Evaluation of shale gas reservoir in Barakar and barren measures formations of north and south Karanpura Coalfields, Jharkhand

摘要

India recognizes the strategic importance for developing shale gas resources like other countries in the world. Shale gas reservoirs are known to be difficult for extracting gas in comparison to conventional reservoirs. Recently, due to high prices of gas, rising demand and enhancement in recovery technologies has attracted the Indian energy industries to explore the shale gas resource. Coal and lignite are the prime source of energy in India and these resources are well explored, while shale is ignored, despite it being associated with coal and lignite bearing formations. The paper presents reservoir characteristics of shale horizons in Barren Measures and Barakar formations of north and south Karanpura coalfields. Shale core samples were collected from exploratory boreholes in air tight canisters. In-situ gas content and adsorption capacities ascertained to be 0.51-1.69 m(3)/t and 3.90-5.82 m(3)/trespectively. Desorbed gas derived from canisters contains CH4, C2H6, C3H8, CO2, N-2 and O-2 and varies from 76.19-82.63, 0.38-0.76, 0.10-0.50, 8.65-12.34, 9.89-19.34 and 0.56-2.24 vol. % respectively. The permeability and porosity determined under reservoir simulated confining pressure is varying from 0.41-0.75 mD and 0.89-2.28 % respectively. The plots of Rock Eval S(2)vs TOC and HI against Calc. VRo% indicates that all shale samples belong to Type III kerogen, which is prone to generate gas. It is evaluated that insitu gas content, sorption capacity, saturation level and low permeability of shale beds are critical parameters for development of shale gas resource in the studied area.