Method and system for identifying lateral pinch-out of riverway type lithologic trap and readable storage medium

Abstract

The present application relates to a kind of river course type lithologic trap lateral pinch-out identification method, system and readable storage medium, which includes the following steps: by phase conversion technique, the key geological features in seismic data are clearer, and lateral pinch-out phenomenon is facilitated to identify.Then, using isochronous strata slice technology, the abnormality and fracture in stratum can be accurately found, whether lateral pinch-out appears in river channel sand body is preliminarily judged.Next, time-frequency analysis enables in-depth understanding of seismic signal.Finally, by integrating information under different frequencies, a comprehensive description about river channel sand body distribution and thickness variation is obtained.The present application solves the problems of insufficient evaluation of lateral pinch-out conditions and insufficient accuracy of judgment results for river course type lithologic trap, realizes qualitative and quantitative evaluation of lateral pinch-out, and improves the accuracy and reliability of evaluation.

Description

Technical Field

[0001] The present invention relates to the field of geological exploration technology, and in particular to a method, system and readable storage medium for identifying lateral pinch-out of channel-type lithologic traps. Background Art

[0002] The current development status of the analysis technology for lateral pinch-out conditions of channel-type lithologic traps is mainly reflected in the following aspects: (1) by extracting seismic attributes. That is, by interpreting the top and bottom interfaces of the sand body and using seismic data to extract the attributes between the two layers to determine the lateral pinch-out of the channel sand body; (2) by using reservoir inversion methods. That is, within a certain stratigraphic framework, reservoir inversion methods are used to obtain the planar distribution of the channel sand body to determine the lateral pinch-out of the channel sand body. For the evaluation of lateral pinch-out conditions of thin-layer bifurcated channel-type lithologic traps, the above technical methods are relatively simple, and it is impossible to accurately determine the lateral pinch-out of the channel sand body through any of the above methods. There is no effective method for systematic evaluation in this field. Summary of the Invention

[0003] The present application provides a method, system and readable storage medium for identifying lateral pinch-out of channel-type lithologic traps, which can solve the problems of insufficient evaluation of lateral pinch-out conditions of channel-type lithologic traps and insufficient accuracy of judgment results.

[0004] In order to solve the above technical problems: a method for identifying lateral pinch-out of channel-type lithologic traps includes: S1: acquiring seismic data of a channel target area and performing phase conversion on the seismic data; S2: performing isochronous stratigraphic slicing on the phase-converted seismic data, judging whether there is a lateral pinch-out phenomenon in the channel sand body in the channel target area based on the isochronous stratigraphic slicing, and obtaining a preliminary qualitative judgment result on the lateral pinch-out of the channel sand body; S3: if there is a lateral pinch-out phenomenon, performing time-frequency analysis on the phase-converted seismic data, selecting a number of frequency-divided energy attribute body slices of specific frequencies from the time-frequency analysis results for fusion, and obtaining a mixed-frequency energy attribute slice; analyzing the distribution of the channel sand body and the relative thickness change relationship based on the mixed-frequency energy attribute slice, and obtaining a qualitative and semi-quantitative judgment result on the lateral pinch-out of the channel sand body.

[0005] In one embodiment, the method further includes: S4: performing rock physical analysis on the phase-converted seismic data, performing elastic parameter inversion based on the thickness of the channel sand body, and obtaining a quantitatively predicted channel sand body thickness.

[0006] In one embodiment, after obtaining the quantitatively predicted channel sand body thickness, the method further includes: identifying different channel characteristics based on the seismic data, and analyzing the separation distance between different channels based on the thickness of different channel sand bodies.

[0007] In one embodiment, performing elastic parameter inversion based on the thickness of the channel sand body to obtain a quantitative prediction of the thickness of the channel sand body includes: using a longitudinal wave impedance elastic parameter inversion method through a preset threshold value to obtain a quantitative prediction of the thickness of the channel sand body.

[0008] In one embodiment, S1 includes: acquiring seismic data of a target area of ​​a river channel, performing a 90° phase conversion on the seismic data so that the seismic data after the phase conversion reflects information of the stratum, wherein the information of the stratum includes the thickness, lithology and interlayer relationship of the stratum.

[0009] In one embodiment, S2 includes: tracking the interface between the upper mudstone layer and the lower mudstone layer through phase-converted seismic data, performing proportional interpolation within the tracked interface between the upper mudstone layer and the lower mudstone layer, extracting corresponding attribute data from the proportionally interpolated strata, and performing isochronous stratum slice analysis using the extracted attribute data to obtain a preliminary qualitative judgment of the lateral pinch-out result of the channel sand body, wherein the upper mudstone is the mudstone layer overlying the channel sand body, and the lower mudstone layer is the mudstone layer underlying the channel sand body.

[0010] In one embodiment, S3 includes: if there is a lateral pinch-out phenomenon, time-frequency analysis is performed on the phase-converted seismic data to obtain frequency domain characteristic data of the seismic data, and a number of frequency-divided energy attribute body slices corresponding to specific frequencies are extracted and fused, and the plane fusion attributes of the target layer are extracted from the mixed energy attribute slices obtained after fusion. By analyzing the extracted plane fusion attributes, a semi-quantitative judgment of the distribution of the river sand body and the relative thickness change relationship is obtained.

[0011] In one embodiment, the specific frequencies include but are not limited to 20 Hz, 40 Hz, and 70 Hz.

[0012] The present application also provides a computer device system, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-mentioned method for identifying lateral pinch-out of channel-type lithologic traps.

[0013] The present application also provides a computer-readable storage medium having a computer program / instruction stored thereon. When the computer program / instruction is executed by a processor, the steps of the above-mentioned method for identifying lateral pinch-out of channel-type lithologic traps are implemented.

[0014] The implementation of the present invention has the following beneficial effects: the present invention provides a method for identifying lateral pinch-out of channel-type lithologic traps. The method comprises the following steps: by using phase conversion technology, the key geological features in the seismic data are made clearer, which facilitates the identification of lateral pinch-out. Then, by using isochronous stratigraphic slicing technology, anomalies and fractures in the strata can be accurately discovered, and a preliminary judgment can be made as to whether lateral pinch-out occurs in the channel sand body. Next, time-frequency analysis enables an in-depth understanding of the seismic signal. Finally, by integrating information at different frequencies, a comprehensive description of the distribution and thickness changes of the channel sand body is obtained. The present invention solves the problems of insufficient evaluation of lateral pinch-out conditions of channel-type lithologic traps and insufficient accuracy of judgment results, realizes qualitative and quantitative evaluation of lateral pinch-out, and improves the accuracy and reliability of the evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 A schematic flow chart of a method for identifying lateral pinch-out of a channel-type lithologic trap according to an embodiment;

[0017] Figure 2 A flowchart of a method for identifying lateral pinch-out of a channel-type lithologic trap according to an embodiment;

[0018] Figure 3 This is a comparative analysis diagram of the vanishing point characteristics before and after 90-degree phase adjustment in an embodiment;

[0019] Figure 4 This is a diagram showing a stratum slice below an isochronous stratum grid according to an embodiment;

[0020] Figure 5 This is a frequency division RGB fusion display effect diagram based on time-frequency analysis of an embodiment;

[0021] Figure 6 is a petrophysical analysis diagram of an embodiment;

[0022] Figure 7 The present invention is a reservoir quantitative characterization prediction map of an embodiment. DETAILED DESCRIPTION

[0023] In order to make the objects, features and advantages of the present application more apparent, further detailed description will be made to the present application in combination with the drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0024] The present application provides a river channel type lithologic trap lateral pinch-out identification method, system and readable storage medium. In one embodiment, a river channel type lithologic trap lateral pinch-out identification method includes the following steps:

[0025] As shown in Figure 1 and Figure 2 , S1: obtaining seismic data of a river channel target area, and performing phase conversion on the seismic data; further, S1 includes: obtaining seismic data of a river channel target area, and performing 90° phase conversion on the seismic data, so that the seismic data after phase conversion reflects the information of the stratum, wherein the information of the stratum includes the thickness, lithology and interlayer relationship of the stratum.

[0026] As shown in Figure 3 , specifically, in seismic exploration, in order to accurately identify and analyze the reflection signals of underground strata, 90-degree phase adjustment is performed on seismic data. The main purpose is to optimize the seismic reflection signals and ensure that the reflection troughs accurately correspond to the target layer sand bodies. When seismic waves propagate underground, due to physical phenomena such as reflection, refraction and scattering, the received seismic signals will produce phase difference and amplitude change. In order to overcome these influences, 90-degree phase adjustment technology is adopted to rotate the phase angle in the seismic data by 90 degrees, so that the reflection troughs accurately correspond to the target layer sand bodies. It can effectively reduce the interference effect between wavelets, make the main lobe of the reflection wave more prominent, and be closer to the center of the thin layer. 90-degree phase adjustment not only helps to reduce noise and interference, but also improves the signal-to-noise ratio of seismic data, providing a more accurate and reliable basis for subsequent stratum analysis.

[0027] As shown in Figure 4 , S2: performing isochronous stratum slicing on the phase-converted seismic data, judging whether the river channel sand body in the river channel target area exists lateral pinch-out phenomenon according to the isochronous stratum slicing, and obtaining a preliminary qualitative judgment result of the lateral pinch-out of the river channel sand body.

[0028] Furthermore, S2 includes: tracking the interface between the upper mudstone layer and the lower mudstone layer through the phase-converted seismic data, performing proportional interpolation within the tracked interface between the upper mudstone layer and the lower mudstone layer, extracting corresponding attribute data from the proportionally interpolated strata, and performing isochronous stratigraphic slice analysis using the extracted attribute data to obtain a preliminary qualitative judgment on the lateral pinch-out result of the channel sand body, wherein the upper mudstone is the mudstone layer overlying the channel sand body, and the lower mudstone layer is the mudstone layer underlying the channel sand body.

[0029] Specifically, first, the interface between the upper and lower mudstone layers must be traced in the phase-converted seismic data. Here, the upper mudstone layer refers to the stable mudstone layer above the channel sandstone, while the lower mudstone layer refers to the stable mudstone layer below the channel sandstone. Proportional interpolation is performed within the traced interface between the upper and lower mudstone layers. The purpose of this step is to extract more detailed and accurate geological information between the strata. Based on the strata obtained through proportional interpolation, corresponding attribute data is further extracted. This attribute data includes, but is not limited to, stratum thickness, lithologic variations, and reflection intensity. Using this extracted attribute data, isochronous stratigraphic slice analysis is performed. Isochronous stratigraphic slices reveal the geological structure of strata from the same geological period and are suitable for identifying lateral pinch-out in channel sandstones. By observing the continuity, thickness variations, and contact relationship of the channel sandstone with the surrounding rock layers in the isochronous stratigraphic slices, a preliminary assessment can be made as to whether the channel sandstone exhibits lateral pinch-out. Lateral pinch-out refers to the phenomenon in which the channel sandstone gradually thins in a particular direction until it disappears. If the channel sand body in the slice has poor continuity, gradually decreases in thickness, and has a significant change in contact relationship with the surrounding rock layers, it may indicate the presence of lateral pinch-out.

[0030] Furthermore, isochronous stratigraphic slicing can be used to reconstruct the evolution of river channels. By comparing the distribution and morphology of channel sand bodies in slices taken at different times, we can understand the migration, expansion, or contraction of river channels at different times, and further determine whether channels are connected.

[0031] like Figure 5 As shown in FIG3 , S3: If lateral pinch-out exists, time-frequency analysis is performed on the phase-converted seismic data, and several frequency-divided energy attribute slices of specific frequencies are selected from the time-frequency analysis results for fusion to obtain mixed-frequency energy attribute slices; the distribution of the channel sand bodies and the relationship between the relative thickness changes are analyzed based on the mixed-frequency energy attribute slices to obtain qualitative and semi-quantitative judgment results on the lateral pinch-out of the channel sand bodies.

[0032] In one embodiment, the plane fusion attributes of the target layer are extracted from the mixed energy attribute slices obtained after fusion. Further, by analyzing the extracted plane fusion attributes, the distribution of the channel sand body and the relative thickness change relationship are semi-quantitatively determined.

[0033] Specifically, based on the time-frequency analysis, a number of frequency-divided energy attribute volume slices of specific frequencies are selected for fusion. The selection of these specific frequencies is generally based on the geological characteristics of the study area and the characteristics of the seismic data. For example, in this example, three frequency-divided energy attribute volume slices of 20 Hz, 40 Hz, and 70 Hz are selected. By fusing the frequency-divided energy attribute volume slices of these three different frequencies, a mixed frequency energy attribute slice is obtained. In other embodiments, frequency-divided energy attribute volume slices corresponding to other frequencies may also be selected.

[0034] Mixed-frequency energy attribute slices comprehensively display the geological response of channel sand bodies at different frequencies, thereby more comprehensively reflecting the distribution and relative thickness of channel sand bodies. By observing mixed-frequency energy attribute slices, the lateral pinch-out of channel sand bodies can be qualitatively and semi-quantitatively determined.

[0035] In one embodiment, the planar fusion attributes of the target layer are first extracted from the fused mixed energy attribute slices. This step allows for a more accurate analysis of the distribution and thickness variations of the channel sand bodies at specific horizons. By analyzing the extracted planar fusion attributes, the distribution and relative thickness variations of the channel sand bodies can be semi-quantitatively determined.

[0036] like Figure 6 As shown, S4: rock physics analysis is performed on the seismic data after phase conversion, and elastic parameter inversion is performed based on the thickness of the river channel sand body to obtain a quantitative prediction of the river channel sand body thickness. Furthermore, after obtaining the quantitative prediction of the river channel sand body thickness, it also includes: identifying different river channel characteristics based on the seismic data, combining the thickness of different river channel sand bodies, and analyzing the separation distance between different river channels. Specifically: based on the previous qualitative judgment of the lateral pinch-out of the river channel sand body, further rock physics analysis is performed, and elastic parameter inversion is performed based on the thickness of the river channel sand body to quantitatively predict the river channel sand body thickness and the separation distance between different river channels.

[0037] Furthermore, elastic parameter inversion is performed based on the thickness of the channel sand body to obtain a quantitative prediction of the thickness of the channel sand body, including: using a preset threshold value and a longitudinal wave impedance elastic parameter inversion method to obtain a quantitative prediction of the thickness of the channel sand body.

[0038] like Figure 7 Specifically, first, a rock physics analysis is performed to understand the differences in physical properties between the channel sandstone and the surrounding mudstone. This analysis can determine the degree of differentiation of the wave impedance of the target layer, that is, sandstone generally exhibits low wave impedance characteristics, while mudstone exhibits high wave impedance characteristics. Then, based on the results of the rock physics analysis, a threshold value is preset to distinguish between sandstone and mudstone. In this example, the threshold value is selected as 6.8×106m / s·kg / m 3When the longitudinal wave impedance value is less than the threshold value, it represents sandstone; otherwise, it represents mudstone. Then, the seismic data is processed using the longitudinal wave impedance elastic parameter inversion method. Through this method, the distribution of underground elastic parameters can be inverted based on the reflected wave information in the seismic data, and the thickness of the river channel sand body can be quantitatively predicted. The results of this method are consistent with the actual drilled sand body thickness, especially for the target layer underwater diversion channel and surrounding estuary bar sand body. The longitudinal thickness and lateral distribution of the sand body are clearly depicted. After obtaining the quantitative prediction of the river channel sand body thickness, the different river channel characteristics are further identified based on the seismic data, and the separation distance between different river channels is analyzed in combination with the thickness of the different river channel sand bodies.

[0039] Compared with the existing technology, the main advantages of the technical solution of the present invention are as follows: seismic sedimentology utilizes the ability of seismic data with a lateral resolution greater than a vertical resolution to depict the channel distribution and evolution process, while introducing the core idea of ​​reservoir quantitative prediction technology from qualitative to quantitative. First, starting with a 90-degree phase adjustment, isochronous stratigraphic slice research is carried out to qualitatively evaluate the method; at the same time, based on time-frequency analysis, frequency division fusion display is carried out to semi-quantitatively judge the channel sand body distribution and relative thickness changes; and reservoir inversion technology is introduced. Through rock physics analysis, effective elastic parameters are screened. According to the thickness of the channel sand body, an effective inversion method is selected to obtain the accurate thickness and planar distribution of the channel sand body, quantitatively depict the relationship between the channel sand, and form a set of lateral pinch-out condition evaluation technology for thin-layer bifurcated channel-type lithologic traps from qualitative to quantitative.

[0040] The present application also provides a computer device system, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method for identifying lateral pinch-out of channel-type lithologic traps in any of the above embodiments.

[0041] The present application also provides a computer-readable storage medium having a computer program / instruction stored thereon. When the computer program / instruction is executed by a processor, the steps of the method for identifying lateral pinch-out of channel-type lithologic traps in any of the above embodiments are implemented.

[0042] It is understandable that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A method for identifying lateral pinch-out of channel-type lithologic traps, characterized in that: The method comprises the following steps: S1: Acquire seismic data of a target area of ​​a river channel and perform phase conversion on the seismic data; S2: performing isochronous stratigraphic slicing on the phase-converted seismic data, and determining whether the channel sand body in the channel target area exhibits lateral pinch-out based on the isochronous stratigraphic slicing, thereby obtaining a preliminary qualitative determination of the lateral pinch-out of the channel sand body; S3: If lateral pinch-out exists, time-frequency analysis is performed on the phase-converted seismic data, and a plurality of frequency-divided energy attribute volume slices of specific frequencies are selected from the time-frequency analysis results for fusion to obtain mixed-frequency energy attribute slices; the distribution of the channel sand body and the relationship between the relative thickness changes are analyzed based on the mixed-frequency energy attribute slices to obtain qualitative and semi-quantitative judgment results on the lateral pinch-out of the channel sand body; S3 includes: performing time-frequency analysis on the phase-converted seismic data to obtain frequency domain characteristic data of the seismic data, extracting a number of frequency-divided energy attribute volume slices corresponding to specific frequencies and fusing them, extracting plane fusion attributes of the target layer from the fused mixed energy attribute slices, and obtaining a semi-quantitative distribution and relative thickness variation relationship of the channel sand body by analyzing the extracted plane fusion attributes; A plurality of specific frequencies are obtained based on the geological characteristics of the study area and the characteristics of the seismic data, wherein the plurality of specific frequencies include 20 Hz, 40 Hz and 70 Hz; S4: performing rock physical analysis on the phase-converted seismic data, performing elastic parameter inversion based on the thickness of the channel sand body, and obtaining a quantitatively predicted thickness of the channel sand body.

2. The method for identifying lateral pinch-out of channel-type lithologic traps according to claim 1, characterized in that: After obtaining the quantitatively predicted thickness of the channel sand body, the method further includes: Different channel characteristics are identified based on the seismic data, and the separation distances between different channel channels are analyzed in combination with the thickness of sand bodies in different channel channels.

3. The method for identifying lateral pinch-out of channel-type lithologic traps according to claim 1, characterized in that: The elastic parameter inversion based on the thickness of the channel sand body is carried out to obtain the quantitative prediction of the thickness of the channel sand body, including: By presetting the threshold value and applying the longitudinal wave impedance elastic parameter inversion method, the thickness of the channel sand body can be quantitatively predicted.

4. The method for identifying lateral pinch-out of channel-type lithologic traps according to claim 1, characterized in that: Said S1 comprises: Seismic data of a target area of ​​a river channel is acquired, and a 90° phase shift is performed on the seismic data so that the seismic data after the phase shift reflects information of the strata, wherein the information of the strata includes the thickness, lithology and interlayer relationship of the strata.

5. The method for identifying lateral pinch-out of channel-type lithologic traps according to claim 1, characterized in that: The S2 includes: The interface between the upper and lower mudstone layers is tracked using phase-converted seismic data. Proportional interpolation is performed within the tracked interface between the upper and lower mudstone layers. Corresponding attribute data are extracted based on the proportionally interpolated strata. Isochronous stratigraphic slice analysis is performed using the extracted attribute data, resulting in a preliminary qualitative judgment of the lateral pinch-out of the channel sandbody. The upper mudstone is the overlying mudstone layer of the channel sandbody, and the lower mudstone is the underlying mudstone layer of the channel sandbody.

6. A computer system comprising a memory, a processor, and a computer program stored in the memory, wherein: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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