Fracture initiation by dissolving a soluble formation

Claim 1

The method of initiating a fracture in a disintegrable subterranean stratum which comprises: a. establishing a well bore from the surface of the earth to a depth within said stratum below that of the desired fracture; b. providing two fluid passageways within said bore from the surface of the earth to within said stratum, the first of said passageways terminating at its lower end at about the level of said desired fracture and the second terminating at its lower end a predetermined distance below that of said first; c. selecting a first fluid effective to disintegrate said stratum and a second fluid of lower specific gravity than and substantially immiscible with said first fluid and substantially inert to said stratum; d. passing said first fluid down said first passageway to effect disintegration of said stratum in the region adjacent said lower ends of said first and second passageways and recovering by way of said second passageway first fluid plus disintegrated stratum, while simultaneously maintaining an upper protective blanket layer of said second fluid in said region by injecting said second fluid through a third passageway from the surface of the earth to said region in amount sufficient to maintain the lower surface of said second fluid at a relatively constant level; e. terminating said passing upon the formation in said stratum of an approximately conical cavern of desired dimension having its base at about the level of said desired fracture and its apex therebelow; and f. subsequently subjecting the thus formed cavern to hydraulic pressure to initiate fracture of said stratum at about said base of said conical cavern.

Claim 2

The method of initiating a fracture in a disintegrable subterranean stratum which comprises: a. establishing a well bore from the surface of the earth to a depth within said stratum below that of the desired fracture; b. providing two fluid passageways within said bore from the surface of the earth to within said stratum, the first of said passageways terminating at its lower end at about the level of said desired fracture and the second terminating at its lower end a predetermined distance below that of said first; c. selecting a first fluid effective to disintegrate said stratum and a second fluid of lower specific gravity than and substantially immiscible with said first fluid and substantially inert to said stratum; d. passing said first fluid down said first passageway to effect disintegration of said stratum in the region adjacent said lower ends of said first and second passageways and recovering by way of said second passageway first fluid plus disintegrated stratum, while simultaneously maintaining an upper protective blanket layer of said second fluid in said region by injecting said second fluid through a third passageway from the surface of the earth to said region in amount sufficient to maintain the lower surface of said second fluid at a relatively constant level; e. terminating said passing upon the formation in said stratum of an approximately conical cavern of desired dimension having its base at about the level of said desired fracture and its apex therebelow; and f. subsequently subjecting the thus formed cavern to hydraulic pressure to initiate fracture of said stratum at about said base of said conical cavern.