Experimental study of polyacrylamide polymer gel for profile controlling in high-temperature offshore reservoirs

Thermal stimulation with horizontal wells has been conducted for more than 10 years in Bohai Oilfield. With the increase of the stimulation cycle, the aggravation of steam channeling and non-uniform utilization of horizontal section under high-temperature conditions seriously influence the production performance. For further improving the oil recovery of offshore heavy-oil reservoirs developed with horizontal well thermal stimulation, a new polyacrylamide polymer gel with strong gel strength, controllable gelling time, and good stability for offshore platform was developed. The gel system has good compatibility with produced sewage and is feasible to use production sewage for gel solution preparation instead of distilled water. The plugging rates in both high permeability and low permeability sand packs are over 98% at conditions of 200°C. The corresponding recovery rate of the sand packs is greatly improved by about 16.7% and 32.4%, respectively. The gel agent has good plug removing performance and more than 90% of the gel can be removed in less than 20 hours with the added plug removing agent. The gel has little effect on demulsification and dehydration of the produced water, which could meet the offshore technical requirement. Besides, a formula selection chart is proposed and established for easy and fast determination of the optimized polyacrylamide and resorcinol concentration, which could provide technical support for steam plugging and profile adjustment in offshore high-temperature reservoir.