Method of increasing oil recovery

Claim 1

IN THE METHOD OF SELECTIVELY ADJUSTING THE PERMEABILITY OF OIL PRODUCING FORMATIONS BY THE INTRODUCTION OF PRECIPITATE-FORMING REACTANTS INTO THE FORMATION IN THE VICINITY OF UNDESIRABLE FLUID FLOW, THE IMPROVEMENT WHEREIN THE DESIRED QUANTITY OF REACTANTS MAY BE EMPLOYED AT PRESSURES APPROACHING THE LIMITING INJECTION PRESSURE UNDER EXISTING FIELD CONDITIONS COMPRISING INTRODUCING THE TREATING SOLUTIONS INTO THE FORMATION IN CYCLES, EACH CYCLE CONSISTING OF A PORTION OF SAID TREATING REACTANTS SEPARATED BY AN INERT SPACING MEDIUM, THE RELATIVE AMOUNT OF SPACING MEDIUM EMPLOYED BEING DECREASED DURING THE TREATMENT OPERATION SO THAT THE REACTANTS WILL CONTACT EACH OTHER IN CONCENTRIC REGIONS OF THE FORMATION INCREASINGLY APPROACHING THE INJECTION WELL, WHEREBY THE PRECIPITATES ARE DEPOSITED IN A HEAVY CONCENTRATION OF THE MORE PERMEABLE CHANNELS OF A RELATIVELY LARGE AREA OF THE STRATA SURROUNDING THE INJECTION WELL CAUSING THE SURFACE INJECTION PRESSURE TO APPROACH ITS LIMITING VALUE RENDERING THE INJECTION OF THE DESIRED QUANTITY OF REACTANTS INTO THE FORMATION.