A method for predicting fracture morphology of a conglomerate reservoir and a chart generation method

Abstract

The present application provides a kind of conglomerate reservoir fracture morphology prediction method and chart generation method, belong to the fracturing technical field of oil development.The present application constructs fracture propagation morphology model, establishes conglomerate reservoir fracture morphology prediction chart;According to conglomerate reservoir fracture morphology chart, determine whether the development form of hydraulic fracture is pressure post fracture development vertical fracture or horizontal fracture;For the area of vertical fracture development, collect the geological and mechanical parameters of the fracture that affects the vertical fracture development area and penetrates the layer;Fracture penetration expansion model considering reservoir and interlayer is constructed, and vertical fracture penetration chart is established;According to the collected geological and mechanical parameters of reservoir and interlayer, combined with vertical fracture penetration chart, determine whether hydraulic fracturing can penetrate interlayer.The fracture propagation morphology model constructed by the present application is more accurate, the fracture morphology prediction is more accurate, the selected fracturing operation mode is well matched with the geological characteristics of reservoir, the reservoir modification cost can be reduced, and the development benefit of oil field can be improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and in particular to a method for predicting fracture morphology in conglomerate reservoirs and a method for generating maps. Background Technology

[0002] Currently, fracturing technology has become the primary technology for the effective development of unconventional and low-permeability oil and gas reservoirs. Fracturing is an extremely effective method for enhancing oil flow capacity and increasing well production. Fracturing methods are broadly classified into hydraulic fracturing and high-energy gas fracturing, with hydraulic fracturing showing a significant effect on increasing oil well production, making it the preferred and commonly used technology. Its production enhancement effect is particularly outstanding for oil reservoirs with very small flow channels, i.e., low permeability. Hydraulic fracturing relies on a surface high-pressure pump truck to inject fluid at high speed into the well. The high pressure generated at the bottom of the well causes the oil-bearing rock to fracture, creating fractures. To prevent the fractures from closing automatically after the pump truck stops operating and the pressure drops, sand with a density several times greater than the formation density is mixed into the injected fluid after the formation fractures. This sand enters the fractures along with the fluid and remains permanently within them, keeping the fractures open and ensuring a long-term improved oil flow environment.

[0003] Predicting the morphology of fracturing fractures is crucial for selecting appropriate fracturing methods and thus for more rational reservoir stimulation. It is a key factor affecting whether reservoir stimulation can be carried out economically and rationally.

[0004] For shallow conglomerate reservoirs, there are currently no clear guidelines for fracture morphology during fracturing operations. This leads to fracture orientations deviating from the design during actual fracturing, resulting in poor development outcomes, insufficient reservoir stimulation, and inadequate utilization of the original reservoir. Furthermore, in areas with well-developed interlayers, the longitudinal propagation of vertical fractures has not been adequately considered, making it impossible to determine whether fractures can penetrate the interlayers.

[0005] In recent years, some research has been conducted on hydraulic fracturing fractures both domestically and internationally, and some understanding has been gained. However, there is no quantitative set of fracture morphology prediction and selection methods for shallow conglomerate reservoirs, and no diagrams have been developed to address the issue of interlayer and cross-layer problems in the case of vertical fractures.

[0006] With the large-scale application of fracturing technology in the development of unconventional and low-permeability oil and gas reservoirs, there is an urgent need to develop a set of charts with solid theory and sufficient practical experience to guide the selection of fracturing fracture morphology and provide a theoretical basis for rational fracturing reservoir stimulation construction.

[0007] The existing technology has the following shortcomings:

[0008] 1. For shallow conglomerate reservoirs, there is no quantitative method for predicting fracture morphology;

[0009] 2. The drawing does not consider the issue of interlayer penetration in the case of vertical cracks. Summary of the Invention

[0010] To address the problems existing in the prior art, this invention provides a method for predicting fracture morphology in conglomerate reservoirs and a method for generating fracturing maps. The method collects key parameters affecting fracture morphology in conglomerate reservoirs, including fracturing displacement, fracturing viscosity, and reservoir triaxial stress values. It constructs a fracture propagation morphology model and, based on the calculation results of this model, establishes a conglomerate reservoir fracture morphology prediction map. The method determines whether the hydraulic fracture development is a post-pressure fracture, resulting in vertical or horizontal fractures. For areas with vertical fractures, it collects geological and mechanical parameters affecting fracture penetration. It constructs a fracture penetration propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties, and establishes a vertical fracture penetration map. Based on the collected geological and mechanical parameters of the reservoir and interlayers, combined with the vertical fracture penetration map, it determines whether hydraulic fracturing can penetrate the interlayer. The fracture propagation morphology model constructed by this invention is more accurate, and the fracture morphology prediction is more accurate, allowing for a better match between the selected fracturing operation mode and the geological characteristics of the reservoir. This reduces reservoir stimulation costs and improves oilfield development efficiency.

[0011] This invention provides a method for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0012] A fracture propagation morphology model was constructed, and a fracture morphology prediction chart for conglomerate reservoirs was established based on the calculation results of the fracture propagation morphology model.

[0013] Based on the fracture morphology chart of conglomerate reservoir, determine whether the hydraulic fracture development is a post-pressure fracture, a vertical fracture, or a horizontal fracture.

[0014] For areas with vertical fractures, collect geological and mechanical parameters that affect fracture penetration in the vertical fracture development zone;

[0015] Construct a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties, and establish a vertical fracture propagation chart;

[0016] Based on the collected geological and mechanical parameters of the reservoir and interlayers, combined with the vertical fracture penetration chart, it is determined whether hydraulic fracturing can penetrate the interlayers.

[0017] Preferably, before constructing the fracture propagation morphology model and establishing the fracture morphology prediction chart for conglomerate reservoirs, the method further includes: collecting key parameters that affect the fracture morphology of conglomerate reservoirs, including: construction displacement and reservoir triaxial geostress values.

[0018] Preferably, the construction of the fracture propagation morphology model and the establishment of a fracture morphology prediction chart for conglomerate reservoirs specifically involves: using the finite element cohesion unit fully coupled fracture propagation method, based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs, constructing a fracture propagation morphology model, and establishing a fracture morphology prediction chart for conglomerate reservoirs.

[0019] Preferably, the method of constructing a fracture propagation morphology model using the fully coupled finite element cohesion unit, based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs, specifically includes the following steps:

[0020] Determine the dimensions of the model and establish a finite element geometric model;

[0021] Based on the geometric model, physical and mechanical properties are assigned to the geometric model according to the physical and mechanical properties of the reservoir rock, and a physical model of the fracture propagation morphology model is constructed. The physical and mechanical properties include porosity, permeability, Young's modulus, Poisson's ratio and tensile strength.

[0022] Mesh the physical model of the crack propagation morphology model;

[0023] Boundary conditions and initial field variables are applied to the physical model of the crack propagation morphology model after meshing; the boundary conditions include fixed displacement boundary conditions and pore pressure boundary conditions; the initial field variables include porosity field, geostress field and pore pressure field.

[0024] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables.

[0025] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0026] The fully coupled crack propagation method using finite element cohesion elements mainly consists of three parts: fluid-structure interaction theory, hydraulic crack initiation and propagation criteria, and fluid flow equations within the crack.

[0027] (1) Fluid-structure interaction theory

[0028] Rock is a porous medium. During hydraulic fracturing, the flow of reservoir fluids and the deformation of the rock matrix interact and influence each other. On the one hand, the deformation of the rock leads to changes in pore volume and structure, thereby affecting the seepage field (including pore pressure and flow rate); on the other hand, changes in pore pressure, in turn, affect changes in effective stress.

[0029] The equilibrium equations for the deformation mechanics of a solid rock skeleton are as follows:

[0030]

[0031] In the formula, For the effective stress matrix, Pa; p w δε is the pore pressure, Pa; δε is the virtual strain rate matrix, s. -1 δv is the imaginary velocity vector, m / s; t is the surface force vector, N / m. 2 f is the body force vector, N / m 3 .

[0032] The continuity equation for fluid seepage is:

[0033]

[0034] In the formula, J is the volume change ratio, which is dimensionless; ρ w Fluid density, kg / m³ 3 ;n w V represents porosity, which is dimensionless; w denoted as fluid seepage velocity, m / s; x is a spatial vector, m / s.

[0035] Assume that the flow of fluid within the rock follows Darcy's law, that is:

[0036]

[0037] In the formula, k is the rock permeability tensor, m / s; g is the gravitational acceleration vector, m / s². 2 .

[0038] (2) Criteria for the initiation and propagation of hydraulic fractures

[0039] The cohesive method simulates the initiation and propagation of hydraulic fractures using a stress-displacement (TS) criterion that degrades stiffness. Before fracture initiation, the cohesive element remains undamaged, and its constitutive relation follows a linear elastic law; the loading and unloading process at this stage is reversible. When fracture initiation occurs, the cohesive element experiences initial damage, the fracture propagates, and the stiffness of the cohesive element gradually degrades until the element stiffness drops to zero, at which point the element is completely damaged. Once damage occurs in the cohesive element, the loading and unloading process becomes irreversible.

[0040] 1) Crack initiation

[0041] Currently, there are four commonly used hydraulic fracture initiation criteria: the maximum principal stress criterion, the secondary stress criterion, the maximum strain criterion, and the secondary strain criterion. For example... Figure 4 As shown, to describe the combined tension and shear failure behavior of hydraulic fractures, this invention selects a secondary stress initiation criterion, that is, when the sum of the squares of the ratios of the stress values ​​in the three directions to the corresponding critical values ​​is 1, the cohesive element experiences initial damage, and hydraulic fracture initiation begins.

[0042]

[0043] In the formula, σ n The normal stress applied to the cohesive element is expressed in MPa; τ s τ t These are the shear stresses applied in two directions to the cohesive element, in MPa. The critical normal stress at which the cohesive element fails is given in MPa. These are the critical tangential stresses in MPa at which the cohesive element fails in two directions; the symbols < and > indicate that the cohesive element can only withstand tensile stress and does not produce damage under compressive stress.

[0044] 2) Crack propagation

[0045] The crack propagation process is described using the stiffness decay of cohesive elements, and its expression is as follows:

[0046]

[0047]

[0048]

[0049] In the formula, The stress value is calculated using the cohesive element method under the current strain conditions according to the linear elastic constitutive model of the undamaged stage. These are the stress values ​​calculated according to the linear elastic constitutive model of the undamaged stage along the tangent of the cohesive element under the current strain conditions; t n t s t t These represent the actual stresses experienced by the cohesive element in the normal, first tangential, and second tangential directions, respectively; D is the damage factor.

[0050] The expression for damage factor D is:

[0051]

[0052] In the formula, δ o δ f These represent the initial damage and the displacement at the completion of damage in the cohesive element, respectively; δ m This represents the current displacement of the cohesive element.

[0053] Currently, commonly used criteria for describing the propagation process of hydraulic fractures include linear displacement propagation criteria, nonlinear displacement propagation criteria, and energy propagation criteria. This invention selects the energy criterion (BK criterion) proposed by Benzingagh and Kenane to describe the propagation process of tension-shear composite fractures. This criterion assumes that the energy release rates in the first tangential direction and the second tangential direction are equal, i.e.:

[0054]

[0055] In the formula, Critical energy release rates (N / mm) are given in the normal, first tangential, and second tangential directions of the cohesive element, respectively. n G s G t These represent the energy release rates of the cohesive element in the current normal, first tangential, and second tangential directions, respectively, in N / mm; G C η is the critical energy release rate of a tension-shear combined hydraulic fracture, N / mm; η is a dimensionless constant related to the properties of the rock itself.

[0056] (3) Fluid flow equation within the slit

[0057] The flow of fracturing fluid within a fracture includes tangential flow along the fracture extension direction and normal flow perpendicular to the fracture surface, such as... Figure 5 As shown, with the continuous pumping of fracturing fluid, the liquid propels the fracture forward. Due to the solid-liquid interface, there is a certain hysteresis zone at the liquid front relative to the very tip of the fracture, also known as the "process zone." Based on the fracture opening width, hydraulic fracture tips can be classified into three types: material tips, cohesive unit tips, and mathematical tips. The hydraulic fracture aperture is equal to δ... f The location is called the material crack tip, where the crack aperture is greater than δ. f The cohesive element is completely damaged; the hydraulic fracture aperture is equal to δ. o The position is called the cohesive unit tip. All cohesive units from the material tip to the cohesive unit tip will be damaged, and the degree of damage gradually decreases. The position where the hydraulic crack aperture equals the initial crack aperture is called the mathematical tip. All cohesive units from the cohesive unit tip to the mathematical tip will open to a certain extent, but will not reach the critical value of the initial damage.

[0058] 1) Tangential flow

[0059] Commonly used terms to describe the tangential flow behavior of fracturing fluids within hydraulic fractures include Newtonian flow and power-law flow. In this invention, it is assumed that the fracturing fluid is an incompressible Newtonian fluid, i.e.

[0060]

[0061] In the formula, q is the tangential flow rate of the hydraulic fracture, and m 3 / s; w is the opening width of the hydraulic fracture, m; μ is the viscosity of the fracturing fluid, Pa·s; The fluid pressure gradient along the direction of the hydraulic fracture extension is expressed in Pa / m.

[0062] 2) Normal flow

[0063] In addition to tangential flow within the fracture, fracturing fluid can also be lost into the rock along the upper and lower surfaces of the hydraulic fracture. This loss behavior can be described as follows:

[0064]

[0065] In the formula, q t q b These represent the volumetric flow rates per unit time at the upper and lower surfaces of the hydraulic fracture, respectively, in m³. 3 / s;c t c b The filtration coefficients, m, are the upper and lower surfaces of the hydraulic fracture, respectively. 3 / (Pa·s); p t p b Here, p represents the pore pressure on the upper and lower surfaces of the hydraulic fracture, respectively, in Pa; i The pressure of the fluid within the hydraulic fracture is Pa.

[0066] The fluid inside the hydraulic fracture satisfies the mass conservation equation, namely:

[0067]

[0068] In the formula, Q(t) is the injection rate of fracturing fluid, m 3 / s.

[0069] Substituting the formulas for tangential and normal flow rates into mass conservation equation 3, we obtain the Reynolds wetting equation, namely:

[0070]

[0071] Based on the above theoretical analysis, key parameters affecting the fracture morphology of conglomerate reservoirs were collected, and the above steps for constructing a fracture propagation morphology model were obtained.

[0072] Preferably, the geological and mechanical parameters affecting fracture penetration in the vertical fracture development zone include: the difference in minimum horizontal in-situ stress between the interlayer and the reservoir, and the difference in rock mechanical parameters between the interlayer and the reservoir, wherein the difference in minimum horizontal in-situ stress between the interlayer and the reservoir is S. h,隔层 -S h , 储层 ;

[0073] in,

[0074] S h,隔层 This represents the minimum horizontal ground stress in the interlayer.

[0075] S h,储层 This represents the minimum horizontal geostress of the reservoir.

[0076] Preferably, the difference in rock mechanical parameters between the interlayer and the reservoir is the ratio of their Young's moduli, specifically: E 隔层 / E 储层 ;

[0077] E 隔层 The Young's modulus of the interlayer;

[0078] E 储层 This is the Young's modulus of the reservoir.

[0079] Preferably, the construction of a fracture propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties, and the establishment of a vertical fracture propagation map, specifically involves: constructing a fracture propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties based on the finite element cohesion unit fully coupled fracture propagation method, and establishing a vertical fracture propagation map.

[0080] Preferably, the construction of a fracture propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties, based on the finite element cohesion unit fully coupled fracture propagation method, specifically includes the following steps:

[0081] The dimensions of the model are determined, and a finite element geometric model is established. The geometric model consists of three parts: upper, middle, and lower. The upper and lower parts are interlayers, and the middle part is the reservoir.

[0082] Based on the geometric model, the physical and mechanical properties of the reservoir and interlayer are assigned to the geometric model according to their different physical and mechanical properties, and a physical model for fracture penetration and propagation is constructed.

[0083] Mesh the physical model of the crack propagation across layers;

[0084] Boundary conditions and initial field variables are applied to the physical model of the crack propagation model after mesh generation;

[0085] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables;

[0086] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0087] This invention also provides a method for generating a fracture morphology prediction chart for conglomerate reservoirs, which can be used in any of the above-mentioned methods for predicting fracture morphology in conglomerate reservoirs, and includes the following steps:

[0088] The key parameters affecting the fracture morphology of conglomerate reservoirs were determined. These key parameters included: the fracturing displacement and the geostress pattern, where the geostress pattern was the relative magnitude of the vertical geostress and the horizontal minimum geostress.

[0089] The construction displacement and the difference between the vertical and horizontal minimum ground stress are respectively used as the abscissa and ordinate of the coordinate system; the difference between the vertical and horizontal minimum ground stress is S. v -S h ;

[0090] S v This represents the vertical in-situ stress of the strata.

[0091] S h The minimum horizontal ground stress;

[0092] By combining the two variables of construction discharge rate and the difference between vertical and horizontal minimum ground stress in the stratum in different ways, the crack morphology under different combinations is obtained by using the constructed crack morphology propagation model.

[0093] Based on the obtained construction discharge and the crack morphology under different combinations of the difference between the vertical ground stress and the minimum horizontal ground stress, the coordinate axis region is divided into two regions: the horizontal crack development region and the vertical crack development region.

[0094] Complete the drawing of the prediction map of fracture morphology in conglomerate reservoirs.

[0095] Preferably, a two-dimensional rectangular coordinate system is established in the conglomerate reservoir fracture morphology prediction chart, with the horizontal axis representing the construction displacement and the unit of the horizontal axis being meters. 3 / min, the vertical axis represents the difference S between the vertical in-situ stress and the minimum horizontal in-situ stress of the stratum. v -S h The vertical axis is in MPa, and the conglomerate reservoir fracture morphology prediction map is divided into two regions: the horizontal fracture development zone and the vertical fracture development zone.

[0096] This invention also provides a method for generating a vertical fracture cross-layer map, used in any of the above-mentioned methods for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0097] The key parameters affecting vertical fracture penetration in conglomerate reservoirs were determined. These parameters included the difference in mechanical properties between the interlayer and the reservoir, and the difference in minimum horizontal in-situ stress between them. The minimum horizontal in-situ stress difference between the interlayer and the reservoir was S. h,隔层 -S h,储层 ;

[0098] The differences in mechanical properties between the interlayer and the reservoir, and the differences in the minimum horizontal geostress between the interlayer and the reservoir, are respectively used as the x-axis and y-axis of the coordinate system.

[0099] By combining the two variables of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir in different ways, the fracture penetration and propagation model is used to calculate whether the fracture can penetrate the interlayer under different combinations of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir.

[0100] Based on the results of whether the cracks can penetrate the interlayer under each combination of conditions, the area of ​​the vertical crack penetration diagram is divided into two areas: the vertical crack penetration area and the vertical crack non-penetration area.

[0101] Complete the drawing of the vertical crack through-layer diagram.

[0102] Preferably, the difference in mechanical properties between the interlayer and the reservoir is equal to the ratio of their Young's moduli, E. 隔层 / E 储层 ;

[0103] E 隔层 The Young's modulus of the interlayer;

[0104] E 储层 This is the Young's modulus of the reservoir.

[0105] Preferably, a two-dimensional rectangular coordinate system is established in the vertical fracture penetration diagram, with the horizontal axis representing the ratio E of the Young's modulus of the interlayer and the Young's modulus of the reservoir. 隔层 / E 储层 The units are dimensionless; the vertical axis represents the difference S between the minimum horizontal in-situ stress of the interlayer and the minimum horizontal in-situ stress of the reservoir. h,隔层 -S h,储层 The unit is MPa; the vertical crack penetration map is divided into two regions: the vertical crack penetration region and the vertical crack non-penetrating region; the boundary of each region is controlled by control points, and the boundary line of the vertical crack penetration region is determined by multiple boundary points, which are connected in sequence to form the boundary line.

[0106] Preferably, the boundary line of the vertical crack penetration area is determined by four boundary points: point 1 (1, 5 MPa), point 2 (3, 5 MPa), point 3 (5, 3 MPa), and point 4 (9, 0 MPa). The four points are connected sequentially, with point 2 and point 3 connected by a straight line or an arc, and the other points connected by a straight line.

[0107] This invention also provides a method for selecting a segmented fracturing fracture pattern, comprising the following steps: a conglomerate reservoir fracture morphology prediction map generated using the aforementioned method for generating any of the conglomerate reservoir fracture morphology prediction maps, and a vertical fracture cross-layer map generated using the aforementioned method for generating any of the vertical fracture cross-layer maps.

[0108] The key parameters affecting fracture morphology after fracturing in conglomerate reservoirs were determined, including geological parameters and construction parameters. Geological factors included the differences in mechanical properties between the reservoir and the interlayer, as well as the triaxial stress values ​​of the reservoir and the interlayer. Construction parameters included the viscosity of the fracturing fluid and the flow rate during fracturing operations.

[0109] The fracture morphology prediction chart of conglomerate reservoir was used for quantitative evaluation to obtain the fracture morphology types developed in the reservoir after fracturing. The fracture morphology types include horizontal fractures and vertical fractures.

[0110] If the obtained fracture morphology is a vertical fracture, then the vertical fracture penetration chart is used to determine whether the vertical fracture can penetrate the upper and lower strata to form a cross-strata fracture. This is determined by the difference in mechanical properties between the strata and the reservoir, as well as the difference in the minimum horizontal in-situ stress S between the strata and the reservoir. h,隔层 -S h,储层 The location of a vertical crack in a trans-layer diagram is used to confirm whether a crack can penetrate a layer. The difference in mechanical properties is represented by the ratio of Young's modulus E. 隔层 / E 储层 .

[0111] Preferably, the stitching pattern includes horizontal cracks, through-layer vertical cracks defined by the through-layer region of vertical cracks, and non-through-layer vertical cracks defined by the non-through-layer region of vertical cracks.

[0112] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0113] (1) The conglomerate reservoir fracture morphology prediction chart and vertical fracture penetration chart generated by this invention can predict whether the fractures after reservoir fracturing will be vertical or horizontal based on the reservoir's geostress pattern and fracturing displacement, thereby assisting in the design of fracturing schemes on site. In addition, for areas containing interlayers and with developed vertical fractures, the difference in Young's modulus and the difference in the minimum principal stress between the interlayers and the reservoir can be compared to quickly determine whether the fractures can penetrate the interlayers, thereby determining the fracture propagation morphology and assisting in the determination of reservoir development and fracturing construction schemes on site. The charts have been verified by wells in Block 7 of Xinjiang Oilfield, and the results are reliable.

[0114] (2) The fracture morphology prediction chart and vertical fracture penetration chart of conglomerate reservoir generated by this invention take into account whether the fracture is horizontal or vertical after fracturing. Furthermore, for vertical fracture areas, it further considers whether the fracture can penetrate the layer based on the difference in minimum horizontal geostress between the interlayer and the reservoir, as well as the difference in rock mechanical parameters between the interlayer and the reservoir, in the case of the presence of an interlayer. This ensures that the selected fracturing construction mode is well matched with the geological characteristics of the reservoir, thereby reducing reservoir stimulation costs and improving the development efficiency of the oilfield.

[0115] (3) By using the conglomerate reservoir fracture morphology prediction chart and vertical fracture cross-layer chart of the present invention, the conglomerate reservoir fracture morphology prediction method of the present invention can be conveniently and quickly realized.

[0116] (4) This invention utilizes the finite element cohesive unit fully coupled fracture propagation method to construct a fracture propagation morphology model based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs, such as construction discharge rate, construction viscosity, and reservoir triaxial geostress value. This makes the constructed fracture propagation morphology model more accurate, thereby making the fracture morphology prediction more accurate. Attached Figure Description

[0117] Figure 1 This is a flowchart of a method for predicting fracture morphology in conglomerate reservoirs according to an embodiment of the present invention.

[0118] Figure 2 This is a flowchart illustrating the generation process of a conglomerate reservoir fracture morphology prediction chart according to an embodiment of the present invention.

[0119] Figure 3 This is a flowchart illustrating the generation process of a vertical crack through-layer diagram according to an embodiment of the present invention.

[0120] Figure 4 This is a cohesive unit crack initiation and propagation criterion according to an embodiment of the present invention;

[0121] Figure 5 This is a schematic diagram of damage and fluid flow in a Cohesive unit according to an embodiment of the present invention.

[0122] Figure 6 This is a schematic diagram of a conglomerate reservoir fracture morphology prediction chart according to an embodiment of the present invention;

[0123] Figure 7 This is a schematic diagram of a vertical crack penetrating layers with control points according to an embodiment of the present invention;

[0124] Figure 8 This is an embodiment of the present invention: the predicted fracture morphology of the conglomerate reservoir in Well W1 of the Badaowan Formation in Block 7 of Xinjiang Oilfield.

[0125] Figure 9This is an embodiment of the present invention, showing the vertical fracture penetration prediction results of Well W1 in the Badaowan Formation of the Seventh District of Xinjiang Oilfield. Detailed Implementation

[0126] The following is in conjunction with the appendix Figure 1-9 The specific embodiments of the present invention will be described in detail below.

[0127] This invention provides a method for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0128] A fracture propagation morphology model was constructed, and a fracture morphology prediction chart for conglomerate reservoirs was established based on the calculation results of the fracture propagation morphology model.

[0129] Based on the fracture morphology chart of conglomerate reservoir, determine whether the hydraulic fracture development is a post-pressure fracture, a vertical fracture, or a horizontal fracture.

[0130] For areas with vertical fractures, collect geological and mechanical parameters that affect fracture penetration in the vertical fracture development zone;

[0131] Construct a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties, and establish a vertical fracture propagation chart;

[0132] Based on the collected geological and mechanical parameters of the reservoir and interlayers, combined with the vertical fracture penetration chart, it is determined whether hydraulic fracturing can penetrate the interlayers.

[0133] According to a specific embodiment of the present invention, before constructing the fracture propagation morphology model and establishing the fracture morphology prediction chart of the conglomerate reservoir, the method further includes: collecting key parameters that affect the fracture morphology of the conglomerate reservoir, including: construction displacement and reservoir triaxial geostress values.

[0134] According to a specific embodiment of the present invention, the construction of the fracture propagation morphology model and the establishment of a fracture morphology prediction chart for conglomerate reservoirs specifically involves: using the finite element cohesion unit fully coupled fracture propagation method, based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs, constructing a fracture propagation morphology model, and establishing a fracture morphology prediction chart for conglomerate reservoirs.

[0135] According to a specific embodiment of the present invention, the method of constructing a fracture propagation morphology model using the finite element cohesion unit fully coupled fracture propagation method, based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs, specifically includes the following steps:

[0136] Determine the dimensions of the model and establish a finite element geometric model;

[0137] Based on the geometric model, physical and mechanical properties are assigned to the geometric model according to the physical and mechanical properties of the reservoir rock, and a physical model of the fracture propagation morphology model is constructed. The physical and mechanical properties include porosity, permeability, Young's modulus, Poisson's ratio and tensile strength.

[0138] Mesh the physical model of the crack propagation morphology model;

[0139] Boundary conditions and initial field variables are applied to the physical model of the crack propagation morphology model after meshing; the boundary conditions include fixed displacement boundary conditions and pore pressure boundary conditions; the initial field variables include porosity field, geostress field and pore pressure field.

[0140] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables;

[0141] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0142] According to a specific embodiment of the present invention, the geological and mechanical parameters affecting fracture penetration in vertical fracture development zones include: the minimum horizontal stress difference between the interlayer and the reservoir, and the difference in rock mechanical parameters between the interlayer and the reservoir, wherein the minimum horizontal stress difference between the interlayer and the reservoir is S. h,隔层 -S h,储层 ;

[0143] in,

[0144] S h,隔层 This represents the minimum horizontal ground stress in the interlayer.

[0145] S h,储层 This represents the minimum horizontal geostress of the reservoir.

[0146] According to a specific embodiment of the present invention, the difference in rock mechanical parameters between the interlayer and the reservoir is the ratio of their Young's moduli, specifically: E 隔层 / E 储层 ;

[0147] E 隔层 The Young's modulus of the interlayer;

[0148] E 储层 This is the Young's modulus of the reservoir.

[0149] According to a specific embodiment of the present invention, the construction of a fracture cross-layer propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties, and the establishment of a vertical fracture cross-layer diagram, specifically involves: constructing a fracture cross-layer propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties, and establishing a vertical fracture cross-layer diagram, based on the finite element cohesive element fully coupled fracture propagation method.

[0150] According to a specific embodiment of the present invention, the construction of a fracture cross-layer propagation model considering the heterogeneity of reservoir and interlayer in-situ stress and mechanical properties based on the finite element cohesion element fully coupled fracture propagation method specifically includes the following steps:

[0151] The dimensions of the model are determined, and a finite element geometric model is established. The geometric model consists of three parts: upper, middle, and lower. The upper and lower parts are interlayers, and the middle part is the reservoir.

[0152] Based on the geometric model, the physical and mechanical properties of the reservoir and interlayer are assigned to the geometric model according to their different physical and mechanical properties, and a physical model for fracture penetration and propagation is constructed.

[0153] Mesh the physical model of the crack propagation across layers;

[0154] Boundary conditions and initial field variables are applied to the physical model of the crack propagation model after mesh generation;

[0155] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables;

[0156] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0157] This invention also provides a method for generating a fracture morphology prediction chart for conglomerate reservoirs, which can be used in any of the above-mentioned methods for predicting fracture morphology in conglomerate reservoirs, and includes the following steps:

[0158] The key parameters affecting the fracture morphology of conglomerate reservoirs were determined. These key parameters included: the fracturing displacement and the geostress pattern, where the geostress pattern was the relative magnitude of the vertical geostress and the horizontal minimum geostress.

[0159] The construction displacement and the difference between the vertical and horizontal minimum ground stress are respectively used as the abscissa and ordinate of the coordinate system; the difference between the vertical and horizontal minimum ground stress is S. v -S h ;

[0160] S v This represents the vertical in-situ stress of the strata.

[0161] S h The minimum horizontal ground stress;

[0162] By combining the two variables of construction discharge rate and the difference between vertical and horizontal minimum ground stress in the stratum in different ways, the crack morphology under different combinations is obtained by using the constructed crack morphology propagation model.

[0163] Based on the obtained construction discharge and the crack morphology under different combinations of the difference between the vertical ground stress and the minimum horizontal ground stress, the coordinate axis region is divided into two regions: the horizontal crack development region and the vertical crack development region.

[0164] Complete the drawing of the prediction map of fracture morphology in conglomerate reservoirs.

[0165] According to a specific embodiment of the present invention, a two-dimensional rectangular coordinate system is established in the fracture morphology prediction chart of conglomerate reservoirs, with the horizontal axis representing the construction displacement and the unit of the horizontal axis being meters. 3 / min, the vertical axis represents the difference S between the vertical in-situ stress and the minimum horizontal in-situ stress of the stratum. v -S h The vertical axis is in MPa, and the conglomerate reservoir fracture morphology prediction map is divided into two regions: the horizontal fracture development zone and the vertical fracture development zone.

[0166] This invention also provides a method for generating a vertical fracture cross-layer map, used in any of the above-mentioned methods for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0167] The key parameters affecting vertical fracture penetration in conglomerate reservoirs were determined. These parameters included the difference in mechanical properties between the interlayer and the reservoir, and the difference in minimum horizontal in-situ stress between them. The minimum horizontal in-situ stress difference between the interlayer and the reservoir was S. h,隔层 -S h,储层 ;

[0168] The differences in mechanical properties between the interlayer and the reservoir, and the differences in the minimum horizontal geostress between the interlayer and the reservoir, are respectively used as the x-axis and y-axis of the coordinate system.

[0169] By combining the two variables of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir in different ways, the fracture penetration and propagation model is used to calculate whether the fracture can penetrate the interlayer under different combinations of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir.

[0170] Based on the results of whether the cracks can penetrate the interlayer under each combination of conditions, the area of ​​the vertical crack penetration diagram is divided into two areas: the vertical crack penetration area and the vertical crack non-penetration area.

[0171] Complete the drawing of the vertical crack through-layer diagram.

[0172] According to a specific embodiment of the present invention, the difference in mechanical properties between the interlayer and the reservoir is the ratio of their Young's moduli, E.隔层 / E 储层 ;

[0173] E 隔层 The Young's modulus of the interlayer;

[0174] E 储层 This is the Young's modulus of the reservoir.

[0175] According to a specific embodiment of the present invention, a two-dimensional rectangular coordinate system is established in the vertical fracture penetration diagram, with the horizontal axis representing the ratio E of the Young's modulus of the interlayer and the Young's modulus of the reservoir. 隔层 / E 储层 The units are dimensionless; the vertical axis represents the difference S between the minimum horizontal in-situ stress of the interlayer and the minimum horizontal in-situ stress of the reservoir. h,隔层 -S h,储层 The unit is MPa; the vertical crack penetration map is divided into two regions: the vertical crack penetration region and the vertical crack non-penetrating region; the boundary of each region is controlled by control points, and the boundary line of the vertical crack penetration region is determined by multiple boundary points, which are connected in sequence to form the boundary line.

[0176] According to a specific embodiment of the present invention, the boundary line of the vertical crack penetration area is determined by four boundary points: point 1 (1, 5 MPa), point 2 (3, 5 MPa), point 3 (5, 3 MPa), and point 4 (9, 0 MPa). The four points are connected sequentially, with point 2 and point 3 connected by a straight line or an arc, and the other points connected by a straight line.

[0177] This invention also provides a method for selecting a segmented fracturing fracture pattern, comprising the following steps: a conglomerate reservoir fracture morphology prediction map generated using the aforementioned method for generating any of the conglomerate reservoir fracture morphology prediction maps, and a vertical fracture cross-layer map generated using the aforementioned method for generating any of the vertical fracture cross-layer maps.

[0178] The key parameters affecting fracture morphology after fracturing in conglomerate reservoirs were determined, including geological parameters and construction parameters. Geological factors included the differences in mechanical properties between the reservoir and the interlayer, as well as the triaxial stress values ​​of the reservoir and the interlayer. Construction parameters included the viscosity of the fracturing fluid and the flow rate during fracturing operations.

[0179] The fracture morphology prediction chart of conglomerate reservoir was used for quantitative evaluation to obtain the fracture morphology types developed in the reservoir after fracturing. The fracture morphology types include horizontal fractures and vertical fractures.

[0180] If the obtained fracture morphology is a vertical fracture, then the vertical fracture penetration chart is used to determine whether the vertical fracture can penetrate the upper and lower strata to form a cross-strata fracture. This is determined by the difference in mechanical properties between the strata and the reservoir, as well as the difference in the minimum horizontal in-situ stress S between the strata and the reservoir. h,隔层 -S h,储层The location of a vertical crack in a trans-layer diagram is used to confirm whether a crack can penetrate a layer. The difference in mechanical properties is represented by the ratio of Young's modulus E. 隔层 / E 储层 .

[0181] According to one specific embodiment of the present invention, the stitching pattern includes horizontal cracks, through-layer vertical cracks defined by the through-layer regions of vertical cracks, and non-through-layer vertical cracks defined by the non-through-layer regions of vertical cracks.

[0182] Example 1

[0183] According to a specific embodiment of the present invention, the method for predicting fracture morphology in conglomerate reservoirs is described in detail below.

[0184] This invention provides a method for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0185] A fracture propagation morphology model was constructed, and a fracture morphology prediction chart for conglomerate reservoirs was established based on the calculation results of the fracture propagation morphology model.

[0186] Based on the fracture morphology chart of conglomerate reservoir, determine whether the hydraulic fracture development is a post-pressure fracture, a vertical fracture, or a horizontal fracture.

[0187] For areas with vertical fractures, collect geological and mechanical parameters that affect fracture penetration in the vertical fracture development zone;

[0188] Construct a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties, and establish a vertical fracture propagation chart;

[0189] Based on the collected geological and mechanical parameters of the reservoir and interlayers, combined with the vertical fracture penetration chart, it is determined whether hydraulic fracturing can penetrate the interlayers.

[0190] Example 2

[0191] According to a specific embodiment of the present invention, the method for predicting fracture morphology in conglomerate reservoirs is described in detail below.

[0192] This invention provides a method for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0193] Key parameters affecting fracture morphology in conglomerate reservoirs were collected, including: drilling displacement and reservoir triaxial stress values.

[0194] Using the finite element cohesive element fully coupled fracture propagation method, a fracture propagation morphology model is constructed based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs. Based on the calculation results of the fracture propagation morphology model, a fracture morphology prediction chart for conglomerate reservoirs is established.

[0195] Based on the fracture morphology chart of conglomerate reservoir, determine whether the hydraulic fracture development is a post-pressure fracture, a vertical fracture, or a horizontal fracture.

[0196] For areas with developed vertical fractures, geological and mechanical parameters affecting fracture penetration across layers in these areas were collected. These parameters include the minimum horizontal stress difference between the interlayer and the reservoir, and the differences in rock mechanical parameters between the interlayer and the reservoir. The minimum horizontal stress difference between the interlayer and the reservoir is S. h,隔层 -S h,储层 ;

[0197] in,

[0198] S h,隔层 This represents the minimum horizontal ground stress in the interlayer.

[0199] S h,储层 This represents the minimum horizontal geostress of the reservoir.

[0200] The difference in rock mechanical parameters between the interlayer and the reservoir is represented by the ratio of their Young's moduli, specifically: E 隔层 / E 储层 ;

[0201] E 隔层 The Young's modulus of the interlayer;

[0202] E 储层 This is the Young's modulus of the reservoir.

[0203] Construct a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties, and establish a vertical fracture propagation chart;

[0204] Based on the collected geological and mechanical parameters of the reservoir and interlayers, combined with the vertical fracture penetration chart, it is determined whether hydraulic fracturing can penetrate the interlayers.

[0205] The method of fully coupled fracture propagation using finite element cohesion units, based on collected key parameters affecting fracture morphology in conglomerate reservoirs, constructs a fracture propagation morphology model and establishes a fracture morphology prediction chart for conglomerate reservoirs. The specific steps include:

[0206] Determine the dimensions of the model and establish a finite element geometric model;

[0207] Based on the geometric model, physical and mechanical properties are assigned to the geometric model according to the physical and mechanical properties of the reservoir rock, and a physical model of the fracture propagation morphology model is constructed. The physical and mechanical properties include porosity, permeability, Young's modulus, Poisson's ratio and tensile strength.

[0208] Mesh the physical model of the crack propagation morphology model;

[0209] Boundary conditions and initial field variables are applied to the physical model of the crack propagation morphology model after meshing; the boundary conditions include fixed displacement boundary conditions and pore pressure boundary conditions; the initial field variables include porosity field, geostress field and pore pressure field.

[0210] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables;

[0211] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0212] The construction of a fracture cross-layer propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties based on the finite element cohesion unit fully coupled fracture propagation method specifically includes the following steps:

[0213] The dimensions of the model are determined, and a finite element geometric model is established. The geometric model consists of three parts: upper, middle, and lower. The upper and lower parts are interlayers, and the middle part is the reservoir.

[0214] Based on the geometric model, the physical and mechanical properties of the reservoir and interlayer are assigned to the geometric model according to their different physical and mechanical properties, and a physical model for fracture penetration and propagation is constructed.

[0215] Mesh the physical model of the crack propagation across layers;

[0216] Boundary conditions and initial field variables are applied to the physical model of the crack propagation model after mesh generation;

[0217] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables;

[0218] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0219] Example 3

[0220] According to a specific embodiment of the present invention, the method for generating a conglomerate reservoir fracture morphology prediction chart is described in detail below.

[0221] This invention provides a method for generating a fracture morphology prediction map of conglomerate reservoirs, applicable to any of the aforementioned methods for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0222] The key parameters affecting the fracture morphology of conglomerate reservoirs were determined. These key parameters included: the fracturing displacement and the geostress pattern, where the geostress pattern was the relative magnitude of the vertical geostress and the horizontal minimum geostress.

[0223] The construction displacement and the difference between the vertical and horizontal minimum ground stress are respectively used as the abscissa and ordinate of the coordinate system; the difference between the vertical and horizontal minimum ground stress is S. v -S h ;

[0224] S v This represents the vertical in-situ stress of the strata.

[0225] S h The minimum horizontal ground stress;

[0226] By combining the two variables of construction discharge rate and the difference between vertical and horizontal minimum ground stress in the stratum in different ways, the crack morphology under different combinations is obtained by using the constructed crack morphology propagation model.

[0227] Based on the obtained construction discharge and the crack morphology under different combinations of the difference between the vertical ground stress and the minimum horizontal ground stress, the coordinate axis region is divided into two regions: the horizontal crack development region and the vertical crack development region.

[0228] A two-dimensional rectangular coordinate system is established in the conglomerate reservoir fracture morphology prediction chart, with the horizontal axis representing the construction displacement in meters. 3 / min, the vertical axis represents the difference S between the vertical in-situ stress and the minimum horizontal in-situ stress of the stratum. v -S h The vertical axis is in MPa, and the conglomerate reservoir fracture morphology prediction map is divided into two regions: the horizontal fracture development zone and the vertical fracture development zone.

[0229] Complete the drawing of the prediction map of fracture morphology in conglomerate reservoirs.

[0230] Example 4

[0231] According to a specific embodiment of the present invention, the method for generating the vertical crack through-layer diagram of the present invention will be described in detail below.

[0232] This invention provides a method for generating vertical fracture cross-layer maps, applicable to the aforementioned method for predicting fracture morphology in any of the conglomerate reservoirs, comprising the following steps:

[0233] The key parameters affecting vertical fracture penetration in conglomerate reservoirs were determined. These parameters included the difference in mechanical properties between the interlayer and the reservoir, and the difference in minimum horizontal in-situ stress between them. The minimum horizontal in-situ stress difference between the interlayer and the reservoir was S. h,隔层 -S h,储层 The difference in mechanical properties between the interlayer and the reservoir is represented by the ratio of their Young's moduli, E. 隔层 / E 储层 E隔层 E represents the Young's modulus of the interlayer. 储层 The Young's modulus of the reservoir;

[0234] The differences in mechanical properties between the interlayer and the reservoir, and the differences in the minimum horizontal geostress between the interlayer and the reservoir, are respectively used as the x-axis and y-axis of the coordinate system.

[0235] By combining the two variables of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir in different ways, the fracture penetration and propagation model is used to calculate whether the fracture can penetrate the interlayer under different combinations of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir.

[0236] Based on the results of whether the cracks can penetrate the interlayer under each combination of conditions, the area of ​​the vertical crack penetration diagram is divided into two areas: the vertical crack penetration area and the vertical crack non-penetration area.

[0237] Establish a two-dimensional rectangular coordinate system in the vertical fracture penetration diagram, with the horizontal axis representing the ratio E of the Young's modulus of the interlayer and the Young's modulus of the reservoir. 隔层 / E 储层 The units are dimensionless; the vertical axis represents the difference S between the minimum horizontal in-situ stress of the interlayer and the minimum horizontal in-situ stress of the reservoir. h,隔层 -S h , 储层 The unit is MPa; the vertical crack penetration map is divided into two areas: the vertical crack penetration area and the vertical crack non-penetrating area; each area is controlled by control points. The boundary line of the vertical crack penetration area is determined by multiple boundary points, which are connected sequentially to form the boundary line; the boundary line of the vertical crack penetration area is determined by four boundary points: point 1 (1, 5MPa), point 2 (3, 5MPa), point 3 (5, 3MPa), and point 4 (9, 0MPa). The four points are connected sequentially. Points 2 and 3 are connected by a straight line or an arc, and the other points are connected by a straight line.

[0238] Complete the drawing of the vertical crack through-layer diagram.

[0239] Example 5

[0240] According to a specific embodiment of the present invention, the method for selecting the fracture pattern in segmented fracturing is described in detail below.

[0241] This invention provides a method for selecting fracture pattern in segmented fracturing, comprising the following steps: a conglomerate reservoir fracture morphology prediction map generated using the aforementioned method for generating any conglomerate reservoir fracture morphology prediction map, and a vertical fracture cross-layer map generated using the aforementioned method for generating any vertical fracture cross-layer map.

[0242] The key parameters affecting fracture morphology after fracturing in conglomerate reservoirs were determined, including geological parameters and construction parameters. Geological factors included the differences in mechanical properties between the reservoir and the interlayer, as well as the triaxial stress values ​​of the reservoir and the interlayer. Construction parameters included the viscosity of the fracturing fluid and the flow rate during fracturing operations.

[0243] The fracture morphology prediction chart of conglomerate reservoir was used for quantitative evaluation to obtain the fracture morphology types developed in the reservoir after fracturing. The fracture morphology types include horizontal fractures and vertical fractures.

[0244] If the obtained fracture morphology is a vertical fracture, then the vertical fracture penetration chart is used to determine whether the vertical fracture can penetrate the upper and lower strata to form a cross-strata fracture. This is determined by the difference in mechanical properties between the strata and the reservoir, as well as the difference in the minimum horizontal in-situ stress S between the strata and the reservoir. h,隔层 -S h,储层 The location of a vertical crack in a trans-layer diagram is used to confirm whether a crack can penetrate a layer. The difference in mechanical properties is represented by the ratio of Young's modulus E. 隔层 / E 储层 .

[0245] The stitching patterns include horizontal cracks, through-layer vertical cracks defined by the through-layer regions of vertical cracks, and non-through-layer vertical cracks defined by the non-through-layer regions of vertical cracks.

[0246] Example 6

[0247] According to a specific embodiment of the present invention, the method for predicting fracture morphology in conglomerate reservoirs is described in detail below.

[0248] This invention provides a method for predicting fracture morphology in conglomerate reservoirs, comprising the following steps:

[0249] Key parameters affecting fracture morphology in conglomerate reservoirs were collected, including: drilling displacement and reservoir triaxial stress values.

[0250] Using the finite element cohesive element fully coupled fracture propagation method, a fracture propagation morphology model is constructed based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs. Based on the calculation results of the fracture propagation morphology model, a fracture morphology prediction chart for conglomerate reservoirs is established.

[0251] Based on the fracture morphology chart of conglomerate reservoir, determine whether the hydraulic fracture development is a post-pressure fracture, a vertical fracture, or a horizontal fracture.

[0252] For areas with developed vertical fractures, geological and mechanical parameters affecting fracture penetration across layers in these areas were collected. These parameters include the minimum horizontal stress difference between the interlayer and the reservoir, and the differences in rock mechanical parameters between the interlayer and the reservoir. The minimum horizontal stress difference between the interlayer and the reservoir is S. h,隔层 -S h,储层 ;

[0253] in,

[0254] S h,隔层 This represents the minimum horizontal ground stress in the interlayer.

[0255] S h,储层 This represents the minimum horizontal geostress of the reservoir.

[0256] The difference in rock mechanical parameters between the interlayer and the reservoir is represented by the ratio of their Young's moduli, specifically: E 隔层 / E 储层 ;

[0257] E 隔层 The Young's modulus of the interlayer;

[0258] E 储层 This is the Young's modulus of the reservoir.

[0259] Construct a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties, and establish a vertical fracture propagation chart;

[0260] Based on the collected geological and mechanical parameters of the reservoir and interlayers, combined with the vertical fracture penetration chart, it is determined whether hydraulic fracturing can penetrate the interlayers.

[0261] The method of fully coupled fracture propagation using finite element cohesion units, based on collected key parameters affecting fracture morphology in conglomerate reservoirs, constructs a fracture propagation morphology model and establishes a fracture morphology prediction chart for conglomerate reservoirs. The specific steps include:

[0262] Determine the dimensions of the model and establish a finite element geometric model;

[0263] Based on the geometric model, physical and mechanical properties are assigned to the geometric model according to the physical and mechanical properties of the reservoir rock, and a physical model of the fracture propagation morphology model is constructed. The physical and mechanical properties include porosity, permeability, Young's modulus, Poisson's ratio and tensile strength.

[0264] Mesh the physical model of the crack propagation morphology model;

[0265] Boundary conditions and initial field variables are applied to the physical model of the crack propagation morphology model after meshing; the boundary conditions include fixed displacement boundary conditions and pore pressure boundary conditions; the initial field variables include porosity field, geostress field and pore pressure field.

[0266] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables;

[0267] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0268] The construction of a fracture cross-layer propagation model considering the heterogeneity of reservoir and interlayer stress and mechanical properties based on the finite element cohesion unit fully coupled fracture propagation method specifically includes the following steps:

[0269] The dimensions of the model are determined, and a finite element geometric model is established. The geometric model consists of three parts: upper, middle, and lower. The upper and lower parts are interlayers, and the middle part is the reservoir.

[0270] Based on the geometric model, the physical and mechanical properties of the reservoir and interlayer are assigned to the geometric model according to their different physical and mechanical properties, and a physical model for fracture penetration and propagation is constructed.

[0271] Mesh the physical model of the crack propagation across layers;

[0272] Boundary conditions and initial field variables are applied to the physical model of the crack propagation model after mesh generation;

[0273] The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables;

[0274] By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

[0275] The method for generating the fracture morphology prediction map of the conglomerate reservoir includes the following steps:

[0276] The key parameters affecting the fracture morphology of conglomerate reservoirs were determined. These key parameters included: the fracturing displacement and the geostress pattern, where the geostress pattern was the relative magnitude of the vertical geostress and the horizontal minimum geostress.

[0277] The construction displacement and the difference between the vertical and horizontal minimum ground stress are respectively used as the abscissa and ordinate of the coordinate system; the difference between the vertical and horizontal minimum ground stress is S. v -S h ;

[0278] S v This represents the vertical in-situ stress of the strata.

[0279] S h The minimum horizontal ground stress;

[0280] By combining the two variables of construction discharge rate and the difference between vertical and horizontal minimum ground stress in the stratum in different ways, the crack morphology under different combinations is obtained by using the constructed crack morphology propagation model.

[0281] Based on the obtained construction discharge and the crack morphology under different combinations of the difference between the vertical ground stress and the minimum horizontal ground stress, the coordinate axis region is divided into two regions: the horizontal crack development region and the vertical crack development region.

[0282] A two-dimensional rectangular coordinate system is established in the conglomerate reservoir fracture morphology prediction chart, with the horizontal axis representing the construction displacement in meters. 3 / min, the vertical axis represents the difference S between the vertical in-situ stress and the minimum horizontal in-situ stress of the stratum. v -S h The vertical axis is in MPa, and the conglomerate reservoir fracture morphology prediction map is divided into two regions: the horizontal fracture development zone and the vertical fracture development zone.

[0283] Complete the drawing of the prediction map of fracture morphology in conglomerate reservoirs.

[0284] The method for generating the vertical crack through-layer diagram includes the following steps:

[0285] The key parameters affecting vertical fracture penetration in conglomerate reservoirs were determined. These parameters included the difference in mechanical properties between the interlayer and the reservoir, and the difference in minimum horizontal in-situ stress between them. The minimum horizontal in-situ stress difference between the interlayer and the reservoir was S. h,隔层 -S h,储层 The difference in mechanical properties between the interlayer and the reservoir is represented by the ratio of their Young's moduli, E. 隔层 / E 储层 E 隔层 E represents the Young's modulus of the interlayer. 储层 The Young's modulus of the reservoir;

[0286] The differences in mechanical properties between the interlayer and the reservoir, and the differences in the minimum horizontal geostress between the interlayer and the reservoir, are respectively used as the x-axis and y-axis of the coordinate system.

[0287] By combining the two variables of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir in different ways, the fracture penetration and propagation model is used to calculate whether the fracture can penetrate the interlayer under different combinations of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir.

[0288] Based on the results of whether the cracks can penetrate the interlayer under each combination of conditions, the area of ​​the vertical crack penetration diagram is divided into two areas: the vertical crack penetration area and the vertical crack non-penetration area.

[0289] Establish a two-dimensional rectangular coordinate system in the vertical fracture penetration diagram, with the horizontal axis representing the ratio E of the Young's modulus of the interlayer and the Young's modulus of the reservoir. 隔层 / E 储层 The units are dimensionless; the vertical axis represents the difference S between the minimum horizontal in-situ stress of the interlayer and the minimum horizontal in-situ stress of the reservoir. h,隔层 -S h , 储层 The unit is MPa; the vertical crack penetration map is divided into two areas: the vertical crack penetration area and the vertical crack non-penetrating area; each area is controlled by control points. The boundary line of the vertical crack penetration area is determined by multiple boundary points, which are connected sequentially to form the boundary line; the boundary line of the vertical crack penetration area is determined by four boundary points: point 1 (1, 5MPa), point 2 (3, 5MPa), point 3 (5, 3MPa), and point 4 (9, 0MPa). The four points are connected sequentially. Points 2 and 3 are connected by a straight line or an arc, and the other points are connected by a straight line.

[0290] Complete the drawing of the vertical crack through-layer diagram.

[0291] Example 7

[0292] This embodiment describes the steps for predicting fracture morphology after hydraulic fracturing using a chart in the Badaowan Formation of Block 7, Xinjiang Oilfield.

[0293] (1) The triaxial geostress values ​​of well W1 in the Badaowan Formation of the 7th District of Xinjiang Oilfield were collected as follows: S h =19MPa, S v =16MPa, S h,储层 =14.4MPa, S h,隔层 =16.2MPa; E 储层 =10.4 GPa, E 隔层 =16.2 GPa.

[0294] (2) Using a conglomerate reservoir fracture morphology prediction chart, the acquired parameter points are projected onto the chart to determine the fracture morphology. (See...) Figure 8 .

[0295] (3) In areas with vertical crack development, it is necessary to consider whether the crack can penetrate the existing strata above and below. In this case, project the parameters of this area onto the crack penetration chart of the vertical crack development area to determine whether the crack can penetrate the strata above and below. See Figure 9 .

[0296] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for predicting fracture morphology in conglomerate reservoirs, characterized in that, Includes the following steps: A fracture propagation morphology model was constructed, and a fracture morphology prediction chart for conglomerate reservoirs was established based on the calculation results of the fracture propagation morphology model. Based on the fracture morphology chart of conglomerate reservoir, determine whether the hydraulic fracture development is a post-pressure fracture, a vertical fracture, or a horizontal fracture. For areas with vertical fractures, collect geological and mechanical parameters that affect fracture penetration in the vertical fracture development zone; Construct a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties, and establish a vertical fracture propagation chart; Based on the collected geological and mechanical parameters of the reservoir and interlayers, combined with the vertical fracture penetration chart, it is determined whether hydraulic fracturing can penetrate the interlayers. The process of constructing a fracture propagation morphology model and establishing a fracture morphology prediction chart for conglomerate reservoirs based on the calculation results of the model includes the following steps: The key parameters affecting the fracture morphology of conglomerate reservoirs were determined. These key parameters included: the fracturing displacement and the geostress pattern, where the geostress pattern was the relative magnitude of the vertical geostress and the horizontal minimum geostress. The construction displacement and the difference between the vertical and horizontal minimum ground stress are respectively used as the abscissa and ordinate of the coordinate system; the difference between the vertical and horizontal minimum ground stress is S. v -S h ; S v vertical stress on the formation; S h For the minimum stress horizontally; By combining the two variables of construction discharge rate and the difference between vertical and horizontal minimum ground stress in the stratum in different ways, the crack morphology under different combinations is obtained by using the constructed crack morphology propagation model. Based on the obtained construction discharge and the crack morphology under different combinations of the difference between the vertical ground stress and the minimum horizontal ground stress, the coordinate axis region is divided into two regions: the horizontal crack development region and the vertical crack development region. Complete the drawing of a prediction chart of fracture morphology in conglomerate reservoirs; The method for generating a vertical crack cross-layer diagram includes the following steps: Determine the key parameters affecting the vertical fracture penetration of the conglomerate reservoir, the key parameters including: the difference in mechanical properties between the barrier and the reservoir and the horizontal minimum stress difference between the barrier and the reservoir, the horizontal minimum stress difference between the barrier and the reservoir is S h,隔层 -S h,储层 ; The differences in mechanical properties between the interlayer and the reservoir, and the differences in the minimum horizontal geostress between the interlayer and the reservoir, are respectively used as the x-axis and y-axis of the coordinate system. By combining the two variables of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir in different ways, the fracture penetration and propagation model is used to calculate whether the fracture can penetrate the interlayer under different combinations of the mechanical property difference between the interlayer and the reservoir and the difference in the minimum horizontal stress between the interlayer and the reservoir. Based on the results of whether the cracks can penetrate the interlayer under each combination of conditions, the area of ​​the vertical crack penetration diagram is divided into two areas: the vertical crack penetration area and the vertical crack non-penetration area. Complete the drawing of the vertical crack through-layer diagram.

2. The method for predicting fracture morphology in conglomerate reservoirs according to claim 1, characterized in that, Before constructing a fracture propagation morphology model and establishing a prediction chart for fracture morphology in conglomerate reservoirs, the following steps are also taken: collecting key parameters that affect the fracture morphology of conglomerate reservoirs, including: construction displacement and reservoir triaxial geostress values.

3. The method for predicting fracture morphology in conglomerate reservoirs according to claim 2, characterized in that, The specific steps for constructing a fracture propagation morphology model and establishing a fracture morphology prediction chart for conglomerate reservoirs are as follows: using the finite element cohesive unit fully coupled fracture propagation method, based on the collected key parameters affecting the fracture morphology of conglomerate reservoirs, a fracture propagation morphology model is constructed, and a fracture morphology prediction chart for conglomerate reservoirs is established.

4. The method for predicting fracture morphology in conglomerate reservoirs according to claim 3, characterized in that, The method for constructing a fracture propagation morphology model using the fully coupled finite element cohesion unit, based on key parameters influencing fracture morphology in conglomerate reservoirs, specifically includes the following steps: Determine the dimensions of the model and establish a finite element geometric model; Based on the geometric model, physical and mechanical properties are assigned to the geometric model according to the physical and mechanical properties of the reservoir rock, and a physical model of the fracture propagation morphology model is constructed. The physical and mechanical properties include porosity, permeability, Young's modulus, Poisson's ratio and tensile strength. Mesh the physical model of the crack propagation morphology model; Boundary conditions and initial field variables are applied to the physical model of the crack propagation morphology model after meshing; the boundary conditions include fixed displacement boundary conditions and pore pressure boundary conditions; the initial field variables include porosity field, geostress field and pore pressure field. The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables; By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

5. The method for predicting fracture morphology in conglomerate reservoirs according to claim 4, characterized in that, The geological and mechanical parameters affecting the fracture penetration in the vertical fracture development zone include: the minimum horizontal stress difference of the barrier and reservoir and the rock mechanical parameter difference of the barrier and reservoir, the minimum horizontal stress difference of the barrier and reservoir is S h,隔层 -S h,储层 ; in, S h,隔层 Minimum horizontal stress for barrier S h,储层 is the minimum horizontal stress of the reservoir.

6. The method for predicting fracture morphology in conglomerate reservoirs according to claim 5, characterized in that, The difference in rock mechanical parameters between the interlayer and the reservoir is represented by the ratio of their Young's moduli, specifically: E 隔层 / E 储层； E 隔层 The Young's modulus of the interlayer; E 储层 This is the Young's modulus of the reservoir.

7. The method for predicting fracture morphology in conglomerate reservoirs according to claim 6, characterized in that, The specific steps for constructing a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties, and establishing a vertical fracture propagation diagram, are as follows: Based on the finite element cohesive unit fully coupled fracture propagation method, a fracture propagation model that considers the heterogeneity of reservoir and interlayer stress and mechanical properties is constructed, and a vertical fracture propagation diagram is established.

8. The method for predicting fracture morphology in conglomerate reservoirs according to claim 7, characterized in that, Based on the finite element cohesive unit fully coupled fracture propagation method, the construction of a fracture cross-layer propagation model considering the heterogeneity of reservoir and interlayer in-situ stress and mechanical properties includes the following steps: The dimensions of the model are determined, and a finite element geometric model is established. The geometric model consists of three parts: upper, middle, and lower. The upper and lower parts are interlayers, and the middle part is the reservoir. Based on the geometric model, the physical and mechanical properties of the reservoir and interlayer are assigned to the geometric model according to their different physical and mechanical properties, and a physical model for fracture penetration and propagation is constructed. Mesh the physical model of the crack propagation across layers; Boundary conditions and initial field variables are applied to the physical model of the crack propagation model after mesh generation; The injection point, injection flow rate, and injection time were set for the physical model after applying boundary conditions and initial field variables; By changing the physical and mechanical parameters of the above model and performing calculations, the crack propagation morphology under different calculation conditions was obtained.

9. The method for predicting fracture morphology in conglomerate reservoirs according to claim 1, characterized in that, A two-dimensional rectangular coordinate system is established in the conglomerate reservoir fracture morphology prediction chart, with the horizontal axis representing the construction displacement in meters. 3 / min, the vertical axis represents the difference S between the vertical in-situ stress and the minimum horizontal in-situ stress of the stratum. v -S h The vertical axis is in MPa, and the conglomerate reservoir fracture morphology prediction map is divided into two regions: the horizontal fracture development zone and the vertical fracture development zone.

10. The method for predicting fracture morphology in conglomerate reservoirs according to claim 1, characterized in that, The difference in mechanical properties between the interlayer and the reservoir is the ratio of their Young's moduli, E. 隔层 / E 储层 ; E 隔层 The Young's modulus of the interlayer; E 储层 This is the Young's modulus of the reservoir.

11. The method for predicting fracture morphology in conglomerate reservoirs according to claim 10, characterized in that, Establish a two-dimensional rectangular coordinate system in the vertical fracture penetration diagram, with the horizontal axis representing the ratio E of the Young's modulus of the interlayer and the Young's modulus of the reservoir. 隔层 / E 储层 The unit is dimensionless; The vertical axis represents the difference S between the minimum horizontal in-situ stress of the interlayer and the minimum horizontal in-situ stress of the reservoir. h,隔层 -S h,储层 The unit is MPa; The vertical crack penetration map is divided into two areas: the vertical crack penetration area and the vertical crack non-penetrating area. Each area is controlled by control points. The boundary line of the vertical crack penetration area is determined by multiple boundary points, which are connected sequentially to form the boundary line.

12. A method for selecting fracture pattern in segmented hydraulic fracturing, characterized in that, The conglomerate reservoir fracture morphology prediction map generated by the method for generating the conglomerate reservoir fracture morphology prediction map as described in claim 1, and the vertical fracture cross-layer map generated by the method for generating the vertical fracture cross-layer map as described in claim 1, include the following steps: The key parameters affecting fracture morphology after fracturing in conglomerate reservoirs were determined, including geological parameters and construction parameters. Geological factors included the differences in mechanical properties between the reservoir and the interlayer, as well as the triaxial stress values ​​of the reservoir and the interlayer. Construction parameters included the viscosity of the fracturing fluid and the flow rate during fracturing operations. The fracture morphology prediction chart of conglomerate reservoir was used for quantitative evaluation to obtain the fracture morphology types developed in the reservoir after fracturing. The fracture morphology types include horizontal fractures and vertical fractures. If the obtained fracture morphology is a vertical fracture, then the vertical fracture penetration chart is used to determine whether the vertical fracture can penetrate the upper and lower strata to form a cross-strata fracture. This is determined by the difference in mechanical properties between the strata and the reservoir, as well as the difference in the minimum horizontal in-situ stress S between the strata and the reservoir. h,隔层 -S h,储层 The location of a vertical crack in a trans-layer diagram is used to confirm whether a crack can penetrate a layer. The difference in mechanical properties is represented by the ratio of Young's modulus E. 隔层 / E 储层 .

13. The method for selecting the fracture pattern in segmented fracturing according to claim 12, characterized in that, The stitching patterns include horizontal cracks, through-layer vertical cracks defined by the through-layer regions of vertical cracks, and non-through-layer vertical cracks defined by the non-through-layer regions of vertical cracks.

Images