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  • 1
    Publication Date: 2021-08-20
    Description: Seismic facies analysis can generate a map to describe the spatial distribution characteristics of reservoirs, and therefore plays a critical role in seismic interpretation. To analyse the characteristics of the horizon of interest, it is usually necessary to extract seismic waveforms along the target horizon using a selected time window. The inaccuracy of horizon interpretation often produces some inconsistent phases and leads to inaccurate classification. Therefore, the developed adaptive phase K-means algorithm proposed a sliding time window to extract seismic waveforms. However, setting the maximum offset of the sliding window is difficult in a real data application. A value that is too large may cause the cross-layer problem, whereas a value that is too small reduces the flexibility of the algorithm. To address this disadvantage, this paper proposes a robust K-means (R-K-means) algorithm with a Gaussian-weighted sliding window for seismic waveform classification. The used weights punish those windows distant from the interpretation horizon in the objective function, consequently producing a smaller range of horizon adjustments even when using relatively large maximum offsets and benefitting the generation of stable and reliable seismic facies maps. The application of real seismic data from the F3 block proves the effectiveness of the proposed algorithm.
    Print ISSN: 1742-2132
    Electronic ISSN: 1742-2140
    Topics: Geosciences
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  • 2
    Publication Date: 2020-09-23
    Print ISSN: 0016-8025
    Electronic ISSN: 1365-2478
    Topics: Geosciences , Physics
    Published by Wiley
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  • 3
    Publication Date: 2020-10-08
    Description: Seismic facies analysis based on pre-stack data is becoming popular. Vertical elastic transitions produce the spatial structure variation of pre-stack waveforms, while lateral elastic transitions produce the amplitude intensity variation. In the stratigraphic seismic facies analysis, more attention should be paid to waveform spatial structure than amplitude intensity. Conventional classification methods based on distance metric are difficult to adapt to stratigraphic seismic facies analysis because a distance metric is a comprehensive measure of waveform structure and amplitude intensity. A dictionary learning method for pre-stack seismic facies analysis is proposed herein. The proposed method first learns several dictionaries from labeled pre-stack waveform data, and these dictionaries consist of several normalization vector bases. The pre-stack waveform spatial structure is therefore embedded in these learned dictionaries, and the amplitude intensity is eliminated by the normalization process. Afterward, these dictionaries are used to sparsely represent pre-stack seismic data. Seismic facies are classified and determined according to representation error. A source error separation method is used to improve the anti-noise performance of dictionary learning by iteratively segmenting the noise out in the training data. The results on synthetic and real seismic data show that the proposed method has a stronger tolerance to noise, and the obtained seismic facies boundary is more accurate and clearer. This demonstrates that the proposed method is an effective seismic facies analysis technique.
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
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  • 4
    Publication Date: 2020-02-01
    Description: Extracting horizons from a seismic image has been playing an important role in seismic interpretation. However, how to fully use global-level information contained in the seismic images such as the order of horizon sequences is not well-studied in existing works. To address this issue, we have developed a novel method based on a directed and colored graph, which encodes effective context information for horizon extraction. Following the commonly used framework, which generates horizon patches and then groups them into horizons, we first build a directed and colored graph by representing horizon patches as vertices. In addition, edges in the graph encode the relative spatial positions of horizon patches. This graph explicitly captures the geologic context, which guides the grouping of the horizon patches. Then, we conduct premerging to group horizon patches through matching some predefined subgraph patterns that are designed to capture some special spatial distributions of horizon patches. Finally, we have developed an ordered clustering method to group the rest of the horizon patches into horizons based on the pairwise similarities of horizon patches while preserving geologic reasonability. Experiments on real seismic data indicate that our method can outperform the autotracking approach solely based on the similarity of local waveforms and can correctly pick the horizons even across the fault without any crossing, which demonstrates the effectiveness of exploring the spatial information, i.e., the order of horizon sequences and special spatial distribution of horizon patches.
    Print ISSN: 2324-8858
    Electronic ISSN: 2324-8866
    Topics: Geosciences
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  • 5
    Publication Date: 2021-02-05
    Description: Traditional constant time window-based waveform classification method is a robust tool for seismic facies analysis. However, when the interval thickness is seismically variable, the fixed time window is not able to contain the complete geologic information of interest. Therefore, the constant time window-based waveform classification method is inapplicable to conduct seismic facies analysis. To expand the application scope of seismic waveform classification in the strata with varying thickness, we propose a novel scheme for unsupervised seismic facies analysis of variable window length. The input of top and bottom horizons can guarantee the comprehensive geologic information of target interval. Throughout the whole workflow, we utilize DTW (Dynamic Time Warping) distance to measure the similarities between seismic waveforms of different lengths. Firstly, we improve the traditional spectral clustering algorithm by replacing the Euclidean distance with DTW-distance. Therefore, it can be applicable in the interval of variable thickness. Secondly, to solve the problem of large computation when applying the improved spectral clustering approach, we propose the method of seismic data thinning based on the technology of superpixel. Lastly, we combine these two algorithms and perform the integrated workflow of improved spectral clustering. The experiments on synthetic data show that the proposed workflow outperforms the traditional fixed time window-based clustering algorithm in recognizing the boundaries of different lithologies and lithologic associations with varying thickness. The practical application shows great promise for reservoir characterization of interval with varying thickness. The plane map of waveform classification provides convincing reference to delineate reservoir distribution of data set.
    Print ISSN: 2324-8858
    Electronic ISSN: 2324-8866
    Topics: Geosciences
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