Unconventional Shale Gas Resources in Cambay Basin, India

The rising oil prices, high input cost in exploration and production of hard oil resources and relative abundance of gas resources have fuelled the interest towards gas resources. But the consumption of natural gas is increasing rapidly and the large gap between natural gas consumption and supply has spurred interest in development of unconventional gas resources. India has the immense prospects of unconventional shale gas resources. Commercial exploration of these shale gas resources can effectively make the global natural gas curve more elastic. The commercial shale gas exploration requires exhaustive investigation of all the shale rock properties of hydrocarbon bearing shale beds having significant organic matter and maturity. This paper presents the geochemical studies of Cambay shale to evaluate its shale gas prospects. It also attempts to discuss the systematic approach using integrated methodology of geological, geophysical, geochemical, geomechanical etc for shale gas resource evaluation to analyse the sedimentology of shale rock, gas generation and retention mechanism within the shale rock.

A total of 22 cutting samples of Cambay shale formation from two wells are selected for Rock- Eval Pyrolysis. Most of the studied samples show fair hydrocarbon generation potential as shown from the results of measured total organic carbon (TOC) content, hydrogen index (HI), S1, S2 and Tmax. The TOC average value is 3.3% and comprises of both oil and gas prone organic matter. A numerical calculation approach is adopted to calculate the thermal maturity. The highest TOC and maturity stage of gas window coincides with the depocentres of the basin.