Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Zhou, Hui
Dictionary learning based on dip patch selection training for random noise attenuation
Zu, Shaohuan (China University of Petroleum, University of California) | Zhou, Hui (China University of Petroleum) | Wu, Rushan (University of California) | Jiang, Maocai (Hezhou Pinggui District Bureau of Land and Resources) | Chen, Yangkang (Zhejiang University)
ABSTRACT In recent years, sparse representation is seeing increasing application to fundamental signal and image-processing tasks. In sparse representation, a signal can be expressed as a linear combination of a dictionary (atom signals) and sparse coefficients. Dictionary learning has a critical role in obtaining a state-of-the-art sparse representation. A good dictionary should capture the representative features of the data. The whole signal can be used as training patches to learn a dictionary. However, this approach suffers from high computational costs, especially for a 3D cube. A common method is to randomly select some patches from given data as training patches to accelerate the learning process. However, the random selection method without any prior information will damage the signal if the selected patches for training are inappropriately chosen from a simple structure (e.g., training patches are chosen from a simple structure to recover the complex structure). We have developed a dip-oriented dictionary learning method, which incorporates an estimation of the dip field into the selection procedure of training patches. In the proposed approach, patches with a large dip value are selected for the training. However, it is not easy to estimate an accurate dip field from the noisy data directly. Hence, we first apply a curvelet-transform noise reduction method to remove some fine-scale components that presumably contain mostly random noise, and we then calculate a more reliable dip field from the preprocessed data to guide the patch selection. Numerical tests on synthetic shot records and field seismic image examples demonstrate that the proposed method can obtain a similar result compared with the method trained on the entire data set and obtain a better denoised result compared with the random selection method. We also compare the performance using of the proposed method and those methods based on curvelet thresholding and rank reduction on a synthetic shot record.
Effective Q-compensated reverse time migration using new decoupled fractional Laplacian viscoacoustic wave equation
Li, Qingqing (China University of Petroleum) | Fu, Li-Yun (China University of Petroleum) | Zhou, Hui (China University of Petroleum) | Wei, Wei (Institute of Geology and Geophysics) | Hou, Wanting (China University of Petroleum)
ABSTRACT Seismic waves are attenuated and distorted during propagation because of the conversion of acoustic energy to heat energy. We focus on intrinsic attenuation, which is caused by , which is the portion of energy lost during each cycle or wavelength. Amplitude attenuation can decrease the energy of the wavefields, and dispersion effects distort the phase of seismic waves. Attenuation and dispersion effects can reduce the resolution of image, and they can especially distort the real position of interfaces. On the basis of the viscoacoustic wave equation consisting of a single standard linear solid, we have derived a new viscoacoustic wave equation with decoupled amplitude attenuation and phase dispersion. Subsequently, we adopt a theoretical framework of viscoacoustic reverse time migration that can compensate the amplitude loss and the phase dispersion. Compared with the other variable fractional Laplacian viscoacoustic wave equations with decoupled amplitude attenuation and phase dispersion terms, the order of the Laplacian operator in our equation is a constant. The amplitude attenuation term is solved by pseudospectral method, and only one fast Fourier transform is required in each time step. The phase dispersion term can be computed using a finite-difference method. Numerical examples prove that our equation can accurately simulate the attenuation effects very well. Simulation of the new viscoacoustic equation indicates high efficiency because only one constant fractional Laplacian operator exists in this new viscoacoustic wave equation, which can reduce the number of inverse Fourier transforms to improve the computation efficiency of forward modeling and -compensated reverse time migration (-RTM). We tested the -RTM by using Marmousi and BP gas models and compared the -RTM images with those without compensation and attenuation (the reference image). -RTM results match well with the reference images. We also compared the field data migration images with and without compensation. Results demonstrate the accuracy and efficiency of the presented new viscoacoustic wave equation.
- Research Report > New Finding (0.48)
- Research Report > Experimental Study (0.48)
CuQ-RTM: A CUDA-based code package for stable and efficient Q-compensated reverse time migration
Wang, Yufeng (China University of Petroleum-Beijing) | Zhou, Hui (China University of Petroleum-Beijing) | Zhao, Xuebin (China University of Petroleum-Beijing) | Zhang, Qingchen (Chinese Academy of Geosciences) | Zhao, Poru (China National Petroleum Corporation) | Yu, Xiance (China National Petroleum Corporation) | Chen, Yangkang (Zhejiang University)
ABSTRACT Reverse time migration (RTM) in attenuating media should take absorption and dispersion effects into consideration. The latest proposed viscoacoustic wave equation with decoupled fractional Laplacians facilitates separate amplitude compensation and phase correction in -compensated RTM (-RTM). However, intensive computation and enormous storage requirements of -RTM prevent it from being extended into practical application, especially for large-scale 2D or 3D cases. The emerging graphics processing unit (GPU) computing technology, built around a scalable array of multithreaded streaming multiprocessors, presents an opportunity for greatly accelerating -RTM by appropriately exploiting GPUs architectural characteristics. We have developed the cu-RTM, a CUDA-based code package that implements -RTM based on a set of stable and efficient strategies, such as streamed CUDA fast Fourier transform, checkpointing-assisted time-reversal reconstruction, and adaptive stabilization. The cu-RTM code package can run in a multilevel parallelism fashion, either synchronously or asynchronously, to take advantages of all the CPUs and GPUs available, while maintaining impressively good stability and flexibility. We mainly outline the architecture of the cu-RTM code package and some program optimization schemes. The speedup ratio on a single GeForce GTX760 GPU card relative to a single core of Intel Core i5-4460 CPU can reach greater than 80 in a large-scale simulation. The strong scaling property of multi-GPU parallelism is demonstrated by performing -RTM on a Marmousi model with one to six GPU(s) involved. Finally, we further verified the feasibility and efficiency of the cu-RTM on a field data set.
- Information Technology > Hardware (1.00)
- Information Technology > Data Science > Data Quality > Data Transformation (0.68)
Source-independent elastic least-squares reverse time migration
Fang, Jinwei (China University of Petroleum) | Zhou, Hui (China University of Petroleum) | Chen, Hanming (China University of Petroleum) | Wang, Ning (China University of Petroleum) | Wang, Yufeng (China University of Petroleum) | Sun, Pengyuan (BGP Research and Development Center) | Zhang, Jianlei (BGP Research and Development Center)
ABSTRACT Elastic least-squares reverse time migration (LSRTM) has been developed recently for its high accuracy imaging ability. The theory is based on minimizing the misfit between the observed and simulated data by an iterative algorithm to refine seismic images toward the true reflectivity. We have developed a new elastic LSRTM with the same modeling equations for source and receiver wavefield extrapolations, except for their source terms. The LSRTM has a natural advantage to solve the source and receiver wavefields using the same modeling system; thus, it is easy to implement LSRTM. In practice, it is difficult to obtain an accurate source wavelet, so a convolution-based objective function is used in our source-independent elastic LSRTM. Such an objective function can relax the requirement of an accurate wavelet, and improve the robustness of the inverse problem in the presence of noise. The numerical examples indicate that our method has the ability to recover the reflectivity models with an incorrect source wavelet from noisy data.
- Geophysics > Seismic Surveying > Seismic Processing > Seismic Migration (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (0.46)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/8 > Valhall Field > Tor Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/8 > Valhall Field > Hod Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/11 > Valhall Field > Tor Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/11 > Valhall Field > Hod Formation (0.99)
Elastic-impedance inversion based on L1-2 minimization
Wang, Lingqian (State Key Laboratory of Petroleum Resources and Prospecting, CNPC Key Lab of Geophysical Exploration, China University of Petroleum–Beijing) | Zhou, Hui (State Key Laboratory of Petroleum Resources and Prospecting, CNPC Key Lab of Geophysical Exploration, China University of Petroleum–Beijing) | Wang, Yufeng (State Key Laboratory of Petroleum Resources and Prospecting, CNPC Key Lab of Geophysical Exploration, China University of Petroleum–Beijing) | Yu, Bo (State Key Laboratory of Petroleum Resources and Prospecting, CNPC Key Lab of Geophysical Exploration, China University of Petroleum–Beijing) | Long, Teng (State Key Laboratory of Petroleum Resources and Prospecting, CNPC Key Lab of Geophysical Exploration, China University of Petroleum–Beijing)
ABSTRACT It is necessary to estimate the elastic impedance accurately for three-parameter inversion. However, the elastic impedance can be calculated from the reflectivity with the recursive inversion and the generalized linear inversion (GLI) separately. It has been demonstrated that GLI can improve the shortcomings of recursive inversion with respect to relative and absolute scale of the impedance results. But both of them depend on the accuracy of the reflectivity, so it is necessary to get the reflectivity accurately. Here we use alternating direction method of multipliers (ADMM) and difference of convex algorithm (DCA) to solve the minimization problem to obtain a more accurate reflectivity series. Examples have shown the superior performance of the ADMM- inversion result over the solution of OMP algorithm. Presentation Date: Monday, October 15, 2018 Start Time: 1:50:00 PM Location: Poster Station 11 Presentation Type: Poster
A stable approach for Q-compensated viscoelastic reverse time migration using excitation amplitude imaging condition
Zhao, Xuebin (China University of Petroleum-Beijing) | Zhou, Hui (China University of Petroleum-Beijing) | Wang, Yufeng (China University of Petroleum-Beijing) | Chen, Hanming (China University of Petroleum-Beijing) | Zhou, Zheng (China University of Petroleum-Beijing) | Sun, Pengyuan (BGP Research and Development Center of CNPC) | Zhang, Jianlei (BGP Research and Development Center of CNPC)
ABSTRACT The earth filtering causes poor illumination of the subsurface. Compensating for the attenuated amplitude and distorted phase is crucial during elastic reverse time migration (ERTM) to improve the imaging quality. Conventional -compensated ERTM (-ERTM) methods tend to boost the attenuated energy to inverse the effects. These methods usually suffer from severe numerical instability because of the unlimited amplification of the high-frequency noise. Low-pass filtering is generally used to stabilize the process, however, at the expense of precision. We have developed a stable compensation approach in this paper. Based on the decoupled fractional Laplacians viscoelastic wave equation, two compensation operators are obtained by extrapolating wavefield in the dispersion-only and viscoelastic media. Because no explicit amplification is included, these two operators are absolutely stable for implementation. To improve the division morbidity for calculating the compensation operators, we use the excitation amplitude criterion and embed the operators into a vector-based -compensated excitation amplitude imaging condition. With the derived imaging condition, we could compensate for the absorption accurately without needing to concern the stability issue. The -ERTM results for noise-free data are carried out over a simple layered model and a more realistic Marmousi model with an attenuating area to verify the feasibility of the proposed approach. The migration results for noisy data from the Marmousi model further prove that the proposed method performs better fidelity, adaptability, and antinoise performance compared with conventional compensation method with low-pass filtering.
A rectangular-grid lattice spring model for modeling elastic waves in Poisson’s solids
Xia, Muming (China University of Petroleum) | Zhou, Hui (China University of Petroleum) | Chen, Hanming (China University of Petroleum) | Zhang, Qingchen (Institute of Geodesy and Geophysics) | Li, Qingqing (China University of Petroleum (East China))
ABSTRACT The lattice spring model (LSM) combined with the velocity Verlet algorithm is a newly developed scheme for modeling elastic wave propagation in solid media. Unlike conventional wave equations, LSM is established on the basis of micromechanics of the subsurface media, which enjoys better dynamic characteristics of elastic systems. We develop a rectangular-grid LSM scheme for elastic waves simulation in Poisson’s solids, and the direction-dependent elastic constants are deduced to keep the isotropy of the discrete grid. The stability condition and numerical dispersion properties of LSM are discussed and compared with other numerical methods. The 2D and 3D numerical simulations are carried out using the rectangular-grid LSM, as well as the second- and fourth-order accuracy staggered finite-difference method (FDM). Wavefields obtained by LSM are fairly similar with those by analytical solution and FDM, which demonstrates the correctness of the proposed scheme and its capability of modeling elastic wave propagation in heterogeneous media. Moreover, we perform plane P-wave simulation through a semi-infinite cavity model via LSM and FDM, the recorded wavefield snapshots indicate that our proposed rectangular-grid LSM obtains more reasonable wavefield details compared with those of FDM, especially in media with high compliance and structure complexity. Our main contribution lies in offering an alternative simulation scheme for modeling elastic wave propagation in media with some kinds of complexities, which conventional FDM may fail to simulate.
A constant fractional-order viscoelastic wave equation and its numerical simulation scheme
Wang, Ning (China University of Petroleum) | Zhou, Hui (China University of Petroleum) | Chen, Hanming (China University of Petroleum) | Xia, Muming (China University of Petroleum) | Wang, Shucheng (China University of Petroleum) | Fang, Jinwei (China University of Petroleum) | Sun, Pengyuan (BGP Research and Development Center)
ABSTRACT Efficient modeling schemes currently exist to handle the spatially variable-order fractional Laplacians in the fractional Laplacian viscoacoustic wave equation. The simplest approach is to change the spatially variable-order fractional Laplacians into a linear combination of several constant fractional-order Laplacians. We generalize the constant fractional-order scheme to a spatially variable fractional-order viscoelastic wave equation and develop an almost-equivalent constant fractional-order viscoelastic wave equation. Our constant fractional-order scheme avoids the simulation error introduced by directly averaging the spatially varying fractional order; thus, our scheme simulates seismic wave propagation in viscoelastic media with sharp contrasts well. The fast Fourier transform is used in the approximation of the fractional Laplacians, which improves the spectral accuracy in space. Several simulation examples are performed to verify that the numerical solution of a homogeneous model obtained by solving our constant fractional-order viscoelastic wave equation agrees well with that obtained by solving the original viscoelastic wave equation. The numerical simulations for spatially varying models obtained by the new wave equation are more straightforward than those currently in use and match the reference solutions obtained by accurate, but inefficient, methods. This match of simulation results verifies the accuracy of our viscoelastic wave equation.
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling (0.69)
Adaptive stabilization for Q-compensated reverse time migration
Wang, Yufeng (China University of Petroleum-Beijing) | Zhou, Hui (China University of Petroleum-Beijing) | Chen, Hanming (China University of Petroleum-Beijing) | Chen, Yangkang (The University of Texas at Austin, Oak Ridge National Laboratory)
ABSTRACT Reverse time migration (RTM) for attenuating media should take amplitude compensation and phase correction into consideration. However, attenuation compensation during seismic propagation suffers from numerical instability because of the boosted high-frequency ambient noise. We have developed a novel adaptive stabilization method for -compensated RTM (-RTM), which exhibits superior properties of time variance and dependence over conventional low-pass filtering-based method. We derive the stabilization operator by first analytically deriving -space Green’s functions for a constant- wave equation with decoupled fractional Laplacians and its compensated equation. The time propagator of Green’s function for the viscoacoustic wave equation decreases exponentially, whereas that of the compensated equation is exponentially divergent at a high wavenumber, and it is not stable after the wave is extrapolated for a long time. Therefore, the Green’s functions theoretically explain how the numerical instability existing in -RTM arises and shed light on how to overcome this problem pertinently. The stabilization factor required in the proposed method can be explicitly identified by the specified gain limit according to an empirical formula. The -RTM results for noise-free data using low-pass filtering and adaptive stabilization are compared over a simple five-layer model and the BP gas chimney model to verify the superiority of the proposed approach in terms of fidelity and stability. The -RTM result for noisy data from the BP gas chimney model further demonstrates that our method enjoys a better antinoise performance and helps significantly to enhance the resolution of seismic images.
Viscoacoustic wave simulation by lattice Boltzmann method and the relationship between relaxation factor and the quality factor
Wang, Shucheng (China University of Petroleum–Beijing) | Xia, Muming (China University of Petroleum–Beijing) | Zhou, Hui (China University of Petroleum–Beijing) | Wang, Ning (China University of Petroleum–Beijing) | Fang, Jinwei (China University of Petroleum–Beijing)
ABSTRACT In this paper, lattice Boltzmann method (LBM) is employed in forward modeling of seismic P-wave propagation. By choosing different relaxation factors in numerical experiments and using spectrum ratio method, the relationship between the quality factor and the parameters of LBM can be revealed. After a brief introduction of the theory and method behind LBM, some numerical experiments are carried out to certify the new scheme through comparison with the reference solution obtained by finite difference method (FDM). The wavefields given by LBM coincide with those by FDM, which demonstrates the feasibility of LBM. In addition, we find the relaxation factor of LBM has some relationship with the quality factor Presentation Date: Wednesday, September 27, 2017 Start Time: 4:45 PM Location: 381A Presentation Type: ORAL