Feasibility Study of Recrosslinkable Preformed Particle Gels for Natural Gas Injection Profile Control

Summary Recrosslinkable preformed particle gel (RPPG), a preformed particle gel (PPG) of which particles can bond together to form a strong bulk gel system after being placed inside the target formation, has been successfully applied to control conformance problems for waterflooding projects. However, no research has been conducted about whether RPPG is feasible in improving gasflooding performance in mature reservoirs. The study presents a systematic evaluation of acrylamide (AM) and 2-acrylamide-2-methylpropane sulfonate acid (AMPS)-based RPPG including phase stability under different gel-gas kinetics and plugging performance to natural gas and water. Different experimental apparatuses were designed to quantify and visualize the RPPG phase stability under static and dynamic gel-gas interactions. The RPPG phase stability was evaluated under a different range of injection pressure, gas exposure time, and swelling ratio (SR). Also, the RPPG stability was compared to the in-situ gel system hydrolyzed polyacrylamide crosslinked with chromium acetate [HPAM/Cr(III)], which has been applied in oil fields to control gas injection conformance. The RPPG plugging efficiency was evaluated using open fractured cores with different apertures. The results showed that the RPPG was stable under both static and dynamic gel-natural gas interactions and was stable when being exposed to an acidic environment with an insignificant total percentage weight loss (<3%). Additionally, the strength of the RPPG was further improved with the longevity of the gas exposure. Furthermore, different from the in-situ gel system HPAM/Cr(III), which exhibited a high degree of dehydration under natural gas and exhibited substantial syneresis under acidic conditions, the microstructure of the RPPG remained stable after the dynamic gas exposure. The results of the coreflooding experiments demonstrated that the RPPG had excellent plugging efficiency, which was closely related to the SR and the fracture aperture. This is the first study where a polymer gel system has been systematically assessed through varied testing methodologies using natural gas as opposed to other studies where nitrogen (N2) was used to simulate natural gas behavior. The robustness of the RPPG system makes it a viable candidate for improving the gasflooding processes in mature reservoirs dominated by conformance problems such as void space conduits (VSCs), fractures, and high-permeability channels.