Preformed Particle Gel for Conformance Control: Factors Affecting its Properties and Applications

Injecting preformed particle gel (PG) as a fluid-diverting agent to reduce water production is an attractive new procedure designed to minimize some of the risks inherent in gel treatments based on in-situ gelling. The objectives of this paper are: (1) understand how to control PG properties by changing gelant compositions and their fraction when synthesized; (2) determine where PG can be applied and how reservoir conditions affect PG properties; and (3) outline candidate well criteria and the proper injection procedures by illustrating several field applications. Based on laboratory experiments, the following results will show that: (1) PG strength and swelling capacity can be controlled by adjusting gelant compositions; (2) certain additives can improve PG stability at elevated temperatures (120°C); (3) increasing temperature will increase the swelling ratio and the swelling rate of PG, and increasing salinity will reduce the swelling capacity of PG and will increase PG strength; (4) the swelling capacity of PG is insensitive to pH; (5) PG is insoluble in water, but absorbs it, swelling up to 20-200 times of its original size. It is strength- and size-controlled, environment-friendly and not sensitive to reservoir minerals and formation water salinity. Three examples from more than 200 operations were selected to show how to choose candidate wells and how to operate the injection procedures. PG can be used as a conformance control agent to correct permeability heterogeneity for those reservoirs with fractures or channels, both of which are widely found in mature water-flooding oilfields in China