A method and device for fine three-dimensional micro-paleogeomorphology restoration

Abstract

The application discloses a fine three-dimensional micro-paleogeomorphology recovery method and device, and belongs to the technical field of oil and natural gas exploration. The method comprises the following steps: S1, calibrating a target layer of seismic data according to prestack time migration seismic data and a well logging curve, obtaining a stratum velocity v of the target layer, and calculating a plumb thickness h of the target layer; S2, extracting the plumb thickness of the target layer at a reverse fault to obtain a plumb thickness h' of the target layer; S3, calculating a stratum dip angle θ of the target layer; and S4, calculating a true paleogeomorphology thickness k of the target layer by using a formula k=h'x cos θ. The fine three-dimensional micro-paleogeomorphology recovery method and device can directly use prestack time migration data, does not need to convert the prestack time migration data into depth domain seismic data, greatly simplifies an operation process, repeatedly calculates abnormal values by extracting the plumb thickness of the target layer at the reverse fault, solves the problem of repeated calculation of the stratum at the reverse fault, simultaneously calculates the stratum dip angle, and greatly improves the paleogeomorphology recovery precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploration, and relates to a paleo-landform restoration method, in particular to a fine three-dimensional micro paleo-landform restoration method and device. Background Art

[0002] Paleomorphology is an important reference for reservoir sedimentary evolution, especially for carbonate rocks, where high-energy shoals are clearly controlled by paleomorphology. Paleomorphology restoration studies the concavity and convexity indicated by depth contours at a specific interface during a specific period. Currently, paleomorphology restoration techniques can be broadly categorized into two methods: the residual thickness method and the impression method.

[0003] The residual thickness method, which measures the thickness of strata remaining over long periods of geological history, is the most direct method for reconstructing ancient landforms. The residual thickness method relies on relatively uniform strata that have not undergone significant uplift or erosion since deposition. Finding basement isochronal surfaces is crucial for reconstructing ancient landforms using the residual thickness method.

[0004] The impression method is a reverse measurement method. Because the weathering crust is an uneven, undulating surface, the undulating layers are gradually filled in with the continuous deposition of overlying strata. Measuring the thickness from the top of the weathering crust to the overlying marker layer allows one to infer the thickness of the residual weathering crust. The impression method presupposes the existence of a filled-in surface and the absence of significant uplift and erosion. Finding the top marker layer is key to reconstructing paleogeography using the impression method.

[0005] Whether using the residual thickness method or the impression method, the most sophisticated paleogeomorphological reconstruction devices are typically based on prestack time-migrated 3D seismic data. After extracting the top and bottom interface events of a stratum based on prestack time-migrated 3D seismic data, the top and bottom interfaces are subtracted, and then time-depth conversion is performed to produce a paleogeomorphological map of the stratum.

[0006] However, on the one hand, in areas where reverse faults develop, strata often repeat, and based on three-dimensional seismic data, event axis tracking can only correspond to one depth value at the same coordinate point, which results in repeated calculation of the stratum thickness between the upper and lower walls of the reverse fault, and ultimately fails to truly reflect the paleogeomorphic characteristics of the strata. This error is especially prominent when the stratum thickness to be restored is less than the fault throw.

[0007] On the other hand, the existing paleogeomorphic restoration methods do not take into account the inclination of the current structure of the stratum. When the inclination of the stratum is large, the subtraction of the top and bottom phase axes results in the vertical thickness of the current lithologic interface, rather than the normal thickness of the stratum required for paleogeomorphic restoration.

[0008] There is currently no effective solution to the above two problems. Summary of the Invention

[0009] The purpose of the present invention is to provide a fine three-dimensional micro-paleotopography restoration method and device to solve the problem of inaccurate paleotopography restoration due to the existence of stratum repetition or stratum dip.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A fine three-dimensional micro-paleomorphology restoration method comprises the following steps:

[0012] S1. Based on the pre-stack time migration seismic data and well logging curves, calibrate the target layer of the seismic data, obtain the formation velocity v of the target layer, and calculate the plumb bob thickness h of the target layer;

[0013] S2. Evacuate the plumb bob thickness of the target layer at the reverse fault to obtain the plumb bob thickness h' of the target layer;

[0014] S3. Calculate the target layer's formation dip angle θ;

[0015] S4. Calculate the true paleo-relief thickness k of the target layer using the formula k = h' × cosθ.

[0016] As a limitation, in step S2, the plumb bob thickness of the target layer at the reverse fault is evacuated, and the evacuation range is Among them, (x1, y1) is the coordinate of the top breakpoint of the target layer, and (x2, y2) is the coordinate of the bottom breakpoint of the target layer.

[0017] As another limitation, the formula used to obtain the target layer dip angle θ in step S3 is:

[0018] Where ΔT is the time difference between the two seismic traces of the target layer; ΔX is the distance between the two seismic traces of the target layer; and v is the formation velocity of the target layer.

[0019] As a third limitation, step S1 specifically includes:

[0020] S11. Obtain pre-stack time migration seismic data and well log curves, create synthetic records using acoustic time difference curves, and calibrate the target layer of the seismic data;

[0021] S12. Tracking the top event T1 and the bottom event T2 of the target layer;

[0022] S13. Pick up the coordinates of the top breakpoint of the target layer (x1, y1) and the coordinates of the bottom breakpoint of the target layer (x2, y2);

[0023] S14. Based on the prestack time migration seismic data, obtain the target layer formation velocity v according to the well calibration;

[0024] S15. Using formula Calculate the plumb bob thickness h of the target layer, where T1 and T2 are the events of the top and bottom of the target layer respectively; v is the formation velocity of the target layer.

[0025] The present invention also provides a fine three-dimensional micro-paleomorphology restoration device, including a target layer calibration unit, an event tracking unit, a breakpoint identification unit, a formation velocity acquisition unit, a plumb bob thickness calculation unit, a reverse fault evacuation unit, a formation dip angle calculation unit, and a true paleomorphology thickness acquisition unit;

[0026] The target layer calibration unit is used to obtain pre-stack time migration seismic data and well logging curves, make synthetic records using acoustic wave time difference curves, and calibrate the target layer of the seismic data;

[0027] An event tracking unit is used to track the event T1 at the top of the target layer and the event T2 at the bottom of the target layer;

[0028] A breakpoint identification unit is used to pick up the coordinates of the top breakpoint of the target layer (x1, y1) and the coordinates of the bottom breakpoint of the target layer (x2, y2);

[0029] The formation velocity acquisition unit is used to obtain the formation velocity v of the target layer based on the pre-stack time migration seismic data and the well calibration;

[0030] Plumb bob thickness calculation unit, used to use the formula Calculate the plumb bob thickness h of the target layer, where T1 and T2 are the events of the top and bottom of the target layer respectively; v is the formation velocity of the target layer;

[0031] The hollowing unit at the reverse fault is used to hollow out the plumb bob thickness of the target layer at the reverse fault to obtain the plumb bob thickness h' of the target layer;

[0032] Formation dip calculation unit, used to use the formula Calculate the target layer formation dip angle θ, where ΔT is the time difference between two seismic traces of the same target layer; ΔX is the distance between two seismic traces of the same target layer; v is the formation velocity of the target layer;

[0033] The true paleo-landform thickness obtaining unit is used to calculate the true paleo-landform thickness k of the target layer using the formula k=h'×cosθ.

[0034] Due to the adoption of the above technical solution, the present invention has the following technical advancements compared with the prior art:

[0035] The present invention provides a fine three-dimensional micro-paleomorphology restoration method and device, which can directly use pre-stack time migration seismic data without converting it to depth domain seismic data, greatly simplifying the operation process. By repeatedly calculating the abnormal value of the plumb bob thickness of the target layer at the reverse fault, the problem of repeated calculation of the strata at the reverse fault is solved, and the stratum dip angle is obtained at the same time, which greatly improves the accuracy of paleomorphology restoration. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the principle of stratum vacuum interpolation at the reverse fault in Example 1, where Figure 1 a is the target layer before evacuation, and the shaded area is the area that needs to be evacuated; Figure 1 b is the interpolation of the vertical thickness of the target layer at the evacuated reverse fault after repeated calculation of abnormal values;

[0037] Figure 2 This is a schematic diagram of the principle of formation dip correction in Example 1, where Figure 2 a is the schematic diagram of the target layer before correcting the formation dip. Figure 2 b is the true paleo-geomorphic thickness of the target layer after correction of the stratigraphic dip;

[0038] Figure 3 This is a plan view of the target layer before the abnormal thickness at the reverse fault in Example 1 is evacuated;

[0039] Figure 4 This is a plan view of the target layer after the abnormal thickness at the reverse fault in Example 1 is evacuated;

[0040] Figure 5 This is the distribution diagram of the target layer formation dip correction coefficient in Example 1;

[0041] Figure 6 This is the residual thickness map of the target layer after the formation dip angle correction in Example 1. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below by way of specific examples. It should be understood that the described examples are only used to illustrate the present invention and are not intended to limit the present invention.

[0043] Example 1 A method for restoring fine three-dimensional micro-paleomorphology

[0044] This embodiment provides a fine three-dimensional micro-paleomorphology restoration method, which solves the problem of repeated calculation of strata at the reverse fault and the problem of strata dip angle. The principle diagram of strata extraction and interpolation at the reverse fault is shown in the figure. Figure 1 The principle diagram of formation dip correction is shown in Figure 2 As shown, this embodiment performs paleogeomorphological restoration on the Mao-2 subsection of a block in Sichuan, specifically including the following steps:

[0045] S1:

[0046] S11. Obtain pre-stack time migration seismic data and acoustic wave moveout curves, create a synthetic record using the acoustic wave moveout curves, and calibrate it to the target layer of the seismic data;

[0047] S12. Tracking the event T1 at the top of the target layer and the event T2 at the bottom of the target layer;

[0048] S13. Pick the breakpoint coordinates (x1, y1) of the top of the target layer and the breakpoint coordinates (x2, y2) of the bottom of the target layer;

[0049] S14. Based on the prestack time migration seismic data, obtain the formation velocity v of the target layer according to the well calibration;

[0050] S15. Using formula Calculate the vertical thickness h of the target layer,

[0051] Where, T1 and T2 are the events of the top and bottom of the target layer, respectively, in ms; v is the formation velocity of the target layer, in m / s;

[0052] S2: The repeated calculation abnormal value of the vertical thickness of the target layer at the reverse fault is evacuated. The evacuation range is like Figure 3 and Figure 4 As shown, interpolation is performed to obtain the plumb bob thickness h' of the target layer (interpolation only changes the plumb bob thickness at the fault, and does not change the plumb bob thickness of the original stratum).

[0053] Among them, (x1, y1) is the coordinate of the top breakpoint of the target layer, and (x2, y2) is the coordinate of the bottom breakpoint of the target layer;

[0054] S3: According to the formation velocity v of the target layer obtained in step S14, use the formula Calculate the target layer dip angle θ,

[0055] Where, ΔT is the time difference between two seismic traces in the same target layer, in ms; ΔX is the distance between two seismic traces in the same target layer, in meters;

[0056] S4: Calculate the target layer cosine cosθ according to the formation dip angle θ obtained in step S3, as Figure 5 As shown; According to the vertical thickness h' of the target layer obtained in step S2, the normal thickness k of the target layer is calculated using the formula k = h'×cosθ, which is the true paleo-geomorphological thickness k of the target layer, as shown Figure 6 shown.

[0057] Example 2: A fine three-dimensional micro-paleomorphology restoration device

[0058] This embodiment provides a fine three-dimensional micro-paleotopography restoration device, including a target layer calibration unit, an event tracking unit, a breakpoint identification unit, a formation velocity acquisition unit, a plumb bob thickness calculation unit, a reverse fault evacuation unit, a formation dip calculation unit, and a true paleotopography thickness acquisition unit;

[0059] The target layer calibration unit is used to obtain pre-stack time migration seismic data and well logging curves, make synthetic records using acoustic wave time difference curves, and calibrate the target layer of the seismic data;

[0060] An event tracking unit is used to track the event T1 at the top of the target layer and the event T2 at the bottom of the target layer;

[0061] A breakpoint identification unit is used to pick up the coordinates of the top breakpoint of the target layer (x1, y1) and the coordinates of the bottom breakpoint of the target layer (x2, y2);

[0062] The formation velocity acquisition unit is used to obtain the formation velocity v of the target layer based on the pre-stack time migration seismic data and the well calibration;

[0063] Plumb bob thickness calculation unit, used to use the formula Calculate the plumb bob thickness h of the target layer, where T1 and T2 are the events of the top and bottom of the target layer respectively; v is the formation velocity of the target layer;

[0064] The hollowing unit at the reverse fault is used to hollow out the plumb bob thickness of the target layer at the reverse fault to obtain the plumb bob thickness h' of the target layer;

[0065] Formation dip calculation unit, used to use the formula Calculate the target layer formation dip angle θ, where ΔT is the time difference between two seismic traces in the same reference layer; ΔX is the distance between two seismic traces in the same reference layer; v is the target layer formation velocity;

[0066] The true paleo-landform thickness obtaining unit is used to calculate the true paleo-landform thickness k of the target layer using the formula k=h'×cosθ.

Claims

1. A fine three-dimensional micro-paleomorphology restoration method, characterized in that: The following steps are involved: S1. Based on pre-stack time migration seismic data and well logging curves, calibrate the target layer of the seismic data, obtain the formation velocity v of the target layer, and calculate the vertical thickness h of the target layer; S2. The repeated calculation abnormal value of the vertical thickness of the target layer at the reverse fault is emptied. The evacuation range is The vertical thickness h' of the target layer is obtained by interpolation. Interpolation only changes the vertical thickness at the fault and does not change the vertical thickness of the original stratum. (x1, y1) is the coordinate of the top breakpoint of the target layer, and (x2, y2) is the coordinate of the bottom breakpoint of the target layer. S3. Calculate the target layer's formation dip angle θ; S4. Calculate the true paleo-relief thickness k of the target layer using the formula k = h' × cosθ.

2. A fine three-dimensional micro-paleomorphology restoration method according to claim 1, characterized in that: In step S3, the target layer formation dip angle θ is obtained using the formula: Where △T is the time difference between the two seismic traces of the target layer; △X is the distance between the two seismic traces of the target layer; and v is the formation velocity of the target layer.

3. A fine three-dimensional micro-paleomorphology restoration method according to claim 1 or 2, characterized in that: The step S1 specifically includes: S11. Obtain pre-stack time migration seismic data and well log curves, create synthetic records using acoustic time difference curves, and calibrate the target layer of the seismic data; S12. Tracking the top event T1 and the bottom event T2 of the target layer; S13. Pick up the coordinates of the top breakpoint of the target layer (x1, y1) and the coordinates of the bottom breakpoint of the target layer (x2, y2); S14. Based on the prestack time migration seismic data, obtain the target layer formation velocity v according to the well calibration; S15. Using formula Calculate the vertical thickness h of the target layer, where T1 and T2 are the events of the top and bottom of the target layer respectively; v is the formation velocity of the target layer.

4. A fine three-dimensional micro-paleomorphology restoration device, characterized in that: It includes target layer calibration unit, event tracking unit, breakpoint identification unit, formation velocity acquisition unit, vertical thickness calculation unit, reverse fault evacuation unit, formation dip calculation unit and paleo-landform thickness acquisition unit; The target layer calibration unit is used to obtain pre-stack time migration seismic data and well logging curves, make synthetic records using acoustic wave time difference curves, and calibrate the target layer of the seismic data; An event tracking unit is used to track the event T1 at the top of the target layer and the event T2 at the bottom of the target layer; A breakpoint identification unit is used to pick up the coordinates of the top breakpoint of the target layer (x1, y1) and the coordinates of the bottom breakpoint of the target layer (x2, y2); The formation velocity acquisition unit is used to obtain the formation velocity v of the target layer based on the pre-stack time migration seismic data and the well calibration; Plumb thickness calculation unit, used to use the formula Calculate the vertical thickness h of the target layer, where T1 and T2 are the events of the top and bottom of the target layer respectively; v is the formation velocity of the target layer; The reverse fault emptying unit is used to empty the repeated calculation abnormal value of the vertical thickness of the target layer at the reverse fault. The emptying range is The vertical thickness h' of the target layer is obtained by interpolation. Interpolation only changes the vertical thickness at the fault and does not change the vertical thickness of the original stratum. (x1, y1) is the coordinate of the top breakpoint of the target layer, and (x2, y2) is the coordinate of the bottom breakpoint of the target layer. Formation dip calculation unit, used to use the formula Calculate the target layer formation dip angle θ, where △T is the time difference between the two seismic traces of the target layer; △X is the distance between the two seismic traces of the target layer; v is the formation velocity of the target layer; The true paleo-landform thickness obtaining unit is used to calculate the true paleo-landform thickness k of the target layer using the formula k=h'×cosθ.

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