Abstract
Prestack depth migration for seismic reflection data is commonly used tool for imaging complex geological structures such as salt domes, faults, thrust belts, and stratigraphic structures. Phase shift plus interpolation (PSPI) algorithm is a useful tool to directly solve a wave equation and the results have natural properties of the wave equation. Amplitude and phase characteristics, in particular, are better preserved. The PSPI algorithm is widely used in hydrocarbon exploration because of its simplicity, efficiency, and reduced efforts for computation. However, meaningful depth image of 3D subsurface requires parallel computing to handle heavy computing time and great amount of input data. We implemented a parallelized version of 3D PSPI for prestack depth migration using Open-Multi-Processing (Open MP) library. We verified its performance through applications to 3D SEG/EAGE salt model with a small scale Linux cluster. Phase-shift was performed in the vertical and horizontal directions, respectively, and then interpolated at each node. This gave a single image gather according to shot gather. After summation of each single image gather, we got a 3D stacked image in the depth domain. The numerical model example shows good agree- ment with the original geological model.
Highlights
Seismic migration is a process to turn the reflectors on the stack image into true geological interface
Seismic migration based on ray methods such as Kirchhoff (Gray and May, 1994 [1], Bevc, 1997 [2]) and Gaussian beam method (Gray, 2005 [3]) is a popular imaging method
We describe the practical appearance of the implementation on 3D PSPI using Open MP library and the method is tested on a synthetic data set from the 3D SEG/EAGE salt model (Aminzadeh et al, 1997) [13]
Summary
Seismic migration is a process to turn the reflectors on the stack image into true geological interface It can be divided ray- and wave equation-based method. Since the wave equation migration methods control multi-path arrivals, it can give better images than ray methods for complex subsurface structures. Migration by one-way wave equation is the most popular scheme due to less computing time and high efficiency. These methods are well known as phase-shift migration (Gazdag, 1978 [9]) and split-step-Fourier (SSF) (Stoffa et al, 1990) [10] method. The depth extrapolation is composed of entirely concurrent operations, and only the imaging condition requires inter-processor communication or remote memory access This is beneficial for parallel coding for PSPI algorithm. PSPI requires that all small dips be characterized by kx + ky ≤ ω vn
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