Patent ID: 7516784

Claim:
A method for enhancing in-situ coal gasification of subterranean coal by providing a network of fractures in a subterranean formation containing seams of coal, the method comprising the steps of: providing a substantially vertically disposed borehole; providing a plurality of substantially horizontally disposed boreholes in fluid communication with the substantially vertically disposed borehole, wherein at least one substantially horizontally disposed borehole is a fracturing borehole, at least one substantially horizontally disposed borehole is an injection borehole and at least one substantially horizontally disposed borehole is a production borehole; selectively preventing fluid communication between the substantially vertically disposed borehole and the at least one substantially horizontally disposed injection borehole and the at least one substantially horizontally disposed production borehole; introducing an initial quantity of liquified gas into the at least one substantially horizontally disposed fracturing borehole such that the liquified gas communicates with the subterranean formation; permitting the quantity of liquified gas to vaporize in a portion of the at least one substantially horizontally disposed fracturing borehole whereby a resulting increase in pressure in the at least one substantially horizontally disposed fracturing borehole forms fractures in the subterranean formation; introducing an additional quantity of liquified gas into the at least one substantially horizontally disposed fracturing borehole; permitting the additional quantity of liquified gas to vaporize in the at least one substantially horizontally disposed fracturing borehole whereby a resulting increase in pressure in the at least one substantially horizontally disposed fracturing borehole forms additional fractures in the subterranean formation.