Transport and Plugging Performance Evaluation of a Novel Recrosslinkable Microgel Used for Conformance Control in Mature Oil Fields with Superpermeable Channels

Abstract

Summary Although recrosslinkable preformed particle gel (RPPG) has been successfully evaluated in the literature for mitigating conformance problems in open-fracture applications, there are no studies that have examined the transportation and plugging performance of microsized RPPGs (micro-RPPG) in high-permeability channels. We systematically evaluated a novel micro-RPPG and its transportation mechanism in matrix-like media. The micro-RPPG can recrosslink to form a bulk gel after being placed in the reservoir, combining the advantages of both in situ and preformed particle gel (PPG) systems. This recrosslinking ability prevents the gel from being washed out easily, ensuring sustained performance under reservoir conditions. In this study, the micro-RPPG characterization, self-healing process, transportation behavior, and plugging performance were investigated. A sandpack model with multipressure taps was utilized to assess the micro-RPPG suspension’s transport behavior and plugging efficiency. In addition, micro-optical visualization of the gel particles was deployed to study the particle size changes before and after the swelling process. Bottle tests showed that micro-RPPG could be dispersed and remain as separate particles in water with a concentration below 8,000 ppm, which is a favorable concentration for particle gel pumping. However, during the flooding test, the amount of micro-RPPG can be entrapped in the sandpack, resulting in a higher microgel concentration (higher than 8,000 ppm), endowing the gel particles with recrosslinking ability even with excessive water. The micro-RPPG could propagate through the sandpack model, and the required pressure gradient mainly depends on the average particle/pore ratio and gel concentration. The gel suspension significantly reduced channel permeability, providing sufficient resistance to post-waterflooding (more than 99.97% permeability reduction). In addition, the evaluation of micro-RPPG retention revealed that it is primarily affected by both gel concentration particle/pore ratios. We have demonstrated that the novel recrosslinkable micro-RPPG can transport through large channels, and it can also provide effective plugging due to its unique recrosslinking property. However, by this property, the new microgel exhibits enhanced stability and demonstrates resistance to being flushed out in such high-permeability environments. Furthermore, with the help of novel technology, it is possible to overcome the inherited problems commonly associated with in-situ gel treatments, including chromatographic issues, low-quality control, and shearing degradation.