Comparison of P- and S-Wave Seismic Data: A New Method for Detecting Gas Reservoirs

Compressional waves are sensitive to the type of pore fluid within rocks, but shear waves are only slightly affected by changes in fluid type. This suggests that a comparison of compressional- and shear-wave seismic data recorded over a prospect may allow an interpreter to discriminate between gas-related anomalies and those related to lithology. This case study documents that where a compressional-wave ‘bright spot’ or other direct hydrocarbon indicator is present, such a comparison can be used to verify the presence of gas. In practice, the technique can only be used for a qualitative evaluation. However, future improvement of shear-wave data quality may enable the use of more quantitative methods as well.