Application of model based post-stack inversion in the characterization of reservoir sands containing porous, tight and mixed facies: A case study from the Central Indus Basin, Pakistan

Abstract

Porosity is a key parameter for reservoir evaluation. Inferring the porosity from seismic data is often challenging and prone to uncertainties due to number of factors. The main aim of this paper is to show the applicability of seismic inversion on old vintage seismic data to map spatial porosity at reservoir level. 3D-seismic and wireline log data are used to map the reservoir properties of the Lower Goru productive sands in the Gambat Latif block, Central Indus Basin, Pakistan. The Lower Goru formation was interpreted with the help of seismic and well data. Interpreted horizons are thus further used in model-based seismic inversion techniques to map the spatial distribution of porosity. Well-log data are used in the construction of low acoustic impedance models. Calibration of reservoir porosity with inverted acoustic impedance is achieved through well-log data. The results from model-based inversion reasonably estimate the porosity distribution within the C-sand interval of the Lower Goru Member. After post-stack inversion, the porosity values at wells Tajjal-01, Tajjal-02 and Tajjal-03 are 10%, 8% and 12%, respectively. Porosity values calculated from post-stack inversion at the corresponding well locations are in good agreement with the borehole-derived porosity.