The seismic wave propagation across rock masses with thin-layer joints by modified displacement discontinuity method (M-DDM) is of great importance for geophysical surveys. M-DDM introduces a frequency-dependent effective stiffness to describe the dynamic stressclosure relationship of a thin-layer joint. The study verifies the accuracy of M-DDM in studying seismic wave propagation across rock masses with thin-layer joints. Subsequently, we evaluate the influence of the joint thickness and the incident wave frequency on M-DDM accuracy. We analyze the prediction error of the transmission coefficient obtained with M-DDM. The results demonstrate that the frequency-dependent effective joint stiffness increases with increasing incident wave frequency and decreases with increasing joint thickness. Compared with the traditional DDM, M-DDM more accurately predicts the transmission coefficients of seismic waves propagating across thin-layer joints. The transmission coefficient prediction error obtained based on M-DDM increases with increasing joint thickness and incident wave frequency and is always smaller than that obtained based on DDM. Therefore, our proposed M-DDM can be used to effectively investigate seismic wave propagation across rock masses with thin-layer joints.
{"title":"A modified displacement discontinuity method for seismic wave propagation across rock masses with thin-layer joints","authors":"M. Wang, L. Jia, G.Y. Li, W. Wang, L. Fan","doi":"10.1190/geo2023-0390.1","DOIUrl":"https://doi.org/10.1190/geo2023-0390.1","url":null,"abstract":"The seismic wave propagation across rock masses with thin-layer joints by modified displacement discontinuity method (M-DDM) is of great importance for geophysical surveys. M-DDM introduces a frequency-dependent effective stiffness to describe the dynamic stressclosure relationship of a thin-layer joint. The study verifies the accuracy of M-DDM in studying seismic wave propagation across rock masses with thin-layer joints. Subsequently, we evaluate the influence of the joint thickness and the incident wave frequency on M-DDM accuracy. We analyze the prediction error of the transmission coefficient obtained with M-DDM. The results demonstrate that the frequency-dependent effective joint stiffness increases with increasing incident wave frequency and decreases with increasing joint thickness. Compared with the traditional DDM, M-DDM more accurately predicts the transmission coefficients of seismic waves propagating across thin-layer joints. The transmission coefficient prediction error obtained based on M-DDM increases with increasing joint thickness and incident wave frequency and is always smaller than that obtained based on DDM. Therefore, our proposed M-DDM can be used to effectively investigate seismic wave propagation across rock masses with thin-layer joints.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140707217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Detecting leakage in concrete gravity dams presents a formidable challenge. The Flow-Field Fitting (FFF) method is used to identify leaks in Chinas Da-Hedong reservoir dam. We propose vertical- and horizontal-gradient approaches based on the transmitted signal electrical field. A plastic frame is developed to allow the probe to measure horizontal gradients. We determine the exact location of leaks at the reservoirs bottom and upstream face, respectively, assuming that current leakages are located in hydraulic leakage zones. Numerical experiments and water pressure tests reveal that the conductive silt layer beneath the reservoir can lower the response of the potential values at the leakage inlet, and the effect of the silt layer should be considered and not ignored when interpreting measured data. In addition, with regards to the principle of superposition, the contribution associated with metal pipes in the dam body can be roughly determined by subtracting it from the original potential field data, thereby aiding in locating leaks around the metal pipes. Additionally, the FFF measurements from the reservoirs bottom also confirm the position of existing faults in the substratum at the reservoir site. Lastly, the results of the FFF method are tested against supporting evidence including ground penetrating radar and water pressure tests. In conclusion, these independent data confirm the effectiveness of the FFF method for leakage localization in the concrete gravity dam.
{"title":"Leakage detection applied to the Da-Hedong Reservoir dam (China) based on the flow-field fitting method","authors":"Xiang Zhao, Hongbing Zhang, A. Revil, Yandong Liu, Fanxin Zeng, Ping Wang, Q. Ren","doi":"10.1190/geo2023-0288.1","DOIUrl":"https://doi.org/10.1190/geo2023-0288.1","url":null,"abstract":"Detecting leakage in concrete gravity dams presents a formidable challenge. The Flow-Field Fitting (FFF) method is used to identify leaks in Chinas Da-Hedong reservoir dam. We propose vertical- and horizontal-gradient approaches based on the transmitted signal electrical field. A plastic frame is developed to allow the probe to measure horizontal gradients. We determine the exact location of leaks at the reservoirs bottom and upstream face, respectively, assuming that current leakages are located in hydraulic leakage zones. Numerical experiments and water pressure tests reveal that the conductive silt layer beneath the reservoir can lower the response of the potential values at the leakage inlet, and the effect of the silt layer should be considered and not ignored when interpreting measured data. In addition, with regards to the principle of superposition, the contribution associated with metal pipes in the dam body can be roughly determined by subtracting it from the original potential field data, thereby aiding in locating leaks around the metal pipes. Additionally, the FFF measurements from the reservoirs bottom also confirm the position of existing faults in the substratum at the reservoir site. Lastly, the results of the FFF method are tested against supporting evidence including ground penetrating radar and water pressure tests. In conclusion, these independent data confirm the effectiveness of the FFF method for leakage localization in the concrete gravity dam.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140708294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Despite the emergence of statistical and intelligent approaches for quantitative seismic interpretation in recent years, Rock Physics Templates (RPTs) are still preferred because of their simplicity and easy implementation. RPTs have been introduced as a fundamental tool for lithology and fluid discrimination based on well-log and seismic data, which have already been proven in terms of accuracy and reliability. Considering the demand for comprehensive RPTs and improving their efficiency, I proposed a novel three-dimensional prism-shaped template for lithology and fluid discrimination, called a prism-shaped rock physics template (P-RPT). For this, a theoretical methodology for designing conventional RPT was introduced with the aim of bounds and hybrid rock physics models. Next, some novel triangular and rectangular ternary and binary templates were designed and connected to one another to build a prism for fluid discrimination and lithology identification. Two ternary charts were used for fluid and lithology, incorporating the P- and S-wave velocity ratios and Lambda-Mu parameters. Further, binary charts, including acoustic impedance, Lamé parameters, and porosity, were designed and modified from literature for fluid and lithology identification. Next, the obtained templates were successfully validated on blind data sets (ultrasonic, well logging, and seismic data) in different reservoirs with various lithologies and fluid types. The results showed that the P-RPT could integrate the available RPTs into a 3D diagram and give a reliable framework for applications in seismic interpretation. User-friendliness and generalizability are the most prominent advantages of the proposed template for detecting fluid type and lithology based on well logs and seismic inversion, the results of which can be interpreted on a single chart rather than analyzing the data with different templates. The methodology and framework for implementing and generating templates were thoroughly explained in theory and practice to localize P-RPT or update new RPT for another region.
尽管近年来出现了用于地震定量解释的统计和智能方法，但岩石物理模板（RPT）因其简单和易于实施而仍然受到青睐。RPT 是基于井录和地震数据进行岩性和流体判别的基本工具，其准确性和可靠性已得到证实。考虑到对综合 RPT 的需求和提高其效率，我提出了一种用于岩性和流体判别的新型三维棱柱形模板，称为棱柱形岩石物理模板（P-RPT）。为此，以边界和混合岩石物理模型为目标，介绍了设计常规 RPT 的理论方法。接着，设计了一些新颖的三角形和矩形三元和二元模板，并将其相互连接，以构建用于流体识别和岩性鉴定的棱柱。对流体和岩性使用了两个三元图，其中包括 P 波和 S 波速度比以及 Lambda-Mu 参数。此外，还设计了二元图表，包括声阻抗、拉梅参数和孔隙度，并根据文献进行了修改，用于流体和岩性识别。接下来，在不同岩性和流体类型的不同储层中，对所获得的模板在盲数据集（超声波、测井和地震数据）上进行了成功验证。结果表明，P-RPT 可以将可用的 RPT 整合到三维图中，并为地震解释应用提供可靠的框架。基于测井和地震反演的流体类型和岩性检测模板具有用户友好性和通用性等突出优点，其结果可在一张图上解释，而无需使用不同模板分析数据。从理论和实践上全面阐述了实施和生成模板的方法和框架，以实现 P-RPT 的本地化或为另一个区域更新新的 RPT。
{"title":"Prism-shaped rock physics template","authors":"Javad Sharifi","doi":"10.1190/geo2023-0661.1","DOIUrl":"https://doi.org/10.1190/geo2023-0661.1","url":null,"abstract":"Despite the emergence of statistical and intelligent approaches for quantitative seismic interpretation in recent years, Rock Physics Templates (RPTs) are still preferred because of their simplicity and easy implementation. RPTs have been introduced as a fundamental tool for lithology and fluid discrimination based on well-log and seismic data, which have already been proven in terms of accuracy and reliability. Considering the demand for comprehensive RPTs and improving their efficiency, I proposed a novel three-dimensional prism-shaped template for lithology and fluid discrimination, called a prism-shaped rock physics template (P-RPT). For this, a theoretical methodology for designing conventional RPT was introduced with the aim of bounds and hybrid rock physics models. Next, some novel triangular and rectangular ternary and binary templates were designed and connected to one another to build a prism for fluid discrimination and lithology identification. Two ternary charts were used for fluid and lithology, incorporating the P- and S-wave velocity ratios and Lambda-Mu parameters. Further, binary charts, including acoustic impedance, Lamé parameters, and porosity, were designed and modified from literature for fluid and lithology identification. Next, the obtained templates were successfully validated on blind data sets (ultrasonic, well logging, and seismic data) in different reservoirs with various lithologies and fluid types. The results showed that the P-RPT could integrate the available RPTs into a 3D diagram and give a reliable framework for applications in seismic interpretation. User-friendliness and generalizability are the most prominent advantages of the proposed template for detecting fluid type and lithology based on well logs and seismic inversion, the results of which can be interpreted on a single chart rather than analyzing the data with different templates. The methodology and framework for implementing and generating templates were thoroughly explained in theory and practice to localize P-RPT or update new RPT for another region.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140706928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In transient electromagnetic (TEM) methods, the recorded data for both the magnetic field and its time derivative are influenced by the waveforms of the transmitting current. These waveforms are characterized by parameters such as the durations of the turn-on, steady, and turn-off stages, as well as the base frequency, duty cycle, and waveform repetition. The full-waveform effects encompass all counteracting effects observed in TEM responses that arise from using a waveform other than a step-off or step-on waveform. To address these complexities, a 3D forward-modeling solver was developed for TEM methods, capable of calculating TEM responses while considering realistic waveforms with considerations for base frequency, duty cycle, and waveform repetition. The effects of these parameters on the magnetic field and its time derivative were investigated through numerical experiments using models involving deep-buried horizontal and vertical conductors. The results indicated that as the waveform period increases, there is a significant improvement in the detection and discrimination capability of the magnetic field for perfect conductors with a conductivity of 1000 S/m or higher in the models presented in this study. However, the improvement in the time derivative of the magnetic field is minimal. Interestingly, the improvement in both the magnetic field and its time derivative does not show a consistent trend as the conductor conductivity increases. In addition, a novel equivalence phenomenon was uncovered in both the magnetic field and its time derivative data. The results also suggested that as the number of waveform repetitions increases or the duty cycle decreases, the discrepancies between the recorded TEM responses at the two off-time stages within a single period gradually diminish. However, the influence of the full waveform on the TEM responses becomes more pronounced with an increasing number of waveform repetitions or a decrease in the duty cycle, especially for the magnetic field.
在瞬态电磁（TEM）方法中，磁场及其时间导数的记录数据受到发射电流波形的影响。这些波形的特征参数包括接通、稳定和关断阶段的持续时间，以及基频、占空比和波形重复。全波形效应包括在 TEM 响应中观察到的所有抵消效应，这些效应是由于使用了步进关闭或步进开启波形以外的波形而产生的。为了解决这些复杂问题，我们开发了一种用于 TEM 方法的三维正向建模求解器，能够计算 TEM 响应，同时考虑到基频、占空比和波形重复等实际波形。通过使用深埋水平和垂直导体模型进行数值实验，研究了这些参数对磁场及其时间导数的影响。结果表明，随着波形周期的增加，在本研究提出的模型中，对于电导率为 1000 S/m 或更高的完美导体，磁场的探测和分辨能力有显著提高。然而，磁场时间导数的改进却微乎其微。有趣的是，磁场及其时间导数的改善并没有随着导体电导率的增加而呈现一致的趋势。此外，在磁场及其时间导数数据中还发现了一种新的等效现象。结果还表明，随着波形重复次数的增加或占空比的减小，在一个周期内的两个关断时间阶段所记录的 TEM 响应之间的差异会逐渐减小。然而，随着波形重复次数的增加或占空比的降低，全波形对 TEM 响应的影响变得更加明显，尤其是对磁场的影响。
{"title":"Effects of base frequency, duty cycle, and waveform repetition on TEM responses: Insights from models of a deep-buried conductor","authors":"Jianhui Li, Yao Wang","doi":"10.1190/geo2023-0671.1","DOIUrl":"https://doi.org/10.1190/geo2023-0671.1","url":null,"abstract":"In transient electromagnetic (TEM) methods, the recorded data for both the magnetic field and its time derivative are influenced by the waveforms of the transmitting current. These waveforms are characterized by parameters such as the durations of the turn-on, steady, and turn-off stages, as well as the base frequency, duty cycle, and waveform repetition. The full-waveform effects encompass all counteracting effects observed in TEM responses that arise from using a waveform other than a step-off or step-on waveform. To address these complexities, a 3D forward-modeling solver was developed for TEM methods, capable of calculating TEM responses while considering realistic waveforms with considerations for base frequency, duty cycle, and waveform repetition. The effects of these parameters on the magnetic field and its time derivative were investigated through numerical experiments using models involving deep-buried horizontal and vertical conductors. The results indicated that as the waveform period increases, there is a significant improvement in the detection and discrimination capability of the magnetic field for perfect conductors with a conductivity of 1000 S/m or higher in the models presented in this study. However, the improvement in the time derivative of the magnetic field is minimal. Interestingly, the improvement in both the magnetic field and its time derivative does not show a consistent trend as the conductor conductivity increases. In addition, a novel equivalence phenomenon was uncovered in both the magnetic field and its time derivative data. The results also suggested that as the number of waveform repetitions increases or the duty cycle decreases, the discrepancies between the recorded TEM responses at the two off-time stages within a single period gradually diminish. However, the influence of the full waveform on the TEM responses becomes more pronounced with an increasing number of waveform repetitions or a decrease in the duty cycle, especially for the magnetic field.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140717661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Estimating porosity from seismic data is critical for studying underground rock properties, assessing energy reserves, and subsequent reservoir exploration and development. For reservoirs with strong heterogeneity, the endeavor to accurately and stably characterize spatial variations in porosity often encounters considerable challenges due to the rapid lateral changes of formations. In view of this, establishing a robust mapping relationship from seismic data to reservoir properties in three-dimensional (3D) space is important in addressing this challenge. We propose to transform the conventional one-dimensional (1D) sequence-to-point (STP) prediction paradigm into a 3D sequence-to-sequence (STS) prediction paradigm to enable machine learning to extract 3D seismic data features. 3D STS prediction presents valuable potential for enhancing the geological continuity and vertical characterization ability of porosity compared to STP. Building upon the 3D STS prediction model, three strategies from different perspectives are introduced to further enhance the performance of seismic porosity estimation. First, we apply a translation-based data augmentation (DA) strategy to mitigate the problem of sparsely labeled data. Second, we propose spatial constraints (SC) considering absolute coordinates and relative time to boost the spatial delineation of porosity. Third, to incorporate geological insights into machine learning, we impose geologic constraints (GC) by measuring the data distribution similarity between around-the-well predictions and well labels. Compared with data augmentation strategies, incorporating spatial constraints and geologic constraints to STS yields more substantial improvements, which illustrates the importance of prior knowledge for physical parameter inversion. Finally, the combined application of these three strategies and the 3D STS method gives better generalization performance and geological plausibility in the porosity prediction for investigated carbonate reservoirs, outperforming other methods, and decreasing error by an average of 8% across 48 wells compared to STP.
{"title":"Enhancing seismic porosity estimation through 3D sequence-to-sequence deep learning with data augmentation, spatial and geologic constraints","authors":"Minghui Xu, Luanxiao Zhao, Jingyu Liu, Jianhua Geng","doi":"10.1190/geo2023-0614.1","DOIUrl":"https://doi.org/10.1190/geo2023-0614.1","url":null,"abstract":"Estimating porosity from seismic data is critical for studying underground rock properties, assessing energy reserves, and subsequent reservoir exploration and development. For reservoirs with strong heterogeneity, the endeavor to accurately and stably characterize spatial variations in porosity often encounters considerable challenges due to the rapid lateral changes of formations. In view of this, establishing a robust mapping relationship from seismic data to reservoir properties in three-dimensional (3D) space is important in addressing this challenge. We propose to transform the conventional one-dimensional (1D) sequence-to-point (STP) prediction paradigm into a 3D sequence-to-sequence (STS) prediction paradigm to enable machine learning to extract 3D seismic data features. 3D STS prediction presents valuable potential for enhancing the geological continuity and vertical characterization ability of porosity compared to STP. Building upon the 3D STS prediction model, three strategies from different perspectives are introduced to further enhance the performance of seismic porosity estimation. First, we apply a translation-based data augmentation (DA) strategy to mitigate the problem of sparsely labeled data. Second, we propose spatial constraints (SC) considering absolute coordinates and relative time to boost the spatial delineation of porosity. Third, to incorporate geological insights into machine learning, we impose geologic constraints (GC) by measuring the data distribution similarity between around-the-well predictions and well labels. Compared with data augmentation strategies, incorporating spatial constraints and geologic constraints to STS yields more substantial improvements, which illustrates the importance of prior knowledge for physical parameter inversion. Finally, the combined application of these three strategies and the 3D STS method gives better generalization performance and geological plausibility in the porosity prediction for investigated carbonate reservoirs, outperforming other methods, and decreasing error by an average of 8% across 48 wells compared to STP.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140718481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Z. Liu, Jürgen Hoffmann, Etienne Bachmann, Congyue Cui, Frederik J. Simons, J. Tromp
Crosstalk-free source-encoded elastic Full-Waveform Inversion (FWI) using time-domain solvers has demonstrated skill and efficiency at conducting seismic inversions involving multiple sources and receivers with limited computational resources. A drawback of common formulations of the procedure is that, by sweeping through the frequency domain randomly at a rate of one or a few sparsely sampled frequencies per shot, it is difficult to simultaneously incorporate time-selective data windows, as necessary for the targeting of arrivals or wave packets during the various stages of the inversion. Here, we solve this problem by using the Laplace transform of the data. Using complex-valued frequencies allows for damping the records with flexible decay rates and temporal offsets that target specific traveltimes. We present the theory of crosstalk-free source-encoded FWI in the Laplace domain, develop the details of its implementation, and illustrate the procedure with numerical examples relevant to exploration-scale scenarios.
{"title":"Laplace-Domain Crosstalk-Free Source-Encoded Elastic Full Waveform Inversion Using Time-Domain Solvers","authors":"Z. Liu, Jürgen Hoffmann, Etienne Bachmann, Congyue Cui, Frederik J. Simons, J. Tromp","doi":"10.1190/geo2023-0351.1","DOIUrl":"https://doi.org/10.1190/geo2023-0351.1","url":null,"abstract":"Crosstalk-free source-encoded elastic Full-Waveform Inversion (FWI) using time-domain solvers has demonstrated skill and efficiency at conducting seismic inversions involving multiple sources and receivers with limited computational resources. A drawback of common formulations of the procedure is that, by sweeping through the frequency domain randomly at a rate of one or a few sparsely sampled frequencies per shot, it is difficult to simultaneously incorporate time-selective data windows, as necessary for the targeting of arrivals or wave packets during the various stages of the inversion. Here, we solve this problem by using the Laplace transform of the data. Using complex-valued frequencies allows for damping the records with flexible decay rates and temporal offsets that target specific traveltimes. We present the theory of crosstalk-free source-encoded FWI in the Laplace domain, develop the details of its implementation, and illustrate the procedure with numerical examples relevant to exploration-scale scenarios.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140719475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Passive seismic interferometry techniques enable the retrieval of virtual shot gathers at receiver locations. However, it is difficult to distinguish body waves from surface waves in seismic ambient noise data, which leads to failed dispersion measurements, artificial deep reflections, and misleading geological interpretations. We propose a new method that employs the waveforms and their corresponding F-K spectra to identify body waves and surface waves. The proposed technique functions as a data classification procedure before wavefield retrieval and subsequent imaging. A field data example was conducted to test the feasibility of this technique. The field data results demonstrate that the proposed technique can reconstruct satisfactory high signal-to-noise ratio wavefields for reliable imaging and interpretation purposes. The method can also serve as a validation tool for identifying surface-wave-related artificial events in the obtained virtual source reflection image. The marker boundaries of the Songliao Basin in Northeast China are interpreted in the obtained profile and are in agreement with the well logging data. In addition, two normal faults are detected, which corresponds to the extensional rift environment during the early Cretaceous.
{"title":"A seismic ambient noise data classification method based on waveform and frequency-wavenumber analysis: Application to reliable geological interpretation adjacent to Well Songke-2, Northeast China","authors":"Zhong-Yuan Jin, Zhan-Wu Lu, Wei Fu, He-Sheng Hou","doi":"10.1190/geo2023-0340.1","DOIUrl":"https://doi.org/10.1190/geo2023-0340.1","url":null,"abstract":"Passive seismic interferometry techniques enable the retrieval of virtual shot gathers at receiver locations. However, it is difficult to distinguish body waves from surface waves in seismic ambient noise data, which leads to failed dispersion measurements, artificial deep reflections, and misleading geological interpretations. We propose a new method that employs the waveforms and their corresponding F-K spectra to identify body waves and surface waves. The proposed technique functions as a data classification procedure before wavefield retrieval and subsequent imaging. A field data example was conducted to test the feasibility of this technique. The field data results demonstrate that the proposed technique can reconstruct satisfactory high signal-to-noise ratio wavefields for reliable imaging and interpretation purposes. The method can also serve as a validation tool for identifying surface-wave-related artificial events in the obtained virtual source reflection image. The marker boundaries of the Songliao Basin in Northeast China are interpreted in the obtained profile and are in agreement with the well logging data. In addition, two normal faults are detected, which corresponds to the extensional rift environment during the early Cretaceous.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140731791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chuang Xie, Jianhua Wang, Peng Song, Jun Tan, Zhaolun Liu, Yandong Wang
The determination of the P- and S-wave propagation directions is crucial for achieving wavefield decomposition, polarity reversal correction, and noise suppression in elastic reverse time migration (RTM). Compared with the conventional decoupled elastic wave equation, the first-order velocity-dilatation-rotation equations enable a more accurate computation of propagation directions for P- and S-waves. Moreover, compared with the Poynting vector, the optical flow vector signifies the wavefield propagation directions more accurately. To effectively enhance the accuracy of elastic wave imaging, we propose an elastic RTM based on first-order velocity-dilatation-rotation equations using the optical flow vector. Numerical tests illustrate that the proposed method, with or without noise, can better eliminate the migration artifacts and improve the imaging accuracy of the elastic RTM than conventional methods, achieving more accurate wavefield decomposition and superior S-wave polarity reversal correction.
确定 P 波和 S 波的传播方向对于实现波场分解、极性反转校正以及弹性反向时间迁移（RTM）中的噪声抑制至关重要。与传统的解耦弹性波方程相比，一阶速度-膨胀-旋转方程能更精确地计算 P 波和 S 波的传播方向。此外，与 Poynting 向量相比，光流向量能更准确地表示波场的传播方向。为了有效提高弹性波成像的精确度，我们提出了一种基于一阶速度-膨胀-旋转方程的弹性 RTM 方法。数值测试表明，与传统方法相比，无论有无噪声，所提出的方法都能更好地消除迁移伪影，提高弹性 RTM 的成像精度，实现更精确的波场分解和出色的 S 波极性反转校正。
{"title":"Elastic reverse time migration based on first-order velocity-dilatation-rotation equations using the optical flow vector","authors":"Chuang Xie, Jianhua Wang, Peng Song, Jun Tan, Zhaolun Liu, Yandong Wang","doi":"10.1190/geo2023-0198.1","DOIUrl":"https://doi.org/10.1190/geo2023-0198.1","url":null,"abstract":"The determination of the P- and S-wave propagation directions is crucial for achieving wavefield decomposition, polarity reversal correction, and noise suppression in elastic reverse time migration (RTM). Compared with the conventional decoupled elastic wave equation, the first-order velocity-dilatation-rotation equations enable a more accurate computation of propagation directions for P- and S-waves. Moreover, compared with the Poynting vector, the optical flow vector signifies the wavefield propagation directions more accurately. To effectively enhance the accuracy of elastic wave imaging, we propose an elastic RTM based on first-order velocity-dilatation-rotation equations using the optical flow vector. Numerical tests illustrate that the proposed method, with or without noise, can better eliminate the migration artifacts and improve the imaging accuracy of the elastic RTM than conventional methods, achieving more accurate wavefield decomposition and superior S-wave polarity reversal correction.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140736274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Residual moveout (RMO) can have a severe impact on the seismic amplitude with offset (AVO) analysis. It is therefore common practice to quality control and correct the processed seismic data for RMO before AVO analysis. However, a complicating factor is that AVO effect and tuning may result in up- or down-dipping events that are easily mistaken for events with RMO, e.g., AVO Class 2p response. Flattening these events will lead to wrong AVO estimation. We present a new Bayesian joint RMO and AVO inversion to estimate RMO time shifts and AVO intercept and gradient. The joint inversion corrects the seismic data based on RMO and AVO prior models, rather than explicitly assuming that the data should be flattened. The prior models will typically guide towards flat gathers, but will also allow for up and down dipping events when these are possible within the prior model. The method is illustrated on synthetic and real seismic data. For cases where flat events are correct, the results are similar to sequential methods with RMO correction before AVO analysis, but in situations where dipping seismic reflectors may be misinterpreted as events with RMO, the joint inversion provides better results by evaluating RMO and AVO simultaneously. The inversion results include the posterior covariance matrix which represents uncertainties for the AVO intercept and gradient, the RMO time shifts, and the correlations between these at all samples. The RMO time shift uncertainty varies within seismic gathers and depends on how clear and well determined the seismic events are. The uncertainty of the RMO is lower for clear and continuous events, but increases in zones with weaker and noisy events. The uncertainty of the RMO time shifts has a low impact on the uncertainty of the AVO intercept, but increases the uncertainty of the AVO gradient significantly.
{"title":"Bayesian joint AVO and RMO inversion","authors":"Yanis Saadallah, A. Buland","doi":"10.1190/geo2023-0371.1","DOIUrl":"https://doi.org/10.1190/geo2023-0371.1","url":null,"abstract":"Residual moveout (RMO) can have a severe impact on the seismic amplitude with offset (AVO) analysis. It is therefore common practice to quality control and correct the processed seismic data for RMO before AVO analysis. However, a complicating factor is that AVO effect and tuning may result in up- or down-dipping events that are easily mistaken for events with RMO, e.g., AVO Class 2p response. Flattening these events will lead to wrong AVO estimation. We present a new Bayesian joint RMO and AVO inversion to estimate RMO time shifts and AVO intercept and gradient. The joint inversion corrects the seismic data based on RMO and AVO prior models, rather than explicitly assuming that the data should be flattened. The prior models will typically guide towards flat gathers, but will also allow for up and down dipping events when these are possible within the prior model. The method is illustrated on synthetic and real seismic data. For cases where flat events are correct, the results are similar to sequential methods with RMO correction before AVO analysis, but in situations where dipping seismic reflectors may be misinterpreted as events with RMO, the joint inversion provides better results by evaluating RMO and AVO simultaneously. The inversion results include the posterior covariance matrix which represents uncertainties for the AVO intercept and gradient, the RMO time shifts, and the correlations between these at all samples. The RMO time shift uncertainty varies within seismic gathers and depends on how clear and well determined the seismic events are. The uncertainty of the RMO is lower for clear and continuous events, but increases in zones with weaker and noisy events. The uncertainty of the RMO time shifts has a low impact on the uncertainty of the AVO intercept, but increases the uncertainty of the AVO gradient significantly.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140740924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gewei Qi, Jun Tang, Ze He, Wei Shen, Chenchang Zheng, Mengfan Li
Fractures are important seepage channels and storage spaces in tight reservoirs, and are key geological information for exploration and development. Affected by complex tectonic actions, fractures mostly appear in the form of complex fracture belts, which makes it difficult to understand the way wave propagation is affected by the present of fractures with different fracture features. Therefore, we carried out physical experiments of scaled-down physical model wells based on acoustic logging and finite difference numerical simulation research, analyzed the relationship between different fracture characteristics and shear wave and Stoneley wave characteristics, and carried out the fracture width, number, and extensibility. quantitative characterization. The research results show that the amplitude of the direct Stoneley wave decreases exponentially with the increase of the equivalent fracture width. When the equivalent width of the fracture remains constant, the more the number of fractures, the greater the amplitude of the direct Stoneley wave; as the radius of the fracture extension increases, the relative amplitude of the Stoneley wave decreases, showing a logarithmic decrease.
{"title":"Experimental Research on Acoustic Detection of Different Fracture Characteristics","authors":"Gewei Qi, Jun Tang, Ze He, Wei Shen, Chenchang Zheng, Mengfan Li","doi":"10.1190/geo2023-0405.1","DOIUrl":"https://doi.org/10.1190/geo2023-0405.1","url":null,"abstract":"Fractures are important seepage channels and storage spaces in tight reservoirs, and are key geological information for exploration and development. Affected by complex tectonic actions, fractures mostly appear in the form of complex fracture belts, which makes it difficult to understand the way wave propagation is affected by the present of fractures with different fracture features. Therefore, we carried out physical experiments of scaled-down physical model wells based on acoustic logging and finite difference numerical simulation research, analyzed the relationship between different fracture characteristics and shear wave and Stoneley wave characteristics, and carried out the fracture width, number, and extensibility. quantitative characterization. The research results show that the amplitude of the direct Stoneley wave decreases exponentially with the increase of the equivalent fracture width. When the equivalent width of the fracture remains constant, the more the number of fractures, the greater the amplitude of the direct Stoneley wave; as the radius of the fracture extension increases, the relative amplitude of the Stoneley wave decreases, showing a logarithmic decrease.","PeriodicalId":509604,"journal":{"name":"GEOPHYSICS","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140778522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：