Secondary recovery of oil from reservoirs by successive precipitation

Claim 1

AN OIL RECOVERY PROCESS FOR PRODUCING RESIDUAL OIL FROM A PARTIALLY DEPLETED PETROLEUM OIL-BEARING, GEOLOGICAL STRATUM TRAVERSED BY AN INJECTION WELL AND A PRODUCING WELL WHICH COMPRISES INTRODUCING INTO SAID STRATUM A FIRST SOLUTION HEATED AT AN ELEVATED TEMPERATURE ABOUT 50-100* F. ABOVE NORMAL STRATUM TEMPERATURE, SAID SOLUTION CONTAINING OIL-INSOLUBLE SALT SOLUTE WHICH IS SUBSTANTIALLY INSOLUBLE IN SAID SOLUTION T NORMAL FORMATION TEMPERATURE, THE AMOUNT OF SAID SOLLUTON INTRODUCED BEING SUFFICIENT UPON COOLING BY CONTACT WITH THE STRATUM AT NORMAL STRATUM TEMPERATURE TOPRECIPITATE SAID SALT IN AN AMOUNT TO UNIFORMLY REDUCED THE PORE VOLUME OF SAID ZONE WITHIN THE RANGE OF 5% TO 20% WHEREBY THERE IS DISPLACED A PORTION OF SAID RESIDUAL OIL FROM WITHIN SAID ZONE WITHOUT SUBSTANTIALLY INCREASING THE RESISTANCE OF SAID STRATUM TO THE FLOW OF FLUIDS THERETHROUGH, THEREAFTER INTRODUCING INTO SAID STRATUM A MORE DILUTE SOLUTION OF THE SAME SALT HEATED TO AN ELEVATED TEMPERATURE SUBSTANTIALLY ABOVE NORMAL STRATUM TEMPERATURE IN WHICH SOLUTION SAID SALT IS SUBSTANTIALLY INSOLUBLE AT NORMAL STRATUM TEMPERATURE, SAID MORE DILURTE SOLUTION BEING CHARACTERIZED BY THE ABILITY TO REDISSOLVED THE PRECIPITATE FORMED BY SAID SALT AND TO AGAIN PRECIPITATE IT AT FORMATION TEMPERATURE, CONTINUING THE INTRODUCTION OF SAID MORE DILUTE SOLUTION UNTIL INCREASED PRODUCTION OF OIL THROUGH SAID PRODUCING WELL IS EFFECTED.