Steam drive for incompetent tar sands

Claim 1

A PROCESS FOR PRODUCING PETROLEUM FROM A VISCOUS PETROLEUM RESERVOIR THAT IS SUBSTANTIALLY IMPERMEABLE AT RESERVOIR TEMPERATURE, IS SUBSTANTIALLY INCOMPETENT AT A TEMPERATURE THAT THERMALLY MOBILIZES THE RESERVOIR PETROLEUM AND IS PENETRATED BY AT LEAST ONE PAIR OF WELLS THAT ARE INTERCONNECTED BY A HORIZONTAL FRACTURE EXTENDING THROUGH THE RESERVOIR, WHICH PROCESS COMPRIESE: (A) HEATING AQUEOUS LIQUID AT A SURFACE LOCATION AND CIRCULATING THE HEATED LIQUID THROUGH THE FRACTURE BETWEEN SAID PAIR OF WELLS WHILE MAINTAINING A BACK PRESSURE THAT AT LEAST SUBSTANTIALLY EQUALS THE OVERBURDEN PRESSURE AND AN INJECTION PRESSURE THAT CAUSES FLOW AT A RATE ADEQUATE FOR TRANSFERRING HEAT FROM THE SURFACE LOCATION TO THE OPENINGS INTO THE PRODUCTION WELL; (B) INCREASING THE TEMPERATURE OF THE CIRCULATING HEATED AQUEOUS LIQUID UNTIL FLUID FLOWING INTO THE PRODUCTION WELL HAS A TEMPERATURE THAT THERMALLY MOBILIZERS THE RESERVOIR PETROLEUM WHILE INCREASING THE SOFTNESS OF THE AQUEOUS LIQUID TO THE INCREASING T EXTENT REQUIRED TO PROVIDE A LIQUID THAT IS NONSCALLING AT THE TEMPERATURE TO WHICH THE LIQUID IS BEING HEATED; (C) FORMING A PERMEABLE PATH WITHIN THE RESERVOIR BY ENTRAINING THE TERMALLY MOBILIZED RESERVOIR PETROLEUM IN THE CIRCULATING HEATED AQUEOUS LIQUID AND THUS CONVERTING A PORTION OF THE RESERVOIR TO A LAYER OF PETROLEUM-DEPLETED PERMEABLE SAND; (D) REDUCING THE PRESSURE WITHIN THE RESERVOIR TO LESS THAN OVERBURDEN PRESSURE AND CIRCULATING STEAM THROUGH THE RESERVOIR AT A TEMPERATURE AT WHICH SWAID RESERVOIR PETROLEUM IS MOBILIZED AND ENTRAINED; (E) RECOVERING SAID PETROLEUM FROM FLUID THAT HAS CIRCULATED THROUGH THE RESERVOIR.