S-WAVE SEISMIC DATA INTERPRETATION FOR GAS RESERVOIR AT SANHU AREA, QAIDAM BASIN, WEST CHINA

Abstract

The Qigequan Formation at the Sanhu area of the Qaidam Basin in western China is a significant gas production formation. However, the conventional P-wave seismic survey conducted in this region reveals the presence of extensive gas clouds that strongly attenuate P-waves, resulting in substantial uncertainty regarding the subsurface structure. To address this challenge, we undertook a 3D9C (three-dimensional nine-component) seismic survey, producing direct S-wave data unaffected by gas clouds, yielding remarkably clearer subsurface images with a higher level of confidence. The processing of the S-wave data largely utilized conventional P-wave processing techniques, except for shear wave splitting, which produced distinct Fast (S1) and Slow (S2) S-wave datasets. Notably, the S2 data exhibited superior quality compared to the S1 data, enabling us to apply various seismic attributes and inversion techniques to extract geological features. To validate our findings, we cross-referenced the seismic attributes and inversion results with well-log and production data, revealing a pronounced spatial correlation between the gas reservoir and channel structure. Consequently, we have identified channel structures as the prime targets for potential gas reservoirs.#xD;