Geopressure Analysis Of Cretaceous Strata In Zamzama Gas Field, Southern Indus Basin, Pakistan

Abstract

The current research is carried out to identify the subsurface structures, and reservoir properties and evaluate their geopressures for safe hydrocarbon production in the Zamzama area. For this objective seismic and well data is used to perform Seismic Data Interpretations, Petrophysical Analysis, and Geo-pressure evaluations. In seismic data interpretation, structural interpretation is carried out on four dip lines and two strike lines. Five horizons are marked on seismic sections by confirming their position with the help of well-to-seismic ties. These marked horizons are Kirthar, Laki, Dunghan, Pab, and Fort Munro of the Zamzama area. The deformation of the anticline structure is marked by two thrust faults named as F1 and F2. Time and depth contour maps are generated for Pab sandstone due to its primary reservoir property in the area. For petrophysical analysis of Zamzama North-01 well several parameters are evaluated for hydrocarbon-bearing zones. The analysis carried out for Pab sandstone concluded the volume of shale was 17.93 %, the average porosity was 7%, the effective porosity was 5.68%, the water saturation was 61.39 % and the hydrocarbon saturation was 38.61%. For Geopressure evaluation, Hydrostatic pressure, Overburden pressure, and Pore pressure of Paleocene and Cretaceous strata of the Zamzama area are calculated. The abnormal pressure zones are identified using Eaton’s method. The evaluation of pore pressure predicts that there are mainly over-pressured zones in the lower formations of the Zamzama area. A very few underpressure zones are also identified during this evaluation.