Parbatpur Mine Degassing - A Model for Commercial CMM Project in India
Roy, Mohan D.; Choudhury, Bailochan
E&P, Dart Energy, Gurgaon, India.
Commercial exploitation of Coal Mine Methane (CMM) from deeper seams within active coal mines or pre-mining drainage from the mine leasehold is still in infancy in India. The Eastern Indian coal basins of Raniganj, Jharia, Bokaro, Karanpura and Assam have history of "Firedamp" explosions, coal mine fires; that have resulted loss of human lives and closure on many mines. Continuing with the challenges of mining deeper and more gassy coals in Jharia and Raniganj Coalfields in one hand with the societal commitment of green environment on the other, CMM development may usher an era of low methane emitting coal mines.
The 8.8 sq km Parbatpur Mine leasehold is located in the south central part of Jharia coalfield and hosts 18(I to XVIII) major Barakar seams. The pack of Seams XVIII, XVII, XVIA, XVIB, XVA and XVB among these occurring up to 650m depth and with 20-25m net coal are to be mined over the next 30 years; are targets for CMM development. These seams are low to medium volatile (14.9-26.5 VM%), bituminous coal with 29 to 62% of vitrinite content (vmf) with good thermal maturity(RoM1.0-1.45%). With 3-11m3/ton gas content(daf), 60-90% saturation this pack has good potential for multiseam completion for CMM drainage. The GIP estimates of this pack are about 0.29TCF. With low to medium permeability in these coals suitable completion methods will be employed for the quicker drainage of seam gas. The structural complexity and presence of close spaced sub vertical faults the reservoir has been compartmentalized into smaller areas. Vertical well is the only option to degas in this geologic set up. The degassing has to be planned keeping parity with the mine development timeline. Shallower better permeable seams shall be degassed within a period of 4-6yrs through vertical,16" under reammed wells. Larger sized production casing will be used such that post mining(after about 5-6 yrs) the well would be drilled further down up to the deeper seams (XV). Because of lower permeability these wells would be completed by casing/cementing and stimulated by hydrofracking. In the adjoining areas the CBM produced water was found to be potable. Produced water from CMM wells can be used in the pit head washery for the mine as well as for local irrigation ensuring minimum water handling cost.
To make the project commercially successful the gas will be marketed locally as CNG to maximize the revenue.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012