Abstract:
The objectives of the study were to evaluate reservoir properties of Datta Formation using well log data and lab testing of outcrop samples.
The study area (Chand deep-01) is located at Latitude of 33° 13՛ 55.3՛՛ N and Longitude of 71° 30՛ 9.41՛՛ E in Shakardara area in District Kohat of the Khyber Pukhtonkhawa province. It is about 70 Km from Kohat city and is present in Kohat sub-basin of Upper Indus basin.
The methodology adopted for the research work is two folds: Petrophysical analysis to evaluate reservoir properties and outcrop analysis to analyze porosity and permeability of the samples. Petrophysical analysis includes raw log curves, calculation of volume of shale, neutron, density and sonic porosity, resistivity of water and finally, water and hydrocarbon saturation. Outcrop analysis, on the other hand, includes sample collection, sample preservation, sample cleaning drying and porosity and permeability measurement in lab. The outcomes of the two analyses were correlated to evaluate the quantitative differences between surface and subsurface conditions of the Jurassic age sandstone i.e. Datta Formation.
Petrophysical results claim that there are two pay zones present in Datta Formation in Chanda deep-01. Zone 1 ranges from 4750.5m to 4757m and zone 2 ranges from 4785.5 to 4794.5m. In zone 1 volume of shale is 26.09%, Effective porosity is 3.51%, water saturation is 38.78%, hydrocarbon saturation is 61.21% and permeability is 0.0024md. However in zone 2, Volume of shale is 8.53%, effective porosity is 5.59%, water saturation is 42%, hydrocarbon saturation 57.99% and permeability is 13.96md.
Laboratory results show that average porosity calculated for the outcrop samples is 17.3% and average permeability turned out to be 500.32md. The difference in surface and subsurface results is due to different factors affecting porosity and permeability as we go down the surface i.e. variation in textural properties,
