Petrophysical evaluation for reservoir properties of Lower Cretaceous sands in Sawan gas field, central Indus Basin, Pakistan

The Sawan gas field (SGF) is located in Pakistan's central Indus Basin in the Province of Sindh, Pakistan. Tectonically, it is part of the southeastern Jacobabad high; and geographically, it is part of the Thar Desert in the Khairpur district. In the present study, three wells, Sawan 01, Sawan 02 and Sawan 08, were analyzed for reservoir properties of the Lower Goru C sand interval, which has been drilled in the central part of the field. Petrophysical parameters such as effective porosity, the volume of shale, formation water resistivity, and water saturation of the studied basin were calculated. In terms of shale volume, Sawan 01 has 30％–35％ of non-clean (shale) lithology, which is the highest of the three wells. The effective porosity of the three wells ranges from 12％–16％, while the average water saturation in the interval of C sand in these wells stands around 50％–60％. But there are zones with relatively lower water saturation values of approximately 30％–50％. These zones are considered better pay zones than the rest of the intervals. A very interesting phenomenon that may be termed the "Gas effect" is visible on cross plots, representing the neutron-density cross over on the E-Logs layout and representing the presence of lighter hydrocarbons in this reservoir zone.