The Impact of Coal Characteristics on CBM Prospectivity of Barakar Coals of Damodar Valley Coalfields

Rudra, Malay ¹
(1)CBM Block, ONGC, Bokaro, India.

Barakar Formation Coal of Damodar valley Gondwana Permian coalfields deposited in fluvaic/deltaic condition have rank from sub-bit to low volatile bituminous are considered as storehouse of CBM. Coal from western part of the valley has shown some brackish/marine signature. The coal resource are distributed vertically in a multiseam environment rather than spatially as found in US basin. Authors,due to long association in CBM exploration had the opportunity to study and interpret huge quantity of laboratory and other data generated in acreages of five prominent Eastern India Gondwana coal fields. The Study used systematic CBM specific primary data generated from more than 67 coreholes and 35 test wells using more than 1000 coalsamples and secondary data from published sources available from coal mining industry. The study made an effort to establish coal characteristics in terms of maceral composition,maturity, quality in terms of mineral matter component of Barakar coals. Study made an effort to establish CBM potential in terms of gas content vis-à-vis maturity & maceral composition. Effort was made to decipher impact of maceral composition & maturity on gas composition both molecular and isotopic. The study shows that Barakar formation coal of Jharia,Bokaro and Raniganj coalfields has maturity in the range of 0.8 to 1.68 VRo and in the stage of significant methane generation. Maturity range in South Karanpura is 0.7 to 1.0 VRo and in North Karanpura 0.4 to 0.9 VRo. Coals are mainly Vitrinitic Inertinitic type, liptinic content increase from east to west,showing maximum in North Karanpura. For Jharia and Raniganj, molecular gas composition of desorbed gas is dry to very dry with methane mostly constitutes more than 95%. In Bokaro the gas composition often shows significant amount of Carbon Dioxide and further study is required to establish its genesis. Due to more liptinic component of coal desorbed gas from North Karanpura is less dry and have good amount of ethane plus component. Isotopic composition in all the cases follow maturity trend except in Raniganj coalfield which is erratic due to extensive localized intrusive heat effects. Adsorptive capacity of coal are maturity dominated & Inertinitic coal seem to show good adsorptive capacity at higher maturity. It can be assumed that from CBM potential perspective Jharia & Bokaro can be put in best category followed by North Karanpura & Raniganj.Keyword: Gondwana, Barakar

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.