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Summary Coherence measurement is an effective method for representing geological discontinuities such as faults and stratigraphic features in 3-D seismic data volumes. Essentially, the coherency methods use the linear correlation to measure discontinuity, which would not be able to capture the information about dependence between two random variables adequately. This paper proposed a coherence algorithm of discontinuities measure for 3-D seismic data based on nonlinear correlation as rank correlation (Kendall’s tau). This method has a higher resolution to detect minor discontinuities in seismic data robustly. We demonstrated the advantage of this method by real seismic data examples.
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Yian Formation (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Mingshui Formation (0.99)
Summary This paper proposes a new multichannel convolution model for stacked seismic data. This model supposes that the layers are horizontal and the reflection coefficients are sparse. The properties of the layer change weakly and randomly, which means that the reflection coefficients from same interface change randomly with weak amplitude. Based on this model and lateral invariant seismic wavelet, we introduce the time-vary wavelet convolution model of multichannel seismic signal. Therefore the instantaneous linear mix model of independent component analysis (ICA) is satisfied. The time-vary wavelet can be estimated by solving proposed model. The synthetic and field data examples demonstrate the rationality of proposed model and the validity of the seismic wavelet estimated method. The wavelet estimated matched very well with the wavelet that was used in synthesizing data. Using the wavelet estimated by proposed method to deconvolve the real field data, the time-resolution was enhanced evidently, and the high signal-to-noise rate (SNR) was also kept.
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Yian Formation (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Mingshui Formation (0.99)
Summary We implement an efficient time domain viscoelastic forward modeling using Graphics Processing Unit (GPU). A staggered finite difference scheme of second-order temporal accuracy and fourth-order spatial accuracy with the unsplit convolutional perfectly matched layer (CPML) is applied to the 2D viscoelastic stress-velocity wave equations. To calculate the relaxation times for pressure wave and shear wave in wave equations, the t-method is used to approximate a constant Q over the frequency band of the source. The numerical results indicate that the CPML can efficiently absorb waves reaching the absorbing layers at grazing incidence. And our GPU-based viscoelastic forward modeling tests achieved a speedup of a factor 10 relative to a CPU implementation.
- Information Technology > Hardware (1.00)
- Information Technology > Graphics (1.00)
Summary Full waveform inversion (FWI) is often formulated as an optimization problem to derive the best model that can minimize the difference between a field data and the simulated one. Usually, iterative gradient based methods are employed for the problem. These methods require an accurate initial model to avoid cycle-skipping, which cannot be described by the Born approximation. Many methods can be used to build such an initial model for FWI, like reflection tomography and migration-based velocity analysis. In this paper, we propose another way to build the initial model for FWI by using a global optimization method with multigrid technique. This scheme not only takes the advantage of multigrid technique to reduce the model dimension of the inversion, but also benefits from a new highly efficient global optimization method to reduce computation cost. We apply our scheme to a synthetic cross-well data. Numerical results show that this new scheme is robust to build a good initial model to be used for FWI.
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Yian Formation (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Mingshui Formation (0.99)
Summary Numerical simulation of wave propagation in poroelastic media demands significantly more computational capability, include both computational time and memory, compared to those in acoustic, elastic and viscoelastic media. A 3D par-allel poroelastic staggered-grid finite difference (SFD) method is implemented to increase the computational effi-ciency. Parallelization is based on domain decomposition, communication between processors is performed using message passing interface (MPI). Analysis and numerical examples show that parallelized SFD significantly im-proves the simulation efficiency.
Fractional Anisotropic Gradient Based Filtering for Random Noise Attenuation of Seismic Data
Wang, Dehua (Xi'an Jiaotong University) | Gao, Jinghuai (Xi'an Jiaotong University) | Yang, Pengliang (Xi'an Jiaotong University) | Zhang, Chao (Xi'an Jiaotong University) | Li, Qiang (Xi'an Jiaotong University) | Peng, Jigen (Xi'an Jiaotong University)
Summary Motivated by the fact that the fractional derivative operators in existing fractional gradient are unable to separately act on input signals in the horizontal and vertical directions, we first introduce the concept of fractional anisotropic gradient in this paper. Based on this concept, we propose a new denoising model, derive the Euler-Lagrange equation for this new model and present the corresponding numerical algorithm. Finally, we apply our proposed method to the random noise attenuation for real seismic profiles. The theoretical analysis and experimental results indicate that our method can preferably enhance the lateral continuity of seismic events and preserve the line-like texture characters and useful detail information in the vertical direction while improving the signal-to-noise ratio. This provides a reliable basis for seismic data interpretation.
Summary GPU has become a booming technology in RTM to perform the expensive computation. Compared with saving the forward modeled wavefield on the disk, wavefield reconstruction method is a better way because computation is much faster than CPU-GPU data transfer. In this paper, we introduce the concept of effective boundary saving in reconstruction-based back propagation for GPU-based RTM. Starting from the computational strategies by Dussaud et al. (2008), we discuss the minimum requred saving amount in backward wavefield reconstruction for regular and staggered grid finite difference. Particularly, the minimum storage for staggered finite difference scheme using PML boundary condition is first explored. We demonstrate the proposed approach with numerical examples.
- Geophysics > Seismic Surveying > Seismic Modeling (0.94)
- Geophysics > Seismic Surveying > Seismic Processing > Seismic Migration (0.79)
- Information Technology > Hardware (1.00)
- Information Technology > Graphics (1.00)
Summary The Xiashihezi Formation of the Ordos basin is the largest producer of tight gas sand in China. Production patterns vary from one well to another throughout the basin. In this study, we integrated three-dimensional (3-D) seismic and well data to investigate geological controls on production in P1h8 member of Xiashihezi Formation. Our objective was to show the potential of using multiple seismic attributes to characterize the distribution and orientation of tight gas sand. We used the amplitude, the complex traces, the spectral components, and the seismic attenuation attributes derived from 3-D seismic volume to detect gas-bearing sand that might be associated with zones of production. Production data show that higher producing wells are associated with seismically definable larger amplitude, more stable phase, higher frequency, and stronger attenuation features in the study area. Our comprehensive result suggests that 3-D seismic data, integrated with wire-line logs and production data, are useful for characterizing tight gas sand reservoirs.
- Asia > China > Shaanxi Province (0.75)
- Asia > China > Shanxi Province (0.64)
- Asia > China > Gansu Province (0.64)
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation (1.00)
- North America > United States > Wyoming > Wind River Basin (0.99)
- North America > United States > New Mexico > San Juan Basin (0.99)
- North America > United States > Colorado > San Juan Basin (0.99)
- (9 more...)
Summary In this paper, a family of distributions, standard symmetric power distribution (SSPD), which would be proper to describe the seismic reflection coefficient is proposed. Special cases of this family include the triangular distribution, the standard power function distribution, and the uniform distribution. Properties of the distribution are investigated and the moment and entropy estimation is discussed. The two parameter distribution is investigated in the seismic reflection coefficient and the seismic record. And then the deconvolution method based on negentropy is developed using SSPD. The method works in the frequency domain and requires estimation of the signal’s probability density function. Thus, the algorithm uses higher order statistics (except for Gaussian source) and allows non-minimum- phase filter estimation. In practice, a gradient based regularization term for limiting noise amplification is contained in the criterion, which can improve the anti-noise property and the continuity between the adjacent traces of the multichannel seismic record. The gradient function which represents a key point of this algorithm is simplified based on the introduction of SSPD. Finally, experiments point to the relevance of the proposed algorithm: 1) Any filter, minimum phase or not, can be estimated; 2) Based on the SSPD, we can calculate the entropy instead of its asymptotic value and as there is no need to estimate the parameter in this method, it has a good computing speed. 3) The introduction of the gradient regularization term can provide good results with a better performance of the anti-noise property and the continuity between the adjacent traces. Applications of the introduced method to both synthetic and real data show that the proposed method can expand the frequency band of the seismic data with small samples, fast computing speed, good anti-noise quality and continuity between the adjacent traces.
Estimating the Dip by Constructing Gradient Structure Tensor on Instantaneous Phase
Wang, Xiaokai (Chinese Academy of Science) | Yang, Changchun (Chinese Academy of Science) | Chen, Wenchao (Xi'an Jiaotong University) | Gao, Jinghuai (Xi'an Jiaotong University) | Zhu, Zhenyu (Research Center of CNOOC)
Summary Gradient structure tensor (GST) is used in attributes extraction commonly, such as dip, azimuth, and discontinuity detection. Usually the GST is constructed on migrated seismic data directly. One important procedure in GST is spatial derivative. The spatial derivative on migrated data contains not only structure information (such as dip and azimuth) but also the spatial change of wave impedance. We construct GST on instantaneous phase to estimate the dip and azimuth, which reflects the geometric structure of layer and eliminates the influence of the lateral change of wave impedance. The results of synthetic example and field-data example show the correctness and validity of our method.