In many cases, 1D inversion is still an important step in transient electromagnetic data processing. Potential issues may arise in the calculation of apparent resistivity using induced electromotive force (EMF) due to overshoot and the presence of multi-valued functions. Obtaining reliable and consistent inversion results using a uniform half-space as the initial model is challenging, especially when aiming for efficient inversion. Focusing on these problems, we use the land-based transient electromagnetic (TEM) sounding data, which was acquired by using a large fixed-loop transmitter, and adopt a quasi-2D inversion scheme to generate improved images of the subsurface resistivity structure. First, we have considered directly using magnetic field data or converting induced EMF into magnetic field, and then calculating the apparent resistivity over the whole zone. Next, a resistivity profile that varies with depth is obtained through fast smoke ring imaging. This profile serves as the initial model for the subsequent optimal inversion. The inversion scheme uses a nonlinear least-squares method, incorporating lateral and vertical constraints, to produce a quasi-2D subsurface image. The potentiality of the proposed methodology has been exemplified through the interpretation of synthetic data derived from a 3D intricate resistivity model, as well as field data obtained from a TEM survey conducted in a coalmine field. In both cases, the inversion process yields quasi-2D subsurface images that exhibit a reasonable level of accuracy. These images appear to be less moulded by 3D effects and demonstrate a satisfactory level of agreement with the known target area.
在许多情况下，一维反演仍然是瞬态电磁数据处理的重要步骤。由于过冲和多值函数的存在，在使用感应电动势（EMF）计算视电阻率时可能会出现潜在问题。使用均匀半空间作为初始模型，获得可靠一致的反演结果具有挑战性，尤其是在追求高效反演时。针对这些问题，我们利用大型固定环路发射机获取的陆基瞬变电磁（TEM）探测数据，采用准二维反演方案生成改进的地下电阻率结构图像。首先，我们考虑直接使用磁场数据或将感应电磁场转换为磁场，然后计算整个区域的视电阻率。然后，通过快速烟圈成像获得随深度变化的电阻率剖面。该剖面可作为后续优化反演的初始模型。反演方案采用非线性最小二乘法，结合横向和纵向约束，生成准二维地下图像。通过解释从三维错综电阻率模型中获得的合成数据，以及从在煤矿矿区进行的 TEM 勘测中获得的实地数据，证明了所提方法的潜力。在这两种情况下，反演过程产生的准二维地下图像都显示出合理的精确度。这些图像受三维效应的影响较小，与已知目标区域的吻合程度令人满意。
{"title":"Quasi-2D inversion of surface large fixed-loop transient electromagnetic sounding data","authors":"Feng-Ping Li, Jian-Hua Yue, Hai-Yan Yang, Yun Wu, Zhi-Xin Liu, Zhi-Hai Jiang","doi":"10.1093/jge/gxae013","DOIUrl":"https://doi.org/10.1093/jge/gxae013","url":null,"abstract":"In many cases, 1D inversion is still an important step in transient electromagnetic data processing. Potential issues may arise in the calculation of apparent resistivity using induced electromotive force (EMF) due to overshoot and the presence of multi-valued functions. Obtaining reliable and consistent inversion results using a uniform half-space as the initial model is challenging, especially when aiming for efficient inversion. Focusing on these problems, we use the land-based transient electromagnetic (TEM) sounding data, which was acquired by using a large fixed-loop transmitter, and adopt a quasi-2D inversion scheme to generate improved images of the subsurface resistivity structure. First, we have considered directly using magnetic field data or converting induced EMF into magnetic field, and then calculating the apparent resistivity over the whole zone. Next, a resistivity profile that varies with depth is obtained through fast smoke ring imaging. This profile serves as the initial model for the subsequent optimal inversion. The inversion scheme uses a nonlinear least-squares method, incorporating lateral and vertical constraints, to produce a quasi-2D subsurface image. The potentiality of the proposed methodology has been exemplified through the interpretation of synthetic data derived from a 3D intricate resistivity model, as well as field data obtained from a TEM survey conducted in a coalmine field. In both cases, the inversion process yields quasi-2D subsurface images that exhibit a reasonable level of accuracy. These images appear to be less moulded by 3D effects and demonstrate a satisfactory level of agreement with the known target area.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"62 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140108087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Northeast India encompasses numerous thrusts, faults, and lineaments with undulated surface topography and is one of the utmost tectonically active regions in the world. Owing to the results of the collision of the Indian Plate under the Tibetan Plate and Burmese Plate, respectively, this area has affected the highest seismic potential zone-V, triggering many earthquakes. The current study area is located in and around the Shillong plateau, Mikir Hills, Naga Hills, Arakan-Yoma fold belt, Bengal basin, and Mishmi hills of the Himalayan foothills and that fall under the northeast of India. The thrusts and faults information available in this area are very scanty due to limited availability of geoscientific data and revealing seismic survey. Henceforth, it is necessary to get enhanced geoscientific learning for a better understanding of thrusts, faults, and lineaments information, the most positive and most negative curvature attribute analyses have been carried out using ground gravity data in this area. The significant derived results from this study encourage supplementary findings of thrust, fault, and lineament information, which also correlate well with the previously found results of 3D Euler deconvolution and source edge detection. Although, gravity data interpretation has its own limitations, however, the current derived results using the latest curvature analysis approach utilizing gravity data show realistic invigorated solutions for a better understanding of the thrust, fault, and lineament locations in this area.
印度东北部包括众多推力、断层和线状构造，地表地形起伏不定，是世界上构造最活跃的地区之一。由于印度板块分别与西藏板块和缅甸板块碰撞，该地区成为地震潜势最高的 V 区，引发了许多地震。目前的研究区域位于喜马拉雅山麓的志隆高原、米基尔丘陵、那加丘陵、阿拉干-山脉褶皱带、孟加拉盆地和米什米丘陵及其周边地区，属于印度东北部。由于地球科学数据和揭示性地震勘测有限，该地区的推力和断层信息非常少。因此，有必要加强地球科学学习，以便更好地了解推力、断层和线状信息，我们利用该地区的地面重力数据进行了最正和最负曲率属性分析。这项研究得出的重要结果鼓励了对推力、断层和线状信息的补充发现，这也与之前发现的三维欧拉解卷积和源边缘检测结果密切相关。虽然重力数据解释有其自身的局限性，但目前利用重力数据的最新曲率分析方法得出的推导结果显示了现实可行的解决方案，有助于更好地了解该地区的推力、断层和线状构造位置。
{"title":"Automatic thrust/fault and edge location with gravity data across the Shillong plateau and Mikir hill complex in northeastern India using the most positive and most negative curvature interpretation","authors":"Gopal K Ghosh","doi":"10.1093/jge/gxad101","DOIUrl":"https://doi.org/10.1093/jge/gxad101","url":null,"abstract":"Northeast India encompasses numerous thrusts, faults, and lineaments with undulated surface topography and is one of the utmost tectonically active regions in the world. Owing to the results of the collision of the Indian Plate under the Tibetan Plate and Burmese Plate, respectively, this area has affected the highest seismic potential zone-V, triggering many earthquakes. The current study area is located in and around the Shillong plateau, Mikir Hills, Naga Hills, Arakan-Yoma fold belt, Bengal basin, and Mishmi hills of the Himalayan foothills and that fall under the northeast of India. The thrusts and faults information available in this area are very scanty due to limited availability of geoscientific data and revealing seismic survey. Henceforth, it is necessary to get enhanced geoscientific learning for a better understanding of thrusts, faults, and lineaments information, the most positive and most negative curvature attribute analyses have been carried out using ground gravity data in this area. The significant derived results from this study encourage supplementary findings of thrust, fault, and lineament information, which also correlate well with the previously found results of 3D Euler deconvolution and source edge detection. Although, gravity data interpretation has its own limitations, however, the current derived results using the latest curvature analysis approach utilizing gravity data show realistic invigorated solutions for a better understanding of the thrust, fault, and lineament locations in this area.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"291 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139750838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The cross-correlation-based methods, widely used for microseismic monitoring, utilize cross-correlation to extract time differences of signals within station pairs, and subsequently use these time differences for back-projection and localization, without the need for triggering moment scanning. The selection of imaging conditions, applied to the spatial projection of all cross-correlation records determines the noise resistance and resolution of such methods. To fully exploit the azimuthal properties of station pairs for constraining the source imaging, we propose a high-order azimuth coherent imaging condition, which involves the following steps: (1) Choosing station pairs that meet specific inter-station distance criteria; (2) Combining station pairs into dual-station pairs that satisfy a certain inter-station pair angle criterion; (3) Further combining station combinations pairwise to form the final set of station pairs; (4) Multiplying the projection results of station pairs within each combination from the third step; (5) Summing the results of all combinations. This method effectively suppresses the hyperboloid in the spatial projection of a single station, enhances the coherence of seismic source imaging, and maintains noise resistance. Compared to the conventional imaging conditions, the method proposed has demonstrated superior resolution and robustness in both theoretical analysis and practical testing.
{"title":"High-order Azimuth Coherent Imaging for Microseismic Location","authors":"Ying Shi, Xuebao Guo, Youqiang Yu","doi":"10.1093/jge/gxae001","DOIUrl":"https://doi.org/10.1093/jge/gxae001","url":null,"abstract":"\u0000 The cross-correlation-based methods, widely used for microseismic monitoring, utilize cross-correlation to extract time differences of signals within station pairs, and subsequently use these time differences for back-projection and localization, without the need for triggering moment scanning. The selection of imaging conditions, applied to the spatial projection of all cross-correlation records determines the noise resistance and resolution of such methods. To fully exploit the azimuthal properties of station pairs for constraining the source imaging, we propose a high-order azimuth coherent imaging condition, which involves the following steps: (1) Choosing station pairs that meet specific inter-station distance criteria; (2) Combining station pairs into dual-station pairs that satisfy a certain inter-station pair angle criterion; (3) Further combining station combinations pairwise to form the final set of station pairs; (4) Multiplying the projection results of station pairs within each combination from the third step; (5) Summing the results of all combinations. This method effectively suppresses the hyperboloid in the spatial projection of a single station, enhances the coherence of seismic source imaging, and maintains noise resistance. Compared to the conventional imaging conditions, the method proposed has demonstrated superior resolution and robustness in both theoretical analysis and practical testing.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"85 2","pages":""},"PeriodicalIF":1.4,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139383539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Low-frequency seismic data plays a crucial role in seismic data processing and seismic wave inversion. At present, there are two methods to realize the low-frequency excitation of vibrators: one is that the low-frequency vibrators are excited by linear sweep signals, and the other is that the conventional vibrators are excited by nonlinear low-frequency sweep signals. The cost of exploration using low-frequency vibroseis is high, and it is challenging to obtain sufficient low-frequency information using traditional vibrators. To this end, this paper comparatively studies the low-frequency sweep signal characteristics and data effects of low-frequency vibrator and traditional vibrator. Therefore, three kinds of linear and nonlinear low-frequency sweep signals are designed. Theoretical analysis shows that there are certain differences between linear and nonlinear in design methods, signal shapes, etc., but after correlation calculation, the signal spectrums reflecting the seismic response and the related wavelet shapes are basically consistent. Besides, the actual force signal data shows that the linear and nonlinear harmonic distortion are basically equivalent. Finally, based on the forward simulation of three sweep signals and the comparative analysis of field test data, it can be considered that the linear and nonlinear low-frequency sweep signals of vibrator have almost the same denoising ability under the basic conditions of spectrum and wavelet. Both can achieve low-frequency excitation and obtain rich low-frequency information, and the quality of seismic data is basically the same, so they can be applied in practical production.
{"title":"Characteristic analysis and data comparative of linear and nonlinear low frequency sweep in vibroseis","authors":"Jian Zhang, Guoyong Zhao, Leiliang Xu, Xu Zhang, Xiaohan Liu, Jianggui Zhu","doi":"10.1093/jge/gxad108","DOIUrl":"https://doi.org/10.1093/jge/gxad108","url":null,"abstract":"Low-frequency seismic data plays a crucial role in seismic data processing and seismic wave inversion. At present, there are two methods to realize the low-frequency excitation of vibrators: one is that the low-frequency vibrators are excited by linear sweep signals, and the other is that the conventional vibrators are excited by nonlinear low-frequency sweep signals. The cost of exploration using low-frequency vibroseis is high, and it is challenging to obtain sufficient low-frequency information using traditional vibrators. To this end, this paper comparatively studies the low-frequency sweep signal characteristics and data effects of low-frequency vibrator and traditional vibrator. Therefore, three kinds of linear and nonlinear low-frequency sweep signals are designed. Theoretical analysis shows that there are certain differences between linear and nonlinear in design methods, signal shapes, etc., but after correlation calculation, the signal spectrums reflecting the seismic response and the related wavelet shapes are basically consistent. Besides, the actual force signal data shows that the linear and nonlinear harmonic distortion are basically equivalent. Finally, based on the forward simulation of three sweep signals and the comparative analysis of field test data, it can be considered that the linear and nonlinear low-frequency sweep signals of vibrator have almost the same denoising ability under the basic conditions of spectrum and wavelet. Both can achieve low-frequency excitation and obtain rich low-frequency information, and the quality of seismic data is basically the same, so they can be applied in practical production.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"13 10","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139145534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mingkun Zhang, Lingqian Wang, Hanming Chen, Hui Zhou, Peng Liu
Least-squares reverse-time migration (LSRTM) has become an advanced technique for complex structures imaging of the subsurface, as it can provide a higher resolution and more balanced amplitude migrated image than conventional reverse-time migration (RTM). However, the intrinsic attenuation of subsurface introduces amplitude attenuation and phase dispersion of seismic wavefield, which leads to the inverted image kinematically and dynamically inexactitude. Moreover, the imperfect geometry, limited bandwidth of seismic data, and inappropriate modeling kernel etc., would inevitably introduce two side-effects in migrated image, resulting in degradation of LSRTM imaging potential. To alleviate above issues, we present a data-domain sparsity constraint viscoacoustic least-squares reverse-time migration algorithm in this paper. In particular, we utilize the decoupled constant Q fractional Laplacians (DFLs) viscoacoustic wave equation as the modeling kernel to describe the attenuation effects of the subsurface, while a model constraint constructed in the misfit function via L1-2 norm is carried out to clear the migrated artefacts and boost the imaging resolution. Thanks to the excellent performance in sparsity, the drawbacks of unconstraint LSRTM can be effectively mitigated by the L1-2 norm-based regularization. In this paper, we adopt the alternating direction of multipliers method (ADMM) to iteratively address the constrained L1-2 minimization problem by implementing a proximal operator, and three synthetic examples are hired to evaluate the effectiveness and practicability of the proposed strategy. Migration results prove that the proposed scheme can effectively compensate the attenuation effects, improve the resolution, and suppress the migration artifacts of inverted images even in the complex imaging situations.
{"title":"Viscoacoustic least squares reverse-time migration using L1-2 norm sparsity constraint","authors":"Mingkun Zhang, Lingqian Wang, Hanming Chen, Hui Zhou, Peng Liu","doi":"10.1093/jge/gxad107","DOIUrl":"https://doi.org/10.1093/jge/gxad107","url":null,"abstract":"Least-squares reverse-time migration (LSRTM) has become an advanced technique for complex structures imaging of the subsurface, as it can provide a higher resolution and more balanced amplitude migrated image than conventional reverse-time migration (RTM). However, the intrinsic attenuation of subsurface introduces amplitude attenuation and phase dispersion of seismic wavefield, which leads to the inverted image kinematically and dynamically inexactitude. Moreover, the imperfect geometry, limited bandwidth of seismic data, and inappropriate modeling kernel etc., would inevitably introduce two side-effects in migrated image, resulting in degradation of LSRTM imaging potential. To alleviate above issues, we present a data-domain sparsity constraint viscoacoustic least-squares reverse-time migration algorithm in this paper. In particular, we utilize the decoupled constant Q fractional Laplacians (DFLs) viscoacoustic wave equation as the modeling kernel to describe the attenuation effects of the subsurface, while a model constraint constructed in the misfit function via L1-2 norm is carried out to clear the migrated artefacts and boost the imaging resolution. Thanks to the excellent performance in sparsity, the drawbacks of unconstraint LSRTM can be effectively mitigated by the L1-2 norm-based regularization. In this paper, we adopt the alternating direction of multipliers method (ADMM) to iteratively address the constrained L1-2 minimization problem by implementing a proximal operator, and three synthetic examples are hired to evaluate the effectiveness and practicability of the proposed strategy. Migration results prove that the proposed scheme can effectively compensate the attenuation effects, improve the resolution, and suppress the migration artifacts of inverted images even in the complex imaging situations.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"29 2","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139157326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Haihong Xu, Jianshe Wei, Xiaofeng Han, Fei Zhao, Junlin Zhou, Ting Jiang, Jizhong Shi, Wei Xu, Bo Song, Baowen Wang
This research aims to explore petroleum resource distribution characteristics in the Yingen-Ejinaqi Basin and provide a basis for assessing the prospect of petroleum potential in the region. Based on recent and previous gravity and aeromagnetic data obtained in the basin, anomalies including regional and residual gravity and magnetic anomalies, various derivative anomalies, and anomalies in structure-enhancing filtering were determined using multiple techniques. By analysing gravity, magnetic, and seismic anomaly characteristics of existing typical oil and gas wells, the petroleum resource distribution was studied by combining such data with exploration results arising from wells where oil and gas have been discovered. The research shows that the distribution ranges of the sags revealed by seismic profiles correspond to those of negative residual gravity anomalies; the distribution ranges of rocks identified in the sags along the seismic profiles show some correspondence to the positive residual magnetic anomalies. Analysis indicates that various sags corresponding to areas where negative residual gravity anomalies appear in the north and south of the basin are the primary and secondary favourable areas for oil and gas exploration in Mesozoic-Upper Paleozoic strata. Therefore, breakthroughs in oil and gas exploration should be made by focusing on these sags in the region. The positive residual magnetic anomalies in the basin can reflect the distribution of concealed rocks in the region, while concealed rocks in sags are an important area for oil and gas exploration in igneous rocks in the basin.
{"title":"Characteristics of gravity and magnetic anomalies and their petroleum geological significance in the Yingen-Ejinaqi Basin, Inner Mongolia, China","authors":"Haihong Xu, Jianshe Wei, Xiaofeng Han, Fei Zhao, Junlin Zhou, Ting Jiang, Jizhong Shi, Wei Xu, Bo Song, Baowen Wang","doi":"10.1093/jge/gxad102","DOIUrl":"https://doi.org/10.1093/jge/gxad102","url":null,"abstract":"This research aims to explore petroleum resource distribution characteristics in the Yingen-Ejinaqi Basin and provide a basis for assessing the prospect of petroleum potential in the region. Based on recent and previous gravity and aeromagnetic data obtained in the basin, anomalies including regional and residual gravity and magnetic anomalies, various derivative anomalies, and anomalies in structure-enhancing filtering were determined using multiple techniques. By analysing gravity, magnetic, and seismic anomaly characteristics of existing typical oil and gas wells, the petroleum resource distribution was studied by combining such data with exploration results arising from wells where oil and gas have been discovered. The research shows that the distribution ranges of the sags revealed by seismic profiles correspond to those of negative residual gravity anomalies; the distribution ranges of rocks identified in the sags along the seismic profiles show some correspondence to the positive residual magnetic anomalies. Analysis indicates that various sags corresponding to areas where negative residual gravity anomalies appear in the north and south of the basin are the primary and secondary favourable areas for oil and gas exploration in Mesozoic-Upper Paleozoic strata. Therefore, breakthroughs in oil and gas exploration should be made by focusing on these sags in the region. The positive residual magnetic anomalies in the basin can reflect the distribution of concealed rocks in the region, while concealed rocks in sags are an important area for oil and gas exploration in igneous rocks in the basin.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"46 12","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139161966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Maschio, Gilson M. Silva Neto, A. Davolio, Vinicius de Souza Rios, D. Schiozer
The use of 4D seismic (4DS) (or time-lapse seismic, TLS) in data assimilation (DA) makes the process more complex due to the higher amount of data to be assimilated, requiring more robust methods and better computational resources (processing capacity and memory). The development and application of permanent seismic monitoring technologies have increased in the last years, improving the overall 4D seismic quality, in terms of signal resolution and repeatability. However, a massive amount of data is generated from the multiple monitors, making the incorporation of 4DS data in the DA process much more complex. Therefore, robust DA methods capable of dealing with huge amount of data effectively and efficiently are essential. This paper aims to assess the performance of an iterative ensemble smoother method, named Subspace Ensemble Randomized Maximum Likelihood with a local analysis (SEnRML-LA), to assimilate a big data set. The method was applied in a challenging pre-salt-like benchmark case with eight seismic surveys, one base, and seven monitors. The 4DS data are the impedance ratios (between two consecutive monitors) in 15 seismic horizons, totaling 105 maps to be assimilated. To our best knowledge, this is state of the art in terms of practical applications in data assimilation. It was possible to assimilate all the data simultaneously: the 105 horizons for the 4DS data and the wells’ production and pressure data. The data assimilation was successful in terms of results quality and method performance. We also ran a case assimilating only well data for comparison purposes.
{"title":"Performance assessment of an iterative ensemble smoother with local analysis to assimilate big 4D seismic dataset applied to a complex pre-salt-like benchmark case","authors":"C. Maschio, Gilson M. Silva Neto, A. Davolio, Vinicius de Souza Rios, D. Schiozer","doi":"10.1093/jge/gxad099","DOIUrl":"https://doi.org/10.1093/jge/gxad099","url":null,"abstract":"The use of 4D seismic (4DS) (or time-lapse seismic, TLS) in data assimilation (DA) makes the process more complex due to the higher amount of data to be assimilated, requiring more robust methods and better computational resources (processing capacity and memory). The development and application of permanent seismic monitoring technologies have increased in the last years, improving the overall 4D seismic quality, in terms of signal resolution and repeatability. However, a massive amount of data is generated from the multiple monitors, making the incorporation of 4DS data in the DA process much more complex. Therefore, robust DA methods capable of dealing with huge amount of data effectively and efficiently are essential. This paper aims to assess the performance of an iterative ensemble smoother method, named Subspace Ensemble Randomized Maximum Likelihood with a local analysis (SEnRML-LA), to assimilate a big data set. The method was applied in a challenging pre-salt-like benchmark case with eight seismic surveys, one base, and seven monitors. The 4DS data are the impedance ratios (between two consecutive monitors) in 15 seismic horizons, totaling 105 maps to be assimilated. To our best knowledge, this is state of the art in terms of practical applications in data assimilation. It was possible to assimilate all the data simultaneously: the 105 horizons for the 4DS data and the wells’ production and pressure data. The data assimilation was successful in terms of results quality and method performance. We also ran a case assimilating only well data for comparison purposes.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"21 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139197913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Surface offset gathers (SOGs) are crucial in velocity updating in seismic data migration and muting the stretched waveform in shallow parts of migrated seismic data. Kirchhoff-based migration methods can output SOGs because it takes every seismic trace as the input. As a result, the imaging results can be rearranged according to the offset value of the input data to obtain SOGs. However, regarding more accurate wave equation methods (such as reverse time migration (RTM)), the SOGs cannot be obtained directly with a single migration calculation. Attribute migration is an easy-to-implement method to output SOGs of wave equation migration methods. It calculates the offset value of each imaging point by dividing the migration result modulated by the offset attribute with the conventional migration result. However, the division error may cause the calculation result outside the given offset value. This paper proposes a constrained least square inversion method for stable calculation of RTM offset range. The method ensures that the calculated results are within the given offset range. We tested the method against the direct division and least square methods without constraints using the Marmousi model and real 3D dataset. We show that the SOGs obtained by the constrained least squares inversion attribute migration method had the same characteristics as those derived using the division-based attribute migration method, but also has higher vertical resolution, better energy distribution, and improved lateral continuity. In further study, we expect to develop a stable and direct method to efficiently calculate SOGs for RTM and an iterative closed loop for RTM velocity updating.
{"title":"Reverse time migration surface offset gathers by attribute migration and constrained least squares inversion","authors":"Yingdong Zheng, Guofeng Liu","doi":"10.1093/jge/gxad097","DOIUrl":"https://doi.org/10.1093/jge/gxad097","url":null,"abstract":"Surface offset gathers (SOGs) are crucial in velocity updating in seismic data migration and muting the stretched waveform in shallow parts of migrated seismic data. Kirchhoff-based migration methods can output SOGs because it takes every seismic trace as the input. As a result, the imaging results can be rearranged according to the offset value of the input data to obtain SOGs. However, regarding more accurate wave equation methods (such as reverse time migration (RTM)), the SOGs cannot be obtained directly with a single migration calculation. Attribute migration is an easy-to-implement method to output SOGs of wave equation migration methods. It calculates the offset value of each imaging point by dividing the migration result modulated by the offset attribute with the conventional migration result. However, the division error may cause the calculation result outside the given offset value. This paper proposes a constrained least square inversion method for stable calculation of RTM offset range. The method ensures that the calculated results are within the given offset range. We tested the method against the direct division and least square methods without constraints using the Marmousi model and real 3D dataset. We show that the SOGs obtained by the constrained least squares inversion attribute migration method had the same characteristics as those derived using the division-based attribute migration method, but also has higher vertical resolution, better energy distribution, and improved lateral continuity. In further study, we expect to develop a stable and direct method to efficiently calculate SOGs for RTM and an iterative closed loop for RTM velocity updating.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"2 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139211502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hydraulic fracturing, a significant contributor to seismic activity within and around operational fields, has been extensively employed in shale gas production. Magnetotelluric Sounding (MT) as an effective geophysical tool for identifying high-conductivity fluid-filled and/or molten regions. In this study, we deploy a dense grid of rectangular MT sites to investigate the three-dimensional (3-D) geoelectrical resistivity structure beneath the Weiyuan shale gas block (WSGB) and subsequently examine the causes of seismic activity. The resistivity data, obtained through 3-D inversion accounting for topography using ModEM, reveals a shallow low-resistivity layer (< 10 Ω-m) within the WSGB, ranging from approximately 2 to 5 km in depth. This layer exhibits multiple isolated areas with very low resistivity (< 5 Ω-m), indicative of fluid-filled zones associated with hydraulic fracturing or shale gas-bearing formations. In the northwestern WSGB, the Weiyuan anticline presents a high-resistivity dome extending possibly to depths beyond 20 km, without extending beyond the northern boundary of our study area. Conversely, the sedimentary zone in the southeastern WSGB displays a low-resistivity feature, with an extremely low-resistivity center (< 1 Ω-m). Since a consistent high resistivity zone exists beneath each fault and its top depth is less than 5 km, so faults might not extend downward below 5 km. Earthquakes with magnitudes (ML) of 3.0 or higher predominantly occur close to the faults, when considering industrial production data, we found a noteworthy correlation between earthquakes with ML < 3.0 and annual shale gas production within the WSGB. Tectonic faulting is not the leading cause for ML < 3.0 earthquakes but likely the primary contributor to seismic events with ML ≥ 3.0.
{"title":"Crustal electrical structure and seismicity of the Weiyuan shale gas block in Sichuan basin, southwest China","authors":"Yingxing Guo, Tao Zhu, Xingbing Xie, Lei Zhou","doi":"10.1093/jge/gxad100","DOIUrl":"https://doi.org/10.1093/jge/gxad100","url":null,"abstract":"Hydraulic fracturing, a significant contributor to seismic activity within and around operational fields, has been extensively employed in shale gas production. Magnetotelluric Sounding (MT) as an effective geophysical tool for identifying high-conductivity fluid-filled and/or molten regions. In this study, we deploy a dense grid of rectangular MT sites to investigate the three-dimensional (3-D) geoelectrical resistivity structure beneath the Weiyuan shale gas block (WSGB) and subsequently examine the causes of seismic activity. The resistivity data, obtained through 3-D inversion accounting for topography using ModEM, reveals a shallow low-resistivity layer (< 10 Ω-m) within the WSGB, ranging from approximately 2 to 5 km in depth. This layer exhibits multiple isolated areas with very low resistivity (< 5 Ω-m), indicative of fluid-filled zones associated with hydraulic fracturing or shale gas-bearing formations. In the northwestern WSGB, the Weiyuan anticline presents a high-resistivity dome extending possibly to depths beyond 20 km, without extending beyond the northern boundary of our study area. Conversely, the sedimentary zone in the southeastern WSGB displays a low-resistivity feature, with an extremely low-resistivity center (< 1 Ω-m). Since a consistent high resistivity zone exists beneath each fault and its top depth is less than 5 km, so faults might not extend downward below 5 km. Earthquakes with magnitudes (ML) of 3.0 or higher predominantly occur close to the faults, when considering industrial production data, we found a noteworthy correlation between earthquakes with ML < 3.0 and annual shale gas production within the WSGB. Tectonic faulting is not the leading cause for ML < 3.0 earthquakes but likely the primary contributor to seismic events with ML ≥ 3.0.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"115 8","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139246687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hailong Jin, Lin Huang, Chunlai Wang, Changfeng Li, Haer Yizi, Zhian Bai, Liang Sun, Ze Zhao, Biao Chen, Yanjiang Liu
Due to the deep concave mining in Bayan Obo stope, the slope angle is steep, the terrain is high, the outcrop width of the crushing belt is large, the stability of many slopes is poor, and there are potential sliding surfaces. In this paper, through on-site investigation and sampling, the main factors affecting the landslide of the high and steep slopes of Bayan Obo are analysed. Uniaxial compression tests were carried out to obtain the mechanical parameters of dolomite and slate. With the help of the three-dimensional digital speckle system, the whole process of slope landslide under rainfall conditions was studied through similar simulation and numerical simulation experiments. The influence of rainfall on the slope of Bayan Obo and the induced pattern of landslide were revealed. The experimental results show that rainfall is the key to inducing instability, the slippage at the edge of the slope is obvious, and there is seepage in the depth, but the effect is not significant. The landslide can be roughly divided into the damage accumulation stage; the deformation development and expansion stage and the unstable slip stage.
{"title":"Induced pattern of high and steep slope landslide under rainfall conditions","authors":"Hailong Jin, Lin Huang, Chunlai Wang, Changfeng Li, Haer Yizi, Zhian Bai, Liang Sun, Ze Zhao, Biao Chen, Yanjiang Liu","doi":"10.1093/jge/gxad098","DOIUrl":"https://doi.org/10.1093/jge/gxad098","url":null,"abstract":"Due to the deep concave mining in Bayan Obo stope, the slope angle is steep, the terrain is high, the outcrop width of the crushing belt is large, the stability of many slopes is poor, and there are potential sliding surfaces. In this paper, through on-site investigation and sampling, the main factors affecting the landslide of the high and steep slopes of Bayan Obo are analysed. Uniaxial compression tests were carried out to obtain the mechanical parameters of dolomite and slate. With the help of the three-dimensional digital speckle system, the whole process of slope landslide under rainfall conditions was studied through similar simulation and numerical simulation experiments. The influence of rainfall on the slope of Bayan Obo and the induced pattern of landslide were revealed. The experimental results show that rainfall is the key to inducing instability, the slippage at the edge of the slope is obvious, and there is seepage in the depth, but the effect is not significant. The landslide can be roughly divided into the damage accumulation stage; the deformation development and expansion stage and the unstable slip stage.","PeriodicalId":54820,"journal":{"name":"Journal of Geophysics and Engineering","volume":"7 5","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139252827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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