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Journal of Applied Geophysics
Elsevier
Journal of Applied Geophysics

Elsevier

0926-9851

Journal of Applied Geophysics/Journal Journal of Applied GeophysicsAHCIISTPSCIEI
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    Trust-region versus line search globalization strategies for inexact Newton method and application in full waveform inversion

    He, QinglongWang, Yanfei
    17页
    查看更多>>摘要：In this study, we consider the inexact Newton method using the trust-region and line search globalization strategies when solving the large-scale full waveform inversion problem. An elaborate stopping criterion or forcing term is introduced in order to avoid oversolvings of Newton equation. We develop an efficient method to compute (pseudo) Hessian vector products. In addition, a diagonal preconditioner based on the pseudo-Hessian approach is employed to further accelerate the solution of Newton equation. We discuss the specific parameter choices for these present methods. Numerical experiments based on the Marmousi2, BP 2004, and Sigsbee models are conducted to show the numerical performance of proposed inexact Newton methods. Numerical experiments demonstrate that the trust-region can perform better than the line search globalization strategy in the presence of nonlinearity and nonconvexity of the full waveform problem, especially for high contrast velocity models.
      原文链接:
    • NSTL
    • Elsevier

    Seismic AVA inversion of elastic and attenuative parameters in viscoelastic media using the Zoeppritz equations

    Ge, ZijianPan, ShulinLi, JingyeWu, Fan...
    17页
    查看更多>>摘要：When seismic wave passes through oil-gas bearing reservoir, it will cause relatively large attenuation effect due to energy dissipation. Two constants characterizing attenuation strength, P-and S-wave inverse quality factors, are widely used in seismic prediction. Although various attenuation-related petrophysical models have been introduced into the approximate reflection coefficient equations to describe a viscoelastic medium, the low accuracy of the approximation in the range of moderate to large incident angle limits the approximation-based amplitude variation with angle (AVA) inversion methods in estimation of attenuation factors. To avoid the impact caused by the uncertainty of the linear factors in the attenuation model, we propose an AVA inversion based on Zoeppritz equations to directly estimate elastic properties (P-and S-wave velocity, and density) and attenuation factors (P-and S-wave inverse quality factors). First, we introduce the complex velocity model into the Zoeppritz equations to decouple the viscoelastic velocity into elastic velocity and inverse quality factors. Under the generalized linear inversion framework, we then derive the Jacobian matrices and establish a joint PP and PS-wave inversion to improve the stability and accuracy. Tests on both synthetic and real multi-component seismic data sets verify the elastic properties and attenuation factors can be reasonably and stably predicted. It can be concluded that the established approach is an effective tool in attenuation factors estimation, and the predicted attenuation factors appear as an additional proof for the identification of gas-bearing reservoirs.
      原文链接:
    • NSTL
    • Elsevier

    A new linear optimized time-space domain spatial implicit and temporal high-order finite-difference scheme for scalar wave modeling

    Wang, JingLiu, YangZhou, Hongyu
    12页
    查看更多>>摘要：Suppressing the numerical dispersion is one of the key items for the finite-difference (FD) method. Usually, approximating the spatial derivatives by the implicit FD stencil is an effective approach to suppress the spatial dispersion for acoustic wave modeling. However, the temporal accuracy is still limited. To tackle this issue, we propose a new time-space domain (TS-D) implicit FD scheme, which could reach the arbitrary even-order temporal and spatial accuracy by adding a few additional grid points to the original implicit FD stencil. Compared with the existing spatial implicit and temporal high-order methods in the TS-D, our new scheme reduces 4N + 1 grid points, while reaches equivalent temporal and spatial high-order accuracy. To further enhance the simulation accuracy, a linear optimization strategy is developed by combining the Taylor series expansion (TE) and the least-squares methods. Our linear optimization strategy avoids the non-linear iterative optimization of the current spatial implicit and temporal high-order methods. Comparisons of the conventional TE-and optimization-based implicit methods demonstrate the accuracy and efficiency superiorities of our new linear optimized FD scheme.
      原文链接:
    • NSTL
    • Elsevier

    Uses of Green's function for enhancing the image resolution of Ground Radar data

    Gautam, PriyankaGupta, Saurabh Datta
    17页
    查看更多>>摘要：Ground Penetrating Radar (GPR) data plays a vital role in the interpretation of shallow geological features. GPR produces a high-resolution image that is capable of capturing the subtle changes in the sub-surface geology. The work was conducted in the Baliapur region of Dhanbad district of Jharkhand state of India. The area is a part of the Chhota Nagpur plateau with a granitic gneiss complex. Baliapur area consists of multiple dykes formed mainly by igneous rocks and exposes to the surface. The geological ages of the dykes are from the Lower Jurassic to the Cretaceous-Eocene age. The knowledge on the evolvement of these dykes is highly significant for con-trolling the geology of the famous Damodar River Valley basin. The conducted research work has represented the detail of the internal structure of one such dyke in the area based on the high-resolution image of GPR data. The enhancement of image resolution was initiated based on the migration process such as FK and Kirchhoff after all necessary initial processing sequences of GPR data. However, the migration process has shown certain limitations to capture the internal structure of the igneous dyke. Because of such limitations, the Green's Function was introduced during the processing of GPR data to enhance image resolution through wave equation solution. The study shows the prominent features of the internal structure of the dyke after the introduction of Green's Function.
      原文链接:
    • NSTL
    • Elsevier

    The effect of frequency bandwidth on DSI anisotropy evaluation

    Sadeqi, MehrdadManaman, Navid ShadKadkhodaie, AliWood, David A....
    16页
    查看更多>>摘要：Anisotropy evaluation in carbonate rocks plays a pivotal role in their reservoir characterization and modeling. This study demonstrates the benefits of advanced interpretation using the Dipole Shear Sonic Imager (DSI) log data for anisotropy evaluations of porous media. Splitting the shear wave into fast and slow components, with different polarizations and velocities, provides useful indications of formation anisotropy. Fast shear waves travel faster in directions parallel to layering and fracturing while slow shear waves travel more slowly perpendicular to layering and fracture networks. Quantifying the difference between fast and slow shear velocities provides a measure of acoustic anisotropy in the medium penetrated. The purpose of the research is to evaluate the effects of frequency bandwidth on the depth of the wave propagation rates and slowness values for anisotropy analysis, thus four bandwidth frequencies: 1-2 kHz, 2-4 kHz, 4-6 kHz, and 1-5 kHz are selected and examined in a vertical drilled well in the gas reservoirs of Upper Dalan Member, and Kangan Formations in the South Pars Gas-Condensate Field. The frequency filtering, semblance analysis, and slowness picking are done on waveforms for frequency-slowness dispersion analysis and slowness correction. The dispersion correction for bandwidth 4-6 kHz isn't performed completely in good hole condition intervals, because high-frequencies around 6 kHz are absorption due to the intrinsic attenuation of the rocks. Therefore, the considered bandwidth is decreased to 4-5.5 kHz. In the following, Alford rotation, align waveforms, and calculation and evaluation of derived fast and slow com-ponents are done for deriving the azimuth of the fast shear wave for each bandwidth of waveforms. The dominant trend of the azimuth of anisotropy is that aligned with the azimuth of the fast shear wave. The azimuth of the fast shear wave as azimuth of anisotropy and its corresponding intervals are compared with the results of image log data for the same well interval. This made it possible to reject or confirm the findings of the DSI acoustic anisotropy analysis for each bandwidth considered. In the low bandwidth frequency (1-2 kHz), the differences in slowness, energy, travel time, and penetration depth are more extreme than those recorded by the other bandwidths considered. The azimuth of anisotropy is NW-SE with a slight E-W trend. However, the azimuth of anisotropy was found to be contrary to the image log interpretation where the dominant trend is NE-SW. The dominant trend of the azimuth of anisotropy for bandwidth 2-4 kHz is NE-SW with a slight E-W trend. The anisotropy directions and zones are consistent with those identified from the wellbore image log results. Moreover, the penetration depth is meaningful and far away from the borehole drilling and mud effects. These results suggest that the bandwidth (2-4 kHz) is best suited for acoustic anisotropy analysis of wellbore sections using Dipole Shear Sonic Imager (DSI) recorded data in this well. The trends of the azimuth of anisotropy for bandwidth 4-5.5 kHz are NE-SW, and NW-SE, with expanded tolerance azimuth of anisotropy. The results that have been achieved in a small penetration depth and close to the borehole wall are affected by signal absorption and attenuation in flushed and transition areas. This leads to some errors and inconsistencies with the image log interpretation. The trends of the azimuth of anisotropy for bandwidth 1-5 kHz are NE-SW, NW-SE, and E-W. The outcomes are the consequence of the variety of directions and zones associated with this wider bandwidth, together with the penetration depths of the waveforms in the diverse zones considered. However, the azimuth of anisotropy is inconsistent with the image log interpretation.
      原文链接:
    • NSTL
    • Elsevier

    pyCSAMT: An alternative Python toolbox for groundwater exploration using controlled source audio-frequency magnetotelluric

    Kouadio, Kouao LaurentLiu, RongMi, BinbinLiu, Chun-ming...
    13页
    查看更多>>摘要：Controlled source audio-frequency magnetotelluric (CSAMT) is one of the frequently used geophysical methods in various exploration problems such as fault mapping and groundwater exploration around 1 km depth. CSAMT is commonly used in combination with other geophysical methods to emphasize underground structures. Although it seems to be a good alternative, such a survey is expensive and requires more logistics which is not profitable for companies with low operating budgets. In addition, despite the combination of the CSAMT method with other geophysical methods, several boreholes drilled for groundwater exploration have failed due to the inaccurate locations to emphasize the fractures zones. Therefore, we developed the Python toolbox for CSAMT to solve this problem. The toolbox encompasses all the standard data processing as well as the modeling and implements a novel approach called pseudostratigraphic to forecast the strata log at each station. The advantage of this technique is twofold. First, it predicts the strata log at each station by demarcating the fracture zone, and secondly, it estimates the layer thicknesses with less margin error useful before the drilling operations. The approach was tested in the Xingning area, Hunan province, China. As a result, the model predicted with the proposed approach is similar to the mechanical borehole drilled after the geophysical survey with thickness errors of less than six meters. Furthermore, the technique would reduce the rate of unsuccessful drilling and be beneficial for geophysical and drilling companies to save money.
      原文链接:
    • NSTL
    • Elsevier

    A new approximation to the reflection coefficient of the diffusive-viscous wave equation and its evaluation for frequency-dependent AVA inversion

    Wang, ZhiqiangGao, JinghuaiZhao, HaixiaChen, Hongling...
    10页
    查看更多>>摘要：The frequency-dependent seismic anomalies related to the hydrocarbon reservoirs have lately attracted wide attentions, and the diffusive-viscous wave equation was built to explain these anomalies. Frequency-dependent amplitude versus angles of incidence (FAVA) inversion is a commonly used and effective reservoir prediction technique. The existing frequency-dependent reflection coefficient formula based on the diffusive-viscous wave equation is complex and highly nonlinear, containing eight model parameters, then it is difficult to apply for FAVA inversion. In this paper, we firstly apply the exact frequency-dependent reflection coefficient formula to FAVA inversion for two typical models. The inversion results indicate that the reflection coefficient formula can be reasonably simplified. Through a series of mathematical derivations, we obtain a new approximate frequency dependent reflection coefficient formula. The new formula contains half of the model parameters of the exact formula, which greatly shrinks the search space of the global optimization algorithm and improves computational efficiency in FAVA inversion. Finally, the accuracy of the approximate formula is analyzed by the forward modeling and FAVA inversion. The inversion results show that our formula is applicable within incident angle of 35 degrees and the frequency band range of seismic exploration, which supplies a theoretical foundation for the practical application of the FAVA inversion based on the diffusive-viscous wave equation.
      原文链接:
    • NSTL
    • Elsevier

    Reservoir facies classification based on random forest and geostatistics methods in an offshore oilfield

    Rahimi, MehranRiahi, Mohammad Ali
    9页
    查看更多>>摘要：Machine learning methods are increasingly employed in various seismic and petrophysical methods for parameter estimation, interpretation, prediction, and classification. Reservoir facies classification assists the interpretation of seismic data as an important step in petroleum exploration and production monitoring. In this study, we estimate a reservoir facies model by integrating random forest (RF) algorithms and geostatistics modeling. The Surmeh Formation with the Jurassic age is known as one of the most important hydrocarbon reservoirs in the Middle East. The upper part of the Surmeh Formation is equivalent to the Arab Formation, which includes sequences of evaporitic carbonate facies in the study area. Well log data including DT, GR, RHOB, and PHI are used in the RF method for reservoir facies classification. Cross-validation verifies the high accuracy of our classification, with an average accuracy of 95%. The predicted reservoir facies consistently describe the carbonate and evaporitic facies with the geological information of this formation. The decision tree diagrams of the RF algorithm give valuable information on decision limitations and how to select features for efficient computation. We use the classification results for facies modeling. The comparison between facies models and drilling core data shows that the APE value of the sequential indicator simulation model is less than that of the indicator kriging model.
      原文链接:
    • NSTL
    • Elsevier

    High-resoultion shallow anomaly characterization using cross-hole P- and S-wave tomography

    Wang, ChaoShi, ZhanjieYang, WencaWe, Yunon...
    13页
    查看更多>>摘要：Cross-hole seismic tomography is a high-precision method that can obtain the velocity structure between boreholes. At present, single-component geophones are mainly used for P-wave velocity estimation. However, S waves have a shorter wavelength than P waves, incurring a high-resolution tomography image. In this paper, we apply three-component cross-hole seismic tomography to shallow geological survey. First, three-component geophone is used to collect cross-hole seismic data. Secondly, the apparent velocity polarization method is used to separate the P and S wavefields from the recorded three-component waveform data. Then, a damped least-squares traveltime tomography is used to calculate the cross-hole P-and S-wave velocity structures. Finally, the distribution of Poisson's ratio between the boreholes is derived from the inverted P-and S-wave velocities. Numerical model experiments show that this method can solve some typical shallow subsurface problems, such as the detection of karst features and boulders. The proposed method is used to detect an underground air-raid shelter located in Hangzhou, Zhejiang Province, China, and the P-and S-wave velocities and the Poisson's ratio are obtained with high precision. The tomography image of the air-raid shelter agrees well with its known location. and the calculated Poisson's ratio distribution shows that the air-raid shelter may be partially filled with mucky clay. Three-component cross-hole seismic tomography achieves a high data acquisition efficiency and can simultaneously obtain shallow subsurface stratum velocities and Poisson's ratio with high precision. Thus, this technique can be used for shallow-subsurface surveys.
      原文链接:
    • NSTL
    • Elsevier

    Hydrological investigation of subsurface Glacial Lake Outburst Floods at Bindo Gol Valley under changing climate, Pakistan

    Khan, SarfrazHussain, AtharAhmad, NabeelSiddique, Babar...
    11页
    查看更多>>摘要：Climate contributed temperature and precipitation has triggered several glaciological hazards in mountainous regions of Pakistan. The present study identifies glacial architecture of Bindo Gol valley (BGV) glacier present in HinduKush region of Pakistan with emphasis on Glacial Lake Outburst Floods (GLOF) lake development. The study integrates meteorological (temperature, precipitation) and geophysical (Ground Penetrating Radar (GPR)) data to demarcate glacial architecture and possibility of GLOF lake development. Several moraines filled crevasses were identified (from GPR) mostly towards the center and south of the study area. Some of these crevasses were connected to the surficial running water channels that were also detected by GPR. A dense network of cavities was identified towards southeast of the glacier, despite being shallow, these cavities could facilitate the development of GLOF lake. The study indicates a good relationship between geophysical (presence of crevasses and subsurface cavities) and meteorological (variations in temperature and precipitation) data for the identification of source for the accumulation of larger volumes of water possibly resulting in GLOF events.
      原文链接:
    • NSTL
    • Elsevier