Effect of Weak Preformed Particle Gel on Unswept Oil Zones/Areas during Conformance Control Treatments

Preformed particle gel (PPG) has been developed to reduce fluid channels through super-high-permeability streaks/fractures. This was done to decrease water production and improve sweep efficiency for mature oilfields. The success of a PPG treatment depends primarily on whether or not PPG can selectively penetrate into highly permeable channels or fractures while minimizing penetration into lower permeable, unswept zones/areas. The purpose of this work was to determine what factors influence the damage of PPG on low-permeable, unswept zones. A filtration apparatus was designed to determine the possible penetration of PPG into low-permeable sandstone rocks. Filtration curves (the relationship between injection times and filtration volume) were obtained, and the permeability of sandstone cores, both before and after PPG treatment, was measured to determine whether or not PPGs reduce the permeability of low-permeable rocks. A commercial superabsorbent polymer, LiquiBlock 40K gel, was used as a PPG sample for our filtration experiments. LiquiBlock 40K is a weak gel particle with an elastic module of similar to 400 Pa at 0.05% of NaCl (wt %). The particle sizes of the gel ranged from 30 to 120 meshes. Filtration test results showed that 30-120 meshes of LiquiBlock 40K gel did not propagate in the cores with a permeability of <320 mD. This test also indicated that the gel formed a cake on the rock's surface. The damage of particle gel on unswept, low-permeable zones/areas was found to be effectively reduced by controlling both the particle size and the concentration of brine that was used to prepare swollen PPG.