Recovery of hydrocarbons from subsurface reservoirs

Claim 1

IN THE RECOVERY OF OIL SUBSURFACES OIL BEARING FORMATIONS BY FORCING GAS THROUGH THE FORMATION FROM AN INJECTION WELL TOWARD A PRODUCING WELL UNDER A HIGH PRESSURE EFFECTIVE TO CAUSE ENHANCED YIELDS AT THE PRODUCING WELL OF FLUID CONTAINING SAID OIL, THE IMPROVEMENT WHEREIN SAID HIGH PRESSURE GAS INJECTED INTO SAID FORMATION FROM THE INJECTION WELL BORE IS A RETROGRADE-ENRICHED GAS COMPRISING A NORMALLY GASEOUS HYDROCARBON CONTAINING IN SINGLE PHASE ADMIXTURE THEREWITH A SUBSTANTIAL PROPORTION OF A NORMALLY LIQUID SOLVENT HAVING A HIGH SOLVENT CAPACITY FOR HEAVY ASPHALTENE-BITUMEN CONSTITUENTS OF THE FORMATION OIL WHICH TEND TO BE PRECIPITATED BY NORMALLY GASEOUS HYDROCARBONS DISSOLVED BY THE FORMATION OIL AND SUBJECT TO RETROGRADE CONDENSATION UPON ISOTHERMAL PRESSURE DECREASE, THEREBY INHIBITING THE PRECIPITATION OF HEAVY HYDROCARBONS IN SAID SUBSURFACE FORMATION, AND WITHDRAWING THE RESULTING FLOW OF HYDROCARBONS FROM SAID PRODUCTION WELL.