The application of turning effect for the detection of the thin bed less than λ/4 - An example in the Northwest of China

摘要

Over the years, geophysicists have been working hard in pursuit of higher resolutions in the seismic exploration. But, due to the effect of the earth attenuation and the noise interference, the dominant frequency always has certain limit in a given area. Conventionally, this limit is called "1/4 λ" limit. The thickness of the beds smaller than this limit can not be resolved, which is far from the requirement by geologists, particularly for the seismic prospecting in a developed phase. Although some papers have mentioned the possibility of using tuning effect to detect the thin sand body, few successful cases have been published. In this paper, a 3D seismic data has been processed and interpreted with a target formation at 5100 m deep with a thickness of 0 ～ 35 m (pinch out). The amplitude preservation and the resolution improvements are mainly handled during the processing. With the calibration of the sonic logging and VSP data to the 3D seismic survey, by the elaborate structure interpretation combined with horizon amplitude, waveform clustering, modeling, and integrated oil development information analysis, the thin sand lens less than 1/4 λ and pinch-out boundary can be detected by the tuning effect. The strategy presented in this paper can be applied for finding more strati-graphic oil & gas reservoirs in the continental deposi-tional environment in China.