PETROPHYSICAL AND STRUCTURAL ANALYSIS OF LOWER GORU FORMATION, SOUTHERN SINDH MONOCLINE, LOWER INDUS BASIN, PAKISTAN

Abstract

The research area is from the Badin Block of the Lower Indus Basin, Sindh, Pakistan. The area is tectonically stable with a monoclinal structure commonly known as Sindh monocline. The Lower Indus basin tectonically represents an extensional regime. The Lower Indus basin contributes 40% oil and approximately 70% gas of the country’s total production. Badin area is at the forefront of Pakistan’s production with 307 wells drilled to date which explains the hopeful hydrocarbon prospect in this area. The purpose of this study is to apply reservoir rock physics fundamentals for understanding the reservoir architecture for hydrocarbon potential. In this regard, two wells Jabo-1 and Jabo-5 were selected using petrophysical and seismic approach in the Cretaceous Lower Goru Formation, a reservoir of both the wells. In the Badin area, the rock formations show a complex deformation history, which can be classified into three major events 1) Early Cretaceous (Basal Sand to Upper Goru 2) Middle to Late Cretaceous (Basal Sand to Upper Goru) and 3) Post Paleocene (uplifting and doming). Based on the petrophysical analysis, zones were selected for the reservoir at different depths. The effective porosity for both wells ranged from 5.49% to 7.15% with a water saturation ranging from 45.24% to 80.21%. Cross plots generated from different parameters confirm that there are only three types of lithologies in the selected zone of reservoir that are hydrocarbon sands, brine sands, and shales. Petrophysical analysis confirms an increase in the reservoir quality towards the southern part of the oil field. Seismic interpretation revealed the existence of horst and graben structures in the subsurface. Five horizons were picked on the seismic sections by incorporating well data. The generated contour maps depth indicates that the reservoir of the area is dipping in the southwest direction with the major orientation of faults in the northwest direction.