Forward simulation method and device for wellbore fractures based on remote detection electromagnetic wave logging

Abstract

The present application provides a forward modeling method and device for wellbore fractures based on remote detection electromagnetic wave logging. By using boundary conditions equivalent to fractures, the method can significantly reduce the number of grids, reduce the degrees of freedom of solution, improve computational efficiency, and achieve efficient simulation of low-frequency electromagnetic responses of complex multi-scale fractures. The method has important application value in the evaluation of natural fractures and hydraulic fractures in shale oil and gas and tight oil and gas reservoirs.

Description

Technical Field

[0001] The present invention relates to the technical field of geophysical logging characterization of wellside structures, and in particular to a forward simulation method and device for wellbore fractures based on remote detection electromagnetic wave logging. Background Art

[0002] The development of shale oil and tight oil and gas reservoirs is crucial for increasing and stabilizing oil and gas production. These reservoirs have low matrix porosity and permeability, requiring natural fractures or hydraulic fracturing to create favorable fractures for oil and gas flow before they can be economically exploited. Therefore, the evaluation of natural or hydraulic fractures plays a crucial role in guiding fracturing operations and improving oil recovery.

[0003] The remote electromagnetic wave logging instrument is a low-frequency electromagnetic induction logging instrument in wells with good application prospects in the field of evaluating natural fractures and hydraulic fractures. In order to use the remote electromagnetic wave logging instrument to effectively evaluate fractures, it is necessary to establish a numerical simulation algorithm for the remote electromagnetic wave logging fracture response. Fracture morphology is irregular. When simulating the response of remote electromagnetic wave logging in fractured formations, the finite element method's ability to process complex geometric shapes is more suitable. However, the scale difference between the aperture and extension depth of the fracture is too large. When the fracture is discretized into a solid mesh, a large number of filling units are generated, and the degrees of freedom of the solution increase sharply. This not only consumes a huge amount of computing resources, but also easily fails in meshing when the fracture extension is relatively long or there are multiple complex fractures. As a result, the remote electromagnetic wave logging response of these models cannot be solved. Summary of the Invention

[0004] The present invention provides a forward modeling method and device for wellbore fractures based on remote detection electromagnetic wave logging, which are used to realize rapid and accurate simulation of electromagnetic responses of wellbore fractures.

[0005] In a first aspect, the present invention provides a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging, comprising:

[0006] Based on the acquired target well and peri-well fracture information, a corresponding formation model including the wellbore, peri-well fractures and peri-well formations is established;

[0007] Determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right-hand end term of the unit;

[0008] Using a gridding technique, the portion of the formation model excluding the target fracture is discretized into continuous tiny units to form a corresponding grid topology;

[0009] Selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value using an analytical algorithm;

[0010] Determining a unit left-end term and a unit right-end term according to an interpolation basis function, assembling the unit left-end term and the unit right-end term into a large sparse linear equation system in combination with the grid topology, solving the system to obtain an electromagnetic field scattered field distribution value, and combining the system with the electromagnetic field background field distribution value to obtain a total electromagnetic field;

[0011] Based on the total electromagnetic field, a remote detection electromagnetic wave logging response is obtained.

[0012] Optionally, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions and introducing the target fracture into the right-hand side term of the unit includes:

[0013] Selecting cracks with high conductivity, a crack curvature radius greater than the corresponding crack thickness, and a crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks as the target cracks;

[0014] The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

[0015] Optionally, according to the interpolation basis function, the unit left-end term and the unit right-end term are determined, and in combination with the grid topology, the unit left-end term and the unit right-end term are assembled into a large sparse linear equation system, and the electromagnetic field scattered field distribution value is obtained by solving it, and combined with the electromagnetic field background field distribution value to obtain the total electromagnetic field, including:

[0016] Calculating the left-end term of the unit corresponding to the electromagnetic field scattering field by constructing the interpolation basis function;

[0017] Calculate the right-hand side term of the unit by using the right-hand side term formula;

[0018] Based on the grid topological relationship, the unit left-end terms and the unit right-end terms are assembled into a large sparse linear equation group, and the electromagnetic field scattering field distribution value is obtained by solving the equation group.

[0019] Optionally, calculating the left-hand term of the unit corresponding to the electromagnetic field scattering field by constructing the interpolation basis function includes:

[0020] Discretizing the electromagnetic field scattering field by constructing the interpolation basis function;

[0021] The left-end term of the element corresponding to the discrete element is calculated using the stiffness matrix formula and the density matrix formula corresponding to the interpolation basis function.

[0022] Optionally, the right-hand side term of a cell is calculated by a right-hand side term formula, including:

[0023] determining whether the unit contains the target crack;

[0024] If not, the right-hand side term of the unit is calculated using the interpolation basis function and the electromagnetic field background field;

[0025] If so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to equate the fracture in the formation.

[0026] Optionally, obtaining a remote detection electromagnetic wave logging response based on the total electromagnetic field includes:

[0027] In the location unit containing the receiving coil, interpolation processing is performed on the total electromagnetic field to obtain the magnetic field at the center of the receiving coil or the electric field on the coil conductor;

[0028] Based on the magnetic field at the center of the receiving coil or the electric field on the coil conductor, the remote detection electromagnetic wave logging response is obtained through Maxwell equations or integration along the conductor.

[0029] In a second aspect, the present invention provides a forward modeling device for wellbore fractures based on remote detection electromagnetic wave logging, comprising:

[0030] A model building module is used to build a corresponding formation model including the wellbore, the fractures around the well and the formation around the well according to the acquired target well and the fractures around the well;

[0031] A judgment module, configured to determine a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introduce the target fracture into the right-hand end term of the unit;

[0032] A grid topology relationship forming module is used to discretize the part of the formation model except the target fracture into continuous small units by using a grid partitioning technology to form a corresponding grid topology relationship;

[0033] A background field analytical calculation module is used to select the background medium resistivity value of the formation model and obtain the electromagnetic field background field distribution value using an analytical algorithm;

[0034] an electromagnetic field scattered field distribution value determination module, configured to determine the unit left-end term and the unit right-end term based on the interpolation basis function, assemble the unit left-end term and the unit right-end term into a large sparse linear equation system in combination with the grid topology, solve the system to obtain the electromagnetic field scattered field distribution value, and combine the system with the electromagnetic field background field distribution value to obtain the total electromagnetic field;

[0035] The response module is used to obtain a remote detection electromagnetic wave logging response based on the total electromagnetic field.

[0036] Optionally, the judgment module includes:

[0037] a judgment submodule, configured to sequentially select, from the wellbore perimeter fractures, fractures having high conductivity, a fracture curvature radius greater than the corresponding fracture thickness, and a fracture thickness less than 1 / 100 of the fracture extension length as the target fractures;

[0038] The submodule is introduced to be equivalent to the target crack through boundary conditions and to introduce the right-hand side term of the unit.

[0039] In a third aspect, the present application provides an electronic device comprising a processor and a memory, wherein the memory stores computer-readable instructions. When the computer-readable instructions are executed by the processor, the steps in the method provided in the first aspect are executed.

[0040] In a fourth aspect, the present application provides a storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps in the method provided in the first aspect are executed.

[0041] It can be seen from the above technical solutions that the present invention has the following advantages:

[0042] The present invention provides a forward modeling method and device for wellbore fractures based on remote detection electromagnetic wave logging. The method comprises: establishing a corresponding formation model including a wellbore, wellbore fractures and wellbore formations according to acquired target well and wellbore fracture information; determining a target fracture in the formation model that meets the boundary condition equivalent requirement, and introducing the target fracture into a unit right-end term; using a grid partitioning technology, discretizing the part of the formation model except the target fracture into continuous tiny units to form a corresponding grid topological relationship; selecting a background medium resistivity value of the formation model, and obtaining an electromagnetic field background field distribution value by using an analytical algorithm; determining a unit left-end term and the unit right-end term according to an interpolation basis function, and assembling the unit left-end term and the unit right-end term into a large sparse linear equation group in combination with the grid topological relationship, solving the equation group to obtain an electromagnetic field scattering field distribution value, and combining the electromagnetic field background field distribution value to obtain a total electromagnetic field; and obtaining a remote detection electromagnetic wave logging response based on the total electromagnetic field. Replacing fractures with boundary conditions can significantly reduce the number of grids, reduce the degrees of freedom in solving, improve computational efficiency, and achieve efficient simulation of low-frequency electromagnetic responses of complex multi-scale fractures. This approach has important application value in the evaluation of natural fractures and hydraulic fractures in shale oil and gas and tight oil and gas reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 This is a flowchart of a first embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention;

[0045] Figure 2 Schematic diagram of boundary conditions of equivalent fractures in Example 1 of a forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention;

[0046] Figure 3 This is a flowchart of a second embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention;

[0047] Figure 4 This is a flowchart of a third embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention;

[0048] Figure 5 This is a schematic diagram of the solid mesh division when the crack does not use equivalent boundary conditions;

[0049] Figure 6 Schematic diagram of mesh generation after applying equivalent boundary conditions to the crack;

[0050] Figure 7 This is a comparison chart of the amplitude ratio signals of a 1cm crack with and without boundary conditions.

[0051] Figure 8 This is a comparison diagram of the phase difference signal when the boundary condition is used and not used for a 1cm crack;

[0052] Figure 9 This is a comparison chart of the amplitude ratio signals of a 3mm crack with and without boundary conditions.

[0053] Figure 10 This is a comparison chart of the phase difference signals when the boundary condition is used and not used for a 3mm crack;

[0054] Figure 11 Comparison of relative errors of amplitude ratios after applying boundary conditions to equivalent fractures with different openings;

[0055] Figure 12 Comparison diagram of relative errors of phase difference after applying boundary conditions to cracks with different openings;

[0056] Figure 13 The present invention is a structural block diagram of an embodiment of a forward simulation device for wellbore fractures based on remote detection electromagnetic wave logging. DETAILED DESCRIPTION

[0057] The embodiment of the present invention provides a forward modeling method and device for wellbore fractures based on remote detection electromagnetic wave logging, which are used to achieve rapid and accurate simulation of electromagnetic responses of wellbore fractures.

[0058] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0059] For example 1, please refer to Figure 1 , Figure 1 This is a flowchart of a first embodiment of a forward modeling method for wellbore fractures based on remote electromagnetic wave logging according to the present invention, comprising:

[0060] S101, establishing a corresponding formation model including the wellbore, the fractures around the well and the formation around the well according to the acquired target well and the fractures around the well;

[0061] In an embodiment of the present invention, the established formation model includes the wellbore and the formations around the well, which may also include one or more natural fractures, hydraulic fractures, and other geological structures around the well. The wellbore distribution and attribute information such as radius, resistivity, dielectric constant, etc. are set; the formation distribution and attribute information such as the position of the formation interface, the resistivity and dielectric constant of different layers, etc.; the number, distribution and attributes of the cracks around the well, etc., and the characteristic scale of the cracks is extracted, including but not limited to the position, shape, opening and extension length of the cracks.

[0062] S102, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit;

[0063] In an optional embodiment, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions and introducing the target fracture into the right-hand side of the unit includes:

[0064] Selecting cracks with high conductivity, a crack curvature radius greater than the corresponding crack thickness, and a crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks as the target cracks;

[0065] The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

[0066] In an embodiment of the present invention, a conventional electromagnetic field finite element calculation method is used. After the right-hand side term of the calculation unit is calculated using basis functions and background fields, if the unit contains a fracture that meets the boundary condition equivalence requirements, the boundary condition satisfied by the tangential component of the electric field intensity on the fracture boundary is added to the right side of the conventional unit to equate the fracture in the formation, and the target fracture is no longer subjected to solid meshing. This reduces the number of meshes and improves the calculation speed while ensuring the calculation accuracy.

[0067] In practical implementation, the conditions for determining whether a crack can be equivalent to a boundary condition include: (1) the crack has high conductivity, in which case it can be assumed that the waves inside the conductor propagate only perpendicular to the conductor surface; (2) the crack curvature radius should be greater than its thickness; (3) the crack thickness is much smaller than the crack extension length (less than 1 / 100 of the crack extension length). Figure 2 The figure is a schematic diagram of the boundary conditions of equivalent fractures in Example 1 of a forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging of the present invention. The boundary conditions are specifically as follows:

[0068]

[0069] in,

[0070]

[0071]

[0072]

[0073]

[0074] In the expression, E tan1 and E tan2 are the electric field components parallel to the interface in the media on both sides, Z 11 and Z 12 is the intermediate parameter, J s1 and J s2 are the surface current densities in the media on both sides, H tan1 and H tan2 are the magnetic field components parallel to the interface in the media on both sides, and Respectively represent the normal direction of the medium interface on both sides, j is the imaginary unit, ω is the angular frequency, μ is the magnetic permeability of the medium, k is the wave number, and τ is the distance between the two media.

[0075] S103, using a gridding technique, discretizing the portion of the formation model excluding the target fracture into continuous small units to form a corresponding grid topology;

[0076] In the embodiment of the present invention, the formation model file and the fracture characteristic file of the formation model are read, and the formation model is discretized into small units using a grid partitioning technology, and the grid topology relationship is stored.

[0077] In the implementation, the need for physical meshing of the fractures is determined based on the fracture aperture and electrical contrast with the background medium in the formation model file and the fracture signature file. If the conditions are met, only the fracture boundary information is stored. If not, physical meshing is performed using the frontier advancing method or other existing meshing techniques.

[0078] S104, selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value using an analytical algorithm;

[0079] It should be noted that the background medium is a virtual medium set to facilitate numerical calculations, which represents the average resistivity distribution of the entire model. The background medium resistivity can be selected as the average resistivity of the entire model, or the resistivity when there are no fractures in the formation, or it can be determined by other existing background medium resistivity selection techniques such as the geometric factor method.

[0080] In the embodiment of the present invention, the resistivity of the formation without any cracks or other special geological bodies is directly used as the background medium resistivity, and the electromagnetic field background distribution value is obtained using an analytical algorithm.

[0081] S105, determining a unit left-end term and a unit right-end term according to an interpolation basis function, assembling the unit left-end term and the unit right-end term into a large sparse linear equation system in combination with the grid topology, solving the system to obtain an electromagnetic field scattered field distribution value, and combining the system with the electromagnetic field background field distribution value to obtain a total electromagnetic field;

[0082] It should be noted that electromagnetic field scattering distribution refers to the abnormal electromagnetic field distribution caused by spatial resistivity differences when there is a difference in resistivity between the formation model and the virtual background medium. It indicates the disturbance of the electromagnetic field by fractures or other special geological bodies.

[0083] S106, obtaining a remote detection electromagnetic wave logging response based on the total electromagnetic field.

[0084] It should be noted that remote detection electromagnetic wave instruments generally consist of a transmitting short section and multiple receiving short sections. The transmitting short section is equipped with one or more inclined transmitting coils, and the receiving short section consists of one or more inclined coils, or three orthogonal receiving coils. According to the formation conditions, the source distance and frequency can be flexibly configured. Under normal circumstances, the operating frequency is usually set between 6kHz and 96kHz to ensure that the logging response has a sufficient signal-to-noise ratio.

[0085] For example 2, please refer to Figure 3 , Figure 3 This is a flowchart of a second embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention. The method includes:

[0086] Step S201: establishing a corresponding formation model including the wellbore, the fractures around the well and the formation around the well according to the acquired target well and the fractures around the well;

[0087] Step S202, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit;

[0088] Step S203: using a gridding technique, discretizing the portion of the formation model except the target fracture into continuous tiny units to form a corresponding grid topology;

[0089] Step S204, selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value using an analytical algorithm;

[0090] Step S205, calculating the left-end term of the unit corresponding to the electromagnetic field scattering field by constructing the interpolation basis function;

[0091] Step S206, calculating the right-hand side term of the unit by using the right-hand side term formula;

[0092] Step S207, based on the grid topology, assembling the unit left-end terms and the unit right-end terms into a large sparse linear equation system, and solving them to obtain the electromagnetic field scattering field distribution value;

[0093] In this embodiment of the present invention, based on the grid topology, the left-hand and right-hand terms of the cells are assembled into a large sparse linear equation system. Solving this system of equations yields the distribution of the electromagnetic scattered field. The background field and the scattered field values ​​are then added together to yield the total electromagnetic field.

[0094] Step S208: obtaining a remote detection electromagnetic wave logging response based on the total electromagnetic field.

[0095] For example three, please refer to Figure 4 , Figure 4This is a flowchart of a third embodiment of a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention. The method includes:

[0096] Step S301: establishing a corresponding formation model including the wellbore, the fractures around the well and the formation around the well according to the acquired target well and the fractures around the well;

[0097] Step S302, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right end term of the unit;

[0098] In an optional embodiment, determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions and introducing the target fracture into the right-hand side of the unit includes:

[0099] Selecting cracks with high conductivity, a crack curvature radius greater than the corresponding crack thickness, and a crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks as the target cracks;

[0100] The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

[0101] Step S303: using a gridding technique, discretizing the portion of the formation model except the target fracture into continuous tiny units to form a corresponding grid topology;

[0102] Step S304, selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value using an analytical algorithm;

[0103] Step S305, discretizing the electromagnetic field scattering field by constructing the interpolation basis function;

[0104] Step S306, calculating the element left-end term corresponding to the discrete element by using the stiffness matrix formula and the density matrix formula corresponding to the interpolation basis function;

[0105] In the embodiment of the present invention, an interpolation basis function is constructed to perform numerical discretization on a small unit, and the stiffness matrix and the density matrix are calculated by the finite element equation to obtain the left-hand term of the unit.

[0106] Step S307, calculating the right-hand side term of the unit by using the right-hand side term formula;

[0107] In an optional embodiment, the right-hand side term of the unit is calculated by a right-hand side term formula, including:

[0108] determining whether the unit contains the target crack;

[0109] If not, the right-hand side term of the unit is calculated using the interpolation basis function and the electromagnetic field background field;

[0110] If so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to equate the fracture in the formation.

[0111] Step S308: Based on the grid topology, assemble the unit left-end terms and the unit right-end terms into a large sparse linear equation system, and solve them to obtain the electromagnetic field scattering field distribution value;

[0112] Step S309, performing interpolation processing on the total electromagnetic field in the location unit containing the receiving coil to obtain the magnetic field at the center of the receiving coil or the electric field on the coil conductor;

[0113] Step S310 : Based on the magnetic field at the center of the receiving coil or the electric field on the coil conductor, a remote detection electromagnetic wave logging response is obtained by Maxwell's equations or integration along the conductor.

[0114] In this embodiment of the present invention, the total electromagnetic field is interpolated within the location unit containing the receiving coil to obtain the magnetic field at the center of the receiving coil or the electric field on the coil conductor. Further processing can synthesize and output the phase difference, amplitude ratio and other remote detection electromagnetic wave logging responses.

[0115] Embodiments 1, 2 and 3 of the present invention provide a forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging, comprising: establishing a corresponding formation model including the wellbore, wellbore fractures and wellbore formations based on the acquired target well and wellbore fracture information; determining the target fractures in the formation model that meet the boundary condition equivalence requirements, and introducing the target fractures into the right-hand end term of the unit; using grid segmentation technology, discretizing the part of the formation model except the target fractures into continuous tiny units to form a corresponding grid topological relationship; selecting the background medium resistivity value of the formation model, and obtaining the electromagnetic field background field distribution value using an analytical algorithm; determining the left-hand end term of the unit and the right-hand end term of the unit based on the interpolation basis function, and assembling the left-hand end term of the unit and the right-hand end term of the unit into a large sparse linear equation group in combination with the grid topological relationship, solving the electromagnetic field scattering field distribution value, and obtaining the total electromagnetic field in combination with the electromagnetic field background field distribution value; and obtaining the remote detection electromagnetic wave logging response based on the total electromagnetic field. Replacing fractures with boundary conditions can significantly reduce the number of grids, reduce the degrees of freedom in solving, improve computational efficiency, and achieve efficient simulation of low-frequency electromagnetic responses of complex multi-scale fractures. This approach has important application value in the evaluation of natural fractures and hydraulic fractures in shale oil and gas and tight oil and gas reservoirs.

[0116] Example 4: Assume that there is a horizontal disk-shaped crack in a homogeneous medium that cuts through the wellbore. If the boundary condition is not used to equalize the crack, the crack is divided into solid grids. The grid after division is as follows: Figure 5 The solid mesh partitioning diagram when the boundary conditions are not used to equalize the fractures in the formation is shown in the figure. The fractured formation model is partitioned by using the boundary conditions to equalize the fractures in the formation. The mesh after partitioning is as follows: Figure 6 The schematic diagram of the mesh division after the equivalent boundary conditions are applied to the crack is shown in the figure.

[0117] In the figure, the high conductivity fracture with a certain thickness is equivalent to the boundary condition, and the fracture entity is not segmented, which greatly reduces the number of grids and improves the calculation efficiency. When the fracture opening is 1cm and 3mm respectively, the amplitude ratio and phase difference of the electromagnetic wave logging of the uniform formation without fractures are obtained by using the boundary condition equivalent fracture and the entity grid. Figures 7 to 10 As shown, Figure 7 This is a comparison chart of the amplitude ratio signals of a 1cm crack with and without boundary conditions. Figure 8 This is a comparison chart of the phase difference signals when the boundary condition is used and not used for a 1cm crack. Figure 9 This is a comparison chart of the equivalent amplitude ratio of a 3mm crack with and without boundary conditions. Figure 10 The comparison diagram of the phase difference signal with and without boundary conditions for a 3mm aperture fracture shows that at the same aperture, the amplitude ratio and phase difference show obvious anomalies at the fracture, and the amplitude ratio and phase difference logging responses have good consistency.

[0118] Calculate the relative errors of the amplitude ratio and phase difference of the remote detection electromagnetic wave logging after applying the boundary conditions equivalent to different fracture openings, such as Figure 11 Comparison of relative errors of amplitude ratios of cracks with different openings after applying boundary conditions Figure 12 As shown in the graph comparing the relative errors of phase differences after applying boundary conditions to fractures of different apertures, the relative errors for 3mm fractures using the two methods are less than 1%, for 1cm fractures less than 4%, and for 2cm fractures less than 10%. In actual formations, natural and hydraulic fractures typically have apertures less than 1cm. Therefore, the embodiments of the present invention can achieve high-precision fracture simulation while significantly reducing the computational effort.

[0119] For example five, please refer to Figure 13 , Figure 13 This is a structural block diagram of an embodiment of a forward modeling device for wellbore fractures based on remote detection electromagnetic wave logging according to the present invention, comprising:

[0120] The model building module 501 is used to build a corresponding formation model including the wellbore, the fractures around the well and the formation around the well according to the acquired target well and the fractures around the well;

[0121] A judgment module 502 is used to determine a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introduce the target fracture into the right end term of the unit;

[0122] The grid topology relationship forming module 503 is used to discretize the part of the formation model except the target fracture into continuous small units by using the grid subdivision technology to form a corresponding grid topology relationship;

[0123] The background field analytical calculation module 504 is used to select the background medium resistivity value of the formation model and obtain the electromagnetic field background field distribution value using an analytical algorithm;

[0124] The electromagnetic field scattered field distribution value determination module 505 is used to determine the unit left end term and the unit right end term based on the interpolation basis function, combine the unit left end term and the unit right end term into a large sparse linear equation system in combination with the grid topology relationship, solve the electromagnetic field scattered field distribution value, and combine it with the electromagnetic field background field distribution value to obtain the total electromagnetic field;

[0125] The response module 506 is configured to obtain a remote detection electromagnetic wave logging response based on the total electromagnetic field.

[0126] In an optional embodiment, the determining module 502 includes:

[0127] a judgment submodule, configured to sequentially select, from the wellbore perimeter fractures, fractures having high conductivity, a fracture curvature radius greater than the corresponding fracture thickness, and a fracture thickness less than 1 / 100 of the fracture extension length as the target fractures;

[0128] The submodule is introduced to be equivalent to the target crack through boundary conditions and to introduce the right-hand side term of the unit.

[0129] In an optional embodiment, the electromagnetic field scattered field distribution value determination module 505 includes:

[0130] A unit left-end term determination submodule, configured to calculate the unit left-end term corresponding to the electromagnetic field scattering field by constructing the interpolation basis function;

[0131] A unit right-hand term determination submodule, configured to calculate the unit right-hand term through a right-hand term formula;

[0132] The electromagnetic field scattering field distribution value determination submodule is used to assemble the unit left-end terms and the unit right-end terms into a large sparse linear equation group based on the grid topology relationship, and solve it to obtain the electromagnetic field scattering field distribution value.

[0133] In an optional embodiment, the unit left end item determination submodule includes:

[0134] A discrete submodule, configured to discretize the electromagnetic field scattering field by constructing the interpolation basis function;

[0135] The unit left end term determination unit is used to calculate the unit left end term corresponding to the discrete unit through the stiffness matrix formula and density matrix formula corresponding to the interpolation basis function.

[0136] In an optional embodiment, the unit right end item determination submodule includes:

[0137] A judgment unit is used to judge whether the unit contains the target fracture; if not, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand side term of the unit; if so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand side term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to obtain the equivalent fracture in the formation.

[0138] In an optional embodiment, the response module 506 includes:

[0139] An interpolation submodule, configured to interpolate the total electromagnetic field within a location unit containing a receiving coil to obtain a magnetic field at the center of the receiving coil or an electric field on the coil conductor;

[0140] The response submodule is used to obtain the remote detection electromagnetic wave logging response based on the magnetic field at the center of the receiving coil or the electric field on the coil conductor through Maxwell equations or integration along the conductor.

[0141] An embodiment of the present invention also provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory. When the computer program is executed by the processor, the processor executes the steps of a forward simulation method of wellbore fractures based on remote detection electromagnetic wave logging as described in any of the above embodiments.

[0142] An embodiment of the present invention further provides a computer storage medium storing a computer program, which, when executed by the processor, implements the steps of a forward simulation method for wellbore fractures based on remote detection electromagnetic wave logging as described in any of the above embodiments.

[0143] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0144] In the several embodiments provided in this application, it should be understood that the methods, devices, electronic devices and storage media disclosed in the present invention can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0145] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0146] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0147] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a readable storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned readable storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0148] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging, characterized in that: include: Based on the acquired target well and peri-well fracture information, a corresponding formation model including the wellbore, peri-well fractures and peri-well formations is established; Determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right-hand end term of the unit; Using a gridding technique, the portion of the formation model excluding the target fracture is discretized into continuous tiny units to form a corresponding grid topology; Selecting the background medium resistivity value of the formation model and obtaining the electromagnetic field background field distribution value using an analytical algorithm; Determining a unit left-end term and a unit right-end term according to an interpolation basis function, assembling the unit left-end term and the unit right-end term into a large sparse linear equation system in combination with the grid topology, solving the system to obtain an electromagnetic field scattered field distribution value, and combining the system with the electromagnetic field background field distribution value to obtain a total electromagnetic field; Based on the total electromagnetic field, a remote detection electromagnetic wave logging response is obtained.

2. The forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to claim 1, characterized in that: Determining a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introducing the target fracture into the right-hand side of the unit, including: Selecting cracks with high conductivity, a crack curvature radius greater than the corresponding crack thickness, and a crack thickness less than 1 / 100 of the crack extension length from the wellbore cracks as the target cracks; The target crack is equivalent to the target crack through boundary conditions, and the right-hand side term of the unit is introduced.

3. The forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to claim 1, characterized in that: According to the interpolation basis function, the unit left end term and the unit right end term are determined, and in combination with the grid topology relationship, the unit left end term and the unit right end term are assembled into a large sparse linear equation system, and the electromagnetic field scattered field distribution value is obtained by solving it. In combination with the electromagnetic field background field distribution value, the total electromagnetic field is obtained, including: Calculating the left-end term of the unit corresponding to the electromagnetic field scattering field by constructing the interpolation basis function; Calculate the right-hand side term of the unit by using the right-hand side term formula; Based on the grid topological relationship, the unit left-end terms and the unit right-end terms are assembled into a large sparse linear equation group, and the electromagnetic field scattering field distribution value is obtained by solving the equation group.

4. The forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to claim 3, characterized in that: Calculating the left-end term of the unit corresponding to the electromagnetic field scattering field by constructing the interpolation basis function includes: Discretizing the electromagnetic field scattering field by constructing the interpolation basis function; The left-end term of the element corresponding to the discrete element is calculated using the stiffness matrix formula and the density matrix formula corresponding to the interpolation basis function.

5. The forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to claim 3, characterized in that: Calculate the right-hand side of the cell using the right-hand side formula, including: determining whether the unit contains the target crack; If not, the right-hand side term of the unit is calculated using the interpolation basis function and the electromagnetic field background field; If so, the interpolation basis function and the electromagnetic field background field are used to calculate the right-hand term of the unit, and the boundary conditions satisfied by the tangential component of the electric field intensity of the target fracture are added to equate the fracture in the formation.

6. The forward modeling method for wellbore fractures based on remote detection electromagnetic wave logging according to claim 1, characterized in that: Based on the total electromagnetic field, a remote detection electromagnetic wave logging response is obtained, including: In the location unit containing the receiving coil, interpolation processing is performed on the total electromagnetic field to obtain the magnetic field at the center of the receiving coil or the electric field on the coil conductor; Based on the magnetic field at the center of the receiving coil or the electric field on the coil conductor, the remote detection electromagnetic wave logging response is obtained through Maxwell equations or integration along the conductor.

7. A forward modeling device for wellbore fractures based on remote detection electromagnetic wave logging, characterized in that: include: A model building module is used to build a corresponding formation model including the wellbore, the fractures around the well and the formation around the well according to the acquired target well and the fractures around the well; A judgment module, configured to determine a target fracture in the formation model that meets the equivalent requirements of the boundary conditions, and introduce the target fracture into the right-hand end term of the unit; A grid topology relationship forming module is used to discretize the part of the formation model except the target fracture into continuous small units by using a grid partitioning technology to form a corresponding grid topology relationship; A background field analytical calculation module is used to select the background medium resistivity value of the formation model and obtain the electromagnetic field background field distribution value using an analytical algorithm; an electromagnetic field scattered field distribution value determination module, configured to determine the unit left-end term and the unit right-end term based on the interpolation basis function, assemble the unit left-end term and the unit right-end term into a large sparse linear equation system in combination with the grid topology, solve the system to obtain the electromagnetic field scattered field distribution value, and combine the system with the electromagnetic field background field distribution value to obtain the total electromagnetic field; The response module is used to obtain a remote detection electromagnetic wave logging response based on the total electromagnetic field.

8. The forward simulation device for wellbore fractures based on remote detection electromagnetic wave logging according to claim 7, characterized in that: The judgment module includes: a judgment submodule, configured to sequentially select, from the wellbore perimeter fractures, fractures having high conductivity, a fracture curvature radius greater than the corresponding fracture thickness, and a fracture thickness less than 1 / 100 of the fracture extension length as the target fractures; The submodule is introduced to be equivalent to the target crack through boundary conditions and to introduce the right-hand side term of the unit.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the method according to any one of claims 1 to 6 is executed.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 6 is executed.

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