Thermal process for in-situ decomposition of oil shale

Claim 1

A PROCESS FOR THE RECOVERY OF SHALE OIL FROM A SUBOSURFACE OIL SHALE FORMATION BY IN-SITU DECOMPOSITION WHICH COMPRISES DRILLING AN INPUT WELL TO PROVIDE ACCESS TO THE OIL SHALE FORMATION, INTRODUCING A FLUID PRESSURING MEDIUM INTO THE FORMATION AT AN ELEVATED PRESSURE SUFFICIENT TO CAUSE PARTING AND CRACKING OF THE FORMATION, ESTABLISHING A HOT ZONE WITHIN THE FORMATION BY BURNING FUEL GAS AT THE BOTTOM OF THE INPUT WELL FOR A PERIOD OF TIME SUFFICIENT TO HEAT THE SURROUNDING FORMATION TO AN ELEVATED TEMPERATURE PROMOTING SPONTANEOUS COMBUSTION WITHIN THE FORMATION; DISCONTINUING BURNING AT THE BOTTOM OF THE WELL, INTRODUCING AN UNHEATED SUBSTANTIALLY NON-COMBUSTIBLE OXYGEN-CONTAINING GAS INTO SAID INPUT WELL AND PASSING SAID GAS THROUGH SAID HOT ZONE TO ABSORB HEAT AND TO TRANSFER ABSORBED HEAT TO COOLER REGIONS OF THE SHALE FORMATION BEYOND SAID HOT ZONE, THEREBY MOVIGN SAID HOT ZONE GRADUALLY OUTWARD INTO THE FORMATION; INTRODUCING INTO SAID HOT ZONE A COOL OXYGEN-CONTAINING COMBUSTION-SUPPORTING GAS TO PROMOTE FORWARD MOVEMENT OF SAID HOT ZONE AS A THERMAL WAVE OF RELATIVELY NARROW PROFILE AND HIGH PEAK TEMPRATURE PROMOTING COMBUSTION IN A LIMITED REGION OF THE FORMATION, WHEREBY OIL IS DISTILLED IN THE FORMATION IN FROM OF THE ADVANCING HOT ZONE, AND RECOVERING OIL FROM AN OUTPUT ZONE.