Recovery of hydrocarbon from oil shale adjoining a permeable oilbearing stratum

Claim 1

A PROCESS FOR RECOVERING FLUID HYDROCARBONS FROM AN OIL-BEARING IMPERMEABLE SHALE AND FROM AN ADJOINING PERMEABLE OIL-BEARING STRATUM WHICH COMPRISES FACTURING SAID SHALE HORIZAONTALLY N AT LEAST ONE LEVEL THEREIN SO THAT THE RESULTING FRACTURES CONNECT WITH A PRODUCTION BOREHOLE THEREIN; INITIATING COMBUSTION IN SAID STRATUM AROUND AN IGNITION BOREHOLE THEREIN AND DRIVING THE RESULTING COMBUSTION FROMT THRU SAID STRATUM TO AN INJECTION BOREHOLE THEREIN BY INVERSE AIR INJECTION THRU SAID INJECTION BOREHOLE WHEREBY HEAT OF COMBUSTION IS PASSED DIRECTLY INTO THE ADJOINING SHALE AND DEROGEN THEREIN IS FLUIDIZED AND DRIVEN THEREFROM INTO SAID PRODUCTION BOREHOLE, RENDERING SAID SHALE PERMEABLE FROM SAID STRATUM TO SAID FRACTURES; AS SAID COMBUSTION FRONT REACHES SAID INJECTION BOREHOLE, CONTINUING THE INJECTION OF AIR THRU SAID INJECTION BOREHOLE SO AS TO DRIVE SIAD FRONT BACK THRU SAID STRATUM, FEEDING ON THE CARBON RESIDUE LEFT BY THE FIRST BURN THRU SO AS TO FURTHER HEAT SAID SHALE AND CAUSE HOT GASES TO PASS THRU THE PERMEABLE SHALE INTO SAID FRACTURES, THEREBY PRODUCING ADDITIONAL HYDROCARBONS THEREFROM; AND RECOVERING THE PRODUCED HYDROCARBONS FROM SAID SHALE AND SAID STRATUM.