Reverse-flow solvent flooding method

Claim 1

IN THE RECOVERY OF OIL FROM AN OIL-CONTAINING UNDERGROUND RESERVOIR BY THE JUNCTION OF AQUEOUS LIQUID INTO SAID RESERVOIR THROUGH AN INPUT WELL AND THE CONCOMITANT RECOVERY OF OIL FROM SAID RESERVOIR THROUGH AN OUTPUT WELL, THE RATIO OF WATER-TO-OIL PRODUCED AT SAID OUTPUT WELL HAVING REACHED A VALUE IN EXCESS OF 2 TO 1, THE IMPROVEMENT COMPRISING TERMINATING THE INJECTION OF SAID AQUEOUS LIQUID THROUGH SAID INPUT WELL, INJECTING INTO SAID RESERVOIR THROUGH AN INJECTION WELL A SLUG OF FLUID SOLUBLE IN SAID OIL BUT SUBSTANTIALLY INSOLUBLE IN THE AQUEOUS LIQUIDS IN SAID RESERVOIR, SAID FLUID BEING ADDITIONALLY CHARACTERIZED AS HAVING A VISCOSITY SUBSTANTIALLY LESS THAN THAT OF THE OIL IN SAID RESERVOIR, THEREAFTER INJECTING AQUEOUS FLUID THROUGH SAID INJECTION WELL AND INTO SAID RESERVOIR TO DRIVE SAID SLUG OF FLUID TOWARD A PRODUCING WELL, THE PATH OF FLUID TRAVEL THROUGH SAID RESERVOIR FROM SAID INJECTION WELL TO SAID PRODUCING WELL BEING SUBSTANTIALLY THE SAME AS THE PATH OF FLUID TRAVEL FROM SAID INPUT WELL TO SAID OUTPUT WELL, THE DIRECTION OF FLOW FROM SAID INJECTION WELL TO SAID PRODUCING WELL BEING SUBSTANTIALLY OPPOSITE TO THE DIRECTION OF FLOW FROM SAID INPUT WELL TO SAID OUTPUT WELL, AND PRODUCING OIL FROM SAID PRODUCING WELL.