Optimizing the Strength and Size of Preformed Particle Gels for Better Conformance Control Treatment

Abstract A newer trend in gel treatments is using preformed particle gel (PPG) to reduce fluid channels through super-high permeability streaks/fractures and thus to decrease water production and increase sweep efficiency for mature oilfields. The success of a PPG treatment mainly depends on whether or not the PPG can effectively reduce the permeability of the channels to an appropriate level. This work sought to determine what factors significantly influence the blocking efficiency of PPG in fluid channels. A transparent filtration model was designed to observe the compression of gel particles in fluid channels at several differential pressures and to study the effect of various parameters, such as brine concentrations and particle sizes, on PPG blocking efficiency. The results suggested that rather than fully blocking the channel, a permeable gel pack was formed in the fluid channel by gel particles, and its permeability was dependent on the gel strength, particle size, and load pressure. The gel pack permeability decreased as the gel strength, particle size, and load pressure increased. Thus, the blocking efficiency of the particle gel on a channel is increased if large sizes or/and strong particles are used. The gel pack permeability was a few hundred millidarcies before the load pressure was applied; it decreased to less than 10 md when the load pressure rose. The results also indicated that the PPG pack was compressible and its compressibility decreased as the load pressure increased. These results can be effectively used to optimize a PPG design. A gel pack that has a desired permeability can be devised by selecting the proper gel strength and particle size corresponding to the reservoir pressure. This is essential for a successful gel treatment so as to reduce the permeability to a manageable preplanned degree.