A shale oil exploitation method based on explosive fracturing, computer equipment and medium

Abstract

The application discloses a shale oil exploitation method based on explosive fracturing, computer equipment and a medium, and relates to the technical field of oil reservoir exploitation. The method comprises the following steps: establishing a reservoir model under different explosive preset amounts according to the geological characteristics of a target area; for each explosive preset amount, setting physical parameters of a rock layer model in the reservoir model under the explosive preset amount, explosive material parameters of an explosive model, air material parameters of an air model and failure criteria of an oil reservoir unit, obtaining a parameterized model, determining the number of failure units based on the parameterized model, calculating a fracturing reconstruction ratio corresponding to the explosive preset amount according to the number of failure units and the number of all oil reservoir units, and finally selecting the explosive preset amount corresponding to the fracturing reconstruction ratio with the minimum difference from the preset fracturing reconstruction ratio as the optimal explosive preset amount. The optimal explosive preset amount is determined through numerical simulation of rock layer explosion, the shale oil development cost is reduced, and the method is environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of oil reservoir development technology, and in particular to a shale oil extraction method, computer equipment, and medium based on explosive fracturing. Background Technology

[0002] Unconventional resources hold immense potential, extending the lifespan of the petroleum industry and increasing resource types and reserves. Once technological breakthroughs are achieved, they will inevitably lead to a "second revolution" in conventional oil and gas. Shale oil is a crucial component of unconventional resources, and the "shale oil revolution" will drive the upgrading and rapid development of the entire petroleum industry's theoretical and technological advancements. At this juncture, shale oil development requires more efficient engineering technologies. Formation fracturing is a critical step in shale oil extraction. Currently, hydraulic fracturing and horizontal well volumetric fracturing are commonly used methods in shale oil extraction. However, hydraulic fracturing causes severe environmental pollution and increases the frequency of earthquakes; horizontal well volumetric fracturing requires multiple on-site experiments to determine the optimal explosive dosage, resulting in high engineering costs. Therefore, there is an urgent need for a shale oil extraction technology that is both environmentally friendly and effectively reduces development costs. Summary of the Invention

[0003] The purpose of this invention is to provide a shale oil extraction method, computer equipment, and medium based on explosive fracturing.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A shale oil extraction method based on explosive fracturing, the method comprising:

[0006] Based on the geological characteristics of the target area, reservoir models are established under different preset explosive quantities; the geological characteristics include the rock type of the rock layer; the reservoir model includes an explosive model, a rock layer model, and an air model; both the rock layer model and the air model include several reservoir units;

[0007] For each preset explosive quantity, the physical parameters of the rock layer model, the explosive material parameters of the explosive model, the air material parameters of the air model, and the failure criteria of the reservoir unit are set in the reservoir model under the preset explosive quantity to obtain a parameterized model; the number of failure units is determined based on the parameterized model, and the fracturing stimulation ratio corresponding to the preset explosive quantity is calculated according to the number of failure units and the number of all reservoir units; the failure unit is the reservoir unit that meets the failure criteria;

[0008] The optimal explosive preset amount is selected as the fracturing modification ratio with the smallest difference from the preset fracturing modification ratio.

[0009] Optionally, establishing reservoir models with different preset explosive amounts based on the geological characteristics of the target area specifically includes:

[0010] The target shale oil simulation area is hierarchically divided according to the geological characteristics of the target area to obtain each type of rock layer; a mapping mesh is then performed on each type of rock layer to obtain a rock layer model; the mesh of the rock layer model is obtained using the Lagrange algorithm.

[0011] The size of the explosive region is determined based on the preset amount of explosive; the explosive region is divided into a mapping mesh to obtain the explosive model; the mesh of the explosive model is obtained using the Euler algorithm;

[0012] The size of the air region is determined based on the size of the explosive region; the air region is divided into a mapping mesh to obtain an air model; the mesh of the air model adopts the Eulerian algorithm; each mesh is a reservoir unit.

[0013] The rock layer model, the air model, and the explosive model are coupled in a fluid-structure interaction to obtain the reservoir model of the target area; the explosive model is located inside the rock layer model and is spaced at a preset distance from the rock layer model; the air model surrounds the explosive model.

[0014] Optionally, after obtaining the reservoir model of the target region, the method further includes:

[0015] Create contact surfaces for the reservoir model;

[0016] Apply a non-reflective boundary condition to the contact surface.

[0017] Optionally, after obtaining the reservoir model of the target region, the method further includes:

[0018] Constrain the Z-direction displacement of all nodes in the reservoir model; the nodes are the vertices of the mesh.

[0019] Optionally, the air material parameters include air material constants C0 to C6, volumetric strain μ, relative volume V, internal energy per unit initial volume E, and air density.

[0020] Optionally, the physical parameters include basic physical and mechanical parameters, strength parameters, damage parameters, pressure parameters, and software parameters; wherein, the basic physical and mechanical parameters include density, compressive strength, elastic modulus, Poisson's ratio, porosity, tensile strength, shear modulus, and bulk modulus; the strength parameters include dimensionless viscous strength coefficient, dimensionless pressure hardening coefficient, strain rate coefficient, pressure hardening exponent, and the maximum dimensionless equivalent stress achievable by the rock; the damage parameters include the initial damage constant, the final damage constant, and the minimum plastic strain at rock fracture; the pressure parameters include a first pressure constant, a second pressure constant, a third pressure constant, hydrostatic pressure, volumetric strain, hydrostatic pressure after compaction, and volumetric strain at the compaction limit state; the software parameters include a reference strain rate and failure parameters.

[0021] Optionally, the mapping mesh division specifically includes:

[0022] A single-layer solid mesh modeling method is used for mapping mesh generation.

[0023] Optionally, the preset fracturing transformation ratio is 0.1.

[0024] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor causes the processor to perform the steps of the above-described shale oil extraction method based on explosive fracturing.

[0025] The present invention also provides a computer-readable storage medium storing a computer program adapted to be loaded and executed by a processor for the above-described shale oil extraction method based on explosive fracturing.

[0026] According to specific embodiments provided by the present invention, the following technical effects are disclosed: The shale oil extraction method, computer equipment, and medium based on explosive fracturing provided by the present invention establish reservoir models under different preset explosive amounts according to the geological characteristics of the target area. For each preset explosive amount, the physical parameters of the rock layer model, the explosive material parameters of the explosive model, the air material parameters of the air model, and the failure criteria of the reservoir unit are set in the reservoir model under the preset explosive amount to obtain a parameterized model. Then, the number of failure units is determined based on the parameterized model, and the fracturing stimulation ratio corresponding to the preset explosive amount is calculated according to the number of failure units and the number of all reservoir units. Finally, the preset explosive amount corresponding to the fracturing stimulation ratio with the smallest difference from the preset fracturing stimulation ratio is selected as the optimal preset explosive amount. The present invention determines the optimal preset explosive amount through numerical simulation of rock layer explosion. Compared with the existing horizontal well volumetric fracturing method, which obtains the optimal preset explosive amount by conducting multiple experiments directly in the field, it reduces the shale oil development cost. Moreover, compared with the hydraulic fracturing method, it does not require water mixed with chemicals to be injected into the shale layer, so it is environmentally friendly. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of the shale oil extraction method based on explosive fracturing provided by the present invention;

[0029] Figure 2 This invention provides a reservoir model for the sweet spot zone of shale oil in the Lucaogou Formation of the Jimsar Depression.

[0030] Figure 3 This is a schematic diagram of the Mohr-Coulomb criterion fitting provided by the present invention;

[0031] Figure 4 This is a schematic diagram of the failure surface fitting provided by the present invention;

[0032] Figure 5 This is a schematic diagram of pressure parameter fitting provided by the present invention;

[0033] Figure 6 A schematic diagram of the physical parameter input interface for the mudstone reservoir model provided by this invention;

[0034] Figure 7 A schematic diagram of the failure criterion parameter input interface provided by the present invention;

[0035] Figure 8A schematic diagram of the air model parameter input interface provided by the present invention;

[0036] Figure 9 A schematic diagram of the air material parameter input interface provided by the present invention;

[0037] Figure 10 A schematic diagram of the input interface for the HIGH_EXPLOSIVE_BURN parameter of the explosive provided by the present invention;

[0038] Figure 11 A schematic diagram of the JWL equation of state parameter input interface for explosives provided by the present invention;

[0039] Figure 12 This is a schematic diagram of the RUN operation interface provided by the present invention;

[0040] Figure 13 The response of the sweet spot area in the first stage when the preset amount of explosive provided by the present invention is 352g;

[0041] Figure 14 The response of the dessert zone in the second stage when the preset amount of explosive provided by the present invention is 352g;

[0042] Figure 15 The response of the dessert zone in the third stage when the preset amount of explosive provided by the present invention is 352g;

[0043] Figure 16 The response of the dessert zone in the fourth stage when the preset amount of explosive provided by the present invention is 352g;

[0044] Figure 17 The response of the dessert zone in the fifth stage when the preset amount of explosive provided by the present invention is 352g;

[0045] Figure 18 A schematic diagram of rock crack propagation morphology when the preset explosive amount is 352g, as provided by the present invention.

[0046] Figure 19 A schematic diagram of rock crack propagation morphology when the preset explosive amount is 528g, as provided by the present invention.

[0047] Figure 20 A schematic diagram of rock crack propagation morphology when the preset explosive amount is 616g, as provided by the present invention.

[0048] Figure 21 A schematic diagram of rock crack propagation morphology when the preset explosive amount is 704g, as provided by the present invention.

[0049] Figure 22 This is a schematic diagram of the structure of a computer device provided by the present invention.

[0050] Symbol explanation:

[0051] 1000 - Computer equipment; 1001 - Processor; 1002 - Communication bus; 1003 - User interface; 1004 - Network interface; 1005 - Memory. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] The purpose of this invention is to provide a shale oil extraction method, computer equipment, and medium based on explosive fracturing. The optimal explosive preset amount is determined by numerical simulation of rock layer explosion. Compared with the existing technology, which obtains the optimal explosive preset amount by conducting multiple experiments in the field, this reduces the cost of shale oil development and is environmentally friendly.

[0054] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] like Figure 1 As shown, this invention provides a shale oil extraction method based on explosive fracturing, the method comprising:

[0056] S1: Establish reservoir models with different preset explosive amounts based on the geological characteristics of the target area; the geological characteristics include the rock type of the rock layer; the reservoir model includes an explosive model, a rock layer model, and an air model; both the rock layer model and the air model include several reservoir units.

[0057] S2: For each preset explosive quantity, set the physical parameters of the rock layer model, the explosive material parameters of the explosive model, the air material parameters of the air model, and the failure criteria of the reservoir unit in the reservoir model under the preset explosive quantity to obtain a parameterized model; determine the number of failure units based on the parameterized model, and calculate the fracturing stimulation ratio corresponding to the preset explosive quantity according to the number of failure units and the number of all reservoir units; the failure unit is the reservoir unit that satisfies the failure criteria.

[0058] S3: Select the explosive preset amount corresponding to the fracturing transformation ratio with the smallest difference from the preset fracturing transformation ratio as the optimal explosive preset amount.

[0059] Specifically, S1 includes:

[0060] The target shale oil simulation area is divided into layers according to the geological characteristics of the target area to obtain each type of rock layer; each type of rock layer is divided into a mapping mesh to obtain a rock layer model; the mesh of the rock layer model is obtained using the Lagrange algorithm.

[0061] The size of the explosive region is determined based on the preset amount of explosive; the explosive region is divided into a mapping mesh to obtain the explosive model; the mesh of the explosive model is obtained using the Euler algorithm.

[0062] The size of the air region is determined based on the size of the explosive region; the air region is divided into a mapping mesh to obtain an air model; the mesh of the air model adopts the Euler algorithm; each mesh is a reservoir unit.

[0063] The rock layer model, the air model, and the explosive model are coupled in a fluid-structure interaction to obtain the reservoir model of the target area; the explosive model is located inside the rock layer model and is spaced at a preset distance from the rock layer model; the air model surrounds the explosive model.

[0064] In this embodiment, after obtaining the reservoir model of the target region, the method further includes:

[0065] Create contact surfaces for the reservoir model;

[0066] Apply a non-reflective boundary condition to the contact surface.

[0067] Constrain the Z-direction displacement of all nodes in the reservoir model; the nodes are the vertices of the mesh. A node is the intersection of the lines that make up the mesh.

[0068] This embodiment uses the Jimsar shale gas and oil area as the target region to illustrate the above process. Specifically, based on the geological characteristics of the Jimsar shale gas and oil sweet spot and relying on existing 3D seismic data, ANSYS software is used to establish, as shown in the figure below. Figure 2 The reservoir model (unit: mm) of the sweet spot area of ​​shale oil in the Lucao Gou Formation of the Jimsar Depression is shown to explore the dynamic response and local damage effect of the shale oil sweet spot under explosive loading conditions. The dynamic response mechanism of the shale oil sweet spot under different explosive dosages is obtained, and the optimal oil recovery efficiency (oil recovery efficiency is the fracturing ratio) is derived. The geological characteristics of the Jimsar shale oil sweet spot are the rock types of the rock layers, including mudstone, sandstone, litholithic fine sandstone, and dolomitic sandstone. Based on the geological characteristics of the target area, the target shale oil simulation area is divided into layers to obtain each type of rock layer, such as... Figure 2As shown, the simulated area of ​​the Jimsar shale oil is divided into mudstone layer, sandstone dolomite layer, mudstone layer, lithic feldspar fine sandstone layer, mudstone layer, and dolomite sandstone layer from top to bottom. A mapping mesh is applied to each type of rock layer to obtain a rock layer model, where the mesh uses the Lagrange algorithm. It should be noted that the rock model in this embodiment uses the HJC constitutive model. For the explosive model: the size of the explosive region is determined according to the preset explosive amount. For example, when the preset explosive amount is 352g, the size of the explosive model is 120mm × 120mm × 15mm. A mapping mesh is applied to the explosive region to obtain the explosive model, where the mesh uses the Eulerian algorithm. The explosive model uses a strip-shaped charge structure, and the explosive is placed in the lithic feldspar fine sandstone layer, but this is not a limitation of the invention. It should be noted that the mesh of the explosive model does not include reservoir units. For the air model: The size of the air region is determined based on the dimensions of the explosive region. The size of the air region is no less than ten times the size of the explosive region. Therefore, when the size of the explosive region is 120mm × 120mm × 15mm, the size of the air region is set to 800mm in length and 1600mm in height. The air region is then mapped and meshed to obtain the air model. The mesh of the air model is generated using the Euler algorithm. Figure 2 The shape of the air model is not a limitation of this invention.

[0069] After establishing the aforementioned rock layer model, air model, and explosive model, according to the definition of fluid-structure interaction, two types of meshes with different properties need to be overlapped. When establishing the reservoir model, the air model is used as the coupling medium, and the keyword `ALE_MULTI-MATERIAL_GROUP` is added to allow flow between the fluid media within the mesh. Finally, the fluid media (explosive model and air model) and the solid media (rock layer model) are coupled using the keyword `CONSTRAINED_LAGRANGE_IN_SOLID`. After establishing the reservoir model, this embodiment uses single-layer solid mesh modeling for mapped mesh generation; specifically, the mapped mesh is divided into 101592 elements. Contact surfaces are created around the reservoir model using the `*SET_SEGMENT` keyword, and then `*BOUNDARY_NON_REFLECTING` is used to apply non-reflective boundary conditions to all previously created contact surfaces. Simultaneously, the Z-direction of all nodes in the reservoir model should be constrained using the `*BOUNDARY_SPC_SET` keyword, i.e., displacement in the Z-direction is not considered. The calculation step size of ANSYS software is 0.6 μs, and the numerical calculation uses the cm-g-μs unit system.

[0070] After establishing the reservoir model, it is necessary to calculate the parameters (physical parameters, air material parameters, and explosive material parameters) required for the rock layer model, air model, and explosive model. The physical parameters include the basic physical and mechanical parameters of mudstone, strength parameters, damage parameters, pressure parameters, and software parameters. The basic physical and mechanical parameters of mudstone include density ρ0 and compressive strength f. c The strength parameters include: elastic modulus E, Poisson's ratio v, porosity q, tensile strength T, shear modulus G, and bulk modulus K; the strength parameters include dimensionless viscous strength coefficient A, dimensionless pressure hardening coefficient B, strain rate coefficient C, pressure hardening exponent N, and the maximum dimensionless equivalent stress S achievable by the rock. max The damage parameters include the initial damage constant D1, the final damage constant D2, and the minimum plastic strain EF at rock fracture. min The pressure parameters include a first pressure constant K1, a second pressure constant K2, a third pressure constant K3, and a hydrostatic pressure P. crush Volumetric strain μ crush The hydrostatic pressure P after compaction lock and the volumetric strain μ under the compaction limit state lock The software parameters include a reference strain rate. And failure parameter FS.

[0071] The calculation process for the above physical parameters is introduced using mudstone layers as an example:

[0072] 1. Basic physical and mechanical parameters of mudstone include: density ρ0 = 2450 kg / m³ 3 Compressive strength f c =374.97MPa, elastic modulus E=32GPa, Poisson's ratio v=0.32, porosity q=5.75%. Among them, tensile strength T, shear modulus G and bulk modulus K can be determined according to formulas (1)-(3), as follows:

[0073]

[0074]

[0075]

[0076] We obtain T = 8.23 ​​MPa, G = 12.12 GPa, K = 29.6 GPa, and V is the relative volume.

[0077] 2. Determination of strength parameters

[0078] Parameters A, B, and N are related to the reservoir model yield surface when damage D = 0 and strain rate effects are not considered:

[0079] σ *=A+BP *N (4)

[0080] Where, σ * For the standardized equivalent stress, P * This is the standardized hydrostatic pressure.

[0081] When damage evolution and strain rate effects are not considered, according to the plastic yield surface theory, the corresponding points of the reservoir model and the MC constitutive model under pure shear and uniaxial compression will pass through the compression meridion plane. From this, the dimensionless viscous strength coefficient A, cohesion c, and uniaxial compressive strength f can be obtained. c Relationship:

[0082]

[0083] According to the Mohr-Coulomb strength criterion, the cohesive force c can be obtained from the following formula:

[0084]

[0085] In the formula: σ1 and σ3 are the maximum and minimum principal stresses at static compressive failure, respectively. It is the internal friction angle.

[0086] The Hoek-Brown criterion is generally used to evaluate the strength of rocks under triaxial static compression conditions. When static triaxial compression test data are unavailable, this criterion is used to calibrate the parameters of the RHT model and the JH-2 model, respectively. The static compressive strength data of rocks under different confining pressures are obtained according to the following Hoek-Brown empirical formula, as shown in Table 1:

[0087]

[0088] In the formula: σ ci For static uniaxial compressive strength, σ ci =f c ;m b , s and a are constants, which are generally taken as 24, 1 and 0.5 respectively for intact rocks.

[0089] Table 1 Static compressive strength of rock under different confining pressures

[0090]

[0091] By taking different confining pressures σ3 and combining them with equation (7), the data in Table 1 can be obtained. Then, a linear fit is performed according to equation (6) based on the Mohr-Coulomb criterion, and the fitting results are as follows: Figure 3 As shown, the following expression can be obtained:

[0092] σ1=7σ3+395.6 (8)

[0093] Combining equation (6), we can obtain the answer from the system of equations (9). And c = 74.26 MPa.

[0094]

[0095] From equation (5), we can obtain A = 0.198, then equation (4) can be transformed into σ * =0.198+BP *N Standardized equivalent stress σ * and standardized hydrostatic pressure P * They can be obtained from the following formulas:

[0096]

[0097]

[0098] Substituting the static compression data from Table 1 into equations (10) and (11), we obtain the 7 sets of data in Table 2. These 7 sets of data are then processed according to σ... * =0.198+BP *N By fitting the failure surface, the dimensionless pressure hardening coefficient B = 2.157 and the pressure hardening exponent N = 0.898 can be obtained, as follows: Figure 4 As shown.

[0099] Table 2 Equivalent stress and hydrostatic pressure of mudstone under different confining pressures

[0100]

[0101] Strength parameter: The maximum dimensionless equivalent stress S that the rock can achieve. max σ * No longer following P * The critical limit value that increases with the increase of σ must satisfy the condition σ when taking its value. * ≤S max Based on the maximum value of the second invariant of the deviatoric stress tensor of mudstone under hydrostatic pressure, this embodiment takes S. max =3.

[0102] Since both the triaxial compression process and the confining pressure increase process are static processes, the effect of strain rate on the test is not considered, i.e., the strength parameter C = 0.

[0103] 3. Determination of damage parameters

[0104] The initial damage constant D1 can be determined according to equation (12), where the dimensionless maximum tensile stress T * =T / f c We obtain D1 = 0.05. Parameters D2 and EF... minThe impact on the simulation results is minimal, therefore D2 = 1, EF min =0.01.

[0105] D1 = 0.01 / (1 / 6 + T) * (12)

[0106] 4. Determination of pressure parameters

[0107] When the rock reaches its elastic limit, the hydrostatic pressure P crush and volumetric strain μ crush It can be determined by equations (13) and (14).

[0108] P crush =f c / 3 (13)

[0109] μ crush =P crush / K (14)

[0110] Based on the above value P crush =124.99MPa, μ crush =0.00422.

[0111] μ lock The volumetric strain at the compaction limit state can be determined by the following expression:

[0112] ρ g =ρ0 / (1-q) (15)

[0113] μ lock =ρ g / ρ0-1 (16)

[0114] In the formula, ρ g Let ρ be the density of the material under compression, ρ0 be the initial density of the rock, and q be the initial porosity of the rock, q = 5.75%. μ can be obtained from equations (15) and (16). lock =0.061.

[0115] For common rock materials, when Hugoniot experimental data is lacking, the result can be obtained using empirical formulas:

[0116]

[0117] In the formula, ρ0 is the initial density of the rock, ρ0 = 2450 kg / m³ 3 C0 and S are empirical parameters. For mudstone, it is mainly composed of five elements: Si (66%), Al (17.3%), K (5.4%), Mg (4.9%), and Ca (2.5%). The values ​​of C0 and S in the mixture can be determined by formula (18):

[0118] C0=∑m i C i S = ∑m i S i (18)

[0119] In the formula, m i The percentage of the element is given. From equation (18), we can calculate C0 = 4171.61 m / s and S = 1.211.

[0120] The first pressure constant K1, the second pressure constant K2, and the third pressure constant K3 can be used to fit equation (17) to a cubic polynomial according to equation (19):

[0121] P = K1μ + K2μ 2 +K3μ 3 (19)

[0122] The final set of parameters obtained by fitting is as follows Figure 5 As shown, we can obtain K1 = 44 GPa, K2 = 55 GPa and K3 = 36 GPa.

[0123] P lock The value is the ordinate value corresponding to the intersection of the fitted curves of the plastic stage and the compacted stage in the equation of state, which corrects for the volumetric strain. The relationship curve between the axial static pressure P under different confining pressures can be represented by equation (16).

[0124] The volumetric strain formula is calculated according to equation (20):

[0125]

[0126] Finally, P is obtained. lock = 4.05 GPa.

[0127] 5. Determining Software Parameters

[0128] The failure parameter FS is used to control the deletion of reservoir units due to failure, as detailed below:

[0129] 1) Failure occurs when FS < 0 and damage degree D < 0. When rock material is under pressure, D can be defined as:

[0130]

[0131] When a rock is under tension, D can be defined as:

[0132]

[0133] 2)FS = 0, P * +T * It fails when the value is ≤0.

[0134] 3) FS > 0, failure occurs when the equivalent plastic strain reaches FS.

[0135] Regarding the value of FS, the failure strain (compression failure mode) is an inherent failure type. FS is the threshold of plastic strain for determining whether rock material fractures under hydrostatic pressure P in the reservoir model, and can be expressed by equation (23).

[0136]

[0137] Furthermore, when the pressure on a rock material increases exponentially while the corresponding rate of change in volumetric strain is less than 1%, the rock material has reached its ultimate density ρ. max limiting density ρ max For compaction density ρ g Increasing by 1% simplifies the result to ρ. max =(1+0.01)ρ g , calculate ρ max Substituting into equation (23), we finally obtain FS = 0.463.

[0138] Reference strain rate The value of has little impact on the simulation results; in this embodiment, is taken as . The final determined HJC constitutive parameters of the mudstone are shown in Table 3.

[0139] Table 3 Constitutive parameters of mudstone under HJC conditions

[0140]

[0141]

[0142] The calculation process for the explosive material parameters is as follows:

[0143] The explosive material parameters include the explosive HIGH_EXPLOSIVE_BURN parameter and the explosive JWL equation of state parameter. The calculation process is as follows:

[0144] In ANSYS software, the explosive is assumed to be a homogeneous continuous medium, and the *MAT_HIGH_EXPLOSIVE_BURN model and JWL state equation (24) are used to reflect the relationship between the pressure generated by the blast load and the volume of the blast product:

[0145]

[0146] Where P is the detonation pressure; V is the relative volume; A, B, R1, R2, and ω are dimensionless constants; and E is the internal energy per unit initial volume. TNT explosive is used in this embodiment, and the values ​​of each parameter are shown in Tables 4 and 5.

[0147] Table 4 TNT Explosive HIGH_EXPLOSIVE_BURN Parameters

[0148]

[0149] In Table 4, R0 represents the explosive density, D represents the detonation velocity, and P represents the detonation velocity. cj SIGY represents burst pressure, K represents bulk modulus of elasticity, G represents shear modulus, and SIGY represents yield stress.

[0150] Table 5 Parameters of the JWL Equation of State for TNT Explosives

[0151]

[0152] The calculation process for air material parameters is as follows:

[0153] The air material parameters include the air material constant C0 to C6, μ = 1 / V⁻¹, relative volume V, internal energy per unit initial volume E, and air density.

[0154] In numerical simulations, air is treated as a fluid, described from two perspectives: the equation of state and the constitutive equation. The equation of state is an expression reflecting the relationship between pressure and volume, while the constitutive equation reflects the flow properties of the material using the relationship between stress, strain, and time.

[0155] In this embodiment, the air material uses the *MAT_NULL model and the LINEAR_POLYNOMIAL equation of state (25), and the relevant parameters are shown in Table 6.

[0156] P = C0 + C1μ + C2μ 2 +C3μ 3 +(C4+C5μ+C6μ 2 E (25)

[0157] In the formula, C0 to C6 are constants; μ = 1 / V-1, V is the relative volume; and E is the internal energy per unit initial volume.

[0158] The values ​​of each air material parameter are determined by the relationship between the parameters in formula (25), and the values ​​are shown in Table 6.

[0159] Table 6 Air Material Parameters

[0160]

[0161] After obtaining the above physical parameters, air material parameters, and explosive material parameters, as follows: Figure 6 As shown, the physical parameters of the mudstone reservoir (mudstone HJC constitutive model) are set through the *MAT_JOHNSON_HOLMQUIST_CONCRETE operation in ANSYS software, such as... Figure 7As shown, the failure criteria for reservoir units in the reservoir model are set through the *MAT_ADD_EROSION operation. The failure criteria include a minimum hydrostatic pressure failure criterion and a maximum shear strain failure criterion, used to determine whether the reservoir unit in the reservoir model has failed. Specifically, the minimum hydrostatic pressure failure criterion = -T(1-D), where D is set to 0 in this embodiment; therefore, the minimum hydrostatic pressure failure criterion = -T. The maximum shear strain failure criterion is set to 500 MPa. Figure 8 As shown, the air model parameters are set using the *MAT_NULL operation in the ANSYS software. For example... Figure 9 As shown, the air material parameters are set via *EOS_LINEAR_POLYNOMIAL. (For example...) Figure 10 As shown, the HIGH_EXPLOSIVE_BURN parameter for the explosive is set via *MAT_HIGH_EXPLOSIVE_BURN. For example... Figure 11 As shown, the JWL state equation parameters for the explosive are set via *EOS_JWL. (For example...) Figure 12 As shown, the explosion simulation of rock layers with different preset explosive amounts was performed using the RUN operation in ANSYS software.

[0162] Through the above process, parameterized models corresponding to different preset amounts of explosive can be obtained. The connections between explosive units and structural units are defined through fluid-structure interaction, allowing for a direct observation of the flow of explosion products within the defined mesh after the explosive detonation. Figures 13-17 As shown, the damage pattern under explosive load conditions when the preset explosive charge is 352g is as follows:

[0163] Phase 1: As Figure 13 As shown, at t = 19.74 μs, after the explosive detonates, the resulting shock wave acts directly on the borehole wall. The rock within a small range of the borehole wall is only subjected to compression failure. Subsequently, the rock failure is caused by the combined effects of compression and shear, which causes the unit strain to exceed the set strain value, and a crushing zone begins to form near the borehole wall.

[0164] Phase Two: As Figure 14 As shown, at t = 79.768 μs, the crushing zone further develops, and the shock wave generated by the explosion attenuates into a stress wave that continues to propagate. At this time, the stress wave is less than the compressive strength of the rock and is insufficient to crush the rock. The tensile stress generated causes radial cracks to form outside the crushing zone, thus forming a fracture zone.

[0165] Phase Three: As Figure 15 As shown, at t = 229.68 μs, the crushing zone no longer expanded, and its main crushing area was in the lithic feldspar fine sandstone layer. Furthermore, the radial cracks around the pores further developed, indicating that the propagation of the cracks significantly lagged behind the propagation of the stress wave.

[0166] Phase Four: such as Figure 16 As shown, at t = 549.47 μs, the cracks on both sides continued to extend, and secondary branch cracks also appeared on the main crack. At this time, the stress wave propagated to the non-reflecting surface.

[0167] Fifth stage: such as Figure 17 As shown, at t = 1500 μs, the crack around the borehole extends further and penetrates the entire model, at which point the crack has developed into its final form.

[0168] like Figure 18 As shown, when the explosive charge is 352g, rock cracks propagate through six rock layers, resulting in eight main fractures, the longest of which is 1940mm. The total number of failure units is 6636, and the internal fracturing ratio at failure is 0.074. The fracturing ratio is the ratio of the volume of the fracturing zone to the total reservoir volume, i.e., the ratio of the number of failure units to all reservoir units. The failure units are the blank fracture areas shown in the figure.

[0169] The above dynamic crack propagation process reveals that after the explosive detonates, the rock surrounding the borehole wall is directly crushed by the shock wave. Outside the crushed zone, radial cracks begin to form and develop under tangential tensile stress, eventually leading to through-cracks in the rock strata. Under the action of stress waves, non-directional radial cracks form outside the crushed zone, which is beneficial for increasing the production capacity of Jimsar shale oil.

[0170] This embodiment also simulates different preset amounts of explosives to obtain the damage law of shale oil sweet spots under different load conditions, so as to ensure the reference of the dynamic response performance of rocks of different strengths under explosive load. Except for the different preset amounts of explosives, other parameters are the same.

[0171] like Figure 19 As shown, when the preset explosive charge is 528g, rock cracks propagate through 6 rock layers, resulting in 7 main cracks, the longest of which is 1980mm. The total number of failure units is 8741, and the internal rock fracturing ratio at failure is 0.0975. The fractured area is significantly larger than when the explosive charge is 352g.

[0172] like Figure 20 As shown, when the preset explosive charge is 616g, the rock cracks propagate through 6 rock layers, resulting in 6 main cracks, the longest of which is 1890mm. The total number of failure units is 8942, and the internal rock fracturing ratio at failure is 0.0998.

[0173] like Figure 21As shown, when the preset explosive charge is 704g, the rock cracks propagate through 6 rock layers, resulting in a total of 8 main cracks, the longest of which is 1940mm. The total number of failure units is 10223, and the internal rock fracturing ratio at failure is 0.114.

[0174] The above results show that during explosive fracturing stimulation of low-permeability oil reservoirs, the volume of the fracturing stimulation zone can be increased by increasing the amount of explosives. The larger the volume of the stimulation zone, the higher the production well output. However, when the stimulation volume reaches a certain level, further increasing the volume of the stimulation zone has a diminishing impact on production capacity; therefore, the largest stimulation zone volume does not necessarily achieve the best economic benefits. In this embodiment, the optimal fracturing stimulation ratio is set to 0.1. Therefore, when the designed explosive amount is 616g, the best economic benefits are achieved for the production capacity of the Jimsar shale oil.

[0175] Computational simulation can effectively analyze the high strain rate effect of the research object under explosive loading, the interaction between the explosive shock wave and the rock structure, the dynamic response of the object structure under explosive shock wave loading, and its local damage effect. This embodiment addresses the challenges of developing sweet spots, characterized by deep burial and strong heterogeneity, coupled with market pressures and the urgent need for technological optimization to achieve low-cost shale oil development. Based on the geological characteristics of the Jimsar shale gas and oil sweet spot and utilizing existing 3D seismic data, numerical simulation is used to establish natural fracture models and detonation fracturing fracture models of the shale oil reservoir. The simulation observes the impact of fracture number, fracture length, and fracture distribution on reservoir pressure reduction and the phenomenon of fracture distal reversal and overlap. The volume of the explosive fracturing stimulation area is recorded to derive oil production efficiency and determine the explosive dosage (preset explosive amount). Compared with existing technologies, this invention reduces shale oil development costs and is environmentally friendly.

[0176] In addition to the aforementioned explosive fracturing methods, fracturing or acidizing techniques can also be used to modify low-permeability oil reservoirs. This can create hydraulic fractures with high conductivity and sufficient length in low-permeability reservoirs, thereby enhancing the formation's oil conduction capacity, increasing the oil drainage area, improving formation permeability, and ultimately increasing crude oil recovery, achieving significant production increases, and allowing the exploitation of unconventional shale gas resources.

[0177] Hydraulic fracturing can also be used. Hydraulic fracturing is an effective method of releasing oil and natural gas into shale formations by delivering a mixture of water, chemicals, and sand under high pressure. Hydraulic fracturing has provided significant profits for industry and boosted local economic growth, such as by creating jobs.

[0178] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor causes the processor to perform the steps of the above-described shale oil extraction method based on explosive fracturing.

[0179] Please see Figure 22 , Figure 22 This is a schematic diagram of the structure of a computer device provided in this application. For example... Figure 22 As shown, computer device 1000 may include: processor 1001, network interface 1004, and memory 1005. Furthermore, computer device 1000 may also include: user interface 1003, and at least one communication bus 1002. The communication bus 1002 is used to implement communication between these components. The user interface 1003 may include a display screen and a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be high-speed RAM or non-volatile memory, such as at least one disk storage device. Optionally, the memory 1005 may also be at least one storage device located remotely from the aforementioned processor 1001. Figure 22 As shown, the memory 1005, which serves as a computer storage medium, may include an operating system, a network communication module, a user interface module, and a device control application program.

[0180] exist Figure 22 In the computer device 1000 shown, the network interface 1004 provides network communication functions; the user interface 1003 is mainly used to provide an input interface for users; and the processor 1001 can be used to call the device control application stored in the memory 1005 to implement the shale oil extraction method based on explosive fracturing described in the above embodiments, which will not be described in detail here.

[0181] The present invention also provides a computer-readable storage medium storing a computer program that is adapted to be loaded by a processor and executed by the shale oil extraction method based on explosive fracturing described in the above embodiments, which will not be described in detail here.

[0182] The above program can be deployed and executed on a single computer device, or deployed and executed on multiple computer devices located in one location, or executed on multiple computer devices distributed across multiple locations and interconnected through a communication network. Multiple computer devices distributed across multiple locations and interconnected through a communication network can form a blockchain network.

[0183] The aforementioned computer-readable storage medium can be an internal storage unit of the computer device, such as a hard drive or memory. It can also be an external storage device, such as a plug-in hard drive, smart media card (SMC), secure digital card (SD), or flash card. Furthermore, the computer-readable storage medium can include both internal and external storage units. This computer-readable storage medium is used to store the computer program and other programs and data required by the computer device. It can also be used to temporarily store data that has been output or will be output.

[0184] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0185] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for shale oil extraction based on explosive fracturing, characterized in that, The method includes: Based on the geological characteristics of the target area, reservoir models with different preset explosive charges are established, specifically including: The target shale oil simulation area is hierarchically divided according to the geological characteristics of the target area to obtain each type of rock layer; a mapping mesh is then performed on each type of rock layer to obtain a rock layer model; the mesh of the rock layer model is obtained using the Lagrange algorithm. The size of the explosive region is determined based on the preset amount of explosive; the explosive region is divided into a mapping mesh to obtain the explosive model; the mesh of the explosive model is obtained using the Euler algorithm; The size of the air region is determined based on the size of the explosive region; the air region is divided into a mapping mesh to obtain an air model; the mesh of the air model adopts the Eulerian algorithm; each mesh is a reservoir unit. The rock layer model, the air model, and the explosive model are coupled in a fluid-structure interaction to obtain the reservoir model of the target area. The explosive model is located inside the rock layer model and is spaced at a predetermined distance from it. The air model surrounds the explosive model. The geological features include the rock type of the rock layer. The reservoir model includes the explosive model, the rock layer model, and the air model. Both the rock layer model and the air model include several reservoir units. For each preset explosive quantity, the physical parameters of the rock layer model, the explosive material parameters of the explosive model, the air material parameters of the air model, and the failure criteria of the reservoir unit are set under the preset explosive quantity to obtain a parametric model; the number of failure units is determined based on the parametric model, and the fracturing stimulation ratio corresponding to the preset explosive quantity is calculated according to the number of failure units and the total number of reservoir units; the failure unit is the reservoir unit that satisfies the failure criteria; the physical parameters include basic physical and mechanical parameters, strength parameters, damage parameters, pressure parameters, and software parameters; wherein, the basic physical and mechanical parameters... The mechanical parameters include density, compressive strength, elastic modulus, Poisson's ratio, porosity, tensile strength, shear modulus, and bulk modulus; the strength parameters include dimensionless viscous strength coefficient, dimensionless pressure hardening coefficient, strain rate coefficient, pressure hardening exponent, and the maximum dimensionless equivalent stress achievable by the rock; the damage parameters include the initial damage constant, the final damage constant, and the minimum plastic strain at rock fracture; the pressure parameters include a first pressure constant, a second pressure constant, a third pressure constant, hydrostatic pressure, volumetric strain, hydrostatic pressure after compaction, and volumetric strain at the compaction limit state; the software parameters include reference strain rate and failure parameters. The optimal explosive preset amount is selected as the fracturing modification ratio with the smallest difference from the preset fracturing modification ratio.

2. The explosive-fracturing-based shale oil extraction method according to claim 1, characterized by, After obtaining the reservoir model of the target region, the following steps are also included: Create contact surfaces for the reservoir model; Apply a non-reflective boundary condition to the contact surface.

3. The explosive-fracturing-based shale oil extraction method according to claim 1, characterized by, After obtaining the reservoir model of the target region, the following steps are also included: Constrain the Z-direction displacement of all nodes in the reservoir model; the nodes are the vertices of the mesh.

4. The explosive-fracturing-based shale oil extraction method according to claim 1, characterized by, The air material parameters include air material constants C0~C6, volume strain μ, relative volume , internal energy per unit initial volume , and air density.

5. The explosive-fracturing-based shale oil extraction method according to claim 1, characterized by, The mapping mesh division specifically comprises: The mapping mesh division is performed by using a single-layer entity mesh modeling method.

6. The explosive-fracture-based shale oil extraction method of claim 1, wherein, The preset fracturing reconstruction ratio is 0.

1.

7. A computer device, comprising: The computer readable storage medium stores a computer program, and the computer program is suitable for being loaded and executed by the processor to execute the method in any one of claims 1-6.

8. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the computer program is suitable for being loaded and executed by the processor to execute the method in any one of claims 1-6.

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