Characterization of Datta Formation as Shale Gas Reservoir

The discovery and extension of alternative plays, have been accelerated worldwide due to mounting cost of hydrocarbons. Shale gas is not only copious in Pakistan but also inexpensive. Shale gas plays a key role to overcome the energy crisis existing within the country.No exploration have been made in shale gas reservoirs untila now in Pakistan. To find out the potential of the shale gas in Kohat-Potwar basin, this research work is completed. In this study, the wireline logs and well cuttings, data is utilized to calculate total organic carbon (TOC), thermal maturity, kerogen type, mineralogy, brittleness index (BI) and elastic properties. TOC was measured from well cuttings by Loss on ignition method as well as from wire line logs by using Passey‘s method. Kereogen type, maturity and genetic potential were also evaluated in lab by Rock Eval Pyrolysis. Vitrinite Reflectance of Datta Formation in each well, calculated by the help of burial history curve using PetroMod. BI calculated using formulations proposed by Jarvie and Wang based on brittle and ductile content. The shale gas prospect of Datta formation of Kohat-Potwar Basin is determined on the basis of geochemical studies and on formational evaluation data. Gross thickness of Datta formation ranges from 40-300 meters in the Potwar-Kohat Basin and the formation is almost 80 meters thick in study area and is almost 4.5 Km deep. Geochemical Analysis indicates that TOC of the formation ranges from 0.3 to 2 % by weight with 58-158 mg HC/g Rock Hydrogen Index (Kerogen type III). T max (436 oC) Ro (0.5-1.4%) suggest that kerogen in the Datta Formation is well mature”. In Shale Interval of Datta Formation, clay minerals content is ranging from 35% to 50%, while Brittle mineral content is ranging from 40% to 50% including Quartz. High Brittleness Index, ranging from 0.48 to 0.65, lower values of Poison Raito and higher values of Young’s Modulus shows that Shale of Datta formation lies in brittle region. Hence suitable for hydraulic fracturing for the development of Shale Gas Reservoir in Datta Formation which may have good Shale Gas prospects.