Reservoir Characterization And Provenance Study Of The Early Cambrian Khewra Sandstone In Eastern And Central Salt Range, Pakistan: An Integrated Approach Based On Outcrop And Core Data

Abstract

The present study is aimed to evaluate the reservoir characterization and provenance analysis of the Early Cambrian Khewra Sandstone based on integrated approach of surface and subsurface (core cuttings) data from the Eastern and Central Salt Range, Upper Indus basin, Pakistan. The data set used during this research work is from two outcrop sections (Khewra Gorge & Nilawahan Nala) and two wells (Amirpur-01 & Daiwal-01). The methodology followed for the desired study is comprised of petrographic interpretations as well as core plugs tests. Petrographically the sandstone is classified into various compositional nature based on framework constituents (quartz, feldspar and lithics) among which the major portion from the outcrop samples are divided as sub-arkosic arenites with few samples into arkosic arenites, while the intervals from both the wells are classified to be sub-arkosic arenites entirely. The provenance origin for the Khewra Sandstone interpreted by petrographic observations is craton interior with few outcrop samples from transitional continental region. The estimated visual porosity from Khewra Gorge Section is in range 1 to 18.5 % with the average value of (8.02 %), from Nilawahan Nala Section the range is 0.5 to 17.2% with the average value of 6.51% and the reservoir properties (porosity and permeability) calculated by core plugs method for the Amirpur- 01 well is in range 10.27 to 13.37% (average 12.44%) and 0.58 to 217.57 mili Darcy (average 85.4 mD) while from Daiwal-01 well is 14.64 to 18.14 % (average 16.41 %) and 15.50 to 58.33 mili Darcy (average 42.59 mD). The increasing trend observed for porosity across the sections from lower beds to upper portion indicates the coarsening upward sequence, comparatively good sorting pattern of grains, decrease in matrix contents and also the negligence of overburden pressure. From these detail analysis this formation can be encountered as good reservoir for petroleum exploration especially the upper horizons at outcrop exposure while at the subsurface, the Daiwal-01 well due to its high porosity values (16.41 %) can be focused for future discoveries. The findings of this study can be used as reference material academically as well as helpful in developmental phase of these wells in future.