Laboratory Evaluation of Placement Behavior of Microgels for Conformance Control in Reservoirs Containing Superpermeable Channels

Gel treatment has been proven an effective method to attack excessive water production in many mature oilfields. However, not all of the application projects have successful stories. The effectiveness of a gel treatment largely depends on the transport and placement behavior of gel materials in reservoirs to be treated. In this work, we carried out systematic studies to investigate the transport, placement, water-blocking ability, fluid diversion and sweep improvement, and matrix damage effect of micrometer-sized preformed particle gels (microgels) in reservoirs containing superpermeable (super-K) channels. The impact of the channel/matrix permeability contrast and the particle/pore size ratio in the channels and in the matrices was studied. The favorable conditions for gel treatments were identified. The results show that the microgel particles selectively penetrate, place in, and effectively shut off the super-K channels under proper conditions. The sweep improvement after gel treatments was evaluated through chemical tracer tests. The results clearly demonstrate delayed breakthrough, fluid diversion, and increased swept volume of the subsequent flooding fluid. In the experiments, the sweep improvement was in the range of 0.25-0.43 total pore volumes. A higher sweep improvement was achieved as the permeability contrast was higher (i.e., the reservoir was more heterogeneous). To achieve both good injectivity and water-blocking efficiency for the tested microgels, the particle/pore size ratio in the channel should be below 2. Meanwhile, the particle/pore ratio in the matrices should be kept above 5 to avoid significant damage to the matrices. The results of this study provide support for gel product selection and successful gel treatment designs and implementations.

Automated summary

Gel treatment has proven to be effective in attacking excessive water production in mature oilfields, but not all applications are successful. The effectiveness of gel treatment depends on the transport and placement behavior of gel materials in the reservoir. This study investigates the transport, placement, water-blocking ability, fluid diversion, and sweep improvement of microgels in reservoirs with superpermeable channels. The results show that microgel particles can selectively penetrate and shut off superpermeable channels under certain conditions, leading to improved sweep efficiency.