3D static reservoir modelling to evaluate petroleum potential of Goru C-Interval sands in Sawan Gas Field, Pakistan

Abstract

This study is aimed at building a 3D static model of the C-Interval horizon within the Lower Goru Formation of the Sawan gas field, Pakistan. The C-Interval horizon is a proven gas reservoir with considerable potential for further development. Sequence stratigraphic interpretation reveals that C-Interval horizon was deposited under transgressive-regressive conditions, with forced regression resulting in deposition of sand bodies in a deltaic environment. Well logs and core analysis reveal different lithological facies. Thin interbedded shales induced extreme heterogeneity in C-Interval reservoir properties. Sequential Indicator Simulation (SIS) and Sequential Gaussian Simulation (SGS) have been applied to spatially map the heterogeneities of the reservoir properties such as water saturation (Sw), porosity (ϕ), facies, etc. The models indicate thick reservoir quality sand facies are present in the northeastern half with high effective porosity (ϕe) being consistent with the high sand content near the paleo-coast line. However, the shale content (Vsh) increases towards the southwestern half consistent with more basinward settings. The lithologies in the southwestern half exhibit low ϕe with an increase in Sw. The techniques utilized in this study have implications for other producing hydrocarbon fields with complex reservoir properties and similar geological settings.