In this study a tight carbonate gas reservoir of early Eocene (S1 formation) is studied
for litho-facies estimation and probabilistic estimation of reservoir properties prediction
using quantitative geophysical approach from a mature gas field in the Middle Indus
Basin, onshore Pakistan. Quantitative seismic reservoir characterization approach
relied on well based litho-facies re-classification, Amplitude Variation with Offset (AVO)
attributes analysis and Pre-Stack simultaneous inversion attributes constrained with
customized well-log and seismic data (gathers) conditioning. Three main litho-facies
(hydrocarbon bearing limestone, tight limestone and shale) are classified estimated
based on the precise analysis of well data using petrophysical properties. AVO
attributes (intercept and gradient) conveniently inspection for amplitude behavior
(reflection coefficients) of the possible AVO (class I), fluids and lithology
characteristics. Probable litho-facies (tight limestone and shale) are estimated using
well based litho-facies classification and inverted seismic attributes (p-impedance and
density) from pre-stack simultaneous inversion in a Bayesian framework. Additionally,
petrophysical properties (clay volume and porosity) are derived from probabilistic
neural network approach using well logs and pre-stack inverted attributes (pimpedance
and density) constrained with sample-based seismic attributes
(instantaneous, windowed frequency, filters, derivatives, integrated and time).