A method and system for recovering original topography of a volcanic edifice

Abstract

This invention provides a method and system for restoring the original morphology of a volcanic structure, comprising the following steps: acquiring multi-source data to construct a stratigraphic framework model of the volcanic structure; processing the measured well logging data to obtain an initial velocity curve, performing time-depth conversion based on the initial velocity curve, and performing a first correction on the stratigraphic framework model of the volcanic structure; introducing a fluid overpressure reduction factor into the first-corrected stratigraphic framework model of the volcanic structure for decompaction correction, followed by fault elimination, to obtain a second-corrected stratigraphic framework model of the volcanic structure; performing erosion recovery and layer flattening processing on the second-corrected stratigraphic framework model of the volcanic structure to obtain the final stratigraphic framework model of the volcanic structure. This invention, employing the above-mentioned method and system for restoring the original morphology of a volcanic structure, significantly improves the objectivity, quantification, and accuracy of the restoration results, providing a reliable geological model for volcanic oil and gas reservoir exploration and basin paleoenvironment restoration.

Description

Technical Field

[0001] This invention relates to the field of volcanic restoration, and in particular to a method and system for restoring the original morphology of volcanic structures. Background Technology

[0002] In the field of oil and gas exploration, volcanic rocks themselves can serve as excellent reservoirs, while also playing a significant role in controlling the structure and sedimentary patterns of underlying sedimentary strata. Therefore, reconstructing the original morphology of volcanic structures is crucial for clarifying reservoir distribution, predicting oil and gas reservoirs, and understanding basin evolution.

[0003] However, due to the long geological history of volcanic structures, their current underground morphology is the result of the superposition and modification of multiple geological processes:

[0004] Tectonic alteration: Faulting activity can disrupt its original continuity and morphology.

[0005] Compaction effect: The pressure of the overlying strata compacts and thins the originally loose volcanic debris.

[0006] Erosion: Later uplift was subjected to weathering and erosion, causing the loss of material from the top part.

[0007] Diagenetic alteration, such as hydrothermal alteration, can change the physical properties of rocks.

[0008] Traditional restoration methods rely heavily on geologists' empirical qualitative judgments or the use of simple, homogeneous geophysical models. These methods struggle to accurately quantify the intensity of the various alterations, especially in highly heterogeneous geological bodies like volcanic rocks, often resulting in significant errors and failing to meet the demands of current refined exploration. Summary of the Invention

[0009] The purpose of this invention is to provide a method and system for restoring the original morphology of volcanic structures. This method overcomes the challenges posed by the strong heterogeneity and complex alteration history of volcanic rocks. Through a strategy of "step-by-step stripping and iterative approximation," it gradually restores the complex subsurface conformations observed so far to the original morphology of the volcanic structure at the end of its eruption. This method significantly improves the objectivity, quantification, and accuracy of the restoration results, providing a reliable geological model for volcanic oil and gas reservoir exploration and basin paleoenvironment reconstruction.

[0010] To achieve the above objectives, the present invention provides a method for restoring the original morphology of a volcanic structure, comprising the following steps:

[0011] The first step is to acquire multi-source data to construct a strata model of the volcanic structure;

[0012] The second step is to process the measured VSP logging data to obtain the initial velocity curve. Based on the initial velocity curve, the velocity is divided into zones according to the stratigraphic framework model of the volcanic structure and a spatial variable velocity field is constructed. For the volcanic area, a velocity library of height anomalies is constructed. The spatial variable velocity field and the velocity library of height anomalies are combined to perform time-depth conversion and make a correction to the stratigraphic framework model of the volcanic structure.

[0013] This ensures that the vertical zonation and lateral variations conform to geological laws, avoiding errors from simple extrapolation. The introduction of the velocity database of high-altitude anomalies specifically addresses structural artifacts such as "false synclines" caused by high-velocity bodies like volcanic conduits and dense lava flows, which are beyond the capabilities of conventional velocity modeling methods.

[0014] The fusion of spatial variable velocity fields and velocity libraries of height anomalies, along with the integration method for time-depth transformation, achieves a precise mapping from the time domain to the depth domain. The reliability of the spatial geometry of the corrected stratigraphic lattice model represents a qualitative leap, providing an accurate starting point for subsequent restoration work and avoiding the risk of "input equals error."

[0015] The third step is to introduce a fluid overpressure reduction factor into the stratigraphic framework model of the volcanic structure after the first correction, perform decompaction correction, and then eliminate the fault displacement to obtain the stratigraphic framework model of the volcanic structure after the second correction.

[0016] The fourth step is to restore the erosion amount and flatten the layers of the volcanic structure stratigraphic framework model after the second correction to obtain the final stratigraphic framework model of the volcanic structure.

[0017] Preferably, in the first step, acquiring multi-source data to construct a stratigraphic model of the volcanic structure includes:

[0018] The acquired multi-source data are processed to obtain seismic reflection characteristics, core lithology, and well logging response;

[0019] Based on seismic reflection characteristics, core lithology, and well logging response, a first-level unit was obtained, which includes volcanic conduit facies, eruptive facies, crater facies, and volcanic sedimentary facies.

[0020] Based on the identification of key elements in the primary unit and spatial positioning, secondary elements are obtained, including annular / radial fractures, secondary cones, and lava tube systems.

[0021] Special marker layers are marked according to the primary unit and secondary elements. The special marker layers include the contact interface of the landmark cooling unit and the distribution area of ​​the explosive breccia.

[0022] Based on the above-mentioned primary units, secondary elements, and special marker layers, a stratigraphic framework model of the volcanic structure is constructed.

[0023] Preferably, in the second step, the obtained VSP logging data is processed to obtain the initial velocity curve, including the following steps:

[0024] Align the depth zero line of the measured VSP logging data with a unified elevation reference surface to obtain logging data in a unified coordinate system;

[0025] Identify the VSP round-trip travel time and actual depth corresponding to the first-level unit;

[0026] Select key layers Fit the discretized average velocity function The initial velocity curve is generated from the average velocity; where, Let be the VSP travel time for the i-th layer. Let be the actual depth of the i-th layer.

[0027] This ensured the accuracy of the well point velocity and precisely calibrated it with the geological strata, providing "hard data" control points for constructing a reliable variable velocity field and laying the foundation for high-precision velocity modeling.

[0028] Preferably, in the second step, based on the initial velocity curve, the velocity is partitioned according to the stratigraphic framework model of the volcanic structure, and a spatial variable velocity field is constructed, including the following steps:

[0029] The first-level unit is used as the top-level unit, and the internal sub-layers are further subdivided according to the second-level elements; based on the initial velocity curve, the sub-layers are further subdivided according to the second-level elements, and first-level velocity control items are set. This results in a large set of vertically layered velocity layers;

[0030] ;

[0031] Within the same level unit, the velocity extrapolation is performed along the structural direction using radial basis functions to obtain the velocity gradient bands of the transverse zone;

[0032] A velocity mutation node is set in a special marker layer to force constraints on adjacent meshes.

[0033] The aforementioned spatial velocity field not only achieves vertical stratification but also horizontal zonation, with its variations consistent with the geological structural trends (such as ring faults), thus better conforming to geological laws. Forced abrupt changes in special marker layers accurately characterize the velocity variations at lithological transition interfaces (such as cooling units), further improving the accuracy of the velocity model.

[0034] Preferably, in the second step, a time-depth conversion is performed by combining the spatial variable velocity field and the velocity library of height anomalies to correct the stratigraphic framework model of the volcanic structure, including the following steps:

[0035] The final velocity model is obtained by fusing the spatial variable velocity field and the velocity library of height anomalies, including:

[0036] Using a spatial variable speed field as the background field;

[0037] Treat the geological body defined in the high anomaly velocity library as an independent three-dimensional attribute body or a three-dimensional spatial polygon;

[0038] Traverse every grid node of the spatial variable velocity field;

[0039] Determine if the current node is inside any height anomaly:

[0040] If so: the speed value of the node will be directly replaced with the fixed high-speed value or high-speed value range specified for the anomaly in the speed library;

[0041] If not: then retain the velocity value of the node in the spatial variable speed field;

[0042] At the contact boundary between the anomaly and the surrounding rock, a smoothing process is performed to obtain a final three-dimensional velocity model after fusion.

[0043] Obtain the coordinates of each point in the lattice model of the volcanic structure. ;

[0044] In the final three-dimensional velocity model In the process, from time = 0 to time = T, the velocity is integrated along the perpendicular path from that point to obtain the transformed depth. Update the coordinates of this point to Complete a revised stratigraphic model of the volcanic structure:

[0045] .

[0046] The process described above, which integrates the spatial variable velocity field and the velocity library of high-altitude anomalies to obtain the final velocity model, ensures that the high-speed anomalies are accurately characterized. Furthermore, the reliability of the time-depth conversion results is ensured by using the integral method, an algorithm that is more in line with physical principles.

[0047] Preferably, in the third step, the model after secondary correction undergoes decompaction correction, including:

[0048] Compaction units are divided according to lithofacies assemblage, and corresponding lithological properties are assigned to the grids within each unit.

[0049] Establish a unique porosity-depth curve for each lithology, ensuring that the lithology of each unit has a corresponding surface porosity. and compaction coefficient :

[0050] ;

[0051]

[0052] In the formula, The fluid overpressure reduction factor. This represents the lower limit of residual porosity. For the theoretical static rock pressure gradient, For actual measured fluid pressure;

[0053] Starting from the bottommost unit of the stratigraphic framework model of the volcanic structure, the average porosity of the unit in its current state is calculated based on the depth of its top and bottom boundaries and its porosity-depth relationship curve. ;

[0054] Calculate the original sediment thickness using the decompaction formula : , This is the current thickness after the second correction;

[0055] The thickness value of this unit is updated and calculated. ;

[0056] Its As a new load on the overlying strata, this process is repeated in the next layer until the top layer.

[0057] Preferably, in the third step, the discontinuity is eliminated on the compacted and corrected model, including:

[0058] Paleo-displacement was obtained by comparing the depth of the same stratigraphic unit on both sides of the fault:

[0059] Ancient drop T w = Depth of the top boundary of the hanging strata - Depth of the top boundary of the footing strata;

[0060] Based on the paleo-drop and the dip angle θ of the fault plane, the total slip distance S is calculated as: S = T w / sin(θ), the sliding direction is determined based on the dip angle of the fault plane;

[0061] Slide repositioning is performed according to the sliding direction and the drama, until the fault is continuous on both sides.

[0062] The above-mentioned steps for eliminating fault displacement provide specific and calculable mathematical means, transforming the geological restoration process from qualitative description to quantitative calculation, thus ensuring the repeatability of the method and the objectivity of the results.

[0063] Preferably, in the fourth step, the erosion amount is recovered from the stratigraphic framework model of the secondary corrected volcanic structure, including:

[0064] Identify the unconformities in the stratigraphic framework model of the volcanic mechanism after secondary correction;

[0065] The erosion amount ΔZ of the unconformity surface is calculated, and the erosion amounts calculated at different locations are meshed to generate a continuous three-dimensional erosion data volume.

[0066] The erosion data volume is added as an additional thickness to the top unconformity of the stratigraphic framework model of the secondary-corrected volcanic structure. This involves adding the corresponding erosion amount to the Z-value of each point on the top surface of the stratigraphic framework model of the secondary-corrected volcanic structure, thus completing the erosion recovery. This transforms the erosion recovery from a conceptual step into a spatialized, gridded data operation process, ensuring a solid data foundation for the final paleogeographic reconstruction results.

[0067] A system for restoring the original morphology of a volcanic structure includes:

[0068] The initial model building module is used to acquire multi-source data to construct a hierarchical lattice model of the volcanic structure;

[0069] The model correction module processes the measured VSP logging data to obtain an initial velocity curve. Based on the initial velocity curve, the velocity is partitioned according to the stratigraphic framework model of the volcanic structure, and a spatial variable velocity field is constructed. For the volcanic area, a velocity library of height anomalies is constructed. Time-depth conversion is performed by combining the spatial variable velocity field and the velocity library of height anomalies to perform a first correction on the stratigraphic framework model of the volcanic structure. For the stratigraphic framework model of the volcanic structure after the first correction, a fluid overpressure reduction factor is introduced for decompaction correction, followed by fault elimination to obtain the stratigraphic framework model of the volcanic structure after the second correction. The stratigraphic framework model of the volcanic structure after the second correction is subjected to erosion recovery and layer flattening processing to obtain the final stratigraphic framework model of the volcanic structure.

[0070] Therefore, the present invention employs the above-mentioned method and system for restoring the original morphology of a volcanic structure, and the technical effects are as follows:

[0071] VSP processing and initial velocity curves: ensured the accuracy of well point velocities and accurately calibrated them with geological strata, providing "hard data" control points for constructing reliable variable velocity fields and laying the foundation for high-precision velocity modeling.

[0072] Velocity zoning and construction methods (radial basis functions, velocity abrupt change nodes): This enables the velocity model to not only be vertically layered but also laterally zoned, with its variations consistent with the geological structural trends (such as ring faults), making it more in line with geological laws. Forced jump treatment of special marker layers accurately characterizes the velocity changes at lithological abrupt change interfaces (such as cooling units), further improving the accuracy of the velocity model.

[0073] The fusion and integration algorithms in time-depth transformation have a specific and feasible operation process, which ensures that high-speed anomalies are accurately characterized. Furthermore, the integration method, which is more in line with physical principles, ensures the reliability of the time-depth transformation results.

[0074] Quantitative formulas for decompaction and fault elimination: These provide specific and calculable mathematical means, transforming the geological restoration process from qualitative description to quantitative calculation, ensuring the repeatability of the method and the objectivity of the results.

[0075] The specific operation of erosion recovery: The erosion recovery is transformed from a conceptual step into a spatialized and gridded data operation process, so that the final paleogeographic restoration results have a solid data foundation. Attached Figure Description

[0076] Figure 1 This is a flowchart of a method for restoring the original morphology of a volcanic structure according to the present invention;

[0077] Figure 2 This is a flowchart illustrating the first step.

[0078] Figure 3 This is a schematic diagram of the second step;

[0079] Figure 4 This is a diagram illustrating steps three and four. Detailed Implementation

[0080] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0081] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0082] Example 1

[0083] like Figure 1 As shown, a method for restoring the original morphology of a volcanic structure includes the following steps:

[0084] Step 1, such as Figure 2 As shown, a hierarchical lattice model of the volcanic structure is constructed by acquiring multi-source data, including:

[0085] The acquired multi-source data are processed to obtain seismic reflection characteristics, core lithology, and well logging response; the multi-source data includes seismic data, core data, and well logging data.

[0086] Based on seismic reflection characteristics, core lithology, and well logging response, a first-level unit was obtained, which includes volcanic conduit facies, eruptive facies, crater facies, and volcanic sedimentary facies.

[0087] Based on the identification of key elements in the primary unit and spatial positioning, secondary elements are obtained, including annular / radial fractures, secondary cones, and lava tube systems.

[0088] Special marker layers are marked according to the primary unit and secondary elements. The special marker layers include the contact interface of the landmark cooling unit and the distribution area of ​​the explosive breccia.

[0089] Based on the above-mentioned primary units, secondary elements, and special marker layers, a stratigraphic framework model of the volcanic structure is constructed.

[0090] Step 2, as follows Figure 3 As shown, the measured VSP logging data is processed to obtain the initial velocity curve. Based on the initial velocity curve, the velocity is divided into zones according to the stratigraphic framework model of the volcanic structure and a spatial variable velocity field is constructed. For the volcanic area, a velocity library of height anomalies is constructed. The spatial variable velocity field and the velocity library of height anomalies are combined to perform time-depth conversion and make a correction to the stratigraphic framework model of the volcanic structure.

[0091] The initial velocity profile is obtained by processing the measured VSP logging data, including the following steps:

[0092] Align the depth zero line of the measured VSP logging data with a unified elevation reference surface to obtain logging data in a unified coordinate system;

[0093] Identify the VSP travel time and actual depth corresponding to the primary unit;

[0094] Select key layers Fit the discretized average velocity function The initial velocity curve is generated from the average velocity; where, Let be the VSP travel time for the i-th layer. Let be the actual depth of the i-th layer.

[0095] Based on the initial velocity curve, the velocity is partitioned according to the stratigraphic framework model of the volcanic structure, and a spatially variable velocity field is constructed, including the following steps:

[0096] The first-level unit is used as the top-level unit, and the internal sub-layers are further subdivided according to the second-level elements; based on the initial velocity curve, the sub-layers are further subdivided according to the second-level elements, and first-level velocity control items are set. This results in a large set of vertically layered velocity layers;

[0097] ;

[0098] Within the same level unit, the velocity extrapolation is performed along the structural direction using radial basis functions to obtain the velocity gradient bands of the transverse zone;

[0099] Setting velocity mutation nodes in a special marker layer forces constraints on adjacent meshes, including:

[0100] A velocity jump node is inserted at the cooling interface, and the jump range is determined by the lithological difference (e.g., the velocity drops by about 18% from basalt to volcanic clastic rock).

[0101] A two-layer medium model was used for the eruptive breccia zone, with the upper loose deposits exhibiting low velocity and the lower compacted basement exhibiting high velocity.

[0102] By combining the spatial variable velocity field and the velocity library of height anomalies for time-depth conversion, the stratigraphic framework model of the volcanic structure is corrected.

[0103] The final velocity model is obtained by fusing the spatial variable velocity field and the velocity library of height anomalies, including:

[0104] Using a spatial variable velocity field as the background field (Base Model), this field already contains large velocity trends and lateral variations.

[0105] Treat geological bodies (such as volcanic conduits) defined in the high anomaly velocity library as independent three-dimensional attribute bodies or three-dimensional spatial polygons;

[0106] Traverse every grid node of the spatial variable velocity field;

[0107] Determine if the current node is inside any height anomaly:

[0108] If so: the speed value of the node will be directly replaced with the fixed high-speed value or high-speed value range specified for the anomaly in the speed library;

[0109] If not: then retain the velocity value of the node in the spatial variable speed field;

[0110] The contact boundary between the anomaly and the surrounding rock is smoothed to avoid artificial illusions caused by drastic changes in velocity.

[0111] A final, integrated three-dimensional velocity model was obtained. This model includes both the velocity variations controlled by the stratigraphic framework and accurately describes the distribution of high-velocity anomalies.

[0112] The coordinates (x, y, T) of each point in the strata model of the volcanic structure.

[0113] In the final three-dimensional velocity model In the equation, the velocity is integrated along the perpendicular path from time = 0 to time = T.

[0114] Multiplying the integral result by 1 / 2 gives the depth value Z at that point. The coordinates of this point are then updated to (x, y, Z). After this correction, the horizontal coordinates (X, Y) of the volcanic stratigraphic model remain unchanged, but the vertical coordinates of all points change from time (ms) to depth (m).

[0115] ;

[0116] In the formula, The converted depth.

[0117] Step 3, as follows Figure 4 As shown, for the stratigraphic framework model of the volcanic structure after the first correction, a fluid overpressure reduction factor is introduced for decompaction correction, followed by fault elimination to obtain the stratigraphic framework model of the volcanic structure after the second correction. Compaction units are divided according to lithofacies assemblage, porosity decay curves are established according to grain size classification, and the original sedimentary thickness is extrapolated upward layer by layer to generate a pseudo geological history model after decompaction.

[0118] The model after secondary correction undergoes decompaction correction, including:

[0119] Compaction units are divided according to lithofacies assemblage, and the grid within each unit is enriched with corresponding lithological properties.

[0120] Establish a unique porosity-depth relationship curve for each type of lithology. The lithological abundance of each unit corresponds to the surface porosity. and compaction coefficient ;

[0121] ;

[0122] ;

[0123] In the formula, The fluid overpressure reduction factor. This represents the lower limit of residual porosity. This represents the theoretical static rock pressure gradient (approximately 23 MPa / km). For actual measured fluid pressure;

[0124] Starting from the bottommost element of the model, the average porosity of the element in its current state is calculated based on the depth of its top and bottom boundaries and its porosity-depth relationship curve. ;

[0125] Calculate the original sediment thickness using the decompaction formula : , This is the current thickness after the second correction;

[0126] The thickness value of this unit is updated and calculated. ;

[0127] After completing the calculations for this layer, then... As a new load on the overlying strata, this process is repeated in the next layer until the top layer.

[0128] Decompaction correction restores the original sedimentary thickness of the strata, allowing the model, thinned by compaction, to "grow taller" back to its original state. The key innovation is the introduction of a fluid overpressure reduction factor, which effectively solves the problem of "overcompensation" (i.e., overestimation of the original thickness) that occurs when undercompacted strata are decompacted. This makes the calculation of the decompaction amount more consistent with the actual underground conditions and improves the accuracy of the restoration results.

[0129] After compaction and straightening, the discontinuity of the model is eliminated, including:

[0130] Paleo-displacement was obtained by comparing the depth of the same stratigraphic unit on both sides of the fault:

[0131] Ancient drop (T) w = Depth of the top boundary of the hanging strata - Depth of the top boundary of the footwall strata;

[0132] According to the ancient elevation difference (T) w ) and the dip angle (θ) of the fault plane, calculate the total slip distance S: S=T w / sin(θ), the sliding direction (fault dip-slip direction) is determined based on the dip angle of the fault plane;

[0133] Slide repositioning is performed according to the sliding direction and the drama, until the fault is continuous on both sides, including:

[0134] Normal faults: The Rollover Pivot Point Method is used. The hanging block is rotated in the opposite direction around a pivot point to align the strata on both sides of the fault.

[0135] Strike-slip faults: Applying Wallace's rule, the hanging block is shifted in the opposite direction along the fault strike, so that the displaced geological bodies are reconnected.

[0136] Based on the restoration of the original thickness, paleo-displacement calculations and sliding repositioning were performed, which allowed the faulted blocks to be reassembled, restoring the original spatial continuity and structural morphology of the strata.

[0137] The fourth step involves restoring the erosion amount on the stratigraphic framework model of the volcanic structure after secondary correction, resulting in the final stratigraphic framework model of the volcanic structure, including:

[0138] Identify the unconformities in the stratigraphic framework model of the volcanic mechanism after secondary correction;

[0139] The erosion amount ΔZ of the unconformity surface is calculated, and the erosion amounts calculated at different locations are meshed to generate a continuous three-dimensional erosion data volume.

[0140] The erosion data volume is added as an additional thickness to the top unconformity of the stratigraphic framework model of the volcanic structure after secondary correction. That is, the Z value of each point on the top surface of the stratigraphic framework model of the volcanic structure after secondary correction is added to the erosion amount corresponding to that point.

[0141] The erosion recovery method comprehensively estimates and compensates for the thickness of the eroded strata through multiple methods, which solves the problem of "top missing" caused by later modification and restores the original scale and undulation of the volcanic structure.

[0142] Layer flattening restores the model to a key geological time point (such as the end of an eruption), visually reproducing the paleogeographic pattern of that period. The final model clearly shows the original shape, height, and distribution range of elements such as volcanic cones, lava flows, and craters, achieving a leap from "underground model" to "paleogeographic map".

[0143] When flattening the layers, select a marker layer with good isochronous properties that is distributed throughout the entire model as the reference surface. This layer should represent the time when the main body of the volcanic structure was completed, such as: the interface of the cooling unit at the top of the volcanic structure; the top surface of the regionally distributed thick volcanic clastic rocks; the bottom surface of the first set of volcanic sedimentary facies above the volcanic structure.

[0144] In modeling software, the selected reference plane is used as a fixed horizontal reference plane (for example, the depth value of all its points is set to 0 meters).

[0145] Running the algorithm, all strata below the reference surface in the stratigraphic framework model of the volcanic structure after the second correction will undergo synchronous tectonic deformation (essentially a vertical shearing) according to their relative distance from the reference surface, thereby making the reference surface flat.

[0146] Strata above the reference level (if any) will be "stripped" or not displayed.

[0147] Generate paleogeographic map: After the layers are flattened, the now flat reference surface actually represents the paleo-horizontal surface (or reference surface) when the volcanic structure stopped growing.

[0148] At this point, the topmost structural diagram of the stratigraphic framework model of the volcanic structure after the second correction is the original geomorphological map of the volcanic structure before it was eroded. The contour lines in the diagram clearly show the shape and undulation of elements such as the volcanic cone, lava flow, and crater.

[0149] A system for restoring the original morphology of a volcanic structure includes:

[0150] The initial model building module is used to acquire multi-source data to construct a hierarchical lattice model of the volcanic structure;

[0151] The model correction module processes the measured VSP logging data to obtain an initial velocity curve. Based on the initial velocity curve, the velocity is partitioned according to the stratigraphic framework model of the volcanic structure, and a spatial variable velocity field is constructed. For the volcanic area, a velocity library of height anomalies is constructed. Time-depth conversion is performed by combining the spatial variable velocity field and the velocity library of height anomalies to perform a first correction on the stratigraphic framework model of the volcanic structure. For the stratigraphic framework model of the volcanic structure after the first correction, a fluid overpressure reduction factor is introduced for decompaction correction, followed by fault elimination to obtain the stratigraphic framework model of the volcanic structure after the second correction. The stratigraphic framework model of the volcanic structure after the second correction is subjected to erosion recovery and layer flattening processing to obtain the final stratigraphic framework model of the volcanic structure.

[0152] Therefore, the present invention adopts the above-mentioned method and system for restoring the original morphology of volcanic structures. Based on multi-source data, constrained by a geological framework, and using quantitative algorithms, it systematically eliminates the influence of various post-modification effects through a process-oriented iterative operation of velocity correction, decompaction, structural restoration, and erosion restoration. Ultimately, it reproduces the original morphology of volcanic structures with high precision, thus solving a long-standing technical bottleneck in this field.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for restoring the original morphology of a volcanic structure, characterized in that, Includes the following steps: The first step is to acquire multi-source data to construct a strata model of the volcanic structure; The second step is to process the measured VSP logging data to obtain the initial velocity curve. Based on the initial velocity curve, the velocity is divided into zones according to the stratigraphic framework model of the volcanic structure and a spatial variable velocity field is constructed. For the volcanic area, a velocity library of height anomalies is constructed. The spatial variable velocity field and the velocity library of height anomalies are combined to perform time-depth conversion and make a correction to the stratigraphic framework model of the volcanic structure. The third step is to introduce a fluid overpressure reduction factor into the stratigraphic framework model of the volcanic structure after the first correction, perform decompaction correction, and then eliminate the fault displacement to obtain the stratigraphic framework model of the volcanic structure after the second correction. The fourth step is to restore the erosion amount and flatten the layers of the volcanic structure stratigraphic framework model after the second correction to obtain the final stratigraphic framework model of the volcanic structure.

2. The method for restoring the original morphology of a volcanic structure according to claim 1, characterized in that, The first step involves acquiring multi-source data to construct a layered lattice model of the volcanic structure, including: The acquired multi-source data are processed to obtain seismic reflection characteristics, core lithology, and well logging response; Based on seismic reflection characteristics, core lithology, and well logging response, a first-level unit was obtained, which includes volcanic conduit facies, eruptive facies, crater facies, and volcanic sedimentary facies. Based on the identification of key elements in the primary unit and spatial positioning, secondary elements are obtained, including annular / radial fractures, secondary cones, and lava tube systems. Special marker layers are marked according to the primary unit and secondary elements. The special marker layers include the contact interface of the landmark cooling unit and the distribution area of ​​the explosive breccia. Based on the above-mentioned primary units, secondary elements, and special marker layers, a stratigraphic framework model of the volcanic structure is constructed.

3. The method for restoring the original morphology of a volcanic structure according to claim 1, characterized in that, The second step involves processing the obtained VSP logging data to obtain the initial velocity curve, including the following steps: Align the depth zero line of the measured VSP logging data with a unified elevation reference surface to obtain logging data in a unified coordinate system; Identify the VSP round-trip travel time and actual depth corresponding to the primary unit; Select key layers Fit the discretized average velocity function The initial velocity curve is generated from the average velocity; where, Let be the VSP travel time for the i-th layer. Let be the actual depth of the i-th layer.

4. The method for restoring the original morphology of a volcanic structure according to claim 1, characterized in that, In the second step, based on the initial velocity curve, the velocity is partitioned according to the stratigraphic framework model of the volcanic structure, and a spatial variable velocity field is constructed, including the following steps: The first-level unit is used as the top-level unit, and the internal sub-layers are further subdivided according to the second-level elements; based on the initial velocity curve, the sub-layers are further subdivided according to the second-level elements, and first-level velocity control items are set. This results in a large set of vertically layered velocity layers; ； Within the same level unit, the velocity extrapolation is performed along the structural direction using radial basis functions to obtain the velocity gradient bands of the transverse zone; A velocity mutation node is set in a special marker layer to force constraints on adjacent meshes.

5. The method for restoring the original morphology of a volcanic structure according to claim 1, characterized in that, In the second step, time-depth conversion is performed by combining the spatial variable velocity field and the velocity library of height anomalies to correct the stratigraphic framework model of the volcanic structure. This includes the following steps: The final velocity model is obtained by fusing the spatial variable velocity field and the velocity library of height anomalies, including: Using a spatial variable speed field as the background field; Treat the geological body defined in the high anomaly velocity library as an independent three-dimensional attribute body or a three-dimensional spatial polygon; Traverse every grid node of the spatial variable velocity field; Determine if the current node is inside any height anomaly: If so: the speed value of the node will be directly replaced with the fixed high-speed value or high-speed value range specified for the anomaly in the speed library; If not: then retain the velocity value of the node in the spatial variable speed field; At the contact boundary between the anomaly and the surrounding rock, a smoothing process is performed to obtain a final three-dimensional velocity model after fusion. Obtain the coordinates of each point in the lattice model of the volcanic structure. ; In the final three-dimensional velocity model In the process, from time = 0 to time = T, the velocity is integrated along the perpendicular path from that point to obtain the transformed depth. Update the coordinates of this point to Complete a revised stratigraphic model of the volcanic structure: 。 6. The method for restoring the original morphology of a volcanic structure according to claim 1, characterized in that, The third step involves decompaction correction of the model after the second correction, including: Compaction units are divided according to lithofacies assemblage, and corresponding lithological properties are assigned to the grids within each unit. Establish a unique porosity-depth curve for each lithology, ensuring that the lithology of each unit has a corresponding surface porosity. and compaction coefficient : ； In the formula, The fluid overpressure reduction factor. This represents the lower limit of residual porosity. For the theoretical static rock pressure gradient, For actual measured fluid pressure; Starting from the bottommost unit of the stratigraphic framework model of the volcanic structure, the average porosity of the unit in its current state is calculated based on the depth of its top and bottom boundaries and its porosity-depth relationship curve. ; Calculating the original sediment thickness using the decompaction formula : , This is the current thickness after the second correction; The thickness value of this unit is updated and calculated. ; Its As a new load on the overlying strata, this process is repeated in the next layer until the top layer.

7. The method for restoring the original morphology of a volcanic structure according to claim 1, characterized in that, The third step involves eliminating discontinuities in the compacted and corrected model, including: Paleo-displacement was obtained by comparing the depth of the same stratigraphic unit on both sides of the fault: Ancient drop T w = Depth of the top boundary of the hanging strata - Depth of the top boundary of the footing strata; Based on the paleo-drop and the dip angle θ of the fault plane, the total slip distance S is calculated as: S = T w / sin(θ), the sliding direction is determined based on the dip angle of the fault plane; Slide repositioning is performed according to the sliding direction and the drama, until the fault is continuous on both sides.

8. The method for restoring the original morphology of a volcanic structure according to claim 1, characterized in that, In the fourth step, the erosion amount is recovered from the stratigraphic framework model of the volcanic structure after the second correction, including: Identify the unconformities in the stratigraphic framework model of the volcanic mechanism after secondary correction; The erosion amount ΔZ of the unconformity surface is calculated, and the erosion amounts calculated at different locations are meshed to generate a continuous three-dimensional erosion data volume. The erosion data volume is added as an additional thickness to the top unconformity of the stratigraphic framework model of the volcanic structure after secondary correction. This means adding the Z value of each point on the top surface of the stratigraphic framework model of the volcanic structure corresponding to that point to the erosion amount, thus completing the erosion recovery.

9. A system for restoring the original morphology of a volcanic structure, characterized in that, include: The initial model building module is used to acquire multi-source data to construct a hierarchical lattice model of the volcanic structure; The model correction module processes the measured VSP logging data to obtain an initial velocity curve. Based on the initial velocity curve, the velocity is partitioned according to the stratigraphic framework model of the volcanic structure, and a spatial variable velocity field is constructed. For the volcanic area, a velocity library of height anomalies is constructed. Time-depth conversion is performed by combining the spatial variable velocity field and the velocity library of height anomalies to perform a first correction on the stratigraphic framework model of the volcanic structure. For the stratigraphic framework model of the volcanic structure after the first correction, a fluid overpressure reduction factor is introduced for decompaction correction, followed by fault elimination to obtain the stratigraphic framework model of the volcanic structure after the second correction. The stratigraphic framework model of the volcanic structure after the second correction is subjected to erosion recovery and layer flattening processing to obtain the final stratigraphic framework model of the volcanic structure.

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