A palaeogeomorphology restoration method and device

Abstract

The application provides a palaeogeomorphology recovery method and device, which comprises the following steps: constructing an initial palaeogeomorphology; determining a compaction coefficient based on porosity data and burial depth, and using the compaction coefficient to correct the residual thickness of the initial palaeogeomorphology to obtain a decompacted palaeothickness; determining an absolute palaeowater depth based on uranium element content, and subtracting the absolute palaeowater depth from the decompacted palaeothickness to obtain a palaeotopography of a sediment surface; identifying an unconformity surface, determining an uneroded area and an eroded area according to the unconformity surface, constructing a trend model using the stratigraphic thickness variation trend of the uneroded area, determining the eroded thickness of the eroded area based on the trend model, and obtaining a complete palaeogeomorphology after erosion recovery; taking a selected reference layer as a datum plane, reversely sliding an upper wall of a fault along a fault plane until the upper wall reference layer and a lower wall reference layer are spliced, performing trend interpolation filling on data gaps at the fault to obtain a target palaeogeomorphology after the influence of the fault is removed. The application improves the accuracy and objectivity of palaeogeomorphology recovery.

Description

Technical Field

[0001] This invention relates to the field of geological exploration technology, specifically to a method and apparatus for ancient landform restoration. Background Technology

[0002] The study of paleogeography enables the characterization and reproduction of the evolutionary history of sedimentary basins. It has important guiding significance for the study of geomorphic environment and its changes during geological history, especially in terms of source direction, spatial variation of sedimentary areas and sedimentary centers, distribution of sedimentary facies, reservoir distribution, and hydrocarbon migration and accumulation.

[0003] Existing paleomorphological reconstruction methods are typically based on residual thickness methods or impression methods, directly utilizing the thickness difference between the target layer and the reference layer obtained from seismic interpretation to characterize paleomorphological features. However, this method has the following shortcomings: 1. The compaction of sediments was not taken into account: During the burial process, the porosity of sediments decreases and their thickness thins. Directly using the residual thickness will underestimate the original sediment thickness, resulting in distortion of the paleogeographic amplitude.

[0004] 2. Uncorrected paleowater depth influence: For underwater sedimentary environments, the residual thickness includes water depth information. If the water depth is not deducted, the reconstructed paleolandform actually reflects the total thickness of the water body and sediment, rather than the true topography of the sediment surface.

[0005] 3. Untreated strata erosion: Later tectonic uplift caused some strata to be eroded. The remaining thickness cannot represent the original sedimentary thickness. If erosion is not restored, the range of paleogeographic height will be underestimated or even the source direction will be misjudged.

[0006] 4. Failure to eliminate the influence of fault activity: Co-depositional fault activity can cause stratigraphic displacement and thickness changes, making the residual thickness unable to truly reflect the paleotopography at the time of deposition. Traditional methods often ignore the influence of faults or simply delete faults, resulting in a distortion of the paleogeographic pattern.

[0007] In summary, existing methods lack correction for multiple factors such as compaction, water depth, erosion, and faulting, resulting in low accuracy in paleogeographic reconstruction and failing to meet the needs of detailed exploration in complex tectonic areas. Therefore, there is an urgent need to provide a paleogeographic reconstruction method and apparatus capable of correcting for multiple factors such as compaction, water depth, erosion, and faulting, thereby improving the accuracy of paleogeographic reconstruction and meeting the requirements of detailed exploration. Summary of the Invention

[0008] In view of this, it is necessary to provide a method and apparatus for ancient landform restoration to solve the technical problem that the existing technology lacks correction for multiple factors such as compaction, water depth, erosion, and faulting, resulting in low accuracy of ancient landform restoration results.

[0009] To address the aforementioned technical problems, in a first aspect, the present invention provides a method for ancient landform restoration, comprising: Acquire 3D seismic data and well logging data of the study area, and construct an initial paleogeomorphology based on the 3D seismic data and the well logging data; The compaction coefficient is determined based on the porosity data and burial depth in the well logging data, and the compaction coefficient is used to correct the residual thickness of the initial paleomorphology to obtain the decompacted paleothickness. The absolute paleowater depth is determined based on the uranium content in the well logging data, and the absolute paleowater depth is subtracted from the decompacted paleothickness to obtain the paleotopography of the sediment surface. Based on the three-dimensional seismic data, unconformities are identified, and uneroded and eroded areas are determined according to the unconformities. A trend model is constructed using the stratigraphic thickness variation trend of the uneroded areas, and the erosion thickness of the eroded areas is determined based on the trend model. The erosion thickness is then superimposed onto the paleotopography of the sediment surface to obtain the complete paleotopography after erosion restoration. Using the selected reference layer as the baseline, the hanging wall of the fault is slid in the opposite direction along the fault plane until the reference layer of the hanging wall and the reference layer of the footwall are spliced ​​together. Trend interpolation is performed to fill the data gaps at the fault to obtain the target paleomorphology after removing the influence of the fault.

[0010] In one possible implementation, the construction of the initial paleomorphology based on the three-dimensional seismic data and the well logging data includes: The well logging data is used to calibrate the three-dimensional seismic data to determine the two-way travel time on the seismic profiles of the target layer and the reference layer; the target layer is the stratigraphic interface that needs to be restored to its paleomorphology, and the reference layer is the isochronous interface located above or below the target layer, with continuous seismic reflections and less fault faulting than the target layer. The two-way travel time is converted into depth values ​​through time-depth conversion to obtain the target layer depth and the reference layer depth. The residual thickness is obtained by subtracting the target layer depth from the reference layer depth, and the residual thickness is used as the initial paleomorphology.

[0011] In one possible implementation, the porosity data includes the original porosity and the current porosity, then the compaction coefficient is:

[0012] In the formula, This is the compaction coefficient; Original porosity; This represents the current porosity.

[0013] In one possible implementation, the relationship between the decompacted paleothickness and the residual thickness is as follows:

[0014] In the formula, To reduce the compaction of ancient thickness; This is the residual thickness; This refers to the burial depth.

[0015] In one possible implementation, before determining the compaction coefficient based on the porosity data in the well logging data, the method further includes: Based on the tectonic zoning of the initial paleogeography and the sedimentary facies zones of the well logging data, the study area is divided into multiple zones; The determination of the compaction coefficient based on the porosity data in the well logging data includes: Typical logging data are selected from each of the zones, and the compaction coefficient of each zone is determined based on the porosity data and burial depth of the typical logging data.

[0016] In one possible implementation, determining the absolute paleowater depth based on the uranium content in the well logging data includes: The relative paleowater depth is determined based on the uranium content and the constructed correlation model between uranium content and relative paleowater depth. The relative paleodepth is corrected based on the maximum paleodepth of the study area to obtain the absolute paleodepth.

[0017] In one possible implementation, the absolute paleowater depth is:

[0018]

[0019] In the formula, It is an absolutely ancient and deep place; It is relatively deep in ancient waters; The maximum absolute actual ancient water depth; This represents the maximum relative actual water depth. The uranium content at the i-th sampling point of the target layer, predicted based on well logging data; This represents the total number of samples taken from the target layer.

[0020] In one possible implementation, before determining the absolute paleowater depth based on the uranium content in the well logging data, the method further includes: A linear regression model is established between the natural gamma logging value and the uranium content, where the independent variable of the linear regression model is the natural gamma logging value and the dependent variable is the uranium content. The measured natural gamma values ​​are extracted from the well logging data, and the uranium content is determined based on the measured natural gamma values ​​and the linear regression model.

[0021] In one possible implementation, before sliding the hanging wall along the fault plane in the reverse direction until the hanging wall reference layer and the footwall reference layer are joined, the method further includes: Determine the growth index of each fault within the study area and determine whether the growth index is greater than a preset index value; the growth index is the ratio of the wall thickness to the hanging wall thickness of the fault. The step of sliding the hanging wall along the fault plane in the opposite direction until the hanging wall reference layer and the footwall reference layer are joined includes: When the growth index of the fault exceeds the preset index value, the hanging wall of the fault is slid in the opposite direction along the fault plane until the reference layer of the hanging wall and the reference layer of the footwall are spliced ​​together.

[0022] Secondly, the present invention also provides an ancient landform restoration device, comprising: An initial paleogeographic construction unit is used to acquire three-dimensional seismic data and well logging data of the study area, and to construct an initial paleogeographic feature based on the three-dimensional seismic data and the well logging data. The compaction correction unit is used to determine the compaction coefficient based on the porosity data and burial depth in the well logging data, and to use the compaction coefficient to perform compaction correction on the residual thickness of the initial paleomorphology to obtain the decompacted paleothickness. The paleowater depth subtraction unit is used to determine the absolute paleowater depth based on the uranium content in the well logging data, and to subtract the absolute paleowater depth from the decompacted paleothickness to obtain the paleotopography of the sediment surface. The erosion restoration unit is used to identify unconformities based on the three-dimensional seismic data, determine uneroded areas and eroded areas based on the unconformities, construct a trend model using the stratigraphic thickness variation trend of the uneroded areas, determine the erosion thickness of the eroded areas based on the trend model, and superimpose the erosion thickness onto the paleotopography of the sediment surface to obtain the complete paleotopography after erosion restoration. The fault removal unit is used to slide the hanging wall along the fault plane in the opposite direction until the hanging wall reference layer and the footwall reference layer are spliced ​​together. The data gaps at the fault are filled by trend interpolation to obtain the target paleomorphology after the fault is removed.

[0023] The beneficial effects of this invention are as follows: The paleogeographic restoration method provided by this invention utilizes the relationship between porosity and burial depth in well logging data to determine the compaction coefficient, and performs compaction correction on the residual thickness of the initial paleogeographic features to obtain the decompacted paleothickness, overcoming the problem of paleogeographic amplitude distortion caused by compaction. Furthermore, based on uranium content, the absolute paleowater depth is determined, and the water depth is subtracted from the decompacted paleothickness to obtain the paleotopography of the sediment surface, eliminating the interference of water depth on paleogeographic morphology and ensuring that the restoration result reflects the true undulations of sediment deposition. Further, by identifying unconformities to divide uneroded and eroded zones, the original thickness of the eroded zone is extrapolated using the stratigraphic thickness variation trend of the uneroded zone, and the calculated eroded thickness is superimposed back onto the paleotopography, effectively correcting the thickness loss caused by later erosion. Meanwhile, using the selected reference layer as the datum, the hanging wall of the fault was slid in the opposite direction along the fault plane to the reference layers of the hanging wall and footwall, and data gaps were filled by interpolation, thus eliminating the interference of syn-depositional fault activity on stratigraphic morphology and obtaining the target paleomorphology that reflects the original sedimentary period.

[0024] In other words, this invention sequentially performs compaction correction, water depth deduction, erosion restoration, and fault removal restoration on the constructed initial paleomorphology, significantly improving the accuracy and objectivity of paleomorphology restoration and providing reliable technical support for sedimentary system analysis and oil and gas exploration. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic flowchart of an embodiment of the paleogeographic restoration method provided by the present invention; Figure 2 This is a schematic diagram illustrating an embodiment of the process for constructing an initial paleomorphology provided by the present invention; Figure 3 A schematic diagram illustrating an embodiment of the present invention for determining absolute paleowater depth; Figure 4 A schematic diagram of an embodiment of the present invention for determining uranium content; Figure 5 A schematic diagram of ancient landforms without fault removal treatment; Figure 6 A schematic diagram of the paleolandform after fault removal; Figure 7 This is a schematic diagram of an embodiment of the ancient landform restoration device provided by the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] It should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this invention illustrate operations implemented according to some embodiments of the invention. It should be understood that the operations in the flowcharts may be implemented out of order, and steps without logical contextual relationships may be reversed or performed simultaneously. Furthermore, those skilled in the art, guided by the content of this invention, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] This invention provides a method and apparatus for ancient landform restoration, which will be described below.

[0031] Figure 1 A schematic flowchart of an embodiment of the paleogeographic restoration method provided by the present invention is shown below. Figure 1 As shown, paleomorphological restoration methods include: S101. Obtain 3D seismic data and well logging data of the study area, and construct the initial paleogeography based on the 3D seismic data and well logging data.

[0032] Among them, three-dimensional seismic data refers to a three-dimensional gridded data volume obtained by artificially generating seismic waves and receiving reflected waves at the Earth's surface. Each grid point records the reflection time or depth information of the underground strata interface, which is used to depict the spatial geometry of strata and faults.

[0033] Well logging data refers to geophysical parameter curves continuously measured along the wellbore using downhole instruments, including acoustic velocity, density, natural gamma, and uranium content, which are used to calibrate seismic reflection horizons, determine rock physical properties, and reconstruct paleowater depths.

[0034] To improve data quality, the logging data consists of complete sonic velocity and density curves.

[0035] S102. Based on the porosity data and burial depth in the well logging data, determine the compaction coefficient, and use the compaction coefficient to compact and correct the residual thickness of the initial paleomorphology to obtain the decompacted paleothickness. S103. Determine the absolute paleowater depth based on the uranium content in the well logging data, and subtract the absolute paleowater depth from the decompacted paleothickness to obtain the paleotopography of the sediment surface. S104. Identify unconformities based on 3D seismic data, determine uneroded and eroded zones based on unconformities, construct a trend model using the stratigraphic thickness variation trend of uneroded zones, determine the erosion thickness of eroded zones based on the trend model, and superimpose the erosion thickness onto the paleotopography of sediment surfaces to obtain the complete paleotopography after erosion restoration.

[0036] Specifically, an unconformity is a stratigraphic interface formed when sedimentation ceases and erosion or weathering occurs due to tectonic uplift, sea-level drop, or sedimentary interruption, followed by re-sedimentation. On seismic profiles, unconformities typically manifest as the reflection phase axis of the underlying strata being truncated or terminated by the overlying interface, or as the overlying strata overlapping or overlapping the interface. Therefore, the stratigraphic position where truncation or termination occurs can be identified on seismic reflections to pinpoint the unconformity.

[0037] The trend model is based on the assumption that in the uneroded zone, the stratum thickness exhibits a continuous and smooth variation along a certain direction (e.g., away from the basin edge). Therefore, the unconformity can be first identified on the seismic profile, and the boundary between the eroded and uneroded zones can be delineated. Then, a series of sampling points are selected in the uneroded zone, and their residual thickness and corresponding planar coordinates are measured. A trend model of thickness variation with location is established using methods such as linear regression, exponential fitting, or polynomial fitting. Finally, the trend model is extrapolated to points within the eroded zone to calculate the original thickness that should exist before erosion. Subtracting the residual thickness directly read from the seismic data yields the eroded thickness.

[0038] Specifically, the formula for calculating the erosion thickness is: H e =H original H rem In the formula, H eThe thickness of the erosion. H original This represents the original deposition thickness. H rem This represents the residual thickness.

[0039] S105. Using the selected reference layer as the reference plane, slide the hanging wall along the fault plane in the opposite direction until the reference layer of the hanging wall and the reference layer of the footwall are spliced ​​together. Perform trend interpolation to fill the data gaps at the fault to obtain the target paleomorphology after removing the influence of the fault.

[0040] Specifically, the reference layer refers to an isochronous stratigraphic interface selected above or below the target layer that has continuous seismic reflections and is less affected by later tectonic deformation (especially fault displacement) than the target layer. In paleogeomorphological reconstruction, the reference layer serves as a spatial reference surface for calculating residual thickness and as a standard surface for joining the hanging wall and footwall in fault removal reconstruction.

[0041] The selection of reference layers must simultaneously meet the following criteria: continuous phase axes on the seismic profile, high signal-to-noise ratio, and stable tracking throughout the entire work area; the fault displacement of the faulted layer is significantly smaller than that of the target layer; it is adjacent to the target layer in the sedimentary sequence and forms an isochronous interface, without obvious sedimentary discontinuities or time-crossing phenomena; and it has not undergone strong folding or tilting. Typically, reference layers are selected from marker layers such as mudstone, tuff, or coal seams that are stably developed near the target layer, utilizing a combination of well stratigraphy, seismic properties, and structural maps.

[0042] The hanging wall reference layer refers to the reference layer interface located on the hanging wall of a fault (usually the downthrown block in a normal fault), while the footwall reference layer refers to the same reference layer interface located on the footwall (upthrown block) of the fault. Before fault activity, the hanging wall and footwall reference layers were originally continuous sedimentary layers at the same isochronous interface; after fault activity, they are misaligned, exhibiting vertical and horizontal displacement. During fault restoration, using the reference layer as a benchmark, the hanging wall is reverse-slid to re-align the hanging wall and footwall reference layers, thereby restoring the target layer on the hanging wall to its pre-fault-activity relative position.

[0043] The specific method for filling data gaps at faults using trend interpolation is as follows: First, select known grid points within a certain range around the gap area and extract their stratigraphic thickness or depth values ​​and their planar coordinates; then, select an appropriate trend interpolation model (such as Kriging, inverse distance weighted method, or radial basis function method) based on the data distribution characteristics to fit a continuous surface that varies with spatial location for the thickness or depth; finally, extend this surface to each grid point within the gap area, calculate the corresponding interpolation results, and fill the gaps.

[0044] It should be understood that the paleogeographic restoration method in this embodiment of the invention can be implemented in any system based on the joint interpretation of 3D seismic data and well logging data, such as seismic interpretation workstations, basin simulation software platforms, geological research servers, or reservoir description integrated management systems. Specifically, the paleogeographic restoration method is pre-stored in the memory of the aforementioned device in the form of a computer program. When the device is powered on or the system triggers a paleogeographic reconstruction task, the program is called and executed by the processor to realize the restoration of the paleogeography.

[0045] Compared with existing technologies, the paleogeographic restoration method provided in this invention utilizes the relationship between porosity and burial depth in well logging data to determine the compaction coefficient, and performs compaction correction on the residual thickness of the initial paleogeographic features to obtain the decompacted paleothickness, overcoming the problem of paleogeographic amplitude distortion caused by compaction. Furthermore, it determines the absolute paleowater depth based on uranium content and subtracts the water depth from the decompacted paleothickness to obtain the paleotopography of the sediment surface, eliminating the interference of water depth on paleogeographic morphology and ensuring that the restoration result reflects the true undulations of sediment deposition. Further, by identifying unconformities to divide uneroded and eroded zones, the original thickness of the eroded zone is extrapolated using the stratigraphic thickness variation trend of the uneroded zone, and the calculated eroded thickness is superimposed back onto the paleotopography, effectively correcting the thickness loss caused by later erosion. Meanwhile, using the selected reference layer as the datum, the hanging wall of the fault was slid in the opposite direction along the fault plane to the reference layers of the hanging wall and footwall, and data gaps were filled by interpolation, thus eliminating the interference of syn-depositional fault activity on stratigraphic morphology and obtaining the target paleomorphology that reflects the original sedimentary period.

[0046] In other words, the embodiments of the present invention perform compaction correction, water depth deduction, erosion restoration, and fault removal restoration on the initial paleomorphology obtained by sequentially, which significantly improves the accuracy and objectivity of paleomorphology restoration and provides reliable technical support for sedimentary system analysis and oil and gas exploration.

[0047] In some embodiments of the present invention, such as Figure 2 As shown, step S101, which involves constructing the initial paleomorphology based on 3D seismic data and well logging data, includes: S201. Use well logging data to calibrate three-dimensional seismic data and determine the two-way travel time on the seismic profiles of the target layer and the reference layer. The target layer is the stratigraphic interface that needs to be restored to its paleomorphology, and the reference layer is the isochronous interface located above or below the target layer, with continuous seismic reflection and less fault faulting than the target layer.

[0048] Specifically, the process of calibrating 3D seismic data using well logging data is as follows: First, wells with complete acoustic velocity (DT) and density (RHOB) curves within the study area are selected. The reflection coefficient sequence is calculated using acoustic velocity and density, and a seismic wavelet with the same dominant frequency as the seismic data is extracted or selected. The reflection coefficients and the wavelet are convolved to create a synthetic seismic record. Second, the waveform of the synthetic seismic record is compared with that of the well-side seismic trace. By adjusting the time-depth relationship, wavelet phase, or overall time shift, the reflection wave characteristics of the synthetic record are optimally matched with the main phase axis of the well-side seismic trace. Finally, based on the matching results, the positions of the reflection phase axes corresponding to the target layer and reference layer on the seismic profile and their two-way travel time are determined, thus completing the accurate calibration from well depth to seismic time.

[0049] Two-way travel time (TWT) refers to the total time it takes for a seismic wave to travel from its source to the underground stratum interface, be reflected, and return to the surface to be received by a geophone.

[0050] S202. Convert the two-way travel time into depth values ​​through time-depth conversion to obtain the target layer depth and the reference layer depth.

[0051] S203. Subtract the target layer depth from the reference layer depth to obtain the residual thickness, and use the residual thickness as the initial paleomorphology.

[0052] In some embodiments of the present invention, to execute steps S201 to S203, the three-dimensional seismic data volume, well logging curve data, well location coordinates, and geological stratification data of the study area are first loaded into seismic interpretation software (such as Petrel or Landmark) to establish a three-dimensional seismic study area. This study area provides a unified spatial coordinate system and data management environment for all data and serves as the basic framework for subsequent layer tracing, fault delineation, time-depth conversion, and thickness calculation. After the study area is established, the well-seismic calibration in S201, the time-depth conversion in S202, and the residual thickness calculation in S203 are then performed, thereby directly applying the depth difference between the target layer and the reference layer to the grid surface calculation of the study area to generate an initial paleogeographic map.

[0053] In some embodiments of the present invention, the porosity data includes the original porosity and the current porosity, then the compaction coefficient is:

[0054] In the formula, This is the compaction coefficient; Original porosity; This represents the current porosity.

[0055] Specifically, the relationship between the decompacted paleothite thickness and the residual thickness is as follows:

[0056] In the formula, To reduce the compaction of ancient thickness; This is the residual thickness; This refers to the burial depth.

[0057] Based on the relationship between the decompacted paleothickness and the residual thickness, the decompacted paleothickness can be determined based on the residual thickness.

[0058] During the burial process, the pressure from the overlying strata reduces porosity and compresses volume, resulting in a significantly smaller observed residual thickness compared to the original thickness at the time of deposition. Without correction, directly using the residual thickness to calculate paleotopography would severely underestimate the amplitude of paleotopographic undulations, especially in deeply buried areas or strata with high clay content, where the compaction effect is more pronounced. This invention restores the original sedimentary thickness through decompaction correction, accurately reflecting the topographic morphology at the time of sediment deposition. This provides an accurate thickness benchmark for subsequent paleowater depth correction, erosion restoration, and fault displacement reconstruction, thereby improving the reliability and quantification of paleotopographic reconstruction.

[0059] Because strata in different tectonic locations (such as uplifted and depressed areas) and different sedimentary facies (such as sandstone and mudstone facies) exhibit significant differences in burial history, rock composition, and compaction patterns, using the same compaction coefficient for correction across the entire study area can lead to overcorrection of uplifted areas, undercorrection of depressed areas, or distortion in the recovery of sandstone and mudstone thickness. Consequently, the paleogeographic reconstruction results may fail to accurately reflect the original sedimentary topography.

[0060] To solve the above-mentioned technical problems, in some embodiments of the present invention, before step S102, the following step is further included: Based on the initial paleogeographic tectonic zoning and sedimentary facies zones of well logging data, the study area is divided into multiple zones.

[0061] It should be noted that the tectonic location and sedimentary facies zone of each zone should be basically consistent to ensure the geological rationality of compaction correction.

[0062] Then step S102 includes: Typical logging data were selected from each zone, and the compaction coefficient of each zone was determined based on the porosity data and burial depth of the typical logging data.

[0063] This invention divides the study area into multiple zones based on the initial paleogeographic zoning and sedimentary facies zones of well logging data. Within each zone, well logging data from typical wells are selected to determine the independent compaction coefficient. This effectively eliminates the influence of tectonic location and lithological combination on compaction patterns, making the thickness restoration in each zone more consistent with actual geological conditions. This achieves local refinement of compaction correction, thereby significantly improving the accuracy and reliability of paleogeographic restoration within the study area.

[0064] In some embodiments of the present invention, such as Figure 3 As shown, step S103, determining the absolute paleowater depth based on the uranium content in the well logging data, includes: S301. Determine the relative paleodepth based on the uranium content and the constructed correlation model between uranium content and relative paleodepth; S302. Correct the relative paleodepth based on the maximum paleodepth of the study area to obtain the absolute paleodepth.

[0065] Specifically, the absolute depth of the ancient waters is:

[0066]

[0067] In the formula, It is an absolutely ancient and deep place; It is relatively deep in ancient waters; The maximum absolute actual ancient water depth; This represents the maximum relative actual water depth. The uranium content at the i-th sampling point of the target layer, predicted based on well logging data; This represents the total number of samples taken from the target layer.

[0068] It should be noted that the reason for correcting the relative paleodepth based on the maximum paleodepth is that the relative depth index calculated by the correlation model between uranium content and relative paleodepth is only a dimensionless index. This index only reflects the relative relationship of water depth between different locations and cannot directly provide a depth value with practical geological significance. Therefore, by mapping the relative depth index proportionally to the range from zero to the maximum absolute actual paleodepth, the relative depth can be converted into an absolute paleodepth, thus meeting the quantitative calculation requirement of subtracting water depth from decompacted thickness to obtain the true sedimentary topography.

[0069] The above embodiments are feasible only if the uranium content at each sampling point is obtained. However, in practical applications, there are situations where the uranium content cannot be directly obtained. To accurately determine the absolute paleodepth in such cases, in some embodiments of the present invention, such as... Figure 4 As shown, before step S103, the procedure further includes: S401. Establish a linear regression model between natural gamma logging values ​​and uranium content. The independent variable of the linear regression model is the natural gamma logging value, and the dependent variable is the uranium content.

[0070] Specifically, the linear regression model is as follows:

[0071] In the formula, , These are the linear regression coefficients; Let be the natural gamma logging value of the i-th sampling point.

[0072] S402. Extract the measured natural gamma values ​​from the well logging data, and determine the uranium content based on the measured natural gamma values ​​and the linear regression model.

[0073] This invention establishes a linear regression model characterizing natural gamma-ray logging values ​​and uranium content. This model allows for the determination of uranium content from natural gamma-ray logging values ​​in well logging data, even when the uranium content is unknown. This provides another method for determining absolute paleowater depth, thereby improving the success rate and applicability of paleogeographic reconstruction.

[0074] In real-world scenarios, not all faults within the study area are syn-depositional faults. Some faults formed or became active after the target layer was deposited, and therefore had no impact on paleomorphology; others exhibited extremely weak activity, causing negligible displacement. Indiscriminately performing fault removal reconstruction on all faults would not only increase unnecessary computation but also potentially introduce artificial artifacts, incorrectly misclassifying later-developed or weakly faulted faults as part of the original paleomorphological topography, thus reducing the accuracy of the reconstruction results.

[0075] To solve the above-mentioned technical problems, in some embodiments of the present invention, before step S105, the following step is further included: Determine the growth index of each fault within the study area and determine whether the growth index is greater than the preset index value; the growth index is the ratio of the thickness of the hanging wall to the thickness of the wall.

[0076] The preset index value can be set or adjusted according to the actual application scenario, and no specific limitation is made here.

[0077] Specifically, the thickness of the footwall and hanging wall refers to the vertical thickness of the strata within the target layer, with the fault plane as the boundary. Specifically: the footwall thickness is the vertical distance from the top surface of the reference layer in the footwall to the top surface of the target layer, and the hanging wall thickness is the vertical distance within the corresponding segment of the hanging wall. A larger growth index indicates stronger fault activity.

[0078] The hanging wall will then slide backward along the fault plane until the hanging wall reference layer and the footwall reference layer are joined, including: When the growth index of the fault exceeds the preset index value, the hanging wall of the fault is slid in the opposite direction along the fault plane until the reference layer of the hanging wall and the reference layer of the footwall are spliced ​​together.

[0079] The embodiments of the present invention calculate the growth index of each fault and compare it with the preset index value. This not only eliminates the interference of later non-depositional faults on paleogeographic reconstruction, but also removes faults with weak activity and negligible impact on paleotopography. This improves calculation efficiency while ensuring reconstruction accuracy, making fault removal more targeted and geologically reasonable.

[0080] To verify the effectiveness of the embodiments of the present invention, such as Figure 5 and Figure 6 As shown, Figure 5 This is an ancient landform that has not undergone fault removal treatment. Figure 6 The paleolandform after fault removal treatment Figure 5 and Figure 6 The colors in the text represent the relative elevation of ancient landforms. Red indicates higher ancient landforms, while blue or cool colors indicate lower ancient landforms. The color gradient reflects the changing trend of topographic relief. Figure 5 and Figure 6 The English and letter labels in the text refer to the names of the wells within the study area. Figure 5 and Figure 6 It can be seen that before the fault removal process, there were multiple faults in the ancient landform. After the fault removal process, the faults were eliminated, which verifies the effectiveness of the embodiments of the present invention.

[0081] In summary, the paleogeographic restoration method proposed in this invention, through a progressive processing flow of initial paleogeographic construction, compaction correction, water depth deduction, erosion restoration, and fault removal restoration, solves several technical challenges in traditional paleogeographic restoration methods, such as neglecting compaction effects, water depth interference, erosion loss, and the influence of fault activity. Furthermore, each step of the processing in this invention has clearly defined data inputs and quantifiable parameters, eliminating reliance on human intervention and significantly improving the accuracy, objectivity, and repeatability of paleogeographic restoration. This provides reliable technical support for characterizing sedimentary systems in complex tectonic zones, determining provenance orientation, and optimizing oil and gas exploration targets.

[0082] On the other hand, embodiments of the present invention also provide a paleomorphological restoration device, such as... Figure 7 As shown, the paleomorphological restoration device 700 includes: Initial paleogeographic construction unit 701 is used to acquire 3D seismic data and well logging data of the study area, and to construct the initial paleogeographic features based on the 3D seismic data and well logging data. The compaction correction unit 702 is used to determine the compaction coefficient based on the porosity data and burial depth in the well logging data, and to use the compaction coefficient to perform compaction correction on the residual thickness of the initial paleomorphology to obtain the decompacted paleothickness. The paleowater depth subtraction unit 703 is used to determine the absolute paleowater depth based on the uranium content in well logging data and to subtract the absolute paleowater depth from the decompacted paleothickness to obtain the paleotopography of the sediment surface. The erosion restoration unit 704 is used to identify unconformities based on three-dimensional seismic data, determine uneroded and eroded areas based on unconformities, construct a trend model using the stratigraphic thickness variation trend of uneroded areas, determine the erosion thickness of eroded areas based on the trend model, and superimpose the erosion thickness onto the paleotopography of sediment surfaces to obtain the complete paleotopography after erosion restoration. The fault removal unit 705 is used to slide the hanging wall along the fault plane in the opposite direction until the hanging wall reference layer and the footwall reference layer are spliced ​​together, and to fill the data gaps at the fault by trend interpolation to obtain the target paleomorphology after the fault is removed.

[0083] The paleomorphological restoration device 700 provided in the above embodiments can realize the technical solutions described in the above paleomorphological restoration method embodiments. The specific implementation principles of each module or unit can be found in the corresponding content in the above paleomorphological restoration method embodiments, and will not be repeated here.

[0084] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0085] The present invention has provided a detailed description of a method and apparatus for ancient landform restoration. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will know that there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for ancient landform restoration, characterized in that, include: Acquire 3D seismic data and well logging data of the study area, and construct an initial paleogeomorphology based on the 3D seismic data and the well logging data; The compaction coefficient is determined based on the porosity data and burial depth in the well logging data, and the compaction coefficient is used to correct the residual thickness of the initial paleomorphology to obtain the decompacted paleothickness. The absolute paleowater depth is determined based on the uranium content in the well logging data, and the absolute paleowater depth is subtracted from the decompacted paleothickness to obtain the paleotopography of the sediment surface. Based on the three-dimensional seismic data, unconformities are identified, and uneroded and eroded areas are determined according to the unconformities. A trend model is constructed using the stratigraphic thickness variation trend of the uneroded areas, and the erosion thickness of the eroded areas is determined based on the trend model. The erosion thickness is then superimposed onto the paleotopography of the sediment surface to obtain the complete paleotopography after erosion restoration. Using the selected reference layer as the baseline, the hanging wall of the fault is slid in the opposite direction along the fault plane until the reference layer of the hanging wall and the reference layer of the footwall are spliced ​​together. Trend interpolation is performed to fill the data gaps at the fault to obtain the target paleomorphology after removing the influence of the fault.

2. The paleomorphological restoration method according to claim 1, characterized in that, The construction of the initial paleomorphology based on the three-dimensional seismic data and the well logging data includes: The well logging data is used to calibrate the three-dimensional seismic data to determine the two-way travel time on the seismic profiles of the target layer and the reference layer; the target layer is the stratigraphic interface that needs to be restored to its paleomorphology, and the reference layer is the isochronous interface located above or below the target layer, with continuous seismic reflections and less fault faulting than the target layer. The two-way travel time is converted into depth values ​​through time-depth conversion to obtain the target layer depth and the reference layer depth. The residual thickness is obtained by subtracting the target layer depth from the reference layer depth, and the residual thickness is used as the initial paleomorphology.

3. The paleomorphological restoration method according to claim 1, characterized in that, The porosity data includes the original porosity and the current porosity, then the compaction coefficient is: In the formula, This is the compaction coefficient; Original porosity; This represents the current porosity.

4. The paleomorphological restoration method according to claim 3, characterized in that, The relationship between the decompacted paleothickness and the residual thickness is as follows: In the formula, To reduce the compaction of ancient thickness; This is the residual thickness; This refers to the burial depth.

5. The method for paleomorphological restoration according to claim 1, characterized in that, Before determining the compaction coefficient based on the porosity data in the well logging data, the method further includes: Based on the tectonic zoning of the initial paleogeography and the sedimentary facies zones of the well logging data, the study area is divided into multiple zones; The determination of the compaction coefficient based on the porosity data in the well logging data includes: Typical logging data are selected from each of the zones, and the compaction coefficient of each zone is determined based on the porosity data and burial depth of the typical logging data.

6. The paleomorphological restoration method according to claim 2, characterized in that, The determination of absolute paleowater depth based on the uranium content in the well logging data includes: The relative paleowater depth is determined based on the uranium content and the constructed correlation model between uranium content and relative paleowater depth. The relative paleodepth is corrected based on the maximum paleodepth of the study area to obtain the absolute paleodepth.

7. The paleomorphological restoration method according to claim 6, characterized in that, The absolute paleowater depth is: In the formula, It is an absolutely ancient and deep place; It is relatively deep in ancient waters; The maximum absolute actual ancient water depth; This represents the maximum relative actual water depth. The uranium content at the i-th sampling point of the target layer, predicted based on well logging data; This represents the total number of samples taken from the target layer.

8. The method for paleomorphological restoration according to claim 1, characterized in that, Before determining the absolute paleowater depth based on the uranium content in the well logging data, the method further includes: A linear regression model is established between the natural gamma logging value and the uranium content, where the independent variable of the linear regression model is the natural gamma logging value and the dependent variable is the uranium content. The measured natural gamma values ​​are extracted from the well logging data, and the uranium content is determined based on the measured natural gamma values ​​and the linear regression model.

9. The method for paleomorphological restoration according to claim 1, characterized in that, Before sliding the hanging wall along the fault plane in the opposite direction until the hanging wall reference layer and the footwall reference layer are joined, the following steps are also included: Determine the growth index of each fault within the study area and determine whether the growth index is greater than a preset index value; the growth index is the ratio of the wall thickness to the hanging wall thickness of the fault. The step of sliding the hanging wall along the fault plane in the opposite direction until the hanging wall reference layer and the footwall reference layer are joined includes: When the growth index of the fault exceeds the preset index value, the hanging wall of the fault is slid in the opposite direction along the fault plane until the reference layer of the hanging wall and the reference layer of the footwall are spliced ​​together.

10. A device for restoring ancient landforms, characterized in that, include: An initial paleogeographic construction unit is used to acquire three-dimensional seismic data and well logging data of the study area, and to construct an initial paleogeographic feature based on the three-dimensional seismic data and the well logging data. The compaction correction unit is used to determine the compaction coefficient based on the porosity data and burial depth in the well logging data, and to use the compaction coefficient to perform compaction correction on the residual thickness of the initial paleomorphology to obtain the decompacted paleothickness. The paleowater depth subtraction unit is used to determine the absolute paleowater depth based on the uranium content in the well logging data, and to subtract the absolute paleowater depth from the decompacted paleothickness to obtain the paleotopography of the sediment surface. The erosion restoration unit is used to identify unconformities based on the three-dimensional seismic data, determine uneroded areas and eroded areas based on the unconformities, construct a trend model using the stratigraphic thickness variation trend of the uneroded areas, determine the erosion thickness of the eroded areas based on the trend model, and superimpose the erosion thickness onto the paleotopography of the sediment surface to obtain the complete paleotopography after erosion restoration. The fault removal unit is used to slide the hanging wall along the fault plane in the opposite direction until the hanging wall reference layer and the footwall reference layer are spliced ​​together. The data gaps at the fault are filled by trend interpolation to obtain the target paleomorphology after the fault is removed.

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