A Method and System for Three-Dimensional Inversion Modeling of Gravity and Magnetic Data Constrained by Prior Information

Abstract

This invention discloses a method and system for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information. The method includes: determining the grid spacing of an initial three-dimensional geological model skeleton, the profile spacing of a two-dimensional geological model, and the grid spacing of a direct three-dimensional geological model; constructing the initial three-dimensional geological model skeleton; drawing profiles of the two-dimensional geological model; generating a 2.75-dimensional geological model based on the profiles of the two-dimensional geological model, and assembling the 2.75-dimensional geological model profiles into a mosaic three-dimensional geological model; constructing a direct three-dimensional geological model based on the grid spacing of the direct three-dimensional geological model and the mosaic three-dimensional geological model through three-dimensional inversion of first gravity and magnetic data; repeatedly modifying and iterating between the mosaic three-dimensional geological model and the direct three-dimensional geological model until preset conditions are met to obtain a three-dimensional geological model. Through the processing scheme disclosed in this invention, modeling efficiency can be improved while effectively reducing costs and increasing modeling flexibility.

Description

Technical Field

[0001] This invention relates to the fields of mining and exploration technology, and in particular to a method and system for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information. Background Technology

[0002] Mineral resources, a vital component of natural resources, are an indispensable element in human development. Finding new replacement mineral resources can not only alleviate the shortage of mineral resources but also serve as an important pathway to promote the sustainable development of mineral resources.

[0003] To address this issue, geological prospecting must inevitably shift from shallow to deep exploration. To further discover deep mineral resources, geologists urgently need to understand the geological structure at certain depths (e.g., 500-3000 meters) in order to more accurately predict deep ore bodies. Core drilling is an important method for understanding the deep interior, but due to limitations in funding and technology, large-scale drilling is not feasible in the early stages of geological prospecting. Therefore, the basic approach to deep geological prospecting both domestically and internationally is: first, to establish a three-dimensional (3D) geological model using integrated geophysical prior information methods to obtain the underground structure and material distribution at a certain depth; and then, to predict potential deep ore bodies based on mineralization patterns.

[0004] In recent years, with the increasing maturity of modeling technology and the growing power of 3D modeling software, 3D modeling has been widely applied to the prediction of deep mineralization patterns and the detailed structural depiction of ore body morphology, achieving excellent results. The establishment of 3D geological models is of paramount importance for the search for deep mineral resources, and methods for establishing reliable 3D geological models have become one of the main tasks in this search.

[0005] Gravity and magnetic data, which is the collective term for gravity field and geomagnetic field exploration data, as an important part of geophysical data serving geological prospecting, contains a large amount of rich information about the deep earth. And three-dimensional inversion modeling of gravity and magnetic data is an effective means to obtain the underground structure and establish a reliable three-dimensional geological model. With the progress of data acquisition instruments, computer performance, and visualization technology, the inversion and modeling technology of gravity and magnetic data have also been greatly developed, becoming an important link in geological prospecting work and having important application value. However, due to the non-uniqueness of inversion, it is difficult to obtain a three-dimensional geological model consistent with the actual geological situation by unconstrained inversion. To reduce the non-uniqueness of inversion, the usual approach is to add as much geological and other geophysical prior information such as strata, lithology, structure, boreholes, physical properties (or physical characteristics) during the inversion process. Both inversion theory and modeling examples show that under the constraint of a large amount of geological prior information, three-dimensional inversion of gravity and magnetic data can obtain a reliable three-dimensional geological model consistent with the geological situation. To reduce the non-uniqueness of inversion, using both gravity field and geomagnetic field exploration data for inversion modeling can achieve better geological results. Currently, there are various geophysical inversion modeling methods constrained by prior information. In practical work, the choice of inversion method depends on various factors such as the modeling goal, the type of existing prior information, resolution, accuracy, calculation time, and labor cost. Each method has its own advantages and disadvantages.

[0006] For example, in the existing technologies "Lu Q T, Qi G, Yan J Y, et al. 3D geologic model of Shizishan ore field constrained by gravity and magnetic interactive modeling: A case history[J]. Geophysics, 2013, 78(1): 1-11. (Lu Qingtian, Qi Guang, Yan Jiayong, et al., Three-dimensional geological model of Shizishan ore field constrained by gravity and magnetic interactive modeling: A case history[J]. Geophysics, 2013, 78(1): 1-11)", "Qi G, Lu Q T, Yan J Y, et al., Research on three-dimensional gravity and magnetic inversion modeling constrained by prior geological information - A case study of Nihe Iron Mine in Anhui[J]. Chinese Journal of Geophysics, 2012, 55(12): 13.", and "Qi G, Research on three-dimensional gravity and magnetic inversion modeling method constrained by geological conditions, Jilin University, 2013.", in-depth discussions and studies are mainly carried out on the three-dimensional inversion modeling of gravity and magnetic data using the discrete body method, and an analysis and evaluation implementation plan for its application in geological prospecting work is given. The technical process of its plan is as follows:

[0007] Obtaining a reliable 3D model from gravity and magnetic data inversion requires integrating a large amount of prior geological, borehole, rock properties, and other geophysical information. A reasonable inversion modeling process can achieve twice the result with half the effort and can be used as a reference for others or applied to inversion modeling work in other regions. Many scholars have proposed 3D inversion modeling processes constrained by prior geological information. Although the details of the modeling processes proposed by different scholars differ, they basically include three parts: the construction of the initial model, 2D / 3D inversion of gravity and magnetic data, and display and interpretation of the 3D geological model. Among them, 2D / 3D inversion of gravity and magnetic data plays a crucial role in the modeling process. It further optimizes the initial model and ultimately provides the spatial distribution of the physical and geometric parameters of the geological model. In principle, using gravity and magnetic data together for inversion can significantly reduce the ambiguity of the inversion. For example, the existing technology "Williams N C. Geologically-constrained UBC-GIF gravity and magnetic inversions with examples from the agnew-wiluna greenstone belt, western Australia [D]. Canada: The university of British Columbia, 2008" verifies through practical examples that using prior information on surface, subsurface geology, and geophysics together as constraints can obtain reliable inversion results.

[0008] Existing research has used discrete volume methods for gravity and magnetic data inversion modeling. The general approach is to construct a three-dimensional geological model by assembling 2.5D geological body profiles. This mainly includes steps such as defining the modeling region, processing prior geological information, constructing a two-dimensional geological model, inverting gravity and magnetic data in two- and five-dimensional / three-dimensional directions, and visualization and interpretation.

[0009] While the aforementioned data transmission method can construct three-dimensional geological models to a certain extent, several shortcomings have been found in its structure during practical use, preventing it from achieving optimal performance. These shortcomings can be summarized as follows:

[0010] 1. Regarding the lack of "prior information": As the geological bodies targeted in mineral exploration become deeper, prior geological information such as surface strata, structures, and lithology cannot adequately constrain the deep geological bodies, resulting in a lack of deep geological prior information required for inversion. Due to the high cost of drilling and seismic exploration techniques, these techniques are not implemented in all exploration areas, leading to a lack of geological and geophysical prior information required for inversion. Even if drilling and seismic exploration techniques are planned for a particular exploration area, non-seismic exploration data inversion modeling based on gravity and magnetic data is generally required before implementation. At this point, drilling and seismic exploration techniques have not yet been implemented, thus resulting in a lack of prior information required for non-seismic exploration inversion based on gravity and magnetic data. To control costs, how to accurately establish a preliminary "two-dimensional geological model" using limited geological data and gravity and magnetic data in the absence of "prior information" is an urgent problem to be solved.

[0011] 2. For situations involving complex "prior information": Besides borehole core data which can provide definitive information, other "prior information" exhibits non-homogeneity, leading to multiple possibilities for "two-dimensional geological model construction." Non-homogeneity manifests in the fact that the geophysical prior information (gravity, magnetic, electromagnetic, seismic exploration, etc.) generated by underground geological bodies (rock masses, structures, etc.) does not always correspond to specific effects. For example, an underground geological body exhibiting gravity anomalies may not necessarily produce seismic or magnetic anomalies. Other situations can be compared. Therefore, using complex "prior information" to construct preliminary geological models from non-homogeneous anomalies can result in inefficient situations where it's difficult to select appropriate information.

[0012] 3. For complex geological body models with different orientation ranges or orientations that are not perpendicular to the profile, the "2.5D inversion" technique lacks flexibility.

[0013] The main drawback of existing technical solutions, which suffer from high costs, low efficiency, and poor flexibility, ultimately boils down to high costs. Accurate modeling necessitates maintaining the accuracy of the geological model: when prior information is scarce, existing solutions require drilling and seismic exploration before gravity and magnetic data inversion, significantly increasing implementation costs; when prior information is complex, existing solutions require repeated comparisons of various data points during initial model building, drastically increasing labor costs; and when using 2.5D inversion to model complex geological bodies, existing solutions require establishing multiple different inversion models based on different orientations, further increasing workload.

[0014] Therefore, it is evident that the existing methods for constructing three-dimensional geological models still have inconveniences and shortcomings, and urgently need further improvement. Creating an efficient, flexible, low-cost, and highly accurate method for constructing three-dimensional geological models has become a pressing goal for the industry. Summary of the Invention

[0015] In view of this, the present disclosure provides a method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information, which at least partially solves the problems existing in the prior art.

[0016] In a first aspect, embodiments of this disclosure provide a method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information, the method comprising the following steps:

[0017] The mesh spacing of the initial three-dimensional geological model skeleton and the profile spacing of the two-dimensional geological model are determined based on the prior information categories, and the mesh spacing of the direct three-dimensional geological model is determined based on the first gravity and magnetic data.

[0018] Based on the prior information and previous gravity and magnetic data, an initial three-dimensional geological model framework is constructed through three-dimensional inversion.

[0019] Based on the profile spacing of the two-dimensional geological model, the initial three-dimensional geological model skeleton, and the prior information, all two-dimensional geological model profiles are drawn to obtain the two-dimensional geological model.

[0020] An initial 2.75-dimensional geological model is generated based on the two-dimensional geological model, and the initial 2.75-dimensional geological model is then combined to generate a collage-style three-dimensional geological model.

[0021] Based on the grid spacing of the aforementioned direct 3D geological model and the initial direct 3D geological model, a direct 3D geological model is constructed through 3D inversion of the first gravity and magnetic data; and

[0022] The modification and iteration between the collage-style 3D geological model and the direct 3D geological model are repeatedly performed until the preset conditions are met, thus obtaining a 3D geological model.

[0023] According to a specific implementation of an embodiment of this disclosure, the two-dimensional geological model includes a two-dimensional geological model to be modified and a fixed two-dimensional geological model;

[0024] The two-dimensional geological model profile to be modified is obtained by plotting the preprocessed seismic exploration profile, electromagnetic exploration profile, and geological information obtained through inference on the profile corresponding to the two-dimensional geological model in the prior information.

[0025] By plotting the preprocessed geochronological data, borehole data, rock and mineral physical property data, and surface exposed strata, lithology, and structural data from the prior information onto the corresponding profile of the two-dimensional geological model, the fixed two-dimensional geological model profile is obtained.

[0026] According to a specific implementation of this disclosure, the method further includes: acquiring prior information of a preset area and preprocessing the prior information; wherein the prior information includes geological prior information and geophysical prior information, the geological prior information includes at least one of stratigraphy, lithology, structure, borehole and geochronological data, and the geophysical prior information includes at least one of seismic exploration profiles, electromagnetic exploration profiles, rock and mineral physical property data and previous gravity and magnetic data.

[0027] According to a specific implementation of this disclosure, the preprocessing of the prior information includes abstracting the geological prior information and the geophysical prior information into qualitative and quantitative expressions that can be used for modeling.

[0028] According to a specific implementation of this disclosure, the geochronological data, borehole data, rock and mineral physical property data, and the exposed strata, lithology, and structures on the surface remain unchanged during the three-dimensional geological modeling process.

[0029] The corresponding parts of the mosaic 3D geological model generated based on the fixed 2D geological model remain unchanged during the 3D geological model modeling process.

[0030] According to a specific implementation of this disclosure, the step of generating an initial 2.75-dimensional geological model based on the two-dimensional geological model includes the following steps:

[0031] The model orientation length of each section of the two-dimensional geological model is shortened to the section spacing, and the model orientation is changed to be arbitrary, thus forming a 2.75-dimensional geological model section.

[0032] According to a specific implementation of this disclosure, the step of assembling the initial 2.75-dimensional geological model to generate a mosaic 3D geological model includes the following steps:

[0033] Step 1: Perform forward modeling on the initial 2.75-dimensional geological model to obtain the second gravity and magnetic data;

[0034] Step 2: Compare the difference between the second gravity and magnetic data and the first gravity and magnetic data. If the difference is less than a preset difference value, a 2.75-dimensional geological model is obtained. If the difference is not less than the preset difference value, the portion of the initial 2.75-dimensional geological model generated from the 2D geological model to be modified is modified, and the modified initial 2.75-dimensional geological model replaces the initial 2.75-dimensional geological model from Step 1. Repeat Steps 1 and 2 until the difference between the second gravity and magnetic data and the first gravity and magnetic data is less than the preset difference value, thus obtaining a 2.75-dimensional geological model. The first gravity and magnetic data is the latest measured gravity and magnetic data.

[0035] The 2.75-dimensional geological model is then combined to generate a mosaic 3D geological model.

[0036] According to a specific implementation of this disclosure, the iterative modification between the mosaicked 3D geological model and the direct 3D geological model includes the following steps:

[0037] Compare the collaged 3D geological model and the direct 3D geological model to determine whether they meet preset conditions; wherein, when the preset conditions are met, a 3D geological model is obtained.

[0038] When the preset conditions are not met, modification and iteration are performed. First, the part generated by the profile of the two-dimensional geological model to be modified in the initial 2.75-dimensional geological model corresponding to the 3D geological model to be collaged is modified until the preset conditions are met, resulting in a new two-dimensional geological model to be modified. The model differences corresponding to the part generated by the fixed two-dimensional geological model in the 2.75-dimensional geological model are retained. Then, the new two-dimensional geological model to be modified and the fixed two-dimensional geological model with retained model differences are collaged to obtain a new 3D geological model.

[0039] Secondly, the new collage-style 3D geological model is used as the initial direct 3D geological model, and automatic machine inversion is performed until the preset conditions are met to obtain a new direct 3D geological model.

[0040] The new collage-style 3D geological model and the new direct 3D geological model are compared; when the preset conditions are met, a 3D geological model is obtained; when the preset conditions are not met, the above modification and iteration process is repeated until a 3D geological model is obtained.

[0041] According to a specific implementation of this disclosure, the profile spacing of the two-dimensional geological model is the same as the profile spacing of the mining area; the grid spacing of the direct three-dimensional geological model is the same as the spacing after the first gravity and magnetic data is gridded, and the grid spacing of the direct three-dimensional geological model is smaller than the profile spacing of the two-dimensional geological model.

[0042] The mesh spacing of the initial three-dimensional geological model skeleton is less than or equal to the profile spacing of the two-dimensional geological model, and greater than the mesh spacing of the direct three-dimensional geological model.

[0043] Secondly, embodiments of this disclosure provide a three-dimensional inversion modeling system for gravity and magnetic data constrained by prior information, the system comprising:

[0044] The framework module is configured to determine the mesh spacing of the initial 3D geological model skeleton and the profile spacing of the 2D geological model based on prior information categories, and to determine the mesh spacing of the direct 3D geological model based on the first gravity and magnetic data.

[0045] A two-dimensional modeling module is configured to construct an initial three-dimensional geological model framework based on the prior information and previous gravity and magnetic data through three-dimensional inversion; and

[0046] Based on the profile spacing of the two-dimensional geological model, the initial three-dimensional geological model skeleton, and the prior information, all two-dimensional geological model profiles are drawn to obtain the two-dimensional geological model.

[0047] A 3D modeling module is configured to generate an initial 2.75D geological model based on the 2D geological model, and to combine the initial 2.75D geological models to generate a mosaic 3D geological model; and

[0048] Based on the grid spacing of the aforementioned direct 3D geological model and the initial direct 3D geological model, a direct 3D geological model is constructed through 3D inversion of the first gravity and magnetic data; and

[0049] The modification and iteration between the collage-style 3D geological model and the direct 3D geological model are repeatedly performed until the preset conditions are met, thus obtaining a 3D geological model.

[0050] The prior information-constrained three-dimensional inversion modeling method for gravity and magnetic data in this embodiment uses a three-dimensional geological model skeleton to replace the results obtained by costly technical means such as drilling and seismic exploration as prior constraint information. It uses the grid property method to perform preliminary three-dimensional inversion geological model skeleton of gravity and magnetic data and proposes a 2.75-dimensional model, thereby achieving effective cost control while improving the efficiency and flexibility of model construction. Attached Figure Description

[0051] The above is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Figure 1 A schematic flowchart of a three-dimensional inversion modeling method for gravity and magnetic data constrained by prior information provided in this embodiment of the disclosure;

[0053] Figure 2 A flowchart illustrating a three-dimensional inversion modeling method for gravity and magnetic data constrained by prior information, provided in this embodiment of the disclosure;

[0054] Figure 3 A schematic diagram of a 2.5-dimensional and a 2.75-dimensional geological body model provided for embodiments of this disclosure;

[0055] Figure 4 A schematic diagram of a 2.75-dimensional geological body model and related parameters provided for embodiments of this disclosure;

[0056] Figure 5 A schematic diagram of the parameters and coordinates of a 2.75-dimensional geological body model provided for embodiments of this disclosure; and

[0057] Figure 6 This disclosure provides a three-dimensional inversion modeling system for gravity and magnetic data constrained by prior information. Detailed Implementation

[0058] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0059] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0060] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0061] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this disclosure. The drawings only show the components related to this disclosure and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0062] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0063] This invention provides a method and system for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information. Based on the discrete volume method for gravity and magnetic data inversion modeling, this invention introduces a new mesh property method for gravity and magnetic data inversion modeling, combining and nesting the two techniques. Furthermore, it replaces the 2.5D geological body profile with a 2.75D geological body profile to construct a three-dimensional geological model. Through the solution proposed in this invention, constrained inversion modeling can be flexibly and efficiently performed using various types of data and information, regardless of whether prior information is scarce or complex. Moreover, by using a 2.75D geological body model for inversion, costs are reduced while maintaining the same modeling accuracy and precision.

[0064] First, prior information about a preset area is acquired and preprocessed. The prior information includes geological prior information and geophysical prior information. The geological prior information includes at least one of stratigraphic, lithological, structural, borehole, and geochronological data. The geophysical prior information includes at least one of seismic exploration profiles, electromagnetic exploration profiles, rock and mineral property data, and early gravity and magnetic data (or "early low-precision gravity and magnetic data", such as gravity and magnetic data measured in the last century).

[0065] Here, "gravity and magnetic data" refers to the abbreviation for the data on the Earth's gravitational field and geomagnetic field obtained through measurement.

[0066] In this embodiment of the invention, the preprocessing of the prior information includes abstracting the geological prior information and the geophysical prior information into qualitative and quantitative expressions that can be used for modeling.

[0067] More specifically, based on the research objectives, various geological and geophysical prior information data within the study area are first collected and organized. Then, these data are abstracted into qualitative and quantitative expressions suitable for modeling. The preprocessing of geological prior information mainly includes: qualitative abstract expressions of strata, lithology (here, lithology refers to petrological classification, mainly igneous, metamorphic, and sedimentary rocks), and structures; quantitative abstract expressions of borehole data and geochronological data; quantitative abstract expressions of rock and mineral physical property data (a shorthand for rock and mineral physical property data, including density, magnetic susceptibility, etc.); qualitative abstract expressions of lithology; and corresponding analysis of the relationship between rock and mineral physical property data and lithology.

[0068] It is worth noting that in the processing of geological prior information, uncertain information such as underground structures and lithological changes obtained by inference are not used as information that remains unchanged in the process of building a three-dimensional geological model; complex areas of strata, structures and lithology are not simplified; non-inferred information such as strata, structures and lithology observed on the surface and corresponding information such as the location and thickness of the main strata, structures and lithologies at depth provided by borehole data are considered relatively objective, real and important, and remain unchanged in the final three-dimensional model.

[0069] Preprocessing of geophysical prior information mainly includes qualitative abstraction of non-gravity and magnetic data such as seismic exploration profiles and electromagnetic exploration profiles; preprocessing of gravity and magnetic data (including existing and later calculated gravity and magnetic data) mainly includes filtering processes such as noise reduction and local field separation. Among these, the separation of regional and local field anomalies in gravity and magnetic data is very important in this step, as the separated local field anomalies will serve as the basis for evaluating the rationality of geological models for mineral exploration.

[0070] Figure 1 A schematic diagram of the flowchart 100 of the three-dimensional inversion modeling method for gravity and magnetic data constrained by prior information provided in the embodiments of this disclosure.

[0071] like Figure 1 As shown, in step S110, the grid spacing of the initial three-dimensional geological model skeleton and the profile spacing of the two-dimensional geological model are determined based on the prior information category, and the grid spacing of the direct three-dimensional geological model is determined based on the first gravity and magnetic data.

[0072] More specifically, the scope of the modeling area (including horizontal and depth) is determined based on the size of the research target. The grid spacing of the initial 3D geological model skeleton and the section spacing of the 2D geological model profiles are then determined based on the richness of prior geological and geophysical information and existing key data (such as borehole data). Generally, the grid spacing of the initial 3D geological model skeleton is larger, facilitating the rapid and efficient inversion of the initial 3D geological model skeleton using gravity and magnetic data. The section spacing of the 2D geological model is the same as the section spacing of the mining area exploration profiles.

[0073] For example, when prior information is abundant, the mesh spacing of the initial three-dimensional geological model skeleton should be appropriately denser; when prior information is scarce, the mesh spacing should be appropriately sparser, but always kept between the profile spacing of the two-dimensional geological model and the mesh spacing of gravity and magnetic data.

[0074] Next, determine the grid spacing of the direct 3D geological model. Generally, the grid spacing of the direct 3D geological model is less than or equal to the profile spacing of the 2D geological model, and is the same as the spacing after the gravity and magnetic data are gridded.

[0075] In this embodiment of the invention, the mesh spacing of the initial three-dimensional geological model skeleton is less than or equal to the profile spacing of the two-dimensional geological model, and greater than the mesh spacing of the direct three-dimensional geological model.

[0076] Figure 2 To and Figure 1 The flowchart of the three-dimensional inversion modeling method for gravity and magnetic data constrained by prior information is shown.

[0077] Next, proceed to step S120.

[0078] In step S120, based on the prior information and previous gravity and magnetic data, an initial three-dimensional geological model skeleton is constructed through three-dimensional inversion.

[0079] In this step, based on the pre-processed rock and mineral physical property data and pre-processed gravity and magnetic data within the preset area, the initial three-dimensional geological model skeleton is constructed by preliminary three-dimensional inversion using the grid physical property method.

[0080] "Inversion," short for "Geophysical Inversion," is the process of deriving source properties from the distribution of a field. In geophysics, it uses physical phenomena observed on the Earth's surface to infer the spatial variations and material properties of the Earth's internal media. "Forward modeling," in contrast to inversion, refers to deriving the distribution properties of a field from the properties of the source.

[0081] Before constructing a two-dimensional geological model, a preliminary three-dimensional inversion of gravity and magnetic data is performed by introducing a grid property method with a larger grid spacing to obtain an initial three-dimensional geological model skeleton. This can compensate for the deficiencies caused by the different levels of prior information richness in different modeling areas.

[0082] More specifically, based on the grid spacing of the initial three-dimensional geological model framework, the abstract expression of the quantitative rock and mineral property data, the preprocessing results of gravity and magnetic data (including denoising, local field separation, and other filtering processes), and the local field anomalies of the separated gravity and magnetic data, the initial three-dimensional geological model framework of the study area is constructed through preliminary three-dimensional inversion using the grid property method proposed in the existing technologies “Li Y, DW Oldenburg. 3D inversion of magnetic data[J]. Geophysics, 1996, 61: 394-408. (Li Y, DW, Oldenburg, 3D inversion of magnetic data[J]. Geophysics, 1996, 61: 394-408)” and “Li Y, DW Oldenburg. 3D inversion of gravity data[J]. Geophysics, 1998, 63: 109–119. (Li Y, DW, Oldenburg, 3D inversion of gravity data[J], Geophysics, 1998, 63: 109–119.)”. In this process, except for a few thresholds, such as the fitting error at the cutoff point, which need to be set by the modeler according to the accuracy of the gravity and magnetic data and the needs of the actual geological model, the other values ​​are automatically and quantitatively calculated during the inversion process, which is more objective.

[0083] In cases where prior information is scarce, even in regions where prior information is scarce, the coverage of early gravity and magnetic data is relatively comprehensive. In addition to global satellite gravity and magnetic data, most countries and regions have complete coverage of airborne or ground-based gravity and magnetic data. By using an initial three-dimensional geological model skeleton to replace high-cost technical means such as drilling and seismic exploration, and using the results as prior constraint information, costs can be effectively controlled while laying the foundation for accurate early model construction in the exploration area.

[0084] In situations involving complex "prior information," aside from borehole core data which can provide definitive information, other "prior information" exhibits non-homogeneity, leading to multiple possibilities for "two-dimensional geological model construction." Non-homogeneity manifests in the fact that geophysical prior information (gravity, magnetic, electromagnetic, seismic exploration, etc.) generated by the same subsurface geological body (rock and mineral bodies, structures, etc.) does not necessarily produce corresponding effects. For example, a subsurface geological body exhibiting gravity anomalies may not necessarily produce seismic or electromagnetic anomalies; other cases can be compared. Therefore, using complex "prior information" to construct preliminary geological models from non-homogeneous information can result in low modeling efficiency due to the inability to select appropriate information.

[0085] This step can not only supplement the data for modeling areas lacking geological and geophysical prior information, but also simplify the data for modeling areas with complex geological and geophysical prior information, providing an objective initial three-dimensional geological model skeleton for subsequent inversion and modeling.

[0086] Next, proceed to step S130.

[0087] In step S130, based on the profile spacing of the two-dimensional geological model, the initial three-dimensional geological model skeleton, and the prior information, all two-dimensional geological model profiles are drawn to obtain the two-dimensional geological model.

[0088] The modified two-dimensional geological model profile is obtained by plotting preprocessed seismic and electromagnetic exploration profiles from the prior information, as well as geological information inferred from geologists' experience, onto the corresponding profile of the two-dimensional geological model. The fixed two-dimensional geological model profile is obtained by plotting preprocessed geochronological data, borehole data, rock and mineral property data, and explicit geological information such as surface strata, lithology, and structures from the prior information onto the corresponding profile of the two-dimensional geological model. The two-dimensional geological model consists of the modified two-dimensional geological model and the fixed two-dimensional geological model.

[0089] More specifically, based on the spacing of the two-dimensional geological model profiles determined in step S110, the abstract representation of existing surface geology, other geophysical prior information from non-gravity and magnetic data, borehole data, and the initial three-dimensional geological model skeleton obtained in step S120, all two-dimensional geological model profiles of the modeling area are sequentially drawn. Each two-dimensional geological model profile consists of several closely related geological body models, reflecting the known understanding of the spatial distribution of strata, structures, rock masses, and ore bodies in the area traversed by the profile.

[0090] Prior information obtained by abstracting and expressing information such as geochronological data, borehole data, rock and mineral physical property data, and surface exposed strata, lithology, and structure is plotted on the corresponding two-dimensional geological profile in the two-dimensional geological model and marked as "fixed". Geological information obtained by seismic exploration profiles, electromagnetic exploration profiles, and inference (including but not limited to strata, lithology, and structure) is plotted on the corresponding two-dimensional geological profile in the two-dimensional geological model and marked as "to be modified".

[0091] For other two-dimensional geological profiles in the two-dimensional geological model that have not been plotted, they are first plotted by interpolation, and then plotted on the two-dimensional geological profiles at the corresponding profile spacing of the two-dimensional geological model in a manner determined by the modeler. These profiles are also marked as "to be modified".

[0092] Although each two-dimensional geological profile is drawn by summarizing and organizing qualitative and quantitative abstract expressions, and each two-dimensional geological profile is composed of quantitative geometric shape, burial depth and rock and mineral physical property data, the results marked "to be modified" are determined by inferred data. Therefore, the parts of the constructed two-dimensional geological model that need modification are not objective and realistic enough. The subsequent 3D geological model obtained by 2.75-dimensional inversion is actually a correction and improvement of the parts of the two-dimensional geological model that need modification.

[0093] This step introduces an initial 3D geological model skeleton as a reference for the accurate construction of a 2D geological model, which facilitates the rational and effective selection of prior information, improves the efficiency of initial model construction, and reduces labor costs.

[0094] Next, proceed to step S140.

[0095] In step S140, an initial 2.75-dimensional geological model is generated based on the two-dimensional geological model, and the initial 2.75-dimensional geological model is then combined to generate a collage-style three-dimensional geological model.

[0096] This step mainly includes 2.75-dimensional inversion of gravity and magnetic data, 3D inversion, and repeated correction by cyclic labeling of both. The section spacing of the mosaic 3D geological model obtained by 2.75-dimensional inversion is the same as that of the 2D geological model.

[0097] In this embodiment of the invention, the model orientation length of each profile of the two-dimensional geological model is shortened to the profile spacing, and the model orientation is changed to arbitrary, forming a 2.75-dimensional geological model profile. Each geological body model on the 2.75-dimensional geological model profile is assigned an initial density and magnetic susceptibility intensity; and a 2.75-dimensional inversion of gravity and magnetic data is performed on the portion of the initial 2.75-dimensional geological model generated by the two-dimensional geological model to be modified. Figure 2 The human-computer interaction trial and error method shown in the figure continues until the preset conditions are met, and a 2.75-dimensional geological model profile is obtained.

[0098] More specifically, the initial model is a two-dimensional geological model profile as a 2.75-dimensional geological model profile.

[0099] First, assume that each geological body model in the three-dimensional geological model is long enough along the direction of the two-dimensional geological model profile (the direction is perpendicular to the two-dimensional geological model profile), the cross section of each geological body model on the two-dimensional geological model profile is a polyhedron of arbitrary shape, and the physical properties of each geological body model are consistent along the direction.

[0100] Secondly, the two-dimensional geological model profile is generated into a 2.75-dimensional geological model profile. It is assumed that the length of each geological body model along the strike is finite, and its length along the strike is defined by the coordinates y3 and y4 of the 2.75-dimensional geological body along the strike (the direction perpendicular to the profile is the strike). Its center point along the strike is arbitrary on the x-axis, its direction along the strike is also arbitrary on the x-axis, and its length along the strike is fixed but y3 = y4 is not required. Furthermore, it satisfies the approximate conditions for 2.75-dimensional forward modeling of gravity and magnetic data (the difference between existing 2.5-dimensional geological model profiles and 2.75-dimensional geological model profiles is as follows...). Figure 3 (As shown).

[0101] Then, each geological body model on the 2.75-dimensional geological model profile is assigned an initial density and magnetic susceptibility intensity, using... Figure 2 The human-computer interactive inversion (trial and error method) shown involves manually modifying the geological body models on the initial 2.75-dimensional geological model profile generated from the two-dimensional geological model (to be modified and fixed) until a reasonable geological body model and satisfactory data fitting are obtained. The range of modification of the physical properties and geometric morphology of the geological body model is determined by the physical property data and geological rationality. During the modification process, the exact known information remains unchanged, that is, the initial 2.75-dimensional geological model profile generated from the fixed two-dimensional geological model profile remains unchanged. Finally, the modification of all initial 2.75-dimensional geological model profiles in the modeling area is completed according to the above method.

[0102] More specifically, the process of assembling the initial 2.75-dimensional geological model to generate a mosaic 3D geological model includes the following steps:

[0103] Step 1: Perform automatic forward modeling on the initial 2.75-dimensional geological model to obtain the second gravity and magnetic data;

[0104] Step 2: Compare the difference between the second gravity and magnetic data and the first gravity and magnetic data. When the difference between the second gravity and magnetic data and the first gravity and magnetic data is less than a preset difference value, a 2.75-dimensional geological model is obtained. When the difference between the second gravity and magnetic data and the first gravity and magnetic data is not less than the preset difference value, the part of the initial 2.75-dimensional geological model generated by the 2D geological model to be modified is manually modified, and the initial 2.75-dimensional geological model in Step 1 is replaced with the modified new initial 2.75-dimensional geological model. The operations of Step 1 to Step 2 are repeated until the difference between the second gravity and magnetic data and the first gravity and magnetic data is less than the preset difference value, and a 2.75-dimensional geological model is obtained. The first gravity and magnetic data is the latest measured gravity and magnetic data, and the measured high-precision first gravity and magnetic data includes low-precision previous gravity and magnetic data (high-precision first gravity and magnetic data is obtained by measuring with a higher-precision instrument based on the low-precision previous gravity and magnetic data).

[0105] The 2.75-dimensional geological model is then combined to generate a mosaic 3D geological model.

[0106] More specifically, the 2.75-dimensional geological model profiles are sequentially pieced together to form a 3D geological model according to the spatial order of the profiles.

[0107] The existing "2.5D inversion" technology assumes that the geological model, where each cross-section is an arbitrary polyhedron, is sufficiently long along its strike (defined by coordinates y1 and y2 along the strike). This assumption makes the geological model a three-dimensional model, but because the physical properties of the geological model are consistent along its strike, its center point is located on the x-axis, its strike is perpendicular to the x-axis, and its strike length y1 = y2. However, when faced with situations where the center point of the geological model along its strike is not located on the x-axis, its strike is not perpendicular to the x-axis, and its strike lengths y3 and y4 are not equal, the 2.5D inversion technique lacks flexibility.

[0108] Therefore, replacing the existing 2.5D gravity and magnetic data inversion technology with the more flexible 2.75D gravity and magnetic data inversion technology can improve the accuracy of the assembled 3D geological model. This makes the construction of the assembled 3D geological model more accurate and flexible, avoiding the cost of repeatedly constructing the geological model in order to accurately obtain the 3D geological model.

[0109] Figure 4 A schematic diagram of a 2.75-dimensional geological body model and related parameters provided for an embodiment of this disclosure.

[0110] Figure 5 A schematic diagram of the parameters and coordinates of a 2.75-dimensional geological body model provided in this embodiment of the disclosure.

[0111] More specifically, the main mathematical formulas involved in the inversion of gravity and magnetic data from a 2.75-dimensional geological body model are the forward modeling formulas for the gravity and magnetic data of discrete bodies using a polygonal cross-section method. The derivation of these formulas is briefly described below:

[0112] (1) Gravity

[0113] Depend on Figure 4 , Figure 5And according to existing technologies such as “Rasmussen, R., and Pedersen, LB, 1979, Endcorrections in potential field modeling: Geophysical Prospecting, 27, 749-760” and “Won, IJ, and Bevis, M., 1987, Computing the gravitational and magnetic anomalies due to a polygon: Algorithms and Fortran subroutines: Geophysics, 52, 232-238”, the gravitational and magnetic anomalies caused by a 2.75-dimensional geological body model are as follows:

[0114] ...Equation 1

[0115] Where Fz (2.75) represents the gravity anomaly caused by the 2.75-dimensional geological model, and G is the gravitational constant (usually taken as 6.67×10-11 N·m² / kg²). Let y be the density constant of the geological body, i represent the index of the side of the cross-section of the geological body, N represent the total number of i, and y be the density constant of the geological body. a y b u1, u2, w1, w2, etc. are coordinates; refer to [reference needed] for specific locations. Figure 4 and Figure 5 The rotating system shown, S and C are also referenced. Figure 4 and Figure 5 The rotating system shown, R 11 R 12 R 21 R 22 This represents the distance from each corner point of the polyhedron to the observation coordinate point (which can also be considered as coordinate 0). For details, please refer to [reference needed]. Figure 4 The rotating system shown.

[0116] This method involves coordinate transformation, moving the origin to the observation point. Then Coordinate system around The axis rotates to Coordinate system. In a rotating system, The axis is parallel to the edge or face of the polygon to be integrated. The axis is perpendicular to the surface. shaft and Axis coincidence. Axis winding The angle of inclination of the polygon's edge when rotated clockwise around the axis is... Mathematically speaking, rotation is based on... Figure 5 The matrix equation at the bottom is used for implementation. It assumes that the density of the single geological body model is uniform and constant. .

[0117] (2) Magnetic method

[0118] The 2.75-dimensional geological body model obtained by magnetic method can be derived from the above gravity formula based on the Poisson equation satisfied between the gravitational field and the geomagnetic field, which will not be elaborated here.

[0119] The three-dimensional inversion of gravity and magnetic data is mainly based on "Li Y, DW Oldenburg. 3D inversion of magnetic data[J]. Geophysics, 1996, 61: 394-408. "Li Y, DW Oldenburg. 3D inversion of magnetic data[J]. Geophysics, 1996, 61: 394-408", "Li Y, DW Oldenburg. 3D inversion of gravity data[J]. Geophysics, 1998, 63: 109–119. "Oldenburg DW, Li Y. Inversion for applied geophyscis: a tutorial[J]. Near-surface geophysics, 2005, 13: 89-150. The grid property method proposed in "Li Y, Oldenburg D W. Fast inversion of large-scale magnetic data using wavelet transforms and logarithmic barrier method[J].Geophysics, 2003,152:251-265. (Li Y, Oldenburg D W. Fast inversion of large-scale magnetic data using wavelet transforms and logarithmic barrier method[J], Geophysics, 2003152:251-265)" will not be elaborated on in terms of its principle and process.

[0120] In this embodiment of the invention, the mesh property method proposed in step S140 is used for inversion, but this does not constitute a limitation of the invention. Other inversion methods can also achieve the purpose of the invention.

[0121] Next, proceed to step S150.

[0122] In step S150, based on the grid spacing of the direct three-dimensional geological model and the initial direct three-dimensional geological model, a direct three-dimensional geological model is constructed by three-dimensional inversion of the first gravity and magnetic data.

[0123] The three-dimensional inversion of gravity and magnetic data differs from the preliminary two-dimensional inversion of gravity and magnetic data with a larger grid spacing in step S130. It uses the "grid spacing of the direct three-dimensional geological model" defined in step S110, which has a smaller grid spacing. The grid property method proposed in step S140 is still used to construct a direct three-dimensional geological model of the study area through the three-dimensional inversion of the first gravity and magnetic data.

[0124] In this process, automated quantitative calculations are performed using computers. Figure 2 The machine-automated inversion shown in the figure involves the following steps to construct a direct three-dimensional geological model from gravity and magnetic data:

[0125] Step 1: Using the collaged 3D geological model as the initial direct 3D geological model, perform forward modeling to obtain the third gravity magnetic data;

[0126] Step 2: Compare the differences between the third and first gravity magnetic data. When the difference is less than a preset value, a direct 3D geological model is obtained. When the difference is not less than the preset value, automatic modification is performed, and a new initial direct 3D geological model is obtained. The new initial direct 3D geological model is used as the initial direct 3D geological model in Step 1. Steps 1 to 2 are repeated until the difference between the third and first gravity magnetic data is less than the preset value, thus obtaining a direct 3D geological model.

[0127] Because the calculations are performed automatically by computer, the results are more objective and save on labor costs.

[0128] Compared to tiling three-dimensional geological models, direct three-dimensional geological models obtained through three-dimensional inversion of gravity and magnetic data are more global, taking into account the gravity and magnetic data anomalies caused by geological bodies located next to the two-dimensional geological model profile. The inversion results are more reasonable, and the established geological model is more accurate.

[0129] Next, proceed to step S160.

[0130] In step S160, the modification and iteration between the mosaic 3D geological model and the direct 3D geological model are repeatedly performed until the preset conditions are met, and a 3D geological model is obtained.

[0131] Compare the collaged 3D geological model and the direct 3D geological model to determine whether they meet preset conditions; wherein, when the preset conditions are met, a 3D geological model is obtained.

[0132] When the preset conditions are not met, modification and iteration are performed. First, the part generated by the profile of the two-dimensional geological model to be modified in the initial 2.75-dimensional geological model corresponding to the 3D geological model to be collaged is modified until the preset conditions are met, resulting in a new two-dimensional geological model to be modified. The model differences corresponding to the part generated by the fixed two-dimensional geological model in the 2.75-dimensional geological model are retained. Then, the new two-dimensional geological model to be modified and the fixed two-dimensional geological model with retained model differences are collaged to obtain a new 3D geological model.

[0133] Secondly, using the new collage-style 3D geological model as the initial direct 3D geological model, the above-mentioned procedures were performed. Figure 2 The machine automatically inverts the model until it meets the preset conditions, and then obtains a new direct three-dimensional geological model.

[0134] The new collage-style 3D geological model and the new direct 3D geological model are compared; when the preset conditions are met, a 3D geological model is obtained; when the preset conditions are not met, the above modification and iteration process is repeated until a 3D geological model is obtained.

[0135] In this embodiment of the invention, the preset condition is the comparison and fitting of the gravity and magnetic data obtained by forward modeling generated by inversion with the first gravity and magnetic data, but this does not constitute a limitation on the invention.

[0136] Following the construction of a two-dimensional geological model and the inversion technology of 2.75-dimensional gravity and magnetic data, the iteration between the three-dimensional inversion of gravity and magnetic data with a smaller grid row and the direct three-dimensional geological model is introduced. This not only takes into account the globality between gravity and magnetic data and geological models, but also saves the labor cost of piecing together a three-dimensional geological model that is entirely synthesized by manually modifying the 2.75-dimensional gravity and magnetic data inversion technology in the existing technology.

[0137] Although the forward modeling results (third gravity and magnetic data) from the direct 3D geological model show an unusually good fit with the actual gravity and magnetic data (first gravity and magnetic data), the abstract expression of the "prior information" constraints in the 3D geological model will automatically change with the inversion iteration of the grid property method, causing the prior information constraints to fail. This is especially true for the property constraints of the lithological units and geological units of the surface that are marked as "fixed" and considered to be relatively accurate, as well as the property constraints of the boreholes and the depth constraints of the lithological variation boundaries of the boreholes.

[0138] Therefore, by comparing the direct 3D geological model and the tiled 3D geological model, areas of significant difference between the geological models were selected. For the tiled 3D geological model synthesized from a 2.75D model (with a fixed 2D geological model profile) constrained by relatively accurate prior information, the details of the model differences were preserved. For the differences in the tiled 3D geological model synthesized based on other information (2D geological model profiles to be modified), modifications were made by returning to the 2D geological model profile. At this point, although model modifications were performed on the 2D geological model profile, the calculated anomalies were present in all 3D models. Therefore, the tiled 3D geological models with significant differences were modified.

[0139] In this embodiment of the invention, the geochronological data, borehole data, rock and mineral property data, and the surface-exposed strata, lithology, and structures remain unchanged during the three-dimensional geological modeling process.

[0140] In this embodiment of the invention, the method further includes outputting the three-dimensional geological model to a three-dimensional visualization platform (e.g., Encom PA). TM Spatial analysis can be conducted. When applied to regional 3D modeling, deep mineralization information can be extracted and combined with the mineralization model to predict deep mineralization. When applied to mining area 3D modeling, the spatial relationships between ore-controlling strata, ore bodies, and rock masses can be comprehensively analyzed to establish mineralization models. At the same time, reserves can be calculated, mines can be designed, and deep ore bodies can be predicted.

[0141] Figure 6 The present invention illustrates a three-dimensional inversion modeling system 600 for gravity and magnetic data constrained by prior information, comprising a framework module 610, a two-dimensional modeling module 620, and a three-dimensional modeling module 630.

[0142] The framework module 610 is used to determine the mesh spacing of the initial three-dimensional geological model skeleton and the profile spacing of the two-dimensional geological model based on the prior information category, and to determine the mesh spacing of the direct three-dimensional geological model based on the first gravity and magnetic data.

[0143] The two-dimensional modeling module 620 is configured to construct an initial three-dimensional geological model skeleton through three-dimensional inversion based on the prior information and previous gravity and magnetic data; and to draw all two-dimensional geological model profiles based on the profile spacing of the two-dimensional geological model, the initial three-dimensional geological model skeleton and the prior information to obtain a two-dimensional geological model.

[0144] The 3D modeling module 630 is configured to generate an initial 2.75D geological model based on the 2D geological model, and to combine the initial 2.75D geological model to generate a mosaic 3D geological model; and to construct a direct 3D geological model based on the grid spacing of the direct 3D geological model and the initial direct 3D geological model through 3D inversion of first gravity and magnetic data; and to repeatedly modify and iterate between the mosaic 3D geological model and the direct 3D geological model until a preset condition is met to obtain a 3D geological model.

[0145] In this embodiment of the invention, the prior information-constrained three-dimensional inversion modeling system 600 for gravity and magnetic data further includes a data acquisition module 640, used to acquire prior information of a preset area and preprocess the prior information; wherein, the prior information includes geological prior information and geophysical prior information, the geological prior information includes at least one of stratigraphy, lithology, structure, borehole and geochronological data, and the geophysical prior information includes at least one of seismic exploration profiles, electromagnetic exploration profiles, rock and mineral physical property data and previous gravity and magnetic data.

[0146] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information, characterized in that, The method includes the following steps: The mesh spacing of the initial three-dimensional geological model skeleton and the profile spacing of the two-dimensional geological model are determined based on the prior information categories, and the mesh spacing of the direct three-dimensional geological model is determined based on the first gravity and magnetic data. Based on the prior information and previous gravity and magnetic data, an initial three-dimensional geological model framework is constructed through three-dimensional inversion. Based on the profile spacing of the two-dimensional geological model, the initial three-dimensional geological model skeleton, and the prior information, all two-dimensional geological model profiles are drawn to obtain the two-dimensional geological model. An initial 2.75-dimensional geological model is generated based on the two-dimensional geological model, and the initial 2.75-dimensional geological model is then combined to generate a collage-style three-dimensional geological model. The process of generating an initial 2.75-dimensional geological model based on the two-dimensional geological model includes the following steps: The model orientation length of each of the two-dimensional geological model profiles is shortened to the profile spacing, and the model orientation is changed to be arbitrary, forming a 2.75-dimensional geological model profile. The process of assembling the initial 2.75-dimensional geological model to generate a mosaic 3D geological model includes the following steps: Step 1: Perform forward modeling on the initial 2.75-dimensional geological model to obtain the second gravity and magnetic data; Step 2: Compare the difference between the second gravity and magnetic data and the first gravity and magnetic data. If the difference is less than a preset difference value, a 2.75-dimensional geological model is obtained. If the difference is not less than the preset difference value, the portion of the initial 2.75-dimensional geological model generated from the 2D geological model to be modified is modified, and the modified initial 2.75-dimensional geological model replaces the initial 2.75-dimensional geological model from Step 1. Repeat Steps 1 and 2 until the difference between the second gravity and magnetic data and the first gravity and magnetic data is less than the preset difference value, thus obtaining a 2.75-dimensional geological model. The first gravity and magnetic data is the latest measured gravity and magnetic data. The 2.75-dimensional geological model is then combined to generate a mosaic 3D geological model. Based on the grid spacing of the aforementioned direct 3D geological model and the initial direct 3D geological model, a direct 3D geological model is constructed through 3D inversion of the first gravity and magnetic data; and The modification and iteration between the collage-style 3D geological model and the direct 3D geological model are repeatedly performed until the preset conditions are met, thus obtaining a 3D geological model.

2. The method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information according to claim 1, characterized in that, The two-dimensional geological model includes a two-dimensional geological model to be modified and a fixed two-dimensional geological model; By plotting the preprocessed seismic exploration profile, electromagnetic exploration profile, and inferred geological information from the prior information onto the profile corresponding to the two-dimensional geological model, the two-dimensional geological model profile to be modified is obtained. By plotting the preprocessed geochronological data, borehole data, rock and mineral physical property data, and surface exposed strata, lithology, and structural data from the prior information onto the corresponding profile of the two-dimensional geological model, a fixed two-dimensional geological model profile is obtained.

3. The method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information according to claim 2, characterized in that, The method further includes: acquiring prior information of a preset area and preprocessing the prior information; wherein the prior information includes geological prior information and geophysical prior information, the geological prior information includes at least one of stratigraphy, lithology, structure, borehole and geochronological data, and the geophysical prior information includes at least one of seismic exploration profiles, electromagnetic exploration profiles, rock and mineral physical property data and previous gravity and magnetic data.

4. The method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information according to claim 3, characterized in that, The preprocessing of the prior information includes abstracting the geological and geophysical prior information into qualitative and quantitative expressions that can be used for modeling.

5. The three-dimensional inversion modeling method for gravity and magnetic data constrained by prior information according to claim 3, characterized in that, The aforementioned geochronological data, borehole data, rock and mineral physical property data, as well as the exposed strata, lithology, and structures on the surface remain unchanged during the three-dimensional geological modeling process; The corresponding parts of the mosaic 3D geological model generated based on the fixed 2D geological model remain unchanged during the 3D geological model modeling process.

6. The method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information according to claim 2, characterized in that, The iterative modification between the mosaic 3D geological model and the direct 3D geological model includes the following steps: Compare the collaged 3D geological model and the direct 3D geological model to determine whether they meet preset conditions; when the preset conditions are met, a 3D geological model is obtained. When the preset conditions are not met, modification and iteration are performed. First, the part generated from the profile of the two-dimensional geological model to be modified in the initial 2.75-dimensional geological model corresponding to the 3D geological model to be collaged is modified until the preset conditions are met, resulting in a new two-dimensional geological model to be modified. The model differences corresponding to the part of the 2.75-dimensional geological model generated by the fixed two-dimensional geological model are retained. Then, the new two-dimensional geological model to be modified and the fixed two-dimensional geological model with retained model differences are collaged to obtain a new 3D geological model. Secondly, the new collage-style 3D geological model is used as the initial direct 3D geological model, and automatic machine inversion is performed until the preset conditions are met to obtain a new direct 3D geological model. The new collage-style 3D geological model and the new direct 3D geological model are compared. When the preset conditions are met, a 3D geological model is obtained. When the preset conditions are not met, the above modification and iteration process is repeated until a 3D geological model is obtained.

7. The method for three-dimensional inversion modeling of gravity and magnetic data constrained by prior information according to claim 1, characterized in that, The profile spacing of the two-dimensional geological model is the same as the profile spacing of the mining area; the grid spacing of the direct three-dimensional geological model is the same as the spacing after the first gravity and magnetic data is gridded, and the grid spacing of the direct three-dimensional geological model is smaller than the profile spacing of the two-dimensional geological model. The mesh spacing of the initial three-dimensional geological model skeleton is less than or equal to the profile spacing of the two-dimensional geological model, and greater than the mesh spacing of the direct three-dimensional geological model.

8. A three-dimensional inversion modeling system for gravity and magnetic data constrained by prior information, characterized in that, The system includes: The framework module is configured to determine the mesh spacing of the initial 3D geological model skeleton and the profile spacing of the 2D geological model based on the prior information category, and to determine the mesh spacing of the direct 3D geological model based on the first gravity and magnetic data. A two-dimensional modeling module is configured to construct an initial three-dimensional geological model framework based on the prior information and previous gravity and magnetic data through three-dimensional inversion; and Based on the profile spacing of the two-dimensional geological model, the initial three-dimensional geological model skeleton, and the prior information, all two-dimensional geological model profiles are drawn to obtain the two-dimensional geological model. A 3D modeling module is configured to generate an initial 2.75D geological model based on the 2D geological model, and to combine the initial 2.75D geological model to generate a mosaic 3D geological model; and Based on the grid spacing of the aforementioned direct 3D geological model and the initial direct 3D geological model, a direct 3D geological model is constructed through 3D inversion of the first gravity and magnetic data; and The modification and iteration between the collaged 3D geological model and the direct 3D geological model are repeatedly performed until the preset conditions are met, and a 3D geological model is obtained. The process of generating an initial 2.75-dimensional geological model based on the two-dimensional geological model includes the following steps: The model orientation length of each of the two-dimensional geological model profiles is shortened to the profile spacing, and the model orientation is changed to be arbitrary, forming a 2.75-dimensional geological model profile. The process of assembling the initial 2.75-dimensional geological model to generate a mosaic 3D geological model includes the following steps: Step 1: Perform forward modeling on the initial 2.75-dimensional geological model to obtain the second gravity and magnetic data; Step 2: Compare the difference between the second gravity and magnetic data and the first gravity and magnetic data. If the difference is less than a preset difference value, a 2.75-dimensional geological model is obtained. If the difference is not less than the preset difference value, the portion of the initial 2.75-dimensional geological model generated from the 2D geological model to be modified is modified, and the modified initial 2.75-dimensional geological model replaces the initial 2.75-dimensional geological model from Step 1. Repeat Steps 1 and 2 until the difference between the second gravity and magnetic data and the first gravity and magnetic data is less than the preset difference value, thus obtaining a 2.75-dimensional geological model. The first gravity and magnetic data is the latest measured gravity and magnetic data. The 2.75-dimensional geological model is then combined to generate a mosaic 3D geological model.

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