Method for restoring original ancient floor plan

Abstract

The application discloses a method for recovering original ancient bottom shape, and comprises the following steps: obtaining the seismic reflection time difference maps of two target strata by layer interpretation; multiplying the seismic reflection time difference maps by velocity to obtain the stratum thickness after compaction; then, calculating the compaction rate of each well, and drawing the plane distribution map of the comprehensive compaction rate of the strata in the research area; then, multiplying the stratum thickness distribution map by the comprehensive compaction rate to obtain the original distribution characteristic map before compaction, and the ancient bottom shape map can be obtained through stereoscopic display. The application adopts the well-seismic combination technology, comprehensively considers multiple factors influencing the recovery of the ancient bottom shape, and systematically proposes an ancient bottom shape recovery method based on three-dimensional seismic constraint and single-well decompaction correction technology.

Description

Technical Field

[0001] This invention belongs to the technical field of ancient landform restoration methods, and relates to a method for restoring the original ancient landform. Background Technology

[0002] Commonly used methods for paleobottom reconstruction include: impression method, geophysical method, sedimentological method, residual thickness method, sequence stratigraphy, layer flattening method, and computer simulation method. Each method has its own applicable conditions and advantages, but also certain shortcomings, which directly or indirectly affect the accuracy of paleobottom reconstruction. Therefore, paleobottom reconstructions using relatively limited data and methods are insufficient to meet the needs of modern oil and gas exploration.

[0003] (1) Imprinting method

[0004] The imprint method is a widely used method for semi-quantitative prediction of paleogeography in this area. Its principle is based on the thickness of the overlying marker layer to the erosion surface, using mirror relationships to reflect the paleogeographic pattern of the erosion surface. The detailed steps are as follows: The overlying strata with filling and erosion interfaces are flattened and used as a reference surface. The thickness from the erosion interface to this reference surface is calculated, and a plane contour map is created. Then, the paleogeography of the study area is further subdivided according to the standards for karst paleogeography classification. The advantage of this method is that it can be combined with existing well data to further improve the accuracy of karst geomorphological unit subdivision and reconstruction. The disadvantage is that it is difficult to determine the true thickness between the erosion interface and the reference surface.

[0005] (2) Sedimentological methods

[0006] Sedimentary methods utilize various basic geological maps, combined with paleocurrent analysis, paleotectonic development characteristics, genetic analysis, calculation of topographic slope, and consideration of differences in sedimentation rates among various sediments, to qualitatively reconstruct karst paleomorphological features and reproduce the evolutionary history of karst paleomorphology on a temporal scale. It is important to note that the compaction differences among various lithologies should be considered; using the original sedimentary thickness will yield more accurate calculation results. The advantages of using sedimentary methods to reconstruct karst paleomorphology are its simplicity and ease of understanding, and its ability to roughly reconstruct karst paleomorphological patterns. The disadvantages are that the accuracy of paleomorphological reconstruction is not high under various influencing factors, and it requires a large number of basic maps.

[0007] (3) Residual thickness method

[0008] The residual thickness method is similar in principle to the impression method but also differs. The difference lies in that this method requires finding a reference surface below the isochronous interface and flattening it. The thickness of the overlying strata after flattening reflects the paleomorphological features of that time. A paleomorphological map is then compiled, with thinner sedimentary layers indicating depressions and thicker layers indicating highlands. The advantages of this method are its reliability, intuitiveness, and ability to accurately reflect karst paleomorphology. The disadvantage is that it does not consider the influence of erosion differences and tectonic topography on sedimentary thickness, leading to significant errors in the final map.

[0009] (4) Sequence stratigraphy

[0010] Sequence stratigraphy emphasizes establishing and flattening the isochronous sequence framework of the overlying strata, utilizing the isochronism of sequence boundaries to reflect paleogeographic morphology. The detailed steps are as follows: Sedimentological methods are used to analyze the development and evolution of the overlying strata of the weathering crust to determine the time of filling and completion; benchmark cycles are then correlated with the maximum floodplain and the base level to reflect the paleogeographic morphology before deposition. The advantage of sequence stratigraphy is the relatively strong isochronism of the overlying base level, leading to more reasonable research results. The disadvantage is the difficulty in selecting the base level. Summary of the Invention

[0011] The purpose of this invention is to provide a method for restoring the original ancient landform, which solves the problem of low accuracy in the restoration of ancient landforms in existing valley landform restoration methods.

[0012] The technical solution adopted in this invention is a method for restoring the original paleobottom shape. Based on seismic data and well data, it adopts a well-seismic combination technique and comprehensively considers various factors affecting the restoration of paleobottom shape. A method for restoring paleobottom shape based on three-dimensional seismic constraints and single-well decompaction correction technology is systematically proposed.

[0013] The invention is further characterized in that,

[0014] The specific steps of the method for restoring the original ancient base shape according to the present invention are as follows:

[0015] Step 1: Basic Data Collection and Analysis: Collect geological background data, well logging data, well logging lithology descriptions, seismic results data, well cores and thin sections, and stratigraphic data, and then analyze the data.

[0016] Step 2: Based on geological background data, select framework wells, combine core samples and well logging characteristic curves to find regional marker layers, connect them horizontally and vertically to form a well-connected profile, and trace the strata based on the verified strata data and seismic interpretation data to establish a stratigraphic framework profile.

[0017] Step 3: Conduct key layer division and comparison of completed wells in the area, calculate sand ratio and mud ratio, calculate compaction rate, and then obtain the thickness of the restored formation.

[0018] Step 4: Well-seismic integration: Establish seismic isochronous interfaces and marker layers. Establish seismic facies sequence interfaces in the region by calibrating known well layers. These interfaces are stable and continuously traceable throughout the region and have obvious waveform reflection characteristics. Through the reflection interfaces of different layers, the formation thickness data between different layers can be calculated. The original thickness of the formation can be restored by decompaction correction.

[0019] Step 5: By combining the known well stratum thickness data and the regional seismic reflection layer stratum thickness data, and verifying them with each other, draw the current stratum thickness contour map. Then, through decompaction correction, restore the original stratum thickness, and thus obtain the original distribution characteristic map of the paleobottom shape during this period.

[0020] Step 6: Refine and color the map. Refine and label each stratigraphic thickness unit according to the legend, and complete the corresponding cartographic elements to obtain the restored original paleotopic map.

[0021] The specific steps for establishing the stratigraphic framework in step 2 are as follows: First, select the skeleton wells, combine the core and logging characteristic curves to find the regional marker layers, and connect them horizontally and vertically to form a well-connected profile. Based on the verified layered data and seismic interpretation data, trace the strata and establish the stratigraphic framework profile.

[0022] In step 3, the compaction rate of the target formation in the known well is obtained, and then the original formation thickness is obtained: First, the known sand-to-soil ratio and mud-to-soil ratio are statistically analyzed, the compaction rate is calculated, and then the restored formation thickness is obtained.

[0023] Based on the compaction rate K = K 砂 *Φ 砂 +K 泥 *Φ 泥 After compaction correction, the thickness of the target formation in the known well, H0 = H + H*K, is obtained, and the paleobottom shape distribution pattern is then restored.

[0024] In the formula: K: overall rock compaction rate;

[0025] K 砂 Sandstone compaction rate, experimental value taken as 0.2;

[0026] K 泥 The compaction rate of mudstone was 0.6 in the test.

[0027] Φ 砂 :Sand ratio;

[0028] Φ 泥 : Muddy ground ratio;

[0029] H0: Original stratum thickness before compaction;

[0030] H: Current thickness of the geological strata;

[0031] Different lithologies in the strata were corrected to obtain the original stratum thickness H0 before compaction.

[0032] In step 4, the thickness of the strata at different seismic reflection interfaces is determined. Based on the different seismic reflection characteristics of different strata, seismic isochronous interfaces and marker layers are established. Then, using known well stratigraphic positions, the stratigraphic division is further refined to establish regionally stable and continuously traceable seismic sequence interfaces. The stratigraphic reflection interfaces are selected using seismic wave characteristics, and the stratum thickness H = Δt0*V is calculated using the seismic wave reflection velocity and time at the two interfaces. Since Δt0 = Tp1 - Tp2, the original stratum thickness H0 = H + H*K is obtained after decompaction correction. 砂 *Φ 砂 +H*K 泥 *Φ 泥 Further, the distribution characteristics of the ancient base shape were obtained;

[0033] In the formula:

[0034] H0: Original stratum thickness before compaction;

[0035] Δt0: Seismic reflection time difference;

[0036] V: Seismic inter-layer reflection velocity;

[0037] Tp1: Seismic reflection target layer 1;

[0038] Tp2: Seismic reflection target layer 2.

[0039] Step 5 combines known well stratum thickness data and regional seismic reflection stratum thickness data to cross-reference them and draw a current stratum thickness contour map. Then, through decompaction correction, the original stratum thickness is restored, thereby obtaining the original distribution characteristics map of the paleobottom shape during this period.

[0040] The beneficial effects of this invention are:

[0041] Based on seismic data and known well data, this invention systematically proposes a method for decompaction and restoration of the original paleobottom shape using a combined well-seismic approach. This method effectively utilizes well-seismic data to quantitatively restore the paleobottom shape, which not only improves the accuracy of paleobottom shape restoration but also provides accurate data on sand body distribution, thereby enhancing the economic benefits of exploration. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below:

[0043] Figure 1 This is a flowchart of the ancient base shape restoration method of the present invention;

[0044] Figure 2 This is a schematic diagram of the ancient base shape restoration process of the present invention; Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0046] Example 1

[0047] Based on seismic and well data, a method for restoring the original paleobottom shape is proposed. This method combines well-seismic technology and considers various factors affecting the restoration of the paleobottom shape. It systematically proposes a method for paleobottom shape restoration based on three-dimensional seismic constraints and single-well decompaction correction technology.

[0048] Example 2

[0049] The difference from Example 1 is that,

[0050] The method for restoring the original ancient base shape according to the present invention is as follows: Figure 1-2 As shown, the specific operation steps are as follows:

[0051] Step 1: Basic Data Collection and Analysis: Collect geological background data, well logging data, well logging lithology descriptions, seismic results data, well cores and thin sections, and stratigraphic data, and then analyze the data.

[0052] Step 2: Based on geological background data, select framework wells, combine core samples and well logging characteristic curves to find regional marker layers, connect them horizontally and vertically to form a well-connected profile, and trace the strata based on the verified strata data and seismic interpretation data to establish a stratigraphic framework profile.

[0053] Step 3: Conduct key layer division and comparison of completed wells in the area, calculate sand ratio and mud ratio, calculate compaction rate, and then obtain the thickness of the restored formation.

[0054] Step 4: Well-seismic integration: Establish seismic isochronous interfaces and marker layers. Establish seismic facies sequence interfaces in the region by calibrating known well layers. These interfaces are stable and continuously traceable throughout the region and have obvious waveform reflection characteristics. Through the reflection interfaces of different layers, the formation thickness data between different layers can be calculated. The original thickness of the formation can be restored by decompaction correction.

[0055] Step 5: By combining the known well stratum thickness data and the regional seismic reflection layer stratum thickness data, and verifying them with each other, draw the current stratum thickness contour map. Then, through decompaction correction, restore the original stratum thickness, and thus obtain the original distribution characteristic map of the paleobottom shape during this period.

[0056] Step 6: Refine and color the map. Refine and label each stratigraphic thickness unit according to the legend, and complete the corresponding cartographic elements to obtain the restored original paleotopic map.

[0057] The specific steps for establishing the stratigraphic framework in step 2 are as follows: First, select the skeleton wells, combine the core and logging characteristic curves to find the regional marker layers, and connect them horizontally and vertically to form a well-connected profile. Based on the verified layered data and seismic interpretation data, trace the strata and establish the stratigraphic framework profile.

[0058] In step 3, the compaction rate of the target formation in the known well is obtained, and then the original formation thickness is obtained: First, the sand-to-soil ratio and mud-to-soil ratio of the known well are statistically analyzed, the compaction rate is calculated, and then the formation thickness after restoration is obtained.

[0059] Based on the compaction rate K = K 砂 *Φ 砂 +K 泥 *Φ 泥 After compaction correction, the thickness of the target formation in the known well, H0 = H + H*K, is obtained, and the paleobottom shape distribution pattern is then restored.

[0060] In the formula: K: overall rock compaction rate;

[0061] K 砂 Sandstone compaction rate, experimental value taken as 0.2;

[0062] K 泥 The compaction rate of mudstone was 0.6 in the test.

[0063] Φ 砂 :Sand ratio;

[0064] Φ 泥 : Muddy ground ratio;

[0065] H0: Original stratum thickness before compaction;

[0066] H: Current thickness of the geological strata;

[0067] Different lithologies in the strata were corrected to obtain the original stratum thickness H0 before compaction.

[0068] In step 4, the thickness of the strata at different seismic reflection interfaces is determined. Based on the different seismic reflection characteristics of different strata, seismic isochronous interfaces and marker layers are established. Then, using known well stratigraphic positions, the stratigraphic division is further refined to establish regionally stable and continuously traceable seismic sequence interfaces. The stratigraphic reflection interfaces are selected using seismic wave characteristics, and the stratum thickness H = Δt0*V is calculated using the seismic wave reflection velocity and time at the two interfaces. Since Δt0 = Tp1 - Tp2, the original stratum thickness H0 = H + H*K is obtained after decompaction correction. 砂 *Φ 砂 +H*K 泥 *Φ 泥 Further, the distribution characteristics of the ancient base shape were obtained;

[0069] In the formula:

[0070] H0: Original stratum thickness before compaction;

[0071] Δt0: Seismic reflection time difference;

[0072] V: Seismic inter-layer reflection velocity;

[0073] Tp1: Seismic reflection target layer 1;

[0074] Tp2: Seismic reflection target layer 2.

[0075] Step 5 combines known well stratum thickness data and regional seismic reflection stratum thickness data to cross-reference them and draw a current stratum thickness contour map. Then, through decompaction correction, the original stratum thickness is restored, thereby obtaining the original distribution characteristics map of the paleobottom shape during this period.

[0076] Example 3

[0077] This seismic data interpretation involves five three-dimensional blocks totaling 6516 km. 2 The two-dimensional area spans 2520 km, with key strata in the five three-dimensional blocks denoted as Ttl, Tpq, TP8, TP9, and Tp, respectively. The interpretation density of the key strata in the three-dimensional area is 32*32, which lays a good foundation for the subsequent reconstruction of the paleobottom.

[0078] For the paleobase reconstruction of the first phase of the mountain, the interpretation of the two TP8 and TP9 layers, which are connected in two and three dimensions, was completed first. This was achieved by analyzing the seismic reflection time difference maps (Δt0) of the two target strata, TP8 and TP9. 山1 =Tp9-Tp8) plotted; then the seismic reflection time difference map Δt0 is multiplied by the seismic velocities between layers TP8 and TP9 to obtain the compacted stratum thickness ΔH. 山1 Then, by combining the results from the previously selected 40+ wells, the compaction rate K for each well was calculated. 山1 =Φsand 山1 *(1+K sand) 山1 )+Φmud 山1 *(1+K mud) 山1 The study area's overall compaction rate K was plotted. 山1 The planar distribution map, in which K sand 山1 This refers to the compaction ratio of sandstone, typically taken as 0.6, Kmud 山1 This refers to the compaction ratio of mudstone. Generally, for pure mudstone, it's taken as 0.6-0.7; in this calculation, it's taken as 0.6. (Φ sand) 山1 The percentage of sandstone content in the target formation of the target well, Φ mud 山1 This refers to the percentage of mudstone content in the target formation of the target well; then, the pre-compaction thickness ΔH0 of each well is calculated and restored.山1 Using ΔH0 山1 Correction ΔH 山1 The distribution map (planar distribution map) can be used to obtain the original strata ΔH0 before compaction. 山1 The thickness distribution map, displayed through gradient colors, can be used to obtain the ancient base shape map.

[0079] Example 4

[0080] For the reconstruction of the paleobase of Box 8, the first step was to interpret the two contiguous TP7 and TP8 layers using two- and three-dimensional stratigraphic interpretation. Then, the seismic reflection time difference map (Δt0) of the target strata was generated through this interpretation. 盒8 =Tp7-Tp8) plotted; then multiply the seismic reflection time difference map Δt0 by the velocity to obtain the compacted stratum thickness ΔH. 盒8 Then, by combining the results from the previously selected 40+ wells, the compaction rate K for each well was calculated. 盒8 =Φsand 盒8 *(1+K sand) 盒8 )+Φmud 盒8 *(1+K mud) 盒8 The study area's overall compaction rate K was plotted. 盒8 The planar distribution map, in which K sand 盒8 This refers to the compaction ratio of sandstone, typically taken as 0.6, Kmud 盒8 This refers to the compaction ratio of mudstone. Generally, for pure mudstone, it's taken as 0.6-0.7; in this calculation, it's taken as 0.6. (Φ sand) 盒8 The percentage of sandstone content in the target formation of the target well, Φ mud 山1 This refers to the percentage of mudstone content in the target formation of the target well; then the pre-compaction thickness ΔH0 of each well is calculated and restored. 盒8 Using ΔH0 盒8 Correction ΔH 盒8 The distribution map (planar distribution map) can be used to obtain the original strata ΔH0 before compaction. 盒8 The thickness distribution map, displayed through gradient colors, can be used to obtain the ancient base shape map.

[0081] This invention delineates the seismic reflection time difference map (Δt0 = Tpa - Tpb) of the target formation through stratigraphic interpretation; then, it multiplies the seismic reflection time difference map Δt0 by the velocity to obtain the compacted formation thickness ΔH; finally, it calculates the compaction rate K = Φ for each well. 砂 *(1+K 砂 )+Φ 泥 *(1+K 泥 ), and plotted a planar distribution map of the overall compaction rate K of the strata in the study area, where K 砂 This refers to the compaction ratio of sandstone, typically taken as 0.6, K. 泥 This refers to the compaction ratio of mudstone. Generally, for pure mudstone, this ratio is 0.6-0.7; in this calculation, it is 0.6. Φ 砂The percentage of sandstone content in the target formation of the target well, Φ 泥 The percentage of mudstone content in the target formation of the target well is used; then, by multiplying the ΔH distribution map by the comprehensive compaction rate K, the original ΔH0 thickness distribution map of the formation before compaction can be obtained, and the paleobottom shape map can be obtained by three-dimensional display.

Claims

1. A method for restoring the original ancient base shape, characterized in that, Based on seismic and well data, and employing a combined well-seismic approach, this paper systematically proposes a paleobottom reconstruction method based on 3D seismic constraints and single-well decompaction correction technology, taking into account various factors affecting paleobottom shape reconstruction. The specific operational steps are as follows: Step 1: Basic Data Collection and Analysis: Collect geological background data, well logging data, well logging lithology descriptions, seismic results data, well cores and thin sections, and stratigraphic data, and then analyze the data. Step 2: Based on geological background data, select framework wells, combine core samples and well logging characteristic curves to find regional marker layers, connect them horizontally and vertically to form a well-connected profile, and trace the strata based on the verified strata data and seismic interpretation data to establish a stratigraphic framework profile. Step 3: Conduct key stratigraphic division and comparison of completed wells within the area, statistically analyze the sand-soil ratio and mud-soil ratio, calculate the compaction rate, and then determine the restored formation thickness; details are as follows: To determine the compaction rate of the target formation in a known well, and then to determine the original formation thickness: First, statistically analyze the known sand-to-soil ratio and mud-to-soil ratio, calculate the compaction rate, and then determine the restored formation thickness. Based on the compaction rate K=K 砂 *Φ 砂 +K 泥 *Φ 泥 After compaction correction, the thickness of the target formation in the known well, H0 = H + H*K, is calculated, and the paleobottom shape distribution pattern is then restored. In the formula: K: overall rock compaction rate; K 砂 Sandstone compaction rate, the experimental value is 0.2; K 泥 The compaction rate of mudstone was taken as 0.6 in the test. Φ 砂 : sand ratio; Φ 泥 : Muddy ground ratio; H0: Original stratum thickness before compaction; H: Current thickness of the geological strata; The original stratum thickness H0 before compaction was obtained by correcting for different lithologies in the strata. Step 4: Well-seismic integration: Establish seismic isochronous interfaces and marker layers. Establish seismic facies sequence interfaces in the region by calibrating known well strata. These interfaces are stable and continuously traceable throughout the region and have obvious waveform reflection characteristics. By using the reflection interfaces of different strata, the formation thickness data between different strata are calculated, and the original thickness of the formation is restored by decompaction correction. Step 5: By combining the known well stratum thickness data and the regional seismic reflection layer stratum thickness data, and verifying them with each other, draw the current stratum thickness contour map. Then, through decompaction correction, restore the original stratum thickness, and thus obtain the original distribution characteristic map of the paleobottom shape during this period. Step 6: Refine and color the map. Refine and label each stratigraphic thickness unit according to the legend, and complete the corresponding cartographic elements to obtain the restored original paleotopic map.

2. The method for restoring the original ancient base shape according to claim 1, characterized in that, The specific steps for establishing the stratigraphic framework in step 2 are as follows: First, select the skeleton wells, and combine the core and logging characteristic curves to find the regional marker layers. Connect them horizontally and vertically to form a well-connected profile. Based on the verified stratification data and seismic interpretation data, trace the strata and establish the stratigraphic framework profile.

3. The method for restoring the original ancient base shape according to claim 1, characterized in that, In step 4, the thickness of the strata at different seismic reflection interfaces is determined. Based on the different seismic reflection characteristics of different strata, seismic isochronous interfaces and marker layers are established. Then, using known well stratigraphic positions, the stratigraphic division is further refined to establish regionally stable and continuously traceable seismic sequence interfaces. The stratigraphic reflection interfaces are selected using seismic wave characteristics, and the stratum thickness H = Δt0*V is calculated using the seismic wave reflection velocity and time at the two interfaces. Since Δt0 = Tp1 - Tp2, the original stratum thickness H0 = H + H*K is obtained after decompaction correction. 砂 *Φ 砂 +H*K 泥 *Φ 泥 Further, the distribution characteristics of the ancient base shape were obtained; In the formula: H0: Original stratum thickness before compaction; Δt0: Seismic reflection time difference; V: Seismic inter-layer reflection velocity; Tp1: Seismic reflection target layer 1; Tp2: Seismic reflection target layer 2.

4. The method for restoring the original ancient base shape according to claim 1, characterized in that, Step 5 combines known well stratum thickness data and regional seismic reflection stratum thickness data to cross-reference them and draw a current stratum thickness contour map. Then, through decompaction correction, the original stratum thickness is restored, thereby obtaining the original distribution characteristic map of the paleobottom shape during this period.

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