Abstract

Unconventional shale-gas plays are formed by fine-grained organic-rich shales of tight-porosity and ultralow permeability which act as the source, seal, and the reservoir rock. The shale-as-reservoir has its beginnings in 1820 but commercial shale-gas wells were drilled in 1990s in Mississippian Barnett Shale of USA by Mitchell Energy after prolonged (about 17 years) experimentations and advancements in drilling and stimulation. In North America, shale-gas plays (e.g., Barnett Shale, Eagle Ford Shale, Haynesville Shale, Marcellus Shale etc.) are producing commercially and these are becoming global, now. In India, too, gas from Barren Measure Shale of Damodar Basin has been struck in January 2011