Abstract
For large-scale 3D seismic data, target-oriented reservoir imaging is more attractive than conventional full-volume migration, in terms of computation efficiency. Gaussian beam migration (GBM) is one of the most robust depth imaging method, which not only keeps the advantages of ray methods, such as high efficiency and flexibility, but also allows us to solve caustics and multipathing problems. But conventional Gaussian beam migration requires slant stack for prestack data, and ray tracing from beam center location to subsurface, which is not easy to be directly applied for target-oriented imaging. In this paper, we modify the conventional Gaussian beam migration scheme, by shooting rays from subsurface image points to receivers to implement wavefield back-propagation. This modification helps us to achieve a better subsurface illumination in complex structure and allows simple implementation for target reservoir imaging. Significantly, compared with the wavefield-based GBM, our method does not reconstruct the subsurface snapshots, which has higher efficiency. But the proposed method is not as efficient as the conventional Gaussian beam migration. Synthetic and field data examples demonstrate the validity and the target-oriented imaging capability of our method.
Highlights
Gaussian beam method started its successful path in geophysics in the early 1980s (Popov 1981; Kachalov and Popov 1981; Červený et al 1982; Popov 1982; Červený 1983; Červený and Pšenčík 1983a, b, 1984)
Gaussian beam migration (GBM) avoids the thorny problem of amplitude singularity in the vicinity of caustics using dynamic ray tracing with a complex-valued initial beam parameter
We present an extraction strategy of angle domain common image gathers (ADCIGs) using the proposed method to meet the demands of the iterative velocity-model-building and the AVA analysis
Summary
Gaussian beam method started its successful path in geophysics in the early 1980s (Popov 1981; Kachalov and Popov 1981; Červený et al 1982; Popov 1982; Červený 1983; Červený and Pšenčík 1983a, b, 1984). State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China methods It provides physical insight of the propagation of the seismic wave, which makes it easier for us to describe the wave phenomena in quite complicated geophysical models. Its decomposition of local plane wave in different directions enables it to propagate different angles to subsurface image point independently, which allows us to deal with multipathing. All of these characteristics make GBM a robust and versatile depth imaging tool, with accuracy comparable to wave equation migration and with flexibility and efficiency comparable to Kirchhoff migration
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