Sonic attenuation of shale

What is it about?

Qi et al. found that the Qp/Qs ratio estimated from the sonic waveform data acquired at the gas shale formations at Encounter 1 well, South Australia is highly sensitive to the formation gas saturation. They distinguished the depth intervals with high gas potential from the wet shale based on the Qp/Qs ratio and the results are in good agreement with the prediction from the petrophysics-based saturation log.

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Why is it important?

1. The paper addresses the important issues for an economic development of a shale gas play, which are 1. making accurate assessment of gas distribution and saturation; 2. identifying the target zones that optimizing the impact of hydraulic fracture stimulation and completion. 2. The industry standard methodology for shale gas formation evaluation does not include the acoustic data analysis in its workflow. However, our paper shows a simple and efficient technique, which is based on the attenuation obtained from full waveform acoustic logs, for identifying the zones with high gas potential in a shale gas play. 3. There has been limited research on the influence of gas saturation on attenuation of shales. To our knowledge, the paper is the first example among literatures exploring the P- and S-wave attenuation of gas-saturated shales at sonic logging frequencies. It bridges the resolution gap between the other seismic and ultrasonic frequency-band measurements and studies.