Development of Oil Sludge Preformed Particle Gels (OS-PPG) for Petroleum Reservoir Conformance Control

The resource utilization of oil sludge (OS) is considered a feasible and environmentally friendly approach to effectively address the disposal of OS effectively. In this work, a preformed particle gel (PPG) system was prepared by using OS, which could serve as a high-strength plugging material for conformance control. Based on the free-radical copolymerization method, the OS-PPG was developed by adjusting the chemical composition of the formulation. The effects of each component and its concentration in OS-PPG on the swelling performance and rheological behavior were systematically investigated. Infrared spectroscopy and simultaneous thermal analyses were employed to characterize the structure and thermal stability. The plugging strength was evaluated with a pore-network fluid-loss meter. Results showed that when using 5.71–20.00% monomer (i.e., acrylamide and 2-acrylamido-2-methylpropanesulfonic acid), 0.1–0.5% PCS, 0.05–0.1% MBA, and 0.05–0.4% APS, OS-PPGs with high OS content (20%) could be prepared. The maximum swelling ratio in formation water reached 43.5 times. The storage modulus (G′) was 216.4 Pa, the complex viscosity (η*) was 35514.9 mPa·s, and the maximum plugging strength reached 0.88 MPa, demonstrating good structural strength. The gel particles possessed a stable three-dimensional network structure with OS physically dispersed through a filling mode. The initial decomposition temperature of the system was 246 °C, about 31 °C higher than that of conventional PPG, indicating good thermal stability. This study provided a new method for direct resource utilization of OS in oilfields and offered a novel material with promising application prospects for green profile modification and water plugging in oilfields.