Abstract
The purpose of this study is to verify the applicability of the 3D seismic inversiondata for the hydrocarbon determination. The 3D seismic data consisting of two angle stack data (0-22 .5 degree and 22.5-45 degree), were inverted into acoustic impedance and Poisson's ratio data. The target interval is the Upper Cretaceous, Coniacian sand and we tried to discriminate between the gas sand and the water sand by them.
The two sets of angle stack data were inverted for angle impedance. Angle impedance is a physical quantity which depends on acoustic impedance, shear impedance and the angle of reflection wave.
The match between the angle impedance results from the 3D seismic data and the angle impedance logs is rated from good to very good with respect to both reflector placement and absolute angle impedance value. The near angle stack data results in the better solution than the far angle stack data.
Poisson's ratio and acoustic impedance volumes were calculated from the angle impedance inversion results. Comparison of the calculated AVO attributes with the well log data shows that the acoustic impedance volume is of very good quality and tha Poisson's ratio volume is of good to poor quality.
A lithology cube was produced on the basis of lithology probability calculated from the cross-plotting of Poisson's ratio versus acoustic impedance. Although an amplitude anomaly of full stack data yields only a sand distribution, a gas sand distribution was interpreted by using this cube.
