A method for identifying first and second sequence boundaries based on seismic data

Abstract

The application discloses a method for identifying first and second sequence interfaces based on seismic data, which comprises the following steps: obtaining seismic data, identifying and selecting a target unconformity interface to be determined; taking the interface as a horizontal datum plane to perform palaeogeomorphology recovery processing and generating a flattened data volume; determining first and second sedimentary centers of a basin where the upper and lower stratum units of the interface are located respectively; measuring the lengths of the semi-major axes of the sedimentary basins where the upper and lower strata are located and calculating the planar distance between the two sedimentary centers; according to the ratio of the planar distance to the sum of the lengths of the two semi-major axes, determining whether the target interface belongs to a first sequence interface or a second sequence interface according to a sedimentary center migration mode. The application reduces the dependence on well logging data, introduces a mathematical threshold to abandon subjective experience judgment, realizes the objectification and semi-quantification of sequence interface classification, and provides reliable technical support for oil and gas exploration in areas with few or no wells.

Description

Technical Field

[0001] This invention relates to the field of petroleum geological exploration and sequence stratigraphy, and in particular to a method for identifying first and second-order sequence boundaries based on seismic data. Background Technology

[0002] Sequence stratigraphic framework modeling is fundamental to oil and gas reservoir exploration and development. Accurate identification of sequence boundaries at different levels is crucial for establishing isochronous stratigraphic frameworks, predicting reservoir distribution, and gaining a deeper understanding of basin evolution. With the continuous evolution of oil and gas exploration technologies, traditional sequence delineation methods relying solely on well logging data and core observations are gradually shifting towards sequence identification techniques based on seismic data. Currently, seismic-based sequence identification methods mainly revolve around techniques such as well-seismic joint analysis, time-frequency analysis, and quantitative geomorphological characterization. For example, time-frequency analysis techniques are used to decompose seismic traces near wells at multiple scales, combining high-frequency well logging information with seismic lateral continuity to identify sequence boundaries; or, for specific sedimentary backgrounds, quantitative geomorphological analysis is used to analyze the control mechanisms of local stratigraphic structures. These techniques have improved the accuracy of sequence boundary identification to a certain extent and deepened the theoretical understanding of the sequence genesis of local geological units.

[0003] However, these techniques still have significant limitations in identifying regional low-frequency sequence boundaries. First, existing methods are highly dependent on well logging data, and well-seismic matching often involves deep conversion errors and resolution scale differences, severely restricting their applicability in newly explored areas with few or no wells, or in complex structural zones. Second, existing technologies primarily focus on the detailed characterization of third-order and higher high-frequency sequences, while first- and second-order sequence boundaries are typically passively identified only as an adjunct to the high-frequency framework. There is a pressing need for a systematic and procedural identification scheme specifically for such regional low-frequency boundaries. Furthermore, existing sequence boundary classification heavily relies on the subjective experience of explorers regarding the strength of seismic reflection termination relationships or the size of contact angles, lacking objective and semi-quantitative geological evaluation standards. This results in poor repeatability of identification results and makes it difficult to establish a direct and scientific mapping relationship between apparent seismic unconformities and the dynamic changes in the basin's underlying layers. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the aforementioned existing problems, this invention is proposed. Therefore, this invention provides a method for identifying first and second-order sequence boundaries based on seismic data to solve the problems mentioned in the background art.

[0006] To address the aforementioned technical problems, this invention provides the following technical solution: a method for identifying first- and second-order sequence boundaries based on seismic data, comprising: Acquire seismic data of the area to be measured and visualize it; identify and track seismic angle nonconformities in the seismic data; and select the target nonconformity to be determined. Using the target unconformity interface as a horizontal reference plane, paleomorphological restoration processing is performed to generate a flattened data volume. In the flattened data volume, the target unconformity interface is presented as a horizontal plane. In the flattened data volume, the first sedimentary center of the basin or depression where the first stratigraphic unit above the target unconformity is located, and the second sedimentary center of the basin or depression where the second stratigraphic unit below the target unconformity is located are respectively determined. By comparing the planar positional relationship between the first sedimentation center and the second sedimentation center, the sequence level to which the target unconformity interface belongs is determined based on the sedimentation center migration pattern. The sequence level includes a first-order sequence interface and a second-order sequence interface.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention abandons the subjective experience-based judgment of relying solely on the strength of seismic reflection termination relationships or the size of contact angles in traditional methods, and introduces sedimentary center migration as an objective geological standard. By measuring the distance between the basin's semi-major axis and the sedimentary center, and using the calculated parameter ratios and thresholds for quantitative determination, the accuracy, operability, and repeatability of sequence level (first or second level) determination are significantly improved.

[0008] 2. Existing technologies heavily rely on well logging data and face significant challenges in well-seismic matching. In contrast, this invention directly utilizes seismic data for paleogeographic reconstruction and sedimentary center analysis. It effectively overcomes problems such as scale mismatch and time-depth conversion errors between high-frequency well logging information and low-frequency seismic information, enabling accurate identification and classification of high-level sequence boundaries even in newly explored areas with few or no wells or complex structural zones.

[0009] 3. This invention establishes a scientific mapping relationship between the apparent seismic unconformity characteristics and the deep dynamic transformation process of the basin (first-order interfaces correspond to strain lattice motion, and second-order interfaces correspond to episodic motion). The results obtained from this standardized and systematic workflow can be directly used to identify major tectonic transformation periods in the basin, establish isochronous stratigraphic frameworks, and determine source-reservoir-seal combinations, providing extremely reliable technical support for oil and gas exploration site selection and evaluation. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the 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. Wherein: Figure 1 This is a flowchart illustrating the overall process of a method for identifying first- and second-order sequence boundaries based on seismic data, according to an embodiment of the present invention. Figure 2 This is a diagram illustrating the identification of the first-order sequence interface in a method for identifying first- and second-order sequence interfaces based on seismic data, as described in an embodiment of the present invention. Figure 3 This is a diagram illustrating the identification of the second-order sequence interface in a method for identifying first- and second-order sequence interfaces based on seismic data, as described in an embodiment of the present invention. Detailed Implementation

[0011] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0012] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0013] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0014] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0015] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0016] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1

[0017] Reference Figure 1 This is the first embodiment of the present invention, which provides a method for identifying first and second-order sequence boundaries based on seismic data. The method of the present invention can accurately identify and classify regional sequence boundaries semi-automatically and objectively under well-free conditions, and includes the following steps: S1: Acquire seismic data of the area to be measured and visualize it.

[0018] Specifically, two-dimensional or three-dimensional seismic data of the area to be measured are loaded into professional seismic interpretation software (such as geological software platforms like DSG and Petrel), and the seismic profiles are displayed and browsed using the seismic interpretation software, thereby providing basic data support for interface identification.

[0019] S2: Identify and track seismic angle nonconformities in seismic data, and select the target nonconformity to be determined.

[0020] Furthermore, in seismic interpretation software, based on the termination relationships of seismic reflection phase axes (including but not limited to overshoot, top overshoot, and cutoff), seismic angular unconformities are systematically identified and tracked across the entire region. It should be noted that these unconformities typically manifest as the reflection phase axes of the underlying strata being cut off or truncated at a certain angle by the overlying strata.

[0021] Specifically, firstly, reflection phase axes conforming to the above characteristics are tracked and compared across the entire region, and closed-loop interpretation is performed to generate one or more continuous three-dimensional or two-dimensional seismic horizon data representing regional angular unconformities, which are denoted as the unconformity interface set. ,in Subsequently, the interface collection was never integrated. In the middle, select a target unintegrated interface of the order level to be determined (denoted as...). This serves as the benchmark for paleogeographic reconstruction and sedimentary center feature analysis.

[0022] S3: Perform paleomorphological restoration processing using the target unintegrated interface as the horizontal reference datum to generate a flattened data volume.

[0023] Furthermore, this step primarily relies on sedimentary background reconstruction techniques based on paleogeographic restoration.

[0024] Specifically, by utilizing the layer flattening function of the geological software platform, layers with time or depth values ​​smaller than the target unconformity are flattened. Extract all overlying seismic data; The interface uses a horizontal reference plane to perform spatial geometric correction on the extracted seismic data regarding time-depth relationships. After spatial geometric correction, a new three-dimensional data volume is reconstructed, called the flattened data volume (denoted as ). After flattening the data volume In the middle, the originally fluctuating target interface is not integrated. It will be presented as an absolute horizontal plane, thereby eliminating the influence of later tectonic movements on the sedimentary interface and restoring the paleogeographic features of the interface formation period.

[0025] S4: Obtain the determination parameters and determine the location of the deposition center of the upper and lower strata.

[0026] Furthermore, after completing the interface flattening process, the sedimentary characteristics of the stratigraphic units above and below the unconformity were compared and analyzed. The flattened data volume was then determined. In the context of the target unconformity, the first sedimentary center of the basin (or depression) containing the first stratigraphic unit above the target unconformity and the second sedimentary center of the basin (or depression) containing the second stratigraphic unit below the target unconformity.

[0027] In addition, in order to introduce the objective geological indicator of sedimentary center migration as a quantitative criterion at the sequence level, the following parameters also need to be measured and calculated: The length of the first semi-major axis of the first sedimentary basin (or depression) where the first stratigraphic unit is located is measured and denoted as . ; The length of the second semi-major axis of the second sedimentary basin (or depression) where the second stratigraphic unit is located is measured and denoted as . ; Also, calculate the planar distance between the first sedimentation center and the second sedimentation center, denoted as L.

[0028] S5: Compare the planar positional relationship between the first and second sedimentary centers, and determine the sequence level of the target unconformity interface based on the migration pattern of the sedimentary centers.

[0029] It should be noted that this step abandons the traditional subjective judgment based on the strength of the reflection termination relationship or the size of the contact angle, and uses calculated parameters for quantitative determination. The sum of the lengths of the first and second semi-major axes (i.e., ...) is calculated. ), and calculate the planar distance. The ratio to the sum of the two semi-major axes, i.e., the formula: Furthermore, based on this ratio and the threshold The rules for determining the size relationship are as follows: (1) Judgment rules for first-level hierarchical interfaces. When the formula is satisfied: When the planar distance between the sedimentary center of the basin (or depression) above the flattened interface and the sedimentary center below the interface is greater than or equal to one-third of the sum of the semi-major axes of the two basins, it is determined that the sedimentary center has migrated across tectonic units, and the target unconformity interface is determined to be a first-order sequence interface.

[0030] It should be noted that this migration signifies a fundamental change in the basin's dynamic regime (i.e., a transformation), for example, the shift from a rift stage to a depression stage, the beginning of a dominant stage, which typically represents a timescale of tens of millions to hundreds of millions of years.

[0031] (2) Judgment rules for second-level hierarchical interfaces: When the formula is satisfied: When the planar distance between the sedimentary center of the basin (or depression) above the flattened interface and the sedimentary center below the interface is less than one-third of the sum of the semi-major axes of the two basins, the sedimentary center is considered to have inheritance, and the target unconformity interface is determined to be a second-order sequence interface.

[0032] It should be noted that this inheritance indicates that the interface was formed within the same basin dynamic regime and tectonic framework (i.e., episodic movement), and was controlled by secondary tectonic episodic activities, large-scale sea-level fluctuations, or periodic changes in the source system. This means that the secondary sedimentary cycles within the same tectonic stage of the basin generally represent timescales of millions to tens of millions of years.

[0033] Furthermore, by utilizing the identified first-order and second-order sequence boundaries, an isochronous stratigraphic framework for the area to be tested is established. Based on this isochronous stratigraphic framework, the distribution of source-reservoir-seal assemblages is further defined and predicted, directly serving the evaluation of oil and gas exploration areas. Example 2

[0034] Reference Figure 2 and Figure 3 This is the second embodiment of the present invention, which provides a method for identifying first and second-order sequence boundaries based on seismic data. This embodiment demonstrates the specific application effects and determination calculation process of the method in Embodiment 1 by combining seismic exploration experimental data.

[0035] It should be noted that, in this embodiment, Figure 2 and Figure 3 Experimental comparison diagrams of first-level and second-level hierarchical interface recognition are shown respectively. Figure 2 and Figure 3 In the middle, the top image represents the unprocessed original seismic profile, and the bottom image represents the flattened data volume generated after paleogeographic restoration processing in step S3. The blue solid line represents the selected target non-integrated interface. The yellow dashed lines represent the set of unintegrated interfaces that are being traced and closed. The stratigraphic position in the middle.

[0036] Specifically, Experiment Application 1: Recognition of the first-level hierarchical interface (corresponding to...) Figure 2 When analyzing a region to be measured in a basin, based on the flattened data volume ( Figure 2 (See image below) Identify the target non-integrated interface. Two sedimentary depressions, one above the other. Determination parameters were obtained through software measurement: The semi-major axis of the first depositional depression above the interface km; The semi-major axis of the second depositional depression beneath the interface km; The actual planar distance between the two depression sedimentary centers mentioned above km.

[0037] Substituting the above parameters into the discrimination formula for sediment center migration mode: because, Conforms to the formula The judgment condition is that the actual ratio is much greater than the threshold of one-third.

[0038] It should be noted that this result indicates a significant migration of the sedimentary center across tectonic units in this region, and the target unconformity interface... Formed during a period of fundamental change in the basin's dynamic system, it was objectively and accurately identified as a first-order sequence boundary.

[0039] Specifically, Experiment Application 2: Recognition of Second-Level Hierarchical Interfaces (corresponding to...) Figure 3 When analyzing another basin or another tectonic stage of the same basin, based on the flattened data volume ( Figure 3(See image below) The target interface is not integrated. Measurements were taken of multiple sets of sedimentary depressions, both above and below.

[0040] against Figure 3 The parameters of the first group of corresponding sedimentary depressions identified in the data were obtained through measurement: Semi-major axis of the depositional depression above the interface km; Semi-major axis of the sedimentary depression beneath the interface km; Planar distance between two sedimentary centers km.

[0041] Substitute it into the discriminant formula to calculate: against Figure 3 The parameters of the second group of corresponding sedimentary depressions identified in the data were obtained through measurement: Semi-major axis of the depositional depression above the interface km; Semi-major axis of the sedimentary depression beneath the interface km; Planar distance between two sedimentary centers km.

[0042] Substitute it into the discriminant formula to calculate: Clearly, both 0.062 and 0.044 are much smaller than the threshold. That is, it satisfies the formula: and It should be noted that, based on the experimental results, the depositional centers above and below the interface in this region are essentially coincident, exhibiting strong inheritance. This target unconformity interface... The secondary sedimentary cycle stage, formed under the same tectonic setting, was objectively and accurately identified as a second-order sequence boundary.

[0043] In summary, this embodiment overcomes the subjective ambiguity of traditional seismic identification of first and second-order sequence boundaries by introducing a semi-quantitative mathematical formula to calculate the ratio of the basin's long axis to the center distance. This allows for accurate classification of high-level sequence boundaries even in well-free areas.

[0044] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0045] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0046] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0047] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0048] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0049] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for identifying first and second-order sequence boundaries based on seismic data, characterized in that, include: Acquire seismic data of the area to be measured and visualize it; identify and track seismic angle nonconformities in the seismic data; and select the target nonconformity to be determined. Using the target unconformity interface as a horizontal reference plane, paleomorphological restoration processing is performed to generate a flattened data volume. In the flattened data volume, the target unconformity interface is presented as a horizontal plane. In the flattened data volume, the first sedimentary center of the basin or depression where the first stratigraphic unit above the target unconformity is located, and the second sedimentary center of the basin or depression where the second stratigraphic unit below the target unconformity is located are respectively determined. Compare the planar positional relationship between the first sedimentation center and the second sedimentation center, and determine the sequence level to which the target unconformity interface belongs based on the sedimentation center migration mode. The sequence level includes a first-order sequence interface and a second-order sequence interface. Before determining the sequence level to which the target unconformity interface belongs based on the sedimentary center migration pattern, there is a step of obtaining determination parameters, which includes: Measure the length of the first semi-major axis of the first sedimentary basin or depression in which the first stratigraphic unit is located; Measure the length of the second semi-major axis of the second sedimentary basin or depression in which the second stratigraphic unit is located; Calculate the planar distance between the first deposition center and the second deposition center; The determination of the sequence level to which the target unconformity interface belongs based on the sedimentary center migration mode includes: Calculate the sum of the length of the first semi-major axis and the length of the second semi-major axis; One-third of the sum of the length of the first semi-major axis and the length of the second semi-major axis is used as the threshold for determining stratigraphic migration. By comparing the planar distance with the threshold, the target unintegrated interface is determined to be either a first-level hierarchical interface or a second-level hierarchical interface based on the comparison result. The determination that the target unintegrated interface belongs to the first-level hierarchical interface based on the comparison results includes: When the planar distance is greater than or equal to the threshold, it is determined that the deposition center has migrated across the tectonic unit; The target unconformity interface corresponding to the migration across structural units is determined as the first-level sequence interface; The determination that the target unintegrated interface belongs to a second-level hierarchical interface based on the comparison results includes: When the planar distance is less than the threshold, the deposition center is determined to be inherited. The target unconformity interface corresponding to the sedimentation center inheritance is determined as the second-order sequence interface.

2. The method for identifying first and second-order sequence boundaries based on seismic data as described in claim 1, characterized in that, Identifying and tracing seismic angular unconformities in the seismic data, including: Based on the termination relationship of seismic reflection phase axes, the seismic angular unconformity feature where the reflection phase axes of the underlying strata are cut off or interrupted by the overlying strata at a preset angle is identified throughout the region. The reflection phase axes that conform to the seismic angle unconformity characteristics are tracked, compared and interpreted to generate at least one continuous seismic horizon data, forming an unconformity interface set.

3. The method for identifying first and second-order sequence boundaries based on seismic data as described in claim 2, characterized in that, The termination relationship of the seismic reflection phase axis includes at least one of overshoot, top overshoot, and cut-off.

4. The method for identifying first and second-order sequence boundaries based on seismic data as described in claim 2, characterized in that, Select the target to be judged without integrating the interface, including: From the set of unconformities, select any seismic horizon data that represents regional angular unconformity as the target unconformity to be determined.

5. The method for identifying first and second-order sequence boundaries based on seismic data as described in claim 1, characterized in that, Using the target unconformity interface as a horizontal reference surface, paleogeographic restoration processing is performed to generate a flattened data volume, including: Extract all seismic data whose time or depth value is less than the target unintegrated interface; Using the target unintegrated interface as a horizontal reference plane, the extracted seismic data is subjected to spatial geometric correction of time-depth relationship, and the flattened data volume is reconstructed.

6. The method for identifying first and second-order sequence boundaries based on seismic data as described in claim 1, characterized in that, After determining the hierarchical level of the target unintegrated interface, the process also includes: Using the identified first-order sequence interface and second-order sequence interface, an isochronous stratigraphic framework for the area to be measured is established, and the source-reservoir-seal combination is determined based on the isochronous stratigraphic framework.

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