Fu Wang, Xinming Wu, Hongliu Zeng, X. Janson, C. Kerans
Seismic horizons play a significant role in reservoir model construction and sedimentary facies interpretation, providing crucial low-frequency constraints for seismic inversion. In basin and regional interpretations, the assumption that seismic reflections represent a stratigraphic surface with constant geologic time is significant for guiding seismic interpretation. This assumption may fail when applied to local reservoir scales due to common geologic time transgressions of a particular event in regular wavelet frequency. There will be inconsistencies between seismic events and stratigraphic surfaces. To address this issue and obtain relatively accurate stratal interpretations, we develop a hybrid horizon extraction method honoring both seismic structures and time-stratigraphic frameworks, in which seismic reflection structures provide local details and interpreted geologic time surfaces offer critical constraints. First, we develop concepts and a workflow using a realistic outcrop model. We propose a new geology-guided structure tensor by fitting a gradient vector of seismic images and geologic time surfaces. We also consider existing geologic conditions, such as unconformities, and fuse them into our method to calculate accurate slopes and generate reliable relative geologic time (RGT) images at a fine scale, followed by making slices. Further, we extend the proposed method to 3D seismic data volumes. Our experiments, conducted using simulated and field data, show the superiority and accuracy of our hybrid method compared with the slope-based and stratal slicing methods. These results highlight the potential for applying the proposed method to fine-scale subsurface modeling.
{"title":"Stratal Surfaces Honoring Seismic Structures and Interpreted Geologic Time Surfaces","authors":"Fu Wang, Xinming Wu, Hongliu Zeng, X. Janson, C. Kerans","doi":"10.1190/geo2022-0432.1","DOIUrl":"https://doi.org/10.1190/geo2022-0432.1","url":null,"abstract":"Seismic horizons play a significant role in reservoir model construction and sedimentary facies interpretation, providing crucial low-frequency constraints for seismic inversion. In basin and regional interpretations, the assumption that seismic reflections represent a stratigraphic surface with constant geologic time is significant for guiding seismic interpretation. This assumption may fail when applied to local reservoir scales due to common geologic time transgressions of a particular event in regular wavelet frequency. There will be inconsistencies between seismic events and stratigraphic surfaces. To address this issue and obtain relatively accurate stratal interpretations, we develop a hybrid horizon extraction method honoring both seismic structures and time-stratigraphic frameworks, in which seismic reflection structures provide local details and interpreted geologic time surfaces offer critical constraints. First, we develop concepts and a workflow using a realistic outcrop model. We propose a new geology-guided structure tensor by fitting a gradient vector of seismic images and geologic time surfaces. We also consider existing geologic conditions, such as unconformities, and fuse them into our method to calculate accurate slopes and generate reliable relative geologic time (RGT) images at a fine scale, followed by making slices. Further, we extend the proposed method to 3D seismic data volumes. Our experiments, conducted using simulated and field data, show the superiority and accuracy of our hybrid method compared with the slope-based and stratal slicing methods. These results highlight the potential for applying the proposed method to fine-scale subsurface modeling.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"29 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139200669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Trial-and-error modeling may provide some level of interpretation of the subsurface while sacrificing certainty, and certainty it is a viable alternative for precise three-dimensional (3D) interpretation of real ground-airborne frequency-domain electromagnetic (GAFEM) data. Therefore, a semiautomatic trial-and-error modeling approach has been presented in this study. We first developed a 3D GAFEM forward modeling code. Its accuracy was demonstrated using a 3D synthetic model with a topography and a tilted anomalous body. An initial model was established based on known geological constraints. The code was repeated, and the parameters of the model were renewed semi-automatically based on a predefined geometry-resistivity combination list. The model that could achieve the minimum error between the computed response and collected GAFEM data was selected as the final model. We applied the proposed semi-automatic trial-and-error modeling approach to a geothermal resource survey in the Yishu Faulting Basin, China. The purpose of this survey was to interpret the resistivity structure of the subsurface and evaluate the potential development of geothermal resources in the survey area. The final model obtained by trial-and-error modeling, which was constrained by known geological information and subsurface geoelectric structures inferred from 2D models inverted by the CSAMT and MT data measured at the same location, indicated the existence of geothermal resources. This indication was supported by drilling results from a well site located on the survey line. A comparative analysis was also conducted between the model obtained by trial-and-error modeling and the models obtained by 3D inversion of the GAFEM dataset. The apparent resistivity was calculated using the same data. The results have shown that different approaches can achieve similar subsurface geometries and resistivity distributions for faulting basin structures.
{"title":"Trial-and-error modeling of ground-airborne electromagnetic data in the Yishu faulting basin, China","authors":"Ming Zhang, Colin G Farquharson, Tingting Lin","doi":"10.1190/geo2022-0452.1","DOIUrl":"https://doi.org/10.1190/geo2022-0452.1","url":null,"abstract":"Trial-and-error modeling may provide some level of interpretation of the subsurface while sacrificing certainty, and certainty it is a viable alternative for precise three-dimensional (3D) interpretation of real ground-airborne frequency-domain electromagnetic (GAFEM) data. Therefore, a semiautomatic trial-and-error modeling approach has been presented in this study. We first developed a 3D GAFEM forward modeling code. Its accuracy was demonstrated using a 3D synthetic model with a topography and a tilted anomalous body. An initial model was established based on known geological constraints. The code was repeated, and the parameters of the model were renewed semi-automatically based on a predefined geometry-resistivity combination list. The model that could achieve the minimum error between the computed response and collected GAFEM data was selected as the final model. We applied the proposed semi-automatic trial-and-error modeling approach to a geothermal resource survey in the Yishu Faulting Basin, China. The purpose of this survey was to interpret the resistivity structure of the subsurface and evaluate the potential development of geothermal resources in the survey area. The final model obtained by trial-and-error modeling, which was constrained by known geological information and subsurface geoelectric structures inferred from 2D models inverted by the CSAMT and MT data measured at the same location, indicated the existence of geothermal resources. This indication was supported by drilling results from a well site located on the survey line. A comparative analysis was also conducted between the model obtained by trial-and-error modeling and the models obtained by 3D inversion of the GAFEM dataset. The apparent resistivity was calculated using the same data. The results have shown that different approaches can achieve similar subsurface geometries and resistivity distributions for faulting basin structures.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"33 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139201953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
David Li, Lianjie Huang, Yingcai Zheng, Yingping Li, M. Schoenball, V. Rodríguez-Tribaldos, Jonathan B. Ajo‐Franklin, C. Hopp, Tim C. Johnson, H. Knox, Doug Blankenship, P. Dobson, Tim Kneafsey, M. Robertson
Enhanced geothermal systems (EGS) require cost-effective monitoring of fracture networks. We validate the capability of using borehole distributed-acoustic-sensing (DAS) ambient noise for fracture monitoring using core photos and core logs. The EGS Collab Project conducts 10-m-scale field experiments of hydraulic fracture stimulation using 50-60 m deep experimental wells at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. The first EGS Collab testbed is located at the 1616.67 m (4850 ft) depth at SURF and consists of one injection well, one production well, and six monitoring wells. All wells were drilled sub-horizontally from an access tunnel called a drift. The project uses a single continuous fiber optic cable installed sequentially in the six monitoring wells to record DAS data for monitoring hydraulic fracturing during stimulation. We analyze 60-s time records of the borehole DAS ambient noise data and compute the noise root-mean-squares (RMS) amplitude on each channel (points along the fiber cable) to obtain DAS ambient noise RMS amplitude depth profiles along the monitoring wellbores. Our noise RMS amplitude profiles show amplitude peaks at distinct depths. We compare the DAS noise RMS amplitude profiles with borehole core photos and core logs and find that the DAS noise RMS amplitude peaks correspond to the locations of fractures or lithological changes shown in the core photos or core logs. We then compute the hourly DAS noise RMS amplitude profiles in two monitoring wells during three stimulation cycles in 72 hours and find that the DAS noise RMS amplitude profiles vary with time, indicating the fracture opening/growth or closing during the hydraulic stimulation. Our results demonstrate that borehole DAS passive ambient noise can be used to detect fractures and monitor fracturing processes in EGS reservoirs.
强化地热系统（EGS）需要对断裂网络进行经济有效的监测。我们利用岩心照片和岩心记录，验证了利用井眼分布式声学传感（DAS）环境噪声进行裂缝监测的能力。EGS Collab 项目在南达科他州利德的桑福德地下研究设施（SURF）利用 50-60 米深的实验井进行 10 米规模的水力压裂激励现场实验。第一个 EGS Collab 试验台位于 SURF 1616.67 米（4850 英尺）深处，由一口注入井、一口生产井和六口监测井组成。所有水井均从一个称为漂流的通道中沿水平方向钻出。该项目使用在六口监测井中依次安装的单根连续光缆记录 DAS 数据，以监测水力压裂过程中的刺激情况。我们分析井眼 DAS 环境噪声数据的 60 秒时间记录，并计算每个通道（光缆沿线各点）上的噪声均方根（RMS）振幅，从而获得沿监测井筒的 DAS 环境噪声均方根振幅深度剖面图。我们的噪声 RMS 振幅剖面图在不同深度显示出振幅峰值。我们将 DAS 噪声有效值振幅剖面与井眼岩心照片和岩心测井记录进行比较，发现 DAS 噪声有效值振幅峰值与岩心照片或岩心测井记录中显示的裂缝或岩性变化位置相对应。然后，我们计算了两口监测井在 72 小时内三个水力刺激周期的每小时 DAS 噪声有效值幅值剖面图，发现 DAS 噪声有效值幅值剖面图随时间变化，表明了水力刺激过程中裂缝的开裂/生长或闭合情况。我们的研究结果表明，井眼 DAS 被动环境噪声可用于检测 EGS 储层中的裂缝和监测压裂过程。
{"title":"Detecting fractures and monitoring hydraulic fracturing processes at the first EGS Collab testbed using borehole DAS ambient noise","authors":"David Li, Lianjie Huang, Yingcai Zheng, Yingping Li, M. Schoenball, V. Rodríguez-Tribaldos, Jonathan B. Ajo‐Franklin, C. Hopp, Tim C. Johnson, H. Knox, Doug Blankenship, P. Dobson, Tim Kneafsey, M. Robertson","doi":"10.1190/geo2023-0078.1","DOIUrl":"https://doi.org/10.1190/geo2023-0078.1","url":null,"abstract":"Enhanced geothermal systems (EGS) require cost-effective monitoring of fracture networks. We validate the capability of using borehole distributed-acoustic-sensing (DAS) ambient noise for fracture monitoring using core photos and core logs. The EGS Collab Project conducts 10-m-scale field experiments of hydraulic fracture stimulation using 50-60 m deep experimental wells at the Sanford Underground Research Facility (SURF) in Lead, South Dakota. The first EGS Collab testbed is located at the 1616.67 m (4850 ft) depth at SURF and consists of one injection well, one production well, and six monitoring wells. All wells were drilled sub-horizontally from an access tunnel called a drift. The project uses a single continuous fiber optic cable installed sequentially in the six monitoring wells to record DAS data for monitoring hydraulic fracturing during stimulation. We analyze 60-s time records of the borehole DAS ambient noise data and compute the noise root-mean-squares (RMS) amplitude on each channel (points along the fiber cable) to obtain DAS ambient noise RMS amplitude depth profiles along the monitoring wellbores. Our noise RMS amplitude profiles show amplitude peaks at distinct depths. We compare the DAS noise RMS amplitude profiles with borehole core photos and core logs and find that the DAS noise RMS amplitude peaks correspond to the locations of fractures or lithological changes shown in the core photos or core logs. We then compute the hourly DAS noise RMS amplitude profiles in two monitoring wells during three stimulation cycles in 72 hours and find that the DAS noise RMS amplitude profiles vary with time, indicating the fracture opening/growth or closing during the hydraulic stimulation. Our results demonstrate that borehole DAS passive ambient noise can be used to detect fractures and monitor fracturing processes in EGS reservoirs.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"5 4","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139205735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The impermeable caprock within a geothermal system serves the purpose of effectively sealing the reservoir, resulting in the elevation of both pressure and temperature. This sealing mechanism plays a crucial role in the long-term preservation of the system, while also contributing to its overall sustainability. Caprock failure subsequent to seismic activity near a geothermal site can lead to the permeation of the caprock structure, resulting in diminished sealing capabilities and a decline in the reservoir temperature. Additionally, this process alters the geochemical composition of the water by creating a hydrothermal mixture zone that disrupts the resistivity structure of the caprock, which is typically characterized by low resistivity values due to its substantial clay content and mineral alteration. This study focuses on investigating the integrity of the caprock at ơnakkale-Tuzla geothermal field in Turkey, where the water temperature and conductivity were reported to have decreased after a moderate magnitude earthquake and subsequent aftershocks. For this purpose, we performed magnetotelluric (MT) measurements, a method known for its sensitivity to geochemical reactions. These measurements were conducted along two parallel profiles that encompassed a total of 32 stations. Particle swarm optimization (PSO) technique was employed to overcome subtle difficulties associated with conventional inversion methods when modeling the MT data of complex formations. This is the first study that overcomes the difficulties emanating from the caprock failure by modeling MT data using PSO. Our modeling approach produced resistivity images that we interpreted as the signature of the failed caprock following the earthquake at the study site. Our results appear to confirm the documented geochemical changes or hydrothermal mixture zone about caprock structure.
{"title":"Caprock integrity at Çanakkale-Tuzla hydrothermal system inferred from magnetotelluric modeling using particle swarm optimization","authors":"Ersin Büyük, A. Karaman","doi":"10.1190/geo2023-0192.1","DOIUrl":"https://doi.org/10.1190/geo2023-0192.1","url":null,"abstract":"The impermeable caprock within a geothermal system serves the purpose of effectively sealing the reservoir, resulting in the elevation of both pressure and temperature. This sealing mechanism plays a crucial role in the long-term preservation of the system, while also contributing to its overall sustainability. Caprock failure subsequent to seismic activity near a geothermal site can lead to the permeation of the caprock structure, resulting in diminished sealing capabilities and a decline in the reservoir temperature. Additionally, this process alters the geochemical composition of the water by creating a hydrothermal mixture zone that disrupts the resistivity structure of the caprock, which is typically characterized by low resistivity values due to its substantial clay content and mineral alteration. This study focuses on investigating the integrity of the caprock at ơnakkale-Tuzla geothermal field in Turkey, where the water temperature and conductivity were reported to have decreased after a moderate magnitude earthquake and subsequent aftershocks. For this purpose, we performed magnetotelluric (MT) measurements, a method known for its sensitivity to geochemical reactions. These measurements were conducted along two parallel profiles that encompassed a total of 32 stations. Particle swarm optimization (PSO) technique was employed to overcome subtle difficulties associated with conventional inversion methods when modeling the MT data of complex formations. This is the first study that overcomes the difficulties emanating from the caprock failure by modeling MT data using PSO. Our modeling approach produced resistivity images that we interpreted as the signature of the failed caprock following the earthquake at the study site. Our results appear to confirm the documented geochemical changes or hydrothermal mixture zone about caprock structure.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"106 ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139242993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Liwei Cheng, Ali Tura, James Simmons, Roel Snieder, Petar Vladov Angelov, Rao Narhari Srinivasa, Shamima Akther
Attenuating interference from internal multiples has challenged seismic data imaging in the Middle East basins. The challenge results from the strong short-period internal multiples that exhibit nearly indistinguishable characters from the primaries reflected from the underlying reservoirs due to predominantly horizontal strata and occasional low-relief structures, as shown in the Jurassic formations in Kuwait. To address the internal-multiple issues, multiple prediction followed by adaptive subtraction is the most common approach in the industry. However, due to the similarities between primaries and multiples, applying adaptive subtraction poses a high risk of primary-amplitude damage, preventing quantitative seismic data interpretation. Therefore, we examine the Marchenko method, which retrieves Greens functions from surface seismic data for target-oriented imaging without applying adaptive subtraction. Marchenko imaging has shown promising results on several offshore seismic datasets, but an onshore application is still needed. To better understand the effects of internal multiples and implement Marchenko imaging, we perform integrated analysis through well log, vertical seismic profiling (VSP), and seismic data from a hydrocarbon field in Kuwait. In addition, we use VSP data to cross-check the retrieved Greens functions and estimate the scaling factor of the Marchenko method. The results show that 1) the poor imaging at the center of the field is due to destructive interference of internal multiples, 2) the reverberation of internal multiples between the evaporite formations of the overburden are the most likely candidates that affect the seismic images of the Jurassic reservoirs, 3) the retrieved Greens functions conform to the recorded Greens functions from VSP data, and 4) Marchenko imaging provides a means to improve the seismic images of the Jurassic formations in Kuwait.
{"title":"Marchenko imaging assisted by VSP data for land seismic data in the Middle East","authors":"Liwei Cheng, Ali Tura, James Simmons, Roel Snieder, Petar Vladov Angelov, Rao Narhari Srinivasa, Shamima Akther","doi":"10.1190/geo2023-0167.1","DOIUrl":"https://doi.org/10.1190/geo2023-0167.1","url":null,"abstract":"Attenuating interference from internal multiples has challenged seismic data imaging in the Middle East basins. The challenge results from the strong short-period internal multiples that exhibit nearly indistinguishable characters from the primaries reflected from the underlying reservoirs due to predominantly horizontal strata and occasional low-relief structures, as shown in the Jurassic formations in Kuwait. To address the internal-multiple issues, multiple prediction followed by adaptive subtraction is the most common approach in the industry. However, due to the similarities between primaries and multiples, applying adaptive subtraction poses a high risk of primary-amplitude damage, preventing quantitative seismic data interpretation. Therefore, we examine the Marchenko method, which retrieves Greens functions from surface seismic data for target-oriented imaging without applying adaptive subtraction. Marchenko imaging has shown promising results on several offshore seismic datasets, but an onshore application is still needed. To better understand the effects of internal multiples and implement Marchenko imaging, we perform integrated analysis through well log, vertical seismic profiling (VSP), and seismic data from a hydrocarbon field in Kuwait. In addition, we use VSP data to cross-check the retrieved Greens functions and estimate the scaling factor of the Marchenko method. The results show that 1) the poor imaging at the center of the field is due to destructive interference of internal multiples, 2) the reverberation of internal multiples between the evaporite formations of the overburden are the most likely candidates that affect the seismic images of the Jurassic reservoirs, 3) the retrieved Greens functions conform to the recorded Greens functions from VSP data, and 4) Marchenko imaging provides a means to improve the seismic images of the Jurassic formations in Kuwait.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"21 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139249531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sarp Karakaya, O. Ogiesoba, C. Olariu, Shuvajit Bhattacharya
The deposition and mixing of carbonates and siliciclastics in the Cisco Group of the Eastern Shelf of the Permian Basin are complicated by the temporal overlap between icehouse eustatic sea-level oscillations and fluctuations in sediment influx due to the rejuvenation of the Ouachita fold belt. Previous investigators have used well-log correlation as the primary tool in their interpretations of the area’s reciprocal depositional model, but well-log correlation alone cannot explain the full range of spatial lithology variations in the system. To better understand the lithology variation in the area, we used an integrated technique that combined wireline log information from 17 wells with 625 km2 3D seismic data through post-stack seismic inversion, probabilistic neural networks, and Bayesian classification. We used deterministic matrix inversion to derive lithology classes from well logs. Cross-plot analyses revealed that the acoustic impedance and neutron porosity log pair could be used to differentiate lithologies. We performed model-based post-stack inversion to generate a P-impedance volume and used probabilistic neural networks to generate a neutron porosity volume. We combined these volumes through supervised Bayesian classification to generate lithology probability volumes for each lithology and a most probable lithology volume throughout the seismic data. The lithology volumes highlight dominant lithologies (carbonate, shale, sand, and mixed) that allowed interpretation of major carbonate platforms, sand-to-shale ratio variations, carbonate build-ups between wells, and channel fill lithologies. Our proposed semi-automated lithology detection workflow applies to regional studies and is also valid for reservoir-scale studies to determine variations in lithologies.
{"title":"Generating 3D Lithology Probability Volumes Using Poststack Inversion, Probabilistic Neural Networks, and Bayesian Classification A Case Study from the Mixed Carbonate Siliciclastic Deposits of the Cisco Group of the Eastern Shelf of the Permian Basin, North - Central Texas","authors":"Sarp Karakaya, O. Ogiesoba, C. Olariu, Shuvajit Bhattacharya","doi":"10.1190/geo2023-0157.1","DOIUrl":"https://doi.org/10.1190/geo2023-0157.1","url":null,"abstract":"The deposition and mixing of carbonates and siliciclastics in the Cisco Group of the Eastern Shelf of the Permian Basin are complicated by the temporal overlap between icehouse eustatic sea-level oscillations and fluctuations in sediment influx due to the rejuvenation of the Ouachita fold belt. Previous investigators have used well-log correlation as the primary tool in their interpretations of the area’s reciprocal depositional model, but well-log correlation alone cannot explain the full range of spatial lithology variations in the system. To better understand the lithology variation in the area, we used an integrated technique that combined wireline log information from 17 wells with 625 km2 3D seismic data through post-stack seismic inversion, probabilistic neural networks, and Bayesian classification. We used deterministic matrix inversion to derive lithology classes from well logs. Cross-plot analyses revealed that the acoustic impedance and neutron porosity log pair could be used to differentiate lithologies. We performed model-based post-stack inversion to generate a P-impedance volume and used probabilistic neural networks to generate a neutron porosity volume. We combined these volumes through supervised Bayesian classification to generate lithology probability volumes for each lithology and a most probable lithology volume throughout the seismic data. The lithology volumes highlight dominant lithologies (carbonate, shale, sand, and mixed) that allowed interpretation of major carbonate platforms, sand-to-shale ratio variations, carbonate build-ups between wells, and channel fill lithologies. Our proposed semi-automated lithology detection workflow applies to regional studies and is also valid for reservoir-scale studies to determine variations in lithologies.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"172 ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139249666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xintong Dong, Shaoping Lu, Jun Lin, Shukui Zhang, Kai Ren, M. Cheng
Dense shots can improve the fold of subsurface imaging points, which is essential for the resolution of imaging results. However, dense shots significantly increase the cost of data acquisition, which is one of the major bottlenecks faced by seismic exploration. To address this issue, we speculate whether it is possible to construct an effective method to optimize the image made by stacking sparse shots and then generate an imaging result similar to the image made by stacking dense shots. In other words, we explore the possibility of using an optimization method to replace the dense shots in migration imaging, which is likely to reduce the acquisition cost of seismic data. Deep-learning can establish a non-linear and complex mapping relationship by using data-driven strategies. Inspired by this, we use the convolutional neural network to establish a novel mapping relationship from the sparse-shot image to the dense-shot image by constructing a suitable training dataset and designing a self-guided attention network architecture. We refer to this mapping relationship as shot compensation. We use the 2D Sigsbee2b model and the 3D SEAM (SEG Advanced modeling) model to demonstrate the potential application of shot compensation in reducing the acquisition cost of seismic data. Moreover, a real 2D marine seismic dataset is used to evaluate the effectiveness of shot compensation. Experimental results on both synthetic and real data show that this proposed shot compensation method can improve the quality of sparse-shot images and that the improved imaging results are similar to their corresponding dense-shot images.
{"title":"Can Deep-Learning Compensate the Sparse Shots in Imaging Domain? A Potential Alternative for Reducing the Acquisition-Cost of Seismic Data","authors":"Xintong Dong, Shaoping Lu, Jun Lin, Shukui Zhang, Kai Ren, M. Cheng","doi":"10.1190/geo2022-0711.1","DOIUrl":"https://doi.org/10.1190/geo2022-0711.1","url":null,"abstract":"Dense shots can improve the fold of subsurface imaging points, which is essential for the resolution of imaging results. However, dense shots significantly increase the cost of data acquisition, which is one of the major bottlenecks faced by seismic exploration. To address this issue, we speculate whether it is possible to construct an effective method to optimize the image made by stacking sparse shots and then generate an imaging result similar to the image made by stacking dense shots. In other words, we explore the possibility of using an optimization method to replace the dense shots in migration imaging, which is likely to reduce the acquisition cost of seismic data. Deep-learning can establish a non-linear and complex mapping relationship by using data-driven strategies. Inspired by this, we use the convolutional neural network to establish a novel mapping relationship from the sparse-shot image to the dense-shot image by constructing a suitable training dataset and designing a self-guided attention network architecture. We refer to this mapping relationship as shot compensation. We use the 2D Sigsbee2b model and the 3D SEAM (SEG Advanced modeling) model to demonstrate the potential application of shot compensation in reducing the acquisition cost of seismic data. Moreover, a real 2D marine seismic dataset is used to evaluate the effectiveness of shot compensation. Experimental results on both synthetic and real data show that this proposed shot compensation method can improve the quality of sparse-shot images and that the improved imaging results are similar to their corresponding dense-shot images.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"20 ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139249803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose a waveform matching inversion method to determine the focal mechanism of microseismic events recorded by a single well observation system. Our method employs the cross-correlation technique to mitigate the influence of anisotropy on the S-wave. Then by conducting a grid search for strike, dip, and rake, we match the observed waveforms of P- and S-wave with the corresponding theoretical waveforms. A synthetic test demonstrates the robustness and accuracy of our method in resolving the focal mechanism of microseismic events under a single well observation system. By applying our method to the events that have been categorized into two clusters based on spatial and temporal evolution recorded during the hydraulic fracturing operation in the Weiyuan shale reservoir, we observe the two clusters have distinct focal mechanism and stress characteristics. The events in remote cluster (cluster A) exhibits consistent focal mechanisms, with a concentrated distribution of P-axis orientations. And the inverted maximum principal stress direction of cluster A aligns with local maximum principal stress direction (SHmax). It implies events in cluster A occur in a uniform stress condition. In contrast, the other cluster (cluster B) near the injection well exhibits significant variation in focal mechanisms, with a scattered distribution of P-axis orientations. And the inverted maximum principal stress direction deviates from local maximum principal stress direction (SHmax), indicating that events in cluster B occur in a complicated stress condition.
我们提出了一种波形匹配反演方法，用于确定单井观测系统记录的微地震事件的焦点机制。我们的方法采用了交叉相关技术来减轻各向异性对 S 波的影响。然后，通过对走向、倾角和斜角进行网格搜索，我们将观测到的 P 波和 S 波波形与相应的理论波形相匹配。合成测试证明了我们的方法在单井观测系统下解析微震事件焦点机制的稳健性和准确性。将我们的方法应用于威远页岩储层水力压裂过程中记录到的基于时空演化分为两个群组的事件，我们观察到这两个群组具有不同的聚焦机制和应力特征。偏远群组（群组 A）的事件表现出一致的聚焦机制，P 轴方向集中分布。A组的倒置最大主应力方向与当地最大主应力方向（SHmax）一致。这意味着群集 A 中的事件是在均匀应力条件下发生的。相比之下，注水井附近的另一个群集（群集 B）在病灶机制上表现出明显的差异，P 轴方向呈分散分布。而且倒置的最大主应力方向偏离了当地的最大主应力方向（SHmax），表明群集 B 中的事件发生在复杂的应力条件下。
{"title":"Research on focal mechanism of microseismic events and the regional stress during hydraulic fracturing at a shale play site in southwest China","authors":"Xin-Xing Chen, Xiao-Bo Meng, Hai-Chao Chen, Xin-Yu Chen, Qiu-Yu Li, Ming-Yu Guo","doi":"10.1190/geo2023-0046.1","DOIUrl":"https://doi.org/10.1190/geo2023-0046.1","url":null,"abstract":"We propose a waveform matching inversion method to determine the focal mechanism of microseismic events recorded by a single well observation system. Our method employs the cross-correlation technique to mitigate the influence of anisotropy on the S-wave. Then by conducting a grid search for strike, dip, and rake, we match the observed waveforms of P- and S-wave with the corresponding theoretical waveforms. A synthetic test demonstrates the robustness and accuracy of our method in resolving the focal mechanism of microseismic events under a single well observation system. By applying our method to the events that have been categorized into two clusters based on spatial and temporal evolution recorded during the hydraulic fracturing operation in the Weiyuan shale reservoir, we observe the two clusters have distinct focal mechanism and stress characteristics. The events in remote cluster (cluster A) exhibits consistent focal mechanisms, with a concentrated distribution of P-axis orientations. And the inverted maximum principal stress direction of cluster A aligns with local maximum principal stress direction (SHmax). It implies events in cluster A occur in a uniform stress condition. In contrast, the other cluster (cluster B) near the injection well exhibits significant variation in focal mechanisms, with a scattered distribution of P-axis orientations. And the inverted maximum principal stress direction deviates from local maximum principal stress direction (SHmax), indicating that events in cluster B occur in a complicated stress condition.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"158 ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139251005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The explicit finite-difference (FD) method is widely used in numerical simulation of seismic wave propagation to approximate spatial derivatives. However, both the traditional and optimized high-order explicit FD methods suffer from the saturation effect, which seriously restricts the improvement of numerical accuracy. In contrast, the implicit FD method approximates the spatial derivatives in the form of rational functions and thus can obtain much higher numerical accuracy with relatively low orders; however, its computational cost is expensive due to the need to invert a multi-diagonal matrix. We derive an explicit strategy for the implicit FD method to reduce the computational cost, constructing the implicit FD method with the discrete Fourier matrix; then, we transform the inversion of the multi-diagonal matrix into an explicit matrix multiplication; next, we construct an objective function based on the L1 norm to reduce approximation error of the implicit FD method. The proposed explicit strategy of the implicit FD method can avoid inverting the multi-diagonal matrix, thus improving the computational efficiency. The proposed constant coefficient optimization method reduces the approximation error in the medium-wavenumber range at the cost of tolerable deviation (smaller than 0.0001) in the low-wavenumber range. For the 2D Marmousi model, the root-mean-square error of the numerical results obtained by the proposed method is one-fifth that of the traditional implicit FD method with the same order (i.e., 5/3) and one-third that of the traditional explicit FD method with much higher orders (i.e., 72). The significant reduction of numerical error makes the proposed method promising for numerical simulation in large-scale models, especially for long-time simulations.
{"title":"Simplified implicit finite-difference method of spatial derivative using explicit schemes with optimized constant coefficients based on lt;igt; Llt;/igt;lt;subgt;1lt;/subgt; norm","authors":"Zhongzheng Miao, Jinhai Zhang","doi":"10.1190/geo2023-0246.1","DOIUrl":"https://doi.org/10.1190/geo2023-0246.1","url":null,"abstract":"The explicit finite-difference (FD) method is widely used in numerical simulation of seismic wave propagation to approximate spatial derivatives. However, both the traditional and optimized high-order explicit FD methods suffer from the saturation effect, which seriously restricts the improvement of numerical accuracy. In contrast, the implicit FD method approximates the spatial derivatives in the form of rational functions and thus can obtain much higher numerical accuracy with relatively low orders; however, its computational cost is expensive due to the need to invert a multi-diagonal matrix. We derive an explicit strategy for the implicit FD method to reduce the computational cost, constructing the implicit FD method with the discrete Fourier matrix; then, we transform the inversion of the multi-diagonal matrix into an explicit matrix multiplication; next, we construct an objective function based on the L1 norm to reduce approximation error of the implicit FD method. The proposed explicit strategy of the implicit FD method can avoid inverting the multi-diagonal matrix, thus improving the computational efficiency. The proposed constant coefficient optimization method reduces the approximation error in the medium-wavenumber range at the cost of tolerable deviation (smaller than 0.0001) in the low-wavenumber range. For the 2D Marmousi model, the root-mean-square error of the numerical results obtained by the proposed method is one-fifth that of the traditional implicit FD method with the same order (i.e., 5/3) and one-third that of the traditional explicit FD method with much higher orders (i.e., 72). The significant reduction of numerical error makes the proposed method promising for numerical simulation in large-scale models, especially for long-time simulations.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"4 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139251768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jiandong Huang, Dinghui Yang, Xijun He, Tao Liu, Weijuan Meng
The decoupling of P- and S-waves is an essential prerequisite for elastic reverse time migration (RTM), which effectively reduces crosstalk artifacts, but most wavefield separation algorithms are implemented on uniform rectangular grids. We have developed an amplitude- and phase-preserving P- and S-wavefield separation approach on unstructured meshes, which can effectively decompose the original elastic wavefield into P- and S-wavefields. The isotropic case is considered. With the aid of viscoelastic theory, we choose to attenuate P- or S-waves and preserve the other wave mode, so as to achieve wavefield decomposition. Viscoelastic wave equations are first reformulated as decoupling wave equations with a selective strong attenuation. We then use the discontinuous Galerkin (DG) method to simulate decoupling P or S wavefield propagation on triangular and tetrahedral meshes. We adopt a quadrature-free DG approach and the arbitrary mesh is mapped into the reference mesh for numerical calculation, where no additional volume and surface integrations are involved. The amplitude and phase information of this vector decomposition agrees with that of the original elastic data. Four numerical examples are used to demonstrate the superior performance of this vector decomposition algorithm. The isotropic example shows the applicability and correctness of our proposed scheme and the second example displays the superiority in handling strong velocity contrasts. The third example exhibits the mesh flexibility in dealing with complex structures, such as caves, faults, undulating surfaces, etc. The last example shows the effectiveness of our developed algorithm extended to a 3D case.
P 波和 S 波的解耦是弹性反向时间迁移（RTM）的基本前提，可有效减少串扰伪影，但大多数波场分离算法都是在均匀矩形网格上实现的。我们在非结构网格上开发了一种保留振幅和相位的 P 波场和 S 波场分离方法，可有效地将原始弹性波场分解为 P 波场和 S 波场。考虑的是各向同性情况。借助粘弹性理论，我们选择衰减 P 波或 S 波，保留其他波模，从而实现波场分解。粘弹性波方程首先被重新表述为具有选择性强衰减的解耦波方程。然后，我们使用非连续伽勒金（DG）方法模拟解耦 P 或 S 波场在三角形和四面体网格上的传播。我们采用无正交 DG 方法，将任意网格映射到参考网格中进行数值计算，不涉及额外的体积和表面积分。这种矢量分解的振幅和相位信息与原始弹性数据一致。四个数值示例展示了这种矢量分解算法的优越性能。各向同性示例显示了我们提出的方案的适用性和正确性，第二个示例显示了处理强烈速度对比的优越性。第三个例子展示了网格在处理复杂结构（如洞穴、断层、起伏表面等）时的灵活性。最后一个例子展示了我们开发的算法在三维情况下的有效性。
{"title":"Amplitude-preserving P/S wavefield separation with the discontinuous Galerkin method on unstructured meshes","authors":"Jiandong Huang, Dinghui Yang, Xijun He, Tao Liu, Weijuan Meng","doi":"10.1190/geo2023-0330.1","DOIUrl":"https://doi.org/10.1190/geo2023-0330.1","url":null,"abstract":"The decoupling of P- and S-waves is an essential prerequisite for elastic reverse time migration (RTM), which effectively reduces crosstalk artifacts, but most wavefield separation algorithms are implemented on uniform rectangular grids. We have developed an amplitude- and phase-preserving P- and S-wavefield separation approach on unstructured meshes, which can effectively decompose the original elastic wavefield into P- and S-wavefields. The isotropic case is considered. With the aid of viscoelastic theory, we choose to attenuate P- or S-waves and preserve the other wave mode, so as to achieve wavefield decomposition. Viscoelastic wave equations are first reformulated as decoupling wave equations with a selective strong attenuation. We then use the discontinuous Galerkin (DG) method to simulate decoupling P or S wavefield propagation on triangular and tetrahedral meshes. We adopt a quadrature-free DG approach and the arbitrary mesh is mapped into the reference mesh for numerical calculation, where no additional volume and surface integrations are involved. The amplitude and phase information of this vector decomposition agrees with that of the original elastic data. Four numerical examples are used to demonstrate the superior performance of this vector decomposition algorithm. The isotropic example shows the applicability and correctness of our proposed scheme and the second example displays the superiority in handling strong velocity contrasts. The third example exhibits the mesh flexibility in dealing with complex structures, such as caves, faults, undulating surfaces, etc. The last example shows the effectiveness of our developed algorithm extended to a 3D case.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":"24 S2","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139252434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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