APPLICATION OF TIME-DELAYED GELS FOR FLUID CONTROL AS AN OIL RECOVERY DISPLACEMENT PROCESS

IN MANY FLUID INJECTION PROCESSES USED FOR OIL RECOVERY, SUCH AS WATERFLOODING, THE INJECTED FLUIDS FLOW PREFERENTIALLY THROUGH THE ROCK ZONES OF HIGH FLOW CAPACITY (HIGH PERMEABILITY), BYPASSING OIL THAT IS PRESENT IN THE TIGHTER PARTS OF THE RESERVOIR ROCK. THIS MAY RESULT IN HIGH WATER-TO-OIL-PRODUCING RATIOS AND ABANDONMENT OF A PROJECT AT A RELATIVELY LOW VOLUMETRIC SWEEP EFFICIENCY. ONE APPROACH TO IMPROVED SWEEP EFFICIENCY IS TO PLACE A GELLED POLYMER INTO THE HIGH PERMEABILITY ZONES, THEREBY DIVERTING THE INJECTED FLUID INTO TIGHTER PARTS OF THE ROCK.CURRENT TECHNOLOGY RELIES ON THE INJECTION OF GELLED OR GELLING POLYMER SOLUTIONS INTO THE HIGH PERMEABILITY INTERVALS NEAR THE WELLBORE TO PLUG THEM. THE SOLUTIONS GELWITHIN A DAY OR TWO; THUS TREATMENT IS CONFINED TO THE REGION IN THE IMMEDIATE VICINITY OF THE WELLBORE. THE EFFECTIVENESS OF THIS TREATMENT IS OFTEN LIMITED BY CROSSFLOW OF THE INJECTED FLUID BETWEEN HIGH AND LOW PERMEABILITY REGIONS. THAT IS, WHEN THE TREATMENT IS CONFINED TO THE REGION NEAR THE WELL THE INJECTED FLUID MAY SIMPLY FLOW AROUND THE TREATED REGION AND INTO THE HIGH PERMEABILITY ZONE. IT IS PLANNED TO INVESTIGATE AN INNOVATIVE PROCESS THAT HAS THE POTENTIAL FOR IN-DEPTH PERMEABILITY MODIFICATION, THUS REDUCING THE EFFECT OF CROSSFLOW. THIS PROCESS IS BASED ON DELAYING THE GELATION OF POLYACRYLAMIDE POLYMER BY GENERATING THE CROSSLINKING AGENT, CHROMIUM (III), IN SITU AND CONTROLLING THE RATE OF THIS REACTION THROUGH CHEMICAL KINETICS. PREVIOUS DOE SPONSORED RESEARCH AT THE UNIVERSITY OF KANSAS HAS SHOWN THAT GELATION TIMES OF DAYS TO MONTHS CAN BE OBTAINED IN THELABORATORY BY APPROPRIATED SELECTION OF COMPOSITIONS. HOWEVER, THE PROCESS HAS NOT RECEIVED SUFFICIENT FIELD TESTING. WE WILL EVALUATE THE FEASIBILITY OF IN-DEPTH PERMEABILITY MODIFICATION USING A DELAYED GEL SYSTEM BY FIELD TESTING IN AN OIL RESERVOIR IN SOUTHEAST KANSAS. THE TEST RESERVOIR IS KNOWN TO HAVE A WATER-CHANNELING PROBLEM AND POOR WATERFLOOD SWEEP EFFICIENCY. IN PHASE I THE EMPHASIS WILL BE ON THE GEL SYSTEM DESIGN AND ON THE PLACEMENT OF THE GEL SYSTEM IN THE RESERVOIR.