Hydrothermally forming a flow barrier in a leached subterranean oil shale formation

Claim 1

A process for producing shale oil from a subterranean oil shale which comprises: opening at least one pair of wells into fluid communication with a subterranean oil shale formation which has a composition at least substantially equivalent to that of the oil shale formations encountered in the Piceance Creek Basin of Colorado and which contains a network of relatively permeable interconnected flow channels formed by a natural fracturing or leaching of the oil shale formation; operating the wells so that fluid flows between at least one pair of wells along a selected path within the oil shale formation; adjusting the composition, pressure and temperature of the so-flowed fluid so that oil shale formation components within the selected path are contacted by a relatively hot aqueous alkaline liquid which hydrothermally converts them to particles of clay-like material that are distributed along the flow path; adjusting the composition, pressure and temperature of the so-flowed fluid so that the particles of clay-like materials distributed along the flow path are contacted by an aqueous liquid which is relatively free of electrolytes and is capable of swelling the clay-like particles so that the permeability of the earth formations within the flow path is reduced; and producing shale oil by injecting fluid capable of pyrolyzing oil shale into a portion of the oil shale formation which is bounded by a flow-confining barrier formed by at least one so-plugged selected path of fluid flow and producing shale oil-containing fluid from that portion of the oil shale formation.