Norton, Jeannemarie (Battelle - Oak Ridge Operations) | Beard, Les (Battelle - Oak Ridge Operations) | Gamey, Jeffrey (Battelle - Oak Ridge Operations) | Doll, William (Battelle - Oak Ridge Operations) | Sheehan, Jacob (Battelle - Oak Ridge Operations)
Gasperikova, Erika (Lawrence Berkeley National Laboratory) | Smith, J.T. (Lawrence Berkeley National Laboratory) | Morrison, H.F. (Lawrence Berkeley National Laboratory) | Becker, A. (Lawrence Berkeley National Laboratory) | Kappler, K. (Lawrence Berkeley National Laboratory)
It is difficult to characterize accurately subtle stratigraphic details by surface seismic data with poor vertical resolution. A new method for restoring high frequencies within the seismic bandwidth by utilizing velocity logging data has been proposed in the paper. By assuming seismic wave propagation in formations is attenuated linearly, a theoretical model is derived firstly between surface seismic data and velocity logging data, and then the absorption system response is evaluated based on system identification technology, which can be used to compensate the attenuated high frequencies within the surface seismic bandwidth. The results of high frequency restoration for the forward modeling data and the actual surface seismic data show that the new method can enhance significantly the vertical resolution of the surface seismic data, which will advance the dominant frequency between 10Hz and 20Hz, widen the frequency band about 10Hz, but the principal features of the original surface seismic data still hold.
Zhou, Hongbo (Repsol YPF) | Ortigosa, Francisco (Repsol YPF) | Lesage, Anne Cécile (Barcelona Supercomputing Center) | Polo, Mauricio Araya (Barcelona Supercomputing Center) | Cela, Jose Maria (Barcelona Supercomputing Center)
We propose a 3D reverse-time migration (RTM) using an hybrid Finite Difference (FD) pseudospectral algorithm to solve the two-way acoustic equation. This mainly consists of forward-backward 2D FFT in lateral dimensions (x-y plane) and 1D FD in the depth dimension. This algorithm allows us to get high order accuracy and simplifies the computation of cross derivatives. Therefore our RTM allows to deal with the case of 3D isotropic media, VTI media (Zhou et al., 2006b) and 3D TTI media. The 3D TTI media case lies on a new anisotropic wave equations system (Lesage et al., 2008), which is an extension of 3D VTI media (Zhou et al., 2006b) and 2D TTI media equations (Zhou et al., 2006a) of Zhou et al. . This system is based on the combination of two 3D rotations which permits us to deduce 3D TTI equations from 3D VTI equations. In this work, we recall the formalization for 3D isotropic, 3D VTI and 3D TTI media, we also describe the implementation of the method to solve the proposed 3D TTI equations. To validate our proposal, we carry out impulse response experiments for modeling and migration.
Thanks to high performance computing environments, production imaging for geophysic prospection of earth depth below sea bottom can now be done with 3D isotropic RTM. It uses the two-way acoustic isotropic wave equation and is relevant for challenging geological environment because it does not suffer from dip limitation. But seismic anisotropy in dipping shales can result in imaging and positionning problems for underlying structures. For production-delineation of reservoirs, it is clear that higher-resolution methods must take anisotropy into account (Thomsen, 1986) (Tsvanskin, 2001). In this work, we consider three RTM cases : isotropic and two transversely isotropic cases (VTI and TTI media). VTI yields for TI media with vertical axis of symmetry (observed in sedimentary basins). TTI assumption means a TI media with a tilted axis of symmetry (observed in regions with anticlinal structures and/or thrust sheets). Currently, Zhou et al. (Zhou et al., 2006b) proposed an equivalent coupled system to Alkhalifah''s (Alkhalifah, 2000) "acoustic" approximation for 3D VTI media. This system of lower-order adds even more simplicity to the Alkhalifah''s approximation already attractive for modeling and migration. In (Zhou et al., 2006a), Zhou et al. extended their idea to the 2D TTI case. In this paper, we recall the combination of Zhou et al ideas for 3D VTI and 2D TTI which produces a new 3D TTI equations system (Lesage et al., 2008). This system is based on the combination of two 3D rotations which permits to pass from the vertical axis to the tilted one. To solve the different acoustic equations, we use partially the attractive Pseudospectral (PS) method proposed by Kosloff (Kosloff and Baysal, 1982), which introduces an alternative to the two classic Finite Difference (FD) and Finite Element (FE) methods. The basic idea of the pseudospectral is to expand the field quantities by the mean of a discrete Fast Fourier Transform (FFT) and to compute analytically the spatial derivation in the wave number domain.