based on the established relationship diagram, combined with different fluids, perforation hole diameters, and different string types, the corresponding pore friction and single hole displacement can be obtained. Combined with the pre-pressure test data, the number of test openings and the porosity can be calculated. The pre-pressure test data includes the maximum displacement tested, the pressure under the maximum displacement tested, and the pump stop pressure.

4. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 3, characterized in that: The flow distribution of each cluster of fracturing fluid satisfies the liquid volume conservation equation and the pressure balance equation. The two equations are combined to establish a nonlinear equation group with the flow rate of each cluster of fracturing fluid and the reference point pressure as unknown quantities. Through the iterative solution of the Newton method, the fluid volume of the flow distribution of each cluster of fracturing fluid can be calculated. The fluid volume of the flow distribution of each cluster of fracturing fluid can be used to judge the uniformity of the initiation and expansion of multiple clusters of cracks, and further calculate the initiation and expansion of the multiple clusters of cracks.

5. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 4, characterized in that: The Mohr-Coulomb failure criterion and the maximum tensile stress criterion are used to determine whether the rock block undergoes shear failure or tensile failure.

6. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 5, characterized in that: When the principal stress under maximum pressure is greater than the tensile strength of the rock, the rock block undergoes tensile failure, generating tensile cracks, and the shear amount of the tensile cracks is zero; When the shear stress under the maximum pressure is greater than the sum of the cohesion and the friction, the rock block undergoes shear failure, generating shear cracks, and the normal displacement of the shear cracks is zero.

7. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 6, characterized in that: According to the flow distribution of each cluster of fracturing fluid, the liquid flow equation of each cluster of fracturing fluid can be established by the law of conservation of mass and momentum; Wherein, each cluster of fracturing fluid is regarded as an incompressible Newtonian fluid.

8. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 7, characterized in that: The fractured reservoir is discretized into several matrix block units using discrete element theory. A control volume unit exists between the mutually contacting matrix block units. In the control volume unit, the Barton-Bandis implicit contact force is introduced as the traction force to obtain the matrix block deformation equation. In the control volume, the effects of inertial force and rigid body force on rock deformation are ignored.

9. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 8, characterized in that: The flow of each cluster of fracturing fluid is related to the deformation of the matrix block unit; The change in fluid pressure on the boundary surface of the matrix block unit affects the deformation of the matrix block unit, thereby causing a change in the crack width. The change in the crack width causes a change in the flow rate of each cluster of fracturing fluid, ultimately affecting the distribution of fluid pressure of each cluster of fracturing fluid in the crack.

10. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 9, characterized in that: The correlation between the flow of each cluster of fracturing fluid and the deformation of the matrix block unit adopts a fluid-solid coupling model, and each control equation is solved by coupling the Picard iteration method and the implicit pressure saturation method. The coupled iteration of the fluid pressure field of each cluster of fracturing fluid and the deformation of the matrix block unit is calculated, and the pressure convergence of all nodes is used as the judgment condition.

11. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 10, characterized in that: A fluid-solid coupling model for the initiation and expansion of multiple clusters of fractures is established according to the coupling method, an information file for simulating the initiation and expansion of each cluster of the intra-segment multiple cluster flow-limiting perforation fracturing is generated, the input parameters are set, and a simulation program for the initiation and expansion of each cluster of the intra-segment multiple cluster flow-limiting perforation fracturing is compiled.

12. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within an evaluation section according to claim 11, characterized in that: A simulation program for the opening and expansion of each cluster of perforation fracturing based on the intra-segment multi-cluster flow-limiting method is used to calculate the actual number of perforations in each cluster and the characteristics of fracture initiation and expansion. These are used to determine the number of perforations and the opening of each cluster of fractures, and to guide fracturing optimization design and reservoir construction and reconstruction.

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