초록 ▼

Subterranean oil and gas producing formations are fractured in a first embodiment by providing one or more combustion gas generating units using rocket fuel type propellants disposed in a well casing at preselected depths. The well casing is filled with a compressible hydraulic fracturing fluid comp

Subterranean oil and gas producing formations are fractured in a first embodiment by providing one or more combustion gas generating units using rocket fuel type propellants disposed in a well casing at preselected depths. The well casing is filled with a compressible hydraulic fracturing fluid comprising a mixture of liquid, compressed gas, and propant material and precompressed to a pressure of about 1,000 psi or more greater than the fracture extension pressure at the depth of the zone to be fractured. At least one of the gas generating units is equipped with perforating shaped charges to form fluid exit perforations at the selected depth of the fracture zone. The gas generating units are simultaneously ignited to generate combustion gasses and perforate the well casing. The perforated zone is fractured by the rapid outflow of an initial charge of sand free combustion gas at the compression pressure followed by a charge of fracturing fluid laden with propant material and then a second charge of combustion gas. The column of precompressed fracturing fluid is discharged into the formation until the hydraulic extension pressure is reached and eventually the perforations sanded off. In a first alternative of a second embodiment fracturing is effected by the forces of decompression without use of a combustion gas generating unit. In a second alternative of the second embodiment the fracturing fluid comprises a pure sand free liquid.

대표청구항 ▼

A method for fracturing a subterranean earth formation to stimulate the production of fluid from said formation wherein a wellbore extends at least to said formation from a surface point, said wellbore being provided with casing means forming a substantially fluid-tight interior space, said method c

A method for fracturing a subterranean earth formation to stimulate the production of fluid from said formation wherein a wellbore extends at least to said formation from a surface point, said wellbore being provided with casing means forming a substantially fluid-tight interior space, said method comprising the steps of: providing said wellbore interior space with a fracture fluid comprised of a substantially pure liquid, the fracture liquid extending to a predetermined controlled column height within the wellbore; superposing on the column height of fracture liquid a second controlled column height of a foam pad; and releasing through apertures in the wellbore casing into an adjacent formation to be fractured, the fracture liquid previously pressurized to a pressure value exceeding the fracture value of the formation to effect fracture of the formation by forces of decompression imposed by released fracture fluids.