X. Ren, Mingquan Lai, Luyuan Wang, C. Yin, Yunhe Liu, Yang Su, Bo Zhang
The airborne electromagnetic (AEM) method can be used to effectively explore underground conductivity structures at high resolution. Conventional three-dimensional (3D) AEM inversions are mainly based on gradient-type deterministic methods; however, their results cannot be evaluated without bias because they only provide an updated model from an initial one. Here, we propose a footprint-driven stochastic approximation (FSA) method for 3D time-domain AEM inversion. We first adopt a compressed sensing strategy to speed up the forward modeling process, where random K-set ( K≥1) data are sampled with a preset sampling rate to guarantee a high-precision reconstruction. Then, we establish K-sets of stochastic inversion equations with a preconditioner consisting of the sampling rate and gradient noise and produce K different updates that have different focuses on the underground structure. The final model update in each iteration is obtained using a footprint-driven averaging technique that first considers the contributions of K-set models on the underground structures in terms of AEM footprint, then uses the mean value and standard deviation to determine whether each model is accepted or rejected. Numerical experiments show that the K updates of the FSA inversion gradually reveal similar structures as the inversion proceeds. The small uncertainty and acceptable relative accuracy further demonstrate the efficacy of the proposed parameter selection strategy. As such, the method can provide a reliable conductivity distribution with uncertainty for synthetic data, as well as a practical model from the Lisheen sulfide deposit.
机载电磁（AEM）方法可用于以高分辨率有效勘探地下导电结构。传统的三维（3D）机载电磁反演主要基于梯度型确定性方法；然而，由于这些方法只能提供初始模型的更新模型，因此无法对其结果进行无偏差评估。在此，我们提出了一种用于三维时域 AEM 反演的足迹驱动随机逼近（FSA）方法。我们首先采用压缩传感策略来加速前向建模过程，即以预设采样率对随机 K 集 ( K≥1) 数据进行采样，以保证高精度重建。然后，我们利用由采样率和梯度噪声组成的预处理建立 K 组随机反演方程，并产生 K 种不同的更新，这些更新对地下结构具有不同的侧重点。每次迭代的最终模型更新采用足迹驱动的平均技术，该技术首先考虑 K 组模型对地下结构的 AEM 基底贡献，然后使用平均值和标准偏差来确定是否接受或拒绝每个模型。数值实验表明，FSA 反演的 K 更新随着反演的进行逐渐显示出相似的结构。较小的不确定性和可接受的相对精度进一步证明了所提出的参数选择策略的有效性。因此，该方法可为合成数据提供可靠的不确定性电导率分布，也可为利辛硫化物矿床提供实用模型。
{"title":"Footprint-driven stochastic approximation inversion for time-domain airborne electromagnetic data","authors":"X. Ren, Mingquan Lai, Luyuan Wang, C. Yin, Yunhe Liu, Yang Su, Bo Zhang","doi":"10.1190/geo2023-0751.1","DOIUrl":"https://doi.org/10.1190/geo2023-0751.1","url":null,"abstract":"The airborne electromagnetic (AEM) method can be used to effectively explore underground conductivity structures at high resolution. Conventional three-dimensional (3D) AEM inversions are mainly based on gradient-type deterministic methods; however, their results cannot be evaluated without bias because they only provide an updated model from an initial one. Here, we propose a footprint-driven stochastic approximation (FSA) method for 3D time-domain AEM inversion. We first adopt a compressed sensing strategy to speed up the forward modeling process, where random K-set ( K≥1) data are sampled with a preset sampling rate to guarantee a high-precision reconstruction. Then, we establish K-sets of stochastic inversion equations with a preconditioner consisting of the sampling rate and gradient noise and produce K different updates that have different focuses on the underground structure. The final model update in each iteration is obtained using a footprint-driven averaging technique that first considers the contributions of K-set models on the underground structures in terms of AEM footprint, then uses the mean value and standard deviation to determine whether each model is accepted or rejected. Numerical experiments show that the K updates of the FSA inversion gradually reveal similar structures as the inversion proceeds. The small uncertainty and acceptable relative accuracy further demonstrate the efficacy of the proposed parameter selection strategy. As such, the method can provide a reliable conductivity distribution with uncertainty for synthetic data, as well as a practical model from the Lisheen sulfide deposit.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141385078","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}
Conventional heavy oil exploitation methods involve steam stimulation and flooding. An oil field in northwest China has been producing heavy oil via steam injection for several decades. The production area was seismically quiet until an increase in seismicity occurred several years ago. An array of 40 seismographs was deployed between July and October 2021 to monitor seismicity and resolve the possible causes of the recent seismicity. Using an end-to-end machine learning-based high-precision earthquake location workflow, we analyzed a microseismic sequence comprising 178 events that occurred in the study area. Numerical simulations incorporating Coulomb failure stress suggest that prolonged steam injection can reactivate faults and induce seismic events. Similarly, fluid diffusion through conduits may achieve the same effect. Analysis of the focal mechanism solutions of 21 strike-slip and thrust events with ML≥2 in conjunction with the background stress regime (SHmax azimuth = N15°W) revealed that the stress distribution is compatible with a left-lateral Riedel Shear Structure (RSS) model. Therefore, we can speculate that steam injection may induce earthquakes by reactivating pre-existing RSS fault structures. To conclude, the recent seismic events could have been induced by two possible mechanisms: (i) long-term steam injection may cause the static stress level on the faults beneath the reservoir to build up to critical levels, following which a slight stress disturbance can trigger an earthquake; (ii) fluid conduits may transport condensed water to basement faults, weakening the faults through fluid diffusion.
{"title":"Riedel Shear Structures Reactivation may Induce Earthquakes Through Long-Term Steam Injection: A Case Study of a Heavy Oil Production Field in Northwestern China","authors":"Rui Xu, Chuntao Liang, Zhati Kanni, Meijie Wang, Zhongquan Li, Chaoliang Wang, Zhijin Liu, Chunmei Chen","doi":"10.1190/geo2023-0547.1","DOIUrl":"https://doi.org/10.1190/geo2023-0547.1","url":null,"abstract":"Conventional heavy oil exploitation methods involve steam stimulation and flooding. An oil field in northwest China has been producing heavy oil via steam injection for several decades. The production area was seismically quiet until an increase in seismicity occurred several years ago. An array of 40 seismographs was deployed between July and October 2021 to monitor seismicity and resolve the possible causes of the recent seismicity. Using an end-to-end machine learning-based high-precision earthquake location workflow, we analyzed a microseismic sequence comprising 178 events that occurred in the study area. Numerical simulations incorporating Coulomb failure stress suggest that prolonged steam injection can reactivate faults and induce seismic events. Similarly, fluid diffusion through conduits may achieve the same effect. Analysis of the focal mechanism solutions of 21 strike-slip and thrust events with ML≥2 in conjunction with the background stress regime (SHmax azimuth = N15°W) revealed that the stress distribution is compatible with a left-lateral Riedel Shear Structure (RSS) model. Therefore, we can speculate that steam injection may induce earthquakes by reactivating pre-existing RSS fault structures. To conclude, the recent seismic events could have been induced by two possible mechanisms: (i) long-term steam injection may cause the static stress level on the faults beneath the reservoir to build up to critical levels, following which a slight stress disturbance can trigger an earthquake; (ii) fluid conduits may transport condensed water to basement faults, weakening the faults through fluid diffusion.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141384851","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}
A better understanding of the temperature effects on the propagation characteristics of elastic waves in frozen soils and rocks is imperative for accurately quantifying their freezing degrees. While existing rock-physics models based on the three-phase Biot (TPB) theory adeptly interpret observed velocity versus temperature (VVT) curves, they often lack a comprehensive understanding of the mechanisms underlying attenuation versus temperature (AVT) curves. In this study, we first extend the TPB theory to incorporate the temperature-dependent properties of ice, including changes in volumetric fraction, morphology, and viscoelasticity, by integrating relevant thermodynamic laws. Model parameters related to ice properties and interactions, such as rigidity, shear moduli, density, and friction, are redefined. Then, using a numerical rock-physics modeling approach, we examine influential factors and modes of wave VVT and AVT responses. Our results show that both P- and S-wave velocities increase with source frequency, consolidation degree, and frame-supporting ice content, while decreasing with temperature and pore-floating ice content. Both P- and S-wave attenuation factors increase with frame-supporting ice content and decrease with consolidation degree. Rising temperatures tend to amplify the peak magnitude of P-wave attenuation factors and shift the central frequency of S-wave attenuation factors. Finally, within a temperature-controlled laboratory environment, we conduct ultrasonic wave transmission testing on brine-saturated sediment and rock specimens. Results demonstrate that as the temperature increases from 15 to 3 °C, both the P- and S-wave velocities decrease, while the P-wave attenuation factors decrease and the S-wave attenuation factors initially rise before declining. Our viscoelastic TPB theory outperforms existing ones in interpreting S-wave AVT observations. This temperature-dependent rock-physics model holds promise for interpreting sonic logging data in time-lapse monitoring of permafrost, glaciers, and Antarctica.
要准确量化冻土和岩石的冻结程度，就必须更好地了解温度对弹性波在冻土和岩石中传播特性的影响。现有的岩石物理模型基于三相比奥理论（TPB），能够很好地解释观测到的速度与温度（VVT）曲线，但往往缺乏对衰减与温度（AVT）曲线内在机理的全面了解。在本研究中，我们首先扩展了 TPB 理论，通过整合相关的热力学定律，纳入了冰的温度相关特性，包括体积分数、形态和粘弹性的变化。重新定义了与冰属性和相互作用有关的模型参数，如刚度、剪切模量、密度和摩擦力。然后，利用岩石物理数值建模方法，我们研究了波浪 VVT 和 AVT 响应的影响因素和模式。结果表明，P 波和 S 波速度随源频率、固结程度和框架支撑冰含量的增加而增加，同时随温度和孔隙浮冰含量的增加而减小。P 波和 S 波衰减系数均随框架支撑冰含量的增加而增加，随固结度的增加而减少。温度升高往往会放大 P 波衰减系数的峰值幅度，并移动 S 波衰减系数的中心频率。最后，在温控实验室环境中，我们对盐水饱和的沉积物和岩石试样进行了超声波透射测试。结果表明，当温度从 15 ℃ 升高到 3 ℃ 时，P 波和 S 波的速度都会降低，同时 P 波衰减系数也会降低，S 波衰减系数则会先上升后下降。在解释S波AVT观测结果方面，我们的粘弹性TPB理论优于现有的理论。这种随温度变化的岩石物理模型有望用于解释永冻土、冰川和南极洲延时监测中的声波测井数据。
{"title":"Influence of ice properties on wave propagation characteristics in partially frozen soils and rocks: a temperature-dependent rock-physics model","authors":"Bonan Li, Jun Matsushima","doi":"10.1190/geo2023-0694.1","DOIUrl":"https://doi.org/10.1190/geo2023-0694.1","url":null,"abstract":"A better understanding of the temperature effects on the propagation characteristics of elastic waves in frozen soils and rocks is imperative for accurately quantifying their freezing degrees. While existing rock-physics models based on the three-phase Biot (TPB) theory adeptly interpret observed velocity versus temperature (VVT) curves, they often lack a comprehensive understanding of the mechanisms underlying attenuation versus temperature (AVT) curves. In this study, we first extend the TPB theory to incorporate the temperature-dependent properties of ice, including changes in volumetric fraction, morphology, and viscoelasticity, by integrating relevant thermodynamic laws. Model parameters related to ice properties and interactions, such as rigidity, shear moduli, density, and friction, are redefined. Then, using a numerical rock-physics modeling approach, we examine influential factors and modes of wave VVT and AVT responses. Our results show that both P- and S-wave velocities increase with source frequency, consolidation degree, and frame-supporting ice content, while decreasing with temperature and pore-floating ice content. Both P- and S-wave attenuation factors increase with frame-supporting ice content and decrease with consolidation degree. Rising temperatures tend to amplify the peak magnitude of P-wave attenuation factors and shift the central frequency of S-wave attenuation factors. Finally, within a temperature-controlled laboratory environment, we conduct ultrasonic wave transmission testing on brine-saturated sediment and rock specimens. Results demonstrate that as the temperature increases from 15 to 3 °C, both the P- and S-wave velocities decrease, while the P-wave attenuation factors decrease and the S-wave attenuation factors initially rise before declining. Our viscoelastic TPB theory outperforms existing ones in interpreting S-wave AVT observations. This temperature-dependent rock-physics model holds promise for interpreting sonic logging data in time-lapse monitoring of permafrost, glaciers, and Antarctica.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141385143","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}
Fracture density is a critical fracture evaluation parameter for the optimization and production prediction of hydraulic fracturing models. Non-radioactive tracer techniques (NRT) have successfully used a quantitative fracture density method based on neutron-induced gamma ray from formation elements. Furthermore, fracture density can be calculated using the formation capture cross-section before and after hydraulic fracturing based on pulsed neutron capture logging. However, the response sensitivity of the macroscopic scattering cross section to the fractures will decrease when the fracture density is high due to the neutron self-shielding phenomenon. Therefore, an improved fracture density evaluation method is applied, which combines the macroscopic capture cross section and the neutron self-shielding correction factor. In the new method, the peak area of titanium from the captured gamma spectrum was used to obtain a neutron self-shielding correction factor, in order to improve the sensitivity of fracture density determination. Furthermore, the response of capture cross-section variation to fracture density at various tagged proppant concentrations and formation backgrounds was investigated. The findings indicate that the tagged proppant concentration influences the detection limit of fracture density and the sensitivity of fracture density identification. The accurate calculation range of fracture density using the new method has been extended from 5% to 10% under the condition that the tagged proppant concentration is 0.2%. Meanwhile, water salinity significantly impacts capture cross-section variation, while the effects of porosity, lithology, and fluid type on capture cross-section variation are negligible. A simulated fracturing example demonstrates the method's applicability in various measuring environments. The results show that fracture density and height are consistent with the model settings after correcting for water salinity, and the fracture density calculation error is less than 3%. Therefore, our proposed evaluation method for fracture density corrected for the neutron self-shielding effect improves response sensitivity and fracture density calculation accuracy.
{"title":"An improved method for evaluating fracture density using pulsed neutron capture logging","authors":"Feng Zhang, Bing Xie, Qian Chen, Xiaoyang Zhang, ABuLaHai YiMula, Baoping Lu, Hui Zhang, Jilin Fan","doi":"10.1190/geo2023-0206.1","DOIUrl":"https://doi.org/10.1190/geo2023-0206.1","url":null,"abstract":"Fracture density is a critical fracture evaluation parameter for the optimization and production prediction of hydraulic fracturing models. Non-radioactive tracer techniques (NRT) have successfully used a quantitative fracture density method based on neutron-induced gamma ray from formation elements. Furthermore, fracture density can be calculated using the formation capture cross-section before and after hydraulic fracturing based on pulsed neutron capture logging. However, the response sensitivity of the macroscopic scattering cross section to the fractures will decrease when the fracture density is high due to the neutron self-shielding phenomenon. Therefore, an improved fracture density evaluation method is applied, which combines the macroscopic capture cross section and the neutron self-shielding correction factor. In the new method, the peak area of titanium from the captured gamma spectrum was used to obtain a neutron self-shielding correction factor, in order to improve the sensitivity of fracture density determination. Furthermore, the response of capture cross-section variation to fracture density at various tagged proppant concentrations and formation backgrounds was investigated. The findings indicate that the tagged proppant concentration influences the detection limit of fracture density and the sensitivity of fracture density identification. The accurate calculation range of fracture density using the new method has been extended from 5% to 10% under the condition that the tagged proppant concentration is 0.2%. Meanwhile, water salinity significantly impacts capture cross-section variation, while the effects of porosity, lithology, and fluid type on capture cross-section variation are negligible. A simulated fracturing example demonstrates the method's applicability in various measuring environments. The results show that fracture density and height are consistent with the model settings after correcting for water salinity, and the fracture density calculation error is less than 3%. Therefore, our proposed evaluation method for fracture density corrected for the neutron self-shielding effect improves response sensitivity and fracture density calculation accuracy.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141266796","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}
Wei Liu, Ying Shi, Ning Wang, Weihong Wang, Jinwei Fang
The strong viscosity of the subsurface introduces amplitude absorption and phase-velocity dispersion. Incorrect compensation of the inherent attenuation (the strength of seismic attenuation can be quantified by the inverse of quality factor Q, which is defined as 2π times the ratio of the stored energy to the lost energy in a single cycle of deformation) can significantly affect imaging quality. While Q-least squares reverse time migration allows for the compensation of attenuation effects during the iterations, the traditional L2-norm-minimization, which is highly sensitive to the source wavelet, poses a challenge in accurately estimating source wavelet from field data. Thus, we develop a source-independent Q-least squares reverse time migration, in which a convolutional objective function is introduced to replace the L2-norm constraint in order to mitigate the source wavelet effect. According to the Born approximation, we first linearize the constant-order decoupled fractional Laplacian viscoacoustic wave equation to derive the demigration operator, then construct the corresponding adjoint equation and gradient based on the convolutional objective function, iteratively estimating the reflectivity images. The proposed method relaxes the sensitivity to the wavelet compared to the conventional L2-norm scheme due to the convolutional objective function, which has the ability to construct the same new source for simulated and observed data. Numerical tests on a layered model, the Marmousi model, and field data demonstrate that the proposed source-independent Q-least squares reverse time migration enables us to obtain high quality reflectivity images even when using incorrect source wavelets.
{"title":"Source-independent Q-compensated viscoacoustic least-squares reverse time migration","authors":"Wei Liu, Ying Shi, Ning Wang, Weihong Wang, Jinwei Fang","doi":"10.1190/geo2023-0639.1","DOIUrl":"https://doi.org/10.1190/geo2023-0639.1","url":null,"abstract":"The strong viscosity of the subsurface introduces amplitude absorption and phase-velocity dispersion. Incorrect compensation of the inherent attenuation (the strength of seismic attenuation can be quantified by the inverse of quality factor Q, which is defined as 2π times the ratio of the stored energy to the lost energy in a single cycle of deformation) can significantly affect imaging quality. While Q-least squares reverse time migration allows for the compensation of attenuation effects during the iterations, the traditional L2-norm-minimization, which is highly sensitive to the source wavelet, poses a challenge in accurately estimating source wavelet from field data. Thus, we develop a source-independent Q-least squares reverse time migration, in which a convolutional objective function is introduced to replace the L2-norm constraint in order to mitigate the source wavelet effect. According to the Born approximation, we first linearize the constant-order decoupled fractional Laplacian viscoacoustic wave equation to derive the demigration operator, then construct the corresponding adjoint equation and gradient based on the convolutional objective function, iteratively estimating the reflectivity images. The proposed method relaxes the sensitivity to the wavelet compared to the conventional L2-norm scheme due to the convolutional objective function, which has the ability to construct the same new source for simulated and observed data. Numerical tests on a layered model, the Marmousi model, and field data demonstrate that the proposed source-independent Q-least squares reverse time migration enables us to obtain high quality reflectivity images even when using incorrect source wavelets.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141271741","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 ground-force signal of a Vibroseis truck is unavoidably contaminated by harmonics. To better characterize the subsurface, the fundamental mode in the ground-force signal is the preferred choice for the cross-correlation with raw seismic data measured in the field. We present a novel, efficient and effective harmonics decomposition method to separate different orders of harmonics in the ground-force signal. Our method first builds a mathematical model to describe different orders of harmonics in the ground-force signal by honoring the physical mechanism behind the harmonics generation, and then retrieves different orders of harmonics by solving overdetermined linear problems in the analytic-signal domain. The success of our method is demonstrated using both synthetic and field data examples.
{"title":"Separating harmonics in the ground-force signal of a seismic vibratory source","authors":"Yimin Sun, Mohammed S. Almubarak, Hussain Marzooq","doi":"10.1190/geo2024-0070.1","DOIUrl":"https://doi.org/10.1190/geo2024-0070.1","url":null,"abstract":"The ground-force signal of a Vibroseis truck is unavoidably contaminated by harmonics. To better characterize the subsurface, the fundamental mode in the ground-force signal is the preferred choice for the cross-correlation with raw seismic data measured in the field. We present a novel, efficient and effective harmonics decomposition method to separate different orders of harmonics in the ground-force signal. Our method first builds a mathematical model to describe different orders of harmonics in the ground-force signal by honoring the physical mechanism behind the harmonics generation, and then retrieves different orders of harmonics by solving overdetermined linear problems in the analytic-signal domain. The success of our method is demonstrated using both synthetic and field data examples.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141268858","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}
Natural gas hydrate is a potential novel energy resource widely distributed globally. Acoustic logging can effectively provide information on the surrounding reservoir and plays an important guiding role in gas hydrate exploration and development. Natural gas hydrate-bearing sediments are composed of a solid frame with natural gas hydrates and water filled pores. The borehole mode wave characteristics of two-phase porous media cant be used to evaluate the parameters of such a multi-phase porous medium. We explore factors that influence the monopole Stoneley wave in a borehole embedded in a multi-phase porous medium containing two solids and one fluid and analyze the influence of each factor on monopole Stoneley wave attenuation systematically. The sensitivity analysis results indicate that the Stoneley wave attenuation is highly sensitive to solid frame permeability and gas hydrate saturation. Building upon this foundation, a method to invert for gas hydrate saturation and solid frame permeability is first developed using Stoneley wave attenuation. Synthetic logging data is used to demonstrate the feasibility of this method for inverting for gas hydrate-bearing sediment properties. Even in the presence of considerable noise added to the receiver signal arrays, the inversion method is stable and reliably evaluates gas hydrate saturation and solid frame permeability.
{"title":"Inversion of gas hydrate saturation and solid frame permeability in a gas hydrate-bearing sediment by Stoneley wave attenuation","authors":"Lin Liu, Xiumei Zhang, Xiuming Wang","doi":"10.1190/geo2023-0604.1","DOIUrl":"https://doi.org/10.1190/geo2023-0604.1","url":null,"abstract":"Natural gas hydrate is a potential novel energy resource widely distributed globally. Acoustic logging can effectively provide information on the surrounding reservoir and plays an important guiding role in gas hydrate exploration and development. Natural gas hydrate-bearing sediments are composed of a solid frame with natural gas hydrates and water filled pores. The borehole mode wave characteristics of two-phase porous media cant be used to evaluate the parameters of such a multi-phase porous medium. We explore factors that influence the monopole Stoneley wave in a borehole embedded in a multi-phase porous medium containing two solids and one fluid and analyze the influence of each factor on monopole Stoneley wave attenuation systematically. The sensitivity analysis results indicate that the Stoneley wave attenuation is highly sensitive to solid frame permeability and gas hydrate saturation. Building upon this foundation, a method to invert for gas hydrate saturation and solid frame permeability is first developed using Stoneley wave attenuation. Synthetic logging data is used to demonstrate the feasibility of this method for inverting for gas hydrate-bearing sediment properties. Even in the presence of considerable noise added to the receiver signal arrays, the inversion method is stable and reliably evaluates gas hydrate saturation and solid frame permeability.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141272516","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}
Incorporating anisotropy in seismic modeling and imaging is important to produce correct locations of subsurface reflectors. Traditional wave equations for quasi-P-wave in the transverse isotropic media either suffer from S-wave artifacts or require complicated and expensive computation strategies. To mitigate this issue, we present a novel pure quasi-P-wave equation with an approximated space-domain pseudo-differential operator in the vertical transverse isotropic (VTI) media. For the pure quasi-P-wave equation, we first simplify it to an elliptical anisotropy equation with an additional pseudo-differential correction term. Then, we directly approximate the pseudo-differential term with a space-domain convolution operator that is calculated by solving a nonlinear inverse problem. Phase-velocity analysis and numerical modeling show that the new space-domain pseudo-differential operator has a good accuracy to describe wave propagation in the VTI media. In addition, it is more suitable for the parallel computation with domain-decomposition than the Fourier transform that is necessary for solving traditional pseudo-differential operators. Finally, we apply the proposed quasi-P-wave propagator to reverse-time migration to correct the anisotropic effects in seismic imaging. Numerical experiments for benchmark models and a land survey demonstrate the feasibility and adaptability of the proposed method.
在地震建模和成像中加入各向异性对于确定地下反射体的正确位置非常重要。横向各向同性介质中传统的准 P 波方程要么存在 S 波伪影，要么需要复杂昂贵的计算策略。为了缓解这一问题，我们提出了一种新的纯准 P 波方程，该方程在垂直横向各向同性（VTI）介质中具有近似的空域伪微分算子。对于纯准 P 波方程，我们首先将其简化为带有附加伪微分修正项的椭圆各向异性方程。然后，我们用一个空域卷积算子直接近似伪差分项，该算子是通过求解一个非线性逆问题计算得出的。相位速度分析和数值建模表明，新的空域伪微分算子在描述 VTI 介质中的波传播时具有良好的准确性。此外，与求解传统伪微分算子所需的傅立叶变换相比，它更适合用域分解进行并行计算。最后，我们将提出的准 P 波传播器应用于反向时间迁移，以校正地震成像中的各向异性效应。基准模型和陆地勘测的数值实验证明了所提方法的可行性和适应性。
{"title":"Pure quasi-P-wave modeling and imaging using an approximated space-domain pseudo-differential operator in the VTI media","authors":"Shanyuan Qin, Jidong Yang, Jianping Huang, Yiwei Tian, Haozhe Zhang, Yang Zhao","doi":"10.1190/geo2023-0416.1","DOIUrl":"https://doi.org/10.1190/geo2023-0416.1","url":null,"abstract":"Incorporating anisotropy in seismic modeling and imaging is important to produce correct locations of subsurface reflectors. Traditional wave equations for quasi-P-wave in the transverse isotropic media either suffer from S-wave artifacts or require complicated and expensive computation strategies. To mitigate this issue, we present a novel pure quasi-P-wave equation with an approximated space-domain pseudo-differential operator in the vertical transverse isotropic (VTI) media. For the pure quasi-P-wave equation, we first simplify it to an elliptical anisotropy equation with an additional pseudo-differential correction term. Then, we directly approximate the pseudo-differential term with a space-domain convolution operator that is calculated by solving a nonlinear inverse problem. Phase-velocity analysis and numerical modeling show that the new space-domain pseudo-differential operator has a good accuracy to describe wave propagation in the VTI media. In addition, it is more suitable for the parallel computation with domain-decomposition than the Fourier transform that is necessary for solving traditional pseudo-differential operators. Finally, we apply the proposed quasi-P-wave propagator to reverse-time migration to correct the anisotropic effects in seismic imaging. Numerical experiments for benchmark models and a land survey demonstrate the feasibility and adaptability of the proposed method.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141273143","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}
Envelope full waveform inversion (EI) of seismic data has been proposed to overcome the cycle-skipping issue and recover long-wavelength velocity components for over a decade. However, there are few published successful applications of EI on real data examples (except for some correlation-based or phase-based EI methods) that we are aware of. We implement envelope inversion methods (EI with p=2, EI with p=1 and improved envelope inversion (IEI)) on 2D marine seismic data and find that the amplitude-mismatching between the modeled and observed data is a critical factor that prevents the successful application of EI methods on real data. To match amplitude better, we include a data weighting preconditioner in the objective function of EI methods. The preconditioner term acts as a weighting factor to compensate for the amplitude mismatch between observed and modeled data. We propose a method for calculating the preconditioner term using the amplitude of the head waves as a reference. Furthermore, we derive the adjoint source and gradient of envelope inversion using the data preconditioning method. We illustrate the successful application of envelope inversion methods with the data preconditioning method using the 2D marine seismic data example. In comparison to envelope inversion methods without the data preconditioning method, those employing the data preconditioning yield much more geophysically reasonable velocity models and Kirchhoff image sections and Common Image Gathers (CIGs).
为克服周期跳跃问题并恢复长波长速度成分，地震数据包络全波形反演（EI）已提出十多年。然而，据我们所知，EI 在实际数据实例中的成功应用（除一些基于相关性或相位的 EI 方法外）很少公开发表。我们在二维海洋地震数据上实施了包络反演方法（p=2 的包络反演、p=1 的包络反演和改进的包络反演 (IEI)），发现建模数据和观测数据之间的振幅不匹配是阻碍包络反演方法在实际数据上成功应用的关键因素。为了更好地匹配振幅，我们在 EI 方法的目标函数中加入了数据加权预处理项。前置条件项作为一个加权因子，用于补偿观测数据和建模数据之间的振幅不匹配。我们提出了一种使用头波振幅作为参考来计算前置条件项的方法。此外，我们还利用数据预处理方法推导出了包络反演的邻接源和梯度。我们以二维海洋地震数据为例，说明了包络反演方法与数据预处理方法的成功应用。与不使用数据预处理方法的包络反演方法相比，使用数据预处理方法的包络反演方法得到的速度模型、基尔霍夫像剖面和普通像聚（CIG）在地球物理上更加合理。
{"title":"The importance of data preconditioning strategies for envelope full waveform inversion methods: demonstration on marine seismic data","authors":"Kai Xiong, David Lumley, Wei Zhou","doi":"10.1190/geo2023-0322.1","DOIUrl":"https://doi.org/10.1190/geo2023-0322.1","url":null,"abstract":"Envelope full waveform inversion (EI) of seismic data has been proposed to overcome the cycle-skipping issue and recover long-wavelength velocity components for over a decade. However, there are few published successful applications of EI on real data examples (except for some correlation-based or phase-based EI methods) that we are aware of. We implement envelope inversion methods (EI with p=2, EI with p=1 and improved envelope inversion (IEI)) on 2D marine seismic data and find that the amplitude-mismatching between the modeled and observed data is a critical factor that prevents the successful application of EI methods on real data. To match amplitude better, we include a data weighting preconditioner in the objective function of EI methods. The preconditioner term acts as a weighting factor to compensate for the amplitude mismatch between observed and modeled data. We propose a method for calculating the preconditioner term using the amplitude of the head waves as a reference. Furthermore, we derive the adjoint source and gradient of envelope inversion using the data preconditioning method. We illustrate the successful application of envelope inversion methods with the data preconditioning method using the 2D marine seismic data example. In comparison to envelope inversion methods without the data preconditioning method, those employing the data preconditioning yield much more geophysically reasonable velocity models and Kirchhoff image sections and Common Image Gathers (CIGs).","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140969565","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}
Shuaishuai Li, Xiaotong Zhang, Jiangjie Zhang, Linong Liu
Random noise significantly reduces the signal-to-noise ratio (S/N) of seismic data and affects the accuracy of seismic interpretation. Traditional denoising methods typically require manual parameter tuning to increase the robustness and accuracy across various random noise levels. In this study, based on the statistical definition of random noise, we used the variance of random noise as the level of random noise and proposed an adaptive dual-domain filter (ADDF). The ADDF method estimates the random noise variance in the seismic data and uses this estimation to effectively denoise the seismic data. First, we employ a difference operator in two directions to remove useful structures from the seismic data. The processed data are then used to estimate the global random noise variance through iterative statistical processing. In the denoising process of the ADDF, seismic data are masked by a bilateral filter in the spatial domain, followed by a short-time Fourier transform with wavelet shrinkage in the frequency domain, both controlled by the adaptively estimated random noise variance. The dual-domain filter is applied iteratively for the best performance. Synthetic experiments demonstrate the robustness of the ADDF in accurately estimating the noise variance without tuning parameters, and its superior denoising performance is evident in both synthetic examples and field data when compared to two typical denoising methods: f-x deconvolution and curvelet domain thresholding. As an adaptive random noise estimation and removal method, the ADDF relies only on seismic data, making denoising random noise more objective and accurate without manual adjustment.
{"title":"Adaptive dual-domain filtering for random seismic noise removal","authors":"Shuaishuai Li, Xiaotong Zhang, Jiangjie Zhang, Linong Liu","doi":"10.1190/geo2023-0532.1","DOIUrl":"https://doi.org/10.1190/geo2023-0532.1","url":null,"abstract":"Random noise significantly reduces the signal-to-noise ratio (S/N) of seismic data and affects the accuracy of seismic interpretation. Traditional denoising methods typically require manual parameter tuning to increase the robustness and accuracy across various random noise levels. In this study, based on the statistical definition of random noise, we used the variance of random noise as the level of random noise and proposed an adaptive dual-domain filter (ADDF). The ADDF method estimates the random noise variance in the seismic data and uses this estimation to effectively denoise the seismic data. First, we employ a difference operator in two directions to remove useful structures from the seismic data. The processed data are then used to estimate the global random noise variance through iterative statistical processing. In the denoising process of the ADDF, seismic data are masked by a bilateral filter in the spatial domain, followed by a short-time Fourier transform with wavelet shrinkage in the frequency domain, both controlled by the adaptively estimated random noise variance. The dual-domain filter is applied iteratively for the best performance. Synthetic experiments demonstrate the robustness of the ADDF in accurately estimating the noise variance without tuning parameters, and its superior denoising performance is evident in both synthetic examples and field data when compared to two typical denoising methods: f-x deconvolution and curvelet domain thresholding. As an adaptive random noise estimation and removal method, the ADDF relies only on seismic data, making denoising random noise more objective and accurate without manual adjustment.","PeriodicalId":55102,"journal":{"name":"Geophysics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140972701","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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