Method of recovering oil by in-situ produced carbon dioxide

Claim 1

IN A METHOD OF RECOVERING OIL FROM A RESERVOIR THE STEPS WHICH COMPRISE: INTRODUCING AIR INTO SAID RESERVOIR THROUGH AN INJECTION WELL AND FORCING SAID AIR THROUGH SAID RESERVOIR TO A PRODUCTION WELL TO ESTABLISH GAS PERMEABLILITY WITHIN SAID RESERVOIR; HEATING SAID AROUND SAID INJECTION WELL TO A TEMPERATURE SUFFICIENT TO INITIATE COMBUSTION OF THE NATIVE RESERVOIR MATERIALS WHILE SIMULTANEOUSLY CONTINUING THE INTRODUCTION OF AIR INTO SAID RESERVOIR, SAID COMBUSTION BEING CONTINUED THROUGH APPROXIMATELY 10 PERCENT OF THE DISTANCE FROM SAID INJECTION WELL TOWARD A PRODUCTION WELL; TERMINATING THE FLOW OF AIR INTO SAID RESERVOIR; REDUCING THE PRESSURE WITHIN SAID INJECTION WELL TO A VALUE BELOW THE PRESSURE WITHIN SAID RESERVOIR TO EFFECT BACKFLOW OF FLUIDS FROM THE UNHEATED PORTION OF SAID RESERVOIR INTO THE HEATED PORTION OF SAID RESERVOIR TOWARD SAID INJECTION WELL; CONTINUING SAID BACKFLOW UNTIL TRACE AMOUNTS OF HYDROCARBONS LESS VISCOUS THAN SAID OIL APPEAR IN SAID INJECTION WELL; INTRODUCING INTO SAID RESERVOIR THROUGH SAID INJECTION WELL AN OXIDIZING FLUID COMPRISING AT LEAST 66 PERCENT BY VOLUME PURE OXYGEN; REINITIATING COMBUSTION WITHIN SAID RESERVOIR IN THE PRESENCE OF SAID OXIDIZING FLUID; CONTINUING SAID REINITIATED COMBUSTION TO DEVELOP AN OIL-MISCIBLE GASEOUS PHASE EQUAL IN QUANTITY TO FROM ABOUT 2 PERCENT TO ABOUT 20 PERCENT OF THE HYDROCARBON PORE VOLUME OF SAID RESERVOIR; TERMINATING THE INTRODUCTION OF SAID OXIDIZING FLUID AND SAID COMBUSTION; INTRODUCING A DRIVING FLUID INTO SAID RESERVOIR THROUGH SAID INJECTION WELL TO FORCE FORCE SAID GASEOUS PHASE THROUGH SAID RESERVOIR TO DISPLACE SAID OIL; AND PRODUCING SAID OIL FROM SAID RESERVOIR THROUGH SAID PRODUCTION WELL.