Strength adjustable preformed particle gels for conformance control
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- Petroleum Engineering
"Reservoir heterogeneity and early water breakthrough (also known as fingering) represent two of the greatest challenges to recover crude oil efficiently. Gel treatments have been implemented as a cost-effective method to plug high permeability zones and thus improve sweep efficiency in reservoirs. However, when extensive cross-flows exist between formation layers, gel treatments become less efficient. Polymer was used in polymer flooding to increase the viscosity of the injected fluids and to correct the fingering problem. However, such treatment may be uneconomical since dramatic viscosity loss (80-90%) is caused by shearing degradation during the injection process near the wellbore. This research focused on solving the cross-flow and fingering problems by using preformed thermo-responsive super absorbent particle gels as in-depth fluid diversion and mobility control agents, known as Type I and Type II respectively, for mature reservoirs. Experimental results showed that Type I (PG 1) and II (PG2) particle gels were initially around 1 mm in size with high gel strength. PG 1 became softer and weaker while PG2 transformed into a polymer solution in the designated time period. The transformation time was controlled by the labile crosslinker's concentration. Filtration and sandpack results illustrated that both of them have excellent propagation ability without face plugging. Weak gels that were transformed from PG1 prevented the cross-flow by continuing to divert followed fluids from high to low permeability zones deep within the reservoir. The polymer solution transformed from PG2 worked as in-depth mobility control agents to mitigate the fingering problem"--Abstract, page iii.