Journal of Geophysics and Engineering (J Geophys Eng )

Publisher: Nanjing shi you wu tan yan jiu suo; Institute of Physics (Great Britain)

Description

Published by the Nanjing Institute of Geophysical Prospecting and the Institute of Physics, this major new publication promotes research and developments in geophysics and related areas of engineering. It has predominantly an applied science and engineering focus, but also publishes contributions in all earth-physics disciplines from global geophysics to applied and engineering geophysics.

Impact factor 0.90

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    Impact factor
  • 5-year impact
    0.77
  • Cited half-life
    4.40
  • Immediacy index
    0.11
  • Eigenfactor
    0.00
  • Article influence
    0.27
  • Website
    Journal of Geophysics and Engineering website
  • ISSN
    1742-2140
  • OCLC
    60310620
  • Material type
    Periodical, Internet resource
  • Document type
    Journal / Magazine / Newspaper, Internet Resource

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Imaging conditions can not only affect the computational efficiency and storage cost of reverse time migration (RTM) but determine the quality of the final migrated images. This paper extends the idea of the well amplitude-preserved and highly-efficient excitation amplitude imaging condition from acoustic RTM to elastic RTM. For elastic RTM, the maximum amplitude of the separated P-wave and the corresponding image time of each grid point are saved during the forward modeling of the source wavefield and then PP and PS images are obtained by dividing the separated P- and S-waves of the backward-propagated receiver wavefield by the precomputed P-waves at each grid point that satisfies the image time. However, polarity reversals of the PS image will cause destructive interference when the stacked image is needed. In order to solve this problem, we propose the polarity-consistent excitation amplitude imaging condition by combining the excitation amplitude imaging condition with a shot-domain polarity reversal correction method. Then we provide the detailed realization process of this imaging condition in elastic RTM. By utilizing the relatively stable and well amplitude-preserved source-normalized cross-correlation imaging condition as a comparison, we testify to the feasibility and validity of the proposed imaging condition in the aspects of amplitude preservation property, imaging capability of complex structures, storage cost and computational efficiency. Considering the balance between the efficiency and image quality, the polarity-consistent excitation amplitude imaging condition can be a good choice for elastic RTM.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: Seismic inverse problem of estimating P- and S-wave reflectivity from seismic traces has recently been revisited using a basis pursuit denoising inversion (BPI) approach. The BPI uses a wedge dictionary to define model constraints, which has been successful in resolving thin beds. Here we address two fundamental problems associated with BPI, namely, the uniqueness of the estimate and the choice of regularization weight λ to be used in the model norm. We investigated these using very fast simulated re-annealing (VFSR) and gradient projection sparse reconstruction (GPSR) approaches. For a synthetic model with two reflectors separated by one time sample, we are able to demonstrate convergence of VFSR to the true model with different random starting models. Two numerical approaches to estimating the regularization weight were investigated. One uses λ as a hyper-parameter and the other uses this as a temperature-like annealing parameter. In both cases, we were able to obtain λ fairly rapidly. Finally, an analytic formula for λ that is iteration adaptive was also implemented. Successful applications of our approach to synthetic and field data demonstrate validity and robustness.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: Although the enhanced coal-bed methane (ECBM) recovery process is one of the potential coal bed methane production enhancement techniques, the effectiveness of the process is greatly dependent on the seam and the injecting gas properties. This study has therefore aimed to obtain a comprehensive knowledge of all possible major ECBM process-enhancing techniques by developing a novel 3D numerical model by considering a typical coal seam using the COMET 3 reservoir simulator.Interestingly, according to the results of the model, the generally accepted concept that there is greater CBM (coal-bed methane) production enhancement from CO2 injection, compared to the traditional water removal technique, is true only for high CO2 injection pressures. Generally, the ECBM process can be accelerated by using increased CO2 injection pressures and reduced temperatures, which are mainly related to the coal seam pore space expansion and reduced CO2 adsorption capacity, respectively. The model shows the negative influences of increased coal seam depth and moisture content on ECBM process optimization due to the reduced pore space under these conditions. However, the injection pressure plays a dominant role in the process optimization.Although the addition of a small amount of N2 into the injecting CO2 can greatly enhance the methane production process, the safe N2 percentage in the injection gas should be carefully predetermined as it causes early breakthroughs in CO2 and N2 in the methane production well. An increased number of production wells may not have a significant influence on long-term CH4 production (50 years for the selected coal seam), although it significantly enhances short-term CH4 production (10 years for the selected coal seam). Interestingly, increasing the number of injection and production wells may have a negative influence on CBM production due to the coincidence of pressure contours created by each well and the mixing of injected CO2 with CH4.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: The precision of displacement monitoring for deformable objects with global positioning system (GPS) is severely affected in highly occluded spaces, such as urban canyons and surface mines. This phenomenon is attributed to the presence of few visible GPS satellites with poor geometric structures, thus leading to ineffective positioning in severely occluded areas. An integrated GPS/pseudolite positioning technique is proposed in this paper as an effective solution for precision deformation monitoring in the abovementioned areas. This technique can effectively increase the number of visible satellites, optimize their geometric structure, and improve their positioning precision and reliability. This technique has been used in monitoring related deformable objects and has yielded favorable results. However, the majority of current studies have focused on static positioning, whereas dynamic positioning has largely been ignored. Furthermore, dynamic positioning requires further research to eliminate or reduce unmodeled systematic errors (particularly the multipath error). This paper explains the necessity and effectiveness of pseudolite introduction on the basis of the derivation of the basic deduction formula for integrated GPS/pseudolite positioning. Thereafter, the importance of pseudolite location selection by simulated test verification and analyses is discussed. Several methods for estimating and reducing the multipath error of pseudolite, which is affected by slow or small ground surface deformation and shows high spatial correlation, are also presented in this paper. A dynamic deformation monitoring model is proposed on the basis of the moving average method to improve the precision of dynamic positioning. The standard deviations of the baseline vectors in the X, Y, and Z directions are calculated at 14.0, 35.3, and 9.0 mm, respectively, thus indicating that the positioning precision is improved to different degrees in the proposed model compared with that of the separate GPS system (33.8, 54.4, and 22.3 mm for the X, Y, and Z directions, respectively), the integrated GPS/pseudolite dynamic positioning model prior to the elimination of the multipath errors of pseudolites (24.9, 56.4, and 13.3 mm for the X, Y, and Z directions, respectively), and the integrated GPS/pseudolite dynamic positioning model on the basis of the estimation of multipath error parameters (29.7, 47.9, and 17.8 mm for the X, Y, and Z directions, respectively).
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: The prime objective of this paper is to quantitatively estimate seismic attenuation caused by fractures with different physical parameters. In seismic wave simulation, the fractured media are treated as the anisotropic media and fractures are represented by frequency-dependent elastic constants. Based on numerical experiments with three different parameters, namely viscosity, porosity and the Lamé parameters, this paper has the following observations. First, seismic attenuation is not affected by the viscosity within fractures, although it increases with the increase of porosity and decreases with the increase of the Lamé parameters within fractures. Among the latter two parameters, seismic attenuation is more sensitive to the Lamé parameters than to the porosity. Second, for the attenuation anisotropy, low frequencies have more anisotropic effect than high frequencies. For example, a 50 Hz wavefield has the strongest anisotropy effect if compared to 100 and 150 Hz wavefields. The attenuation anisotropy for low frequency (say 50 Hz) is more sensitive to the viscosity than the porosity and the Lamé parameters have the weakest effect among these three parameters. These observations suggest that low-frequency seismic attenuation, and especially the attenuation anisotropy in low frequency, would have great potential for fluid discrimination within fractured media.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: Columnar jointed rock mass is a kind of structural rock mass commonly encountered in igneous rocks. Due to the effects of columnar joint networks, anisotropy is the typical mechanical property of columnar jointed rock mass, i.e. deformation and strength varying with loading direction. Correct understanding of the mechanical anisotropy of columnar jointed rock mass is a key problem that should be solved for demonstration and design of large scale rock mass projects such as dams and underground cavern excavations constructed in it. Plaster simulated columnar jointed rock mass specimens at dip angles varying from 0° to 90° with respect to the axial stress were tested under uniaxial compression conditions to investigate the mechanical anisotropy and failure modes. Based on analyses of experimental results, it was found that the strength and deformation of columnar jointed rock masses had pronounced ‘U-shaped’ anisotropy. In the anisotropic curves, the maximum and minimum values occurred at β = 90° and β = 45°, respectively. It was also shown that the lateral strain ratio was relatively high, especially when the dip angle was close to (45° − φ j /2), where φ j was the joint friction angle. An empirical expression was adopted to predict the ‘U-shaped’ anisotropy of deformation and strength and the predicted anisotropic curves agreed reasonably well with experimental data. Furthermore, four types of failure modes were summarized based on experimental results and corresponding mechanisms were also discussed.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: Soil characteristics play an important role in the degree of ground shaking due to local site amplification during an earthquake. The objectives of this work are to study shear wave velocity (V s) distribution in the near surface, and to develop a seismic site classification map for soil effect characterization and seismic hazard assessment in Hat Yai district, southern Thailand. The V s determination based on the multichannel analysis of surface waves technique, has been carried out and analyzed at 70 measuring sites throughout the district. On the basis of the weighted-average V s in the upper 30 m depth (V s30), a seismic site classification map, based on the National Earthquake Hazards Reduction Program (NEHRP) standard has been developed. It is found that the NEHRP site class in Hat Yai can be classified into four groups in accordance with the value of V s30 within the range of about 150 to 1160 m s−1. Most parts of the study area are typically classified as site class C and D. Site class C is mostly found within the colluvial and terrace deposits in the western and eastern part of the area, whereas site class D is concentrated in the alluvial sediment of the middle and northern flood plain areas. A small portion of site class B is observed in the western mountain ranges, where there is a thin overburden on the firm rock. There is a remarkably low V s30 value at only one site, located near the main stream in the northern part of the study area. The results imply that the soil characteristics in the central and northern Hat Yai district pose a medium to high amplification rate with respect to the other regions. Although V s data alone are insufficient to verify the potential of the amplification of ground shaking, this study provides an initial attempt to understand seismic hazards in the study area.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: Numerical simulation of the wave equation is widely used to synthesize seismograms theoretically and is also the basis of the reverse time migration and full waveform inversion. For the finite difference methods, grid dispersion often exists because of the discretization of the time and the spatial derivatives in the wave equation. How to suppress the grid dispersion is therefore a key problem for finite difference (FD) approaches. The FD operators for the space derivatives are usually obtained in the space domain. However, the wave equations are discretized in the time and space directions simultaneously. So it would be better to design the FD operators in the time–space domain. We improved the time–space domain method for obtaining the FD operators in an acoustic vertically transversely isotropic (VTI) media so as to cover a much wider range of frequencies. Dispersion analysis and seismic numerical simulation demonstrate the effectiveness of the proposed method.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: The multi-exponential inversion of a NMR relaxation signal plays a key role in core analysis and logging interpretation in the formation of porous media. To find an efficient metod of inverting high-resolution relaxation time spectra rapidly, this paper studies the effect of inversion which is based on the discretization of the original echo in a time domain by using a simulation model. This paper analyzes the ill-condition of discrete equations on the basis of the NMR inversion model and method, determines the appropriate number of discrete echoes and acquires the optimal distribution of discrete echo points by the Lloyd–Max optimal quantization method, in considering the inverse precision and computational complexity comprehensively. The result shows that this method can effectively improve the efficiency of the relaxation time spectra inversion while guaranteeing inversed accuracy.
    Journal of Geophysics and Engineering 02/2015; 12(1).
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    ABSTRACT: Seismic traveltime tomography is an effective method to reconstruct underground anisotropic parameters. Currently, most anisotropic tomographic methods were developed under the assumption of weak anisotropy. The tomographic method proposed here can be implemented for imaging subsurface targets in strongly anisotropic media with a known tilted symmetry axis, since the adopted ray tracing method is suitable for anisotropic media with arbitrary degree. There are three kinds of reflection waves (qP, qSV and qSH waves) that were separately used to invert the blocky abnormal body model. The reflection traveltime tomographiy is developed here because a surface observation system is the most economical and practical way compared with crosswell and VSP. The numerical examples show that the traveltimes of qP reflection wave have inverted parameters &${{c}_{11}},{{c}_{13}},{{c}_{33}}\ \text{and}\ {{c}_{44}}$ ; successfully. Traveltimes of qSV reflection wave have inverted parameters &${{c}_{11}},{{c}_{33}}\ \text{and}\ {{c}_{44}}$ ; successfully, with the exception of the &${{c}_{13}},$ ; since it is less sensitive than other parameters. Traveltimes of qSH reflection wave also have inverted parameters &${{c}_{44}}\ \text{and}\ {{c}_{66}}$ ; successfully. In addition, we find that the velocity sensitivity functions (derivatives of phase velocity with respect to elastic moduli parameters) and raypath illuminating angles have a great influence on the qualities of tomograms according to the inversion of theoretical models. Finally, the numerical examples confirm that the reflection traveltime tomography can be applied to invert strongly anisotropic models.
    Journal of Geophysics and Engineering 12/2014; 11(6).
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    ABSTRACT: Numerical modeling of poroelastic waves by the finite-difference (FD) method is more expensive than that of acoustic or elastic waves. To improve the accuracy and computational efficiency of seismic modeling, variable-grid FD methods have been developed. In this paper, we derived optimal staggered-grid finite difference schemes with variable grid-spacing and time-step for seismic modeling in porous media. FD operators with small grid-spacing and time-step are adopted for low-velocity or small-scale geological bodies, while FD operators with big grid-spacing and time-step are adopted for high-velocity or large-scale regions. The dispersion relations of FD schemes were derived based on the plane wave theory, then the FD coefficients were obtained using the Taylor expansion. Dispersion analysis and modeling results demonstrated that the proposed method has higher accuracy with lower computational cost for poroelastic wave simulation in heterogeneous reservoirs.
    Journal of Geophysics and Engineering 12/2014; 11(6).
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    ABSTRACT: There are many outcropping masses on the Kıratlı travertine fields where a new or open quarry is planned to be exploited. In this study, ground penetrating radar (GPR) and vertical electrical sounding (VES) have been applied on these fields in order to identify massive or weathered blocks and fracture–cracked systems in a short time and at low cost. GPR data were acquired on two areas, named Ocakustu (Ocakustu 1, Ocakustu 2) and Alarduc (Alarduc 1, Alarduc 2), using a 100 MHz unshielded and 250 MHz shielded antennas on 35 profiles. Generally, radargrams obtained from GPR profiles revealed massive or weathered blocks and fracture–cracked systems of these fields. The quarry operation was stopped in Ocakustu 1 due to the intensely fracture–cracked and weathered structures of the travertine field imaged by GPR. Detailed information was not obtained under the topping layer of 4 m from GPR sections on Ocakustu 2 area. Therefore, VES was also performed along four profiles which made it possible to define the areal extension and thickness of the lithotype in this site. Electrical resistivity tomography (ERT) sections have been generated by the inversion of the VES data. The subsurface geometries with resistivity values in the area were determined from these sections. Massive blocks with high resistivity could be seen at depths of 2–10 m and 10–20 m below the surface on these results and it was suggested that the quarry should be extended these parts. In addition, according to the GPR data, fracture–cracked blocks were present in Alarduc where a travertine quarry is thought to be operated. The places that will be started and orientated to quarry can be determined with respect to radargrams on Alarduc 1. Ultimately, the exploitation of a quarry was not recommended due to the extremely fracture–cracked systems found in Alarduc 2.
    Journal of Geophysics and Engineering 11/2014; 11(6):065009.
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    ABSTRACT: Subsurface fractures within many carbonates and unconventional resources play an important role in the storage and movement of fluid. The more reliably the detection of fractures could be performed, the more finely the reservoir description could be made. In this paper, we aim to propose a method which uses two important tools, a fractured anisotropic rock physics effective model and AVAZ (amplitude versus incident and azimuthal angle) inversion, to predict fractures from azimuthal seismic data. We assume that the rock, which contains one or more sets of vertical or sub-vertical fractures, shows transverse isotropy with a horizontal axis of symmetry (HTI). Firstly, we develop one improved fractured anisotropic rock physics effective model. Using this model, we estimate P-wave velocity, S-wave velocity and fracture weaknesses from well-logging data. Then the method is proposed to predict fractures from azimuthal seismic data based on AVAZ inversion, and well A is used to verify the reliability of the improved rock physics effective model. Results show that the estimated results are consistent with the real log value, and the variation of fracture weaknesses may detect the locations of fractures. The damped least squares method, which uses the estimated results as initial constraints during the inversion, is more stable. Tests on synthetic data show that fracture weaknesses parameters are still estimated reasonably with moderate noise. A test on real data shows that the estimated results are in good agreement with the drilling.
    Journal of Geophysics and Engineering 11/2014; 11(6):065007.
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    ABSTRACT: The rock physics model is an important tool for the characterization of shale reservoirs. We propose an improved anisotropic rock physics model of shale by introducing clay lamination (CL) index as a modeling parameter in effective medium theories. The parameter CL describes the degree of preferred orientation in distributions of clay particles, which depends on deposition and diagenesis history and determines intrinsic anisotropy of shales. Those complicated parameters of sophisticated methods that are difficult to quantify are substituted by CL. The applications of the proposed rock physics method include the inversion for anisotropy parameters using log data and the construction of a rock physics template for the evaluation of the Barnett Shale reservoir. Results show reasonable agreement between the P-wave anisotropy parameter ε inverted by the proposed method and those measured from core samples. The constructed rock physics templates are calibrated on well log data, and can be used for the evaluation of porosity, lithology, and brittleness index defined in terms of mineralogy and geomechanical properties of the Barnett Shale. The templates predict that the increase in clay content leads to the increase in Poisson's ratio and the decrease in Young's modulus on each line of constant porosity, which confirms the consistent and reveals quantitative relations of the two ways of defining the brittleness index. Different scenarios of mineralogy substitutions present the varied layout of constant lines on the templates.
    Journal of Geophysics and Engineering 11/2014; 11(6):065006.
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    ABSTRACT: In facies analysis, seismic data are clustered in different groups. Each group represents subsurface points with similar physical properties. Different groups can be related to differences in lithology, physical properties of rocks and fluid changes in the rocks. The supervised and unsupervised data clustering are known as two types of clustering architecture. In supervised clustering, the number of clusters is predefined, while in unsupervised clustering, a collection of patterns partitions into groups without predefined clusters.
    Journal of Geophysics and Engineering 11/2014; 11(6):065005.
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    ABSTRACT: The spatial aliasing of seismic data is usually serious because of the sub-sampling rate of the acquisition system. It induces amplitude artifacts or blurs the migration result when the spatial aliasing is not removed before migration. The compressed sensing (CS) method has been proven to be an effective tool to restore a sub-sampled signal which is compressible in another domain. Since the wave-fronts of seismic data are sparse and linear in a local spatiotemporal window, they can be significantly compressed by linear Radon transform or Fourier transform. Therefore, seismic data interpolation can be considered as a CS problem. The approximate solution of a CS problem using L0-norm can be achieved by matching pursuit (MP) algorithm. MP becomes intractable due to the high computing cost induced by the increasing dimension of the problem. In order to tackle this issue, a variant of MP—weighted matching pursuit (WMP)—is presented in this paper. Since there is little spatial aliasing in the data of low frequency and the events are supposed to be linear, the linear Radon spectrogram of the interpolated data of low frequency can be used to predict the energy distribution of data of high frequency in a frequency-wavenumber (FK) domain. The predicted energy distribution is then utilized to form the weighted factor of WMP. With this factor, WMP possesses the ability to distinguish the linear events from the spatial aliasing in the FK domain. WMP is also proven to be an efficient algorithm. Since projection onto convex sets (POCS) is another common sparsity-based method, we use Fourier POCS and WMP to realize high-dimension interpolation in numerical examples. The numerical examples show that the interpolation result of WMP significantly improves the quality of seismic data, and the quality of the migration result is also improved by the interpolation.
    Journal of Geophysics and Engineering 10/2014; 11(6):065003.