ANALYSIS OF HYDROCARBON RESOURCE POTENTIAL OF CHICHALI AND SAMANA SUK FORMATIONS, KOHAT SUB-BASIN, PAKISTAN

Abstract

The present study is focused on the analysis of hydrocarbon resource potential of Chichali Shale and Samana Suk Limestone in Kohat Sub-basin, Pakistan based on openhole wireline log qualitative and quantitative analysis in well of Makori-01, Manzalai-02 and Maramzai-02. The analysis reveals Chichali Formation comprises two main Shale units with the non-Shale unit in between. The first zone of Shale demonstrates good outcomes regarding unconventional reservoir properties with TOC of 1.3 to 1.91% and Shale porosity of 5.1% to 9.6%. While the second zone shows TOC of 0.52 to 0.73% and Shale porosity of 6.4% to 8.71%. The mineralogical assessment shows Chichali Formation mainly bears Mixed layer clays, Illite, Glauconite and Mica bearing Shale. Mechanical properties assessment through compressional and Shear Sonic log favours Chichali Formation as good brittleness possessing Shale making it an optimistic target for hydraulic fracturing. The Samana Suk Limestone shows good hydrocarbon Saturation with poor porosity and permeability. The Porosity ranges from 1.54% to 3.58% with average permeability of less than 1 mD. The permeability categorises the Samana Suk Formation as a tight reservoir. The analysis shows Samana Suk Limestone bears 23.02% of Sw in Manzalai-02, 27.6% in Makori-01 and 44.06% in Maramzai-02 well. Mapping reveals the source rock potential of the Chichali Formation in terms of organic richness increases from E to W in zone-1, and from SE to NW in zone-2. While Shale porosity increase from NE to SW. Moreover, Samana Suk Limestone illustrates enhancement in reservoir attributes like Sw, PHIA and PHIE while traversing from NE to SW and degradation in hydrocarbon saturation from NE to SW.