Angle-dependent seismic attenuation based gas-bearing detection of sandstone river channel reservoir in western Sichuan Basin

Abstract

The shallow river channel sandstone reservoirs of Jurassic in western Sichuan Basin are rich in natural gas. Gas-bearing sweet-spot has a ‘sausage like’ distribution feature, with complex gas water distribution. Analysis of seismic data at different angles show that gas-bearing reservoir formation has different seismic attenuation features from the water-bearing formations, and such differences have a certain correlation with gas production. Accordingly, a gas-bearing detection technology based on angle-dependent seismic attenuation feature is proposed. Firstly, matching pursuit time-frequency analysis method is used to extract high-resolution time-frequency spectrum from seismic data at different incidence angles. Then, the angle-dependent seismic attenuation attribute is estimated using the extracted time-frequency spectrum. Finally, the attribute is combined with the inverted impedance for gas-bearing detection. With the advantages of lower uncertainty and less affected by reservoir porosity, the application results of developed method have high coincidence rate with the drilled wells, and the drilling wells deployed based on the detection results have achieved high production.