Minimizing formation damage for preformed particle gels treatment in mature reservoirs

This research studied the effect of preformed particle gels (PPGs) on unswept, low-permeable zones/areas. The objective was to find methods that minimized the damage caused by PPGs on unswept, low-permeable zones/areas, thus improving PPG treatment efficiency. These results can help to identify of the best PPG types, particle sizes, and brine concentrations for specific reservoirs and treatments. This study used sandstone core samples with various degrees of permeability. Two types of particle gels, a strong Daqing gel (DQ) and a weak Liquiblock™ 40k gel (40K), were used, each with a different strength. This research included two stages. Firstly, both a static filtration test model and load pressure model were used to evaluate the damage caused by various PPGs on low-permeability sandstone cores. These results were analyzed using quantitative analytical model. This approach identified the type of PPG that can neither penetrate into conventional solid rocks nor form cakes on the rocks\u27 surface. Secondly, the permeabilities of various packed PPGs with different particle sizes and brine concentrations were measured during the second stage of the research. Static filtration models with both various load pressures and various back pressures were used to measure the permeability of a gel pack. Weak PPGs with smaller particles were proved less permeable than strong PPGs with larger particles. The permeability of the gel pack decreased when both the load pressures and the back pressure increased. In addition the both gel compressibility and water loss was measured. Gel strength was measured before and after compression --Abstract, page iii