Abstract: This paper introduces a novel technique in which water blocking technique is combined with acidizing treatment.The blocking system, XN-PP, is made of AM and a kind of small molecular aldehyde. These two components can undergo co-polymerization and form a gel with high viscosity and strength in host reservoirs where the tem-perature is 110 - 120℃and the total salinity is 9-12×105 mg/l. The acid resistance of the blocking agent to self-generating acids was experimentally studied, the blocking ability of the agent under reservoir conditions and the optimum injectivity to large pore channels were investigated, and the protective effect of the preflush on the agent was evaluated. The results indicate that the gel is tolerant of the acids, and it has not only high strength but also high efficiency in water shutoff. A preliminary test of the technique was carried out in two wells in an oilfield. Oil production was greatly enhanced and water production effectively controlled for both wells.

Key words: Water blocking, Performance, Evaluation, Acidizing, Stimulation effect