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

Abstract

The invention relates to the technical field of oil and gas well yield increase and transformation, in particular to a simulation method for opening and expanding of each cluster of perforation fracturing through a multi-cluster flow limiting method in an evaluation section. Establishing a multi-cluster fracture fracturing fluid distribution calculation model in the shaft; a multi-cluster crack initiation and expansion fluid-solid coupling model is established, and a Picard iteration method and an implicit pressure saturation method are used for coupling solution; calculating through a simulation program to obtain the hole number of each cluster and crack initiation extension characteristics so as to judge the hole number of each cluster and the crack opening condition of each cluster; according to the method, through simulation calculation, the problem that whether multiple clusters in the flow-limiting method perforation fracturing middle section are effectively opened and transformed or not is solved, technical guidance is provided for efficient exploration and development of compact oil and gas reservoirs, and meanwhile the practicability and stability of the flow-limiting method perforation fracturing well completion site construction diagnosis technology are improved.

Description

Technical Field

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

[0002] At present, the fracturing of tight oil and gas reservoirs mostly adopts the multi-cluster perforation completion method in the casing cementing section, and the cluster flow limiting method perforation method is mostly used in the transformation process. In the multi-cluster fracturing construction within the section, due to the large differences in geological conditions such as lithology, stress value, and physical conditions of the reservoirs at different perforation cluster locations, the perforation clusters cannot effectively initiate and expand, and the actual number of opened clusters is lower than the expected design, resulting in some layers that cannot be effectively transformed and cannot achieve the designed transformation effect. A fast, effective, and practical simulation method for evaluating the opening and expansion of multi-cluster fractures within the section is urgently needed.

[0003] China Patent Authorization Announcement No.: CN112836446B discloses a method for optimizing the design of clustered flow limiting perforation for horizontal wells in tight reservoirs. The invention discloses a method for optimizing the design of clustered flow limiting perforation for horizontal wells in tight reservoirs, including the following steps: S1 collects basic rock mechanics parameters, minimum horizontal ground stress parameters and fracturing construction engineering parameter values; S2 establishes a multi-perforation cluster position fracturing crack extension model to simulate the fracture morphology of multi-cluster fracture extension with uniform perforation; S3 simulates the induced stress field distribution under the multi-cluster fracture extension morphology and quantitatively characterizes the multi-cluster fracture extension uniformity index; S4 establishes the multi-cluster pressure and flow distribution relationship within the segment and the optimization model of clustered flow limiting perforation number under the condition of no abrasion; S5 designs the clustered flow limiting perforation number under the condition of perforation hole abrasion; S6 verifies the fracture extension effect after the optimization of clustered flow limiting perforation. The invention can effectively avoid the generation of invalid perforation clusters and improve the perforation cluster efficiency of multi-cluster fracturing wells. It is of great significance to scientifically design the optimization design scheme of clustered flow limiting perforation for tight oil and gas reservoirs and efficiently and economically develop tight oil 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. The 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) segment 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. The invention can solve the problems existing in the existing fracturing technology, 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 technology, which effectively increases the gas leakage area, improves the production capacity, and improves the efficiency of perforation clusters in multiple clusters, and achieves uniform transformation of multiple clusters of cracks without increasing the average construction cost; by optimizing the sand adding method and optimizing the well entry material, the proppant laying effect is greatly improved, and the effective crack quality and transformation strength are improved.

[0005] However, the above method has the following problems: the research on intra-segment multi-cluster flow limiting method perforation fracturing is mainly based on optimization design, and no research has been conducted on whether each cluster of intra-segment multi-cluster flow limiting method perforation fracturing should be 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 cost is high, the cycle is long, and the gas well needs to be operated under pressure, which affects the gas test 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 the research on intra-segment multi-cluster flow limiting perforation fracturing in the prior art 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; in 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 cost is high, the cycle is long, and the gas well needs to be operated under pressure downhole, which affects the gas testing and production of the construction well.

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

[0008] The pore friction that affects the porosity and the friction along the fracturing fluid under different completion string conditions were studied, and the calculation method of the number of openings and the porosity was established in combination with the pre-fracturing test data.

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

[0010] According to the rock mechanical failure and the extension criteria of multiple clusters of cracks, the fluid-solid coupling model of the initiation and extension of multiple clusters of cracks is established by using the finite element and discrete element coupling method, and the Picard iteration method and the implicit pressure explicit saturation method are coupled to solve it.

[0011] Write a simulation program for the opening and expansion of each cluster of perforation fracturing in a multi-cluster flow-limiting method within a segment. According to the input parameters, the simulation program calculates the number of openings in each cluster and the characteristics of fracture initiation and expansion, which are used to determine the number of openings in each cluster and the opening of each cluster of fractures, and guide the optimization design of fracturing and the construction and transformation of reservoirs;

[0012] The input parameters include reservoir parameters, wellbore parameters, perforation parameters and test fracturing parameters. Furthermore, the single-hole displacement and single-hole friction resistance of the fluid flowing through the perforation under different perforation diameters are determined through targeted experiments, and the relationship between the friction resistance and flow rate of different fluids flowing 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 under different displacements is established.

[0013] Furthermore, according to the established relationship diagram, in combination with different fluids, perforation hole diameters, and different string types, the corresponding pore friction and single hole displacement can be obtained, and the number of test openings and the opening rate can be calculated in combination with the pre-pressure test data;

[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 uniformity of the initiation and expansion of multiple clusters of cracks can be judged by the fluid volume of the flow distribution of each cluster of fracturing fluid, 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 the maximum pressure is greater than the tensile strength of the rock, the rock block undergoes the 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 and generates 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 through the law of conservation of mass and conservation of 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 a number of matrix block units, and there is a control volume unit 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] Further, the flow of each cluster of fracturing fluid is related to the deformation of the matrix block unit;

[0024] The change of 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 for the initiation and expansion of multiple clusters of fractures is established according to the coupling method, an information file for simulating the opening and expansion of each cluster of multiple clusters of perforating and fracturing by the current limiting method within the segment is formed, the input parameters are set, and a simulation program for the opening and expansion of each cluster of multiple clusters of perforating and fracturing by the current limiting method within the segment is written.

[0027] Furthermore, based on a simulation program for the opening and expansion of each cluster of intra-segment multi-cluster flow limiting perforation fracturing, the actual number of openings in each cluster and the characteristics of fracture initiation and expansion are calculated through the simulation program, which are used to determine the number of perforation openings and the opening status of each cluster of fractures, and to guide fracturing optimization design and reservoir construction reconstruction.

[0028] Compared with the prior art, the beneficial effect of the present invention lies in that, based on the intra-segment multi-cluster flow limiting perforation completion technology, with the goal of uniformly transforming multiple clusters of fractures, and through the established flow limiting fracturing perforation opening number calculation method, while providing technical guidance for the efficient exploration and development of tight oil and gas reservoirs, the practicability and stability of the flow limiting perforation fracturing completion field construction diagnosis process technology are improved.

[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 calculation, the problem of whether the multi-cluster in the middle section of the flow-limiting perforating fracturing is effectively opened and transformed is solved, while the practicality and stability of the on-site construction diagnosis process technology of the flow-limiting perforating fracturing completion is further improved. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] Figure 2 Embodiment 5 of the present invention 1 / 2 The relationship diagram of the friction resistance of different fracturing fluids along the casing hole diameter of 10.2mm;

[0032] Figure 3 Graph showing the relationship 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 only used to explain the present invention and are not used 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 protection scope 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 drawings. This is merely 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] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] See also Figure 1As shown, it is a flow chart of a simulation method for the opening and expansion of each cluster of multi-cluster flow limiting method perforation fracturing in an evaluation section of the present invention. A simulation method for the opening and expansion of each cluster of multi-cluster flow limiting method perforation fracturing in an evaluation section 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 method for calculating the number of openings and the porosity in combination with 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, according to the rock mechanics failure and the extension criteria of multiple clusters of cracks, a fluid-solid coupling model of the initiation and extension of multiple clusters of cracks is established by using the finite element and discrete element coupling method, and the Picard iteration method and the implicit pressure explicit saturation method are coupled to solve it;

[0041] Step S4, compile a simulation program for the opening and expansion of each cluster of intra-segment multi-cluster current limiting method perforation fracturing, and calculate the number of holes in each cluster and the characteristics of fracture initiation and expansion through the simulation program according to the input parameters, so as to determine the number of holes in each cluster and the opening of each cluster of fractures, and guide the optimization design of fracturing and the construction and reconstruction of the reservoir;

[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 of the fluid flowing through the perforation under different perforation diameters are determined through targeted experiments, and a relationship between the change of friction with flow rate when different fluids flow through perforations with different diameters is established. A large amount of measured data is plotted into a curve, and a relationship diagram between the single-hole displacement and single-hole friction of the fluid flowing through the perforation under different displacements 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 along the way of different fracturing fluids with a casing hole diameter of 10.2mm; the friction resistance along the way of different fluids flowing through holes of different perforation diameters at different displacements was measured in the laboratory, and a large amount of measured data was plotted into a curve, and the relationship between perforation parameters, pumping parameters, and fluid type and friction resistance along the way was fitted, and a relationship diagram between the displacement of different fluids flowing through the hole 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 under different apertures of an embodiment of the present invention; the single-hole displacement and single-hole friction resistance of the fluid flowing through the hole under different perforation diameters are determined by 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 the single-hole displacement and single-hole friction resistance of the fluid flowing through the hole under different displacements is established.

[0046] Specifically, in step S1, according to 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, and combined with the pre-pressure test data, the number of test openings and the opening rate 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 ith 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 pressure of the reference point 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 uniformity of the initiation and expansion of multiple clusters of cracks can be judged by the fluid volume of the flow distribution of each cluster of fracturing fluid, and the initiation and expansion of multiple clusters of cracks can be further calculated.

[0053]

[0054]

[0055] Where: q 总 -Total fluid flow rate 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 - Closing pressure (minimum principal stress) of the i-th layer, MPa;

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

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

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

[0063] ΔP fdk - Friction 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 data measured by 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 the 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] -σ 1 >σ T ;

[0069]

[0070] Where: 1 - Maximum compressive principal stress, MPa;

[0071] σ T -Tensile strength, MPa;

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

[0073] τ 0 - 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 through the law of conservation of mass and conservation of 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-coordinates 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 a number of matrix block units. There is a control volume unit 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;

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

[0105] The change of fluid pressure on the boundary surface of matrix block unit affects the deformation of 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, which 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 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.

[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 kth 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- overall stiffness matrix;

[0120] ξ-empirical coefficient;

[0121] F-correction function.

[0122] Specifically, in step S4, a fluid-solid coupling model of multi-cluster fracture initiation and expansion is established according to the coupling method, an information file of simulation of the opening and expansion of each cluster of multi-cluster current limiting perforation fracturing within a segment is formed, input parameters are set, and a simulation program of the opening and expansion of each cluster of multi-cluster current limiting perforation fracturing within a segment is written.

[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 limiting flow 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 transformation.

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

[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 of multi-cluster perforation fracturing by the flow limiting method in DS23-Ping 1 well. From the simulation calculation, we know that the friction resistance along the DS23-Ping 1 well is 15.4MPa, the friction resistance of the pores is 23.7MPa, and the single hole displacement is 0.55m 3 / min, 26 holes were opened, and the opening rate was 81.2%. It can be clearly seen from the multi-cluster perforation test fracturing crack extension simulation diagram that all three clusters of cracks are normally opened. The multi-cluster perforation fracturing transformation process of Well DS23-Ping 1 was monitored and observed using downhole television, indicating that all three clusters of cracks in this section started and extended normally, and the downhole television monitoring was consistent with the multi-cluster perforation test fracturing crack extension simulation.

[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 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 practicability and stability of the on-site construction diagnostic process technology for flow-limiting perforation fracturing completion.

[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 propagation, through simulation calculations, the problem of whether the multi-cluster in the middle section of the flow-limiting perforating fracturing is effectively opened and transformed is solved, while further improving the practicality and stability of the on-site construction diagnosis process technology of the flow-limiting perforating fracturing completion.

[0136] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A simulation method for evaluating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing within a segment, characterized in that: include: The pore friction that affects the porosity and the friction along the fracturing fluid under different completion string conditions were studied, and the calculation method of the number of openings and the porosity was established in combination with the pre-fracturing test data. Combine the liquid volume conservation equation and the pressure balance equation to establish a calculation model for fracturing fluid distribution in multiple fracture clusters in the wellbore. According to the rock mechanical failure and the extension criteria of multiple clusters of cracks, the fluid-solid coupling model of the initiation and extension of multiple clusters of cracks is established by using the finite element and discrete element coupling method, and the Picard iteration method and the implicit pressure explicit saturation method are coupled to solve it. Write a simulation program for the opening and expansion of each cluster of perforation fracturing in a multi-cluster flow-limiting method within a segment. According to the input parameters, the simulation program calculates the number of openings in each cluster and the characteristics of fracture initiation and expansion, which are used to determine the number of openings in each cluster and the opening of each cluster of fractures, and guide the optimization design of fracturing and the construction and transformation of reservoirs; 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 in the 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 the perforation at different perforation diameters are determined, and the relationship between the 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 fluid flowing through the perforation at different displacements is established.

3. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing in the evaluation section according to claim 2, characterized in that: According to 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, and the number of test holes and the opening rate can be calculated in combination with the pre-pressure test data; 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 in the 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 pressure of the reference point 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 uniformity of the initiation and expansion of multiple clusters of cracks can be judged by the fluid volume of the flow distribution of each cluster of fracturing fluid, and the initiation and expansion of the multiple clusters of cracks can be further calculated.

5. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing in the 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 in the evaluation section according to claim 5, characterized in that: When the principal stress under the maximum pressure is greater than the tensile strength of the rock, the rock block undergoes tensile failure and generates 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 and generates 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 in the 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 through the law of conservation of mass and conservation of 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 in the evaluation section according to claim 7, characterized in that: The discrete element theory is applied to discretize the fractured reservoir into several matrix block units. There is a control volume unit 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 in the 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 of 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 in 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 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.

11. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing in 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 opening and expansion of each cluster of multiple clusters of perforating and fracturing by the current limiting method within the segment is formed, the input parameters are set, and a simulation program for the opening and expansion of each cluster of multiple clusters of perforating and fracturing by the current limiting method within the segment is written.

12. The method for simulating the opening and expansion of each cluster of multi-cluster flow-limiting perforation fracturing in an evaluation section according to claim 11, characterized in that: Based on the simulation program of the opening and expansion of each cluster of perforation fracturing by the multi-cluster limiting method within the segment, the actual number of openings of each cluster and the characteristics of fracture initiation and expansion are calculated by the simulation program, which are used to judge the number of perforation openings and the opening of each cluster of fractures, and guide the optimization design of fracturing and reservoir construction and transformation.

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