科研之友
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摘要
The existence of fractures not only provides space for oil and gas to reside in but also creates pathways for their migration. Accurate description of a fractured reservoir is thus an important subject of exploration for geophysicists and petroleum engineers. In reflection seismology, a reservoir of parallel vertical fractures is often considered a transversely isotropic medium with its symmetry axis horizontally oriented and its physical properties varying in azimuth on the horizontal symmetry-axis plane. In the history of fractured reservoir exploration, azimuthal variation in the P-wave amplitude, velocity, and fractional difference of the split S-waves have been popular seismic attributes used to delineate characteristics and extract information from the reservoir. Instead of analysing the reflection signatures of P-wave and S-wave, the objective of this study is to demonstrate the azimuthal variation of the converted wave (C-wave) amplitude in a fractured reservoir. To facilitate our objective, both common offset and end-on shooting reflection experiments were conducted in different azimuths on the horizontal symmetry-axis plane of a horizontal transverse isotropic model. In the acquired profile, reflections of P-wave, PS1-wave (C-1-), and a mixture of PS2-(C-2-) and S-1-waves were observed and identified. Thereafter, the laboratory observations were Hilbert transformed to compute the reflectivity strength of the relative events. Results show that the reflectivity strengths of both P-and C-1-waves are consistently weakened from the direction of the layering strike to the layering normal. However, the azimuthal variation of the C-1-wave amplitude is more significant than that of the P-wave and can be considered another effective seismic attribute for orienting the fracture strike of a reservoir that consists of vertically aligned fractures.
- 出版日期2017-1
- 单位中国地震局地震研究所
