Utilizing High Melting Point Long-Chain Fatty Acid Based CO2 Response ILs for Suppression of CO2 Gas Channeling and Clay Swelling

Abstract

The water-alternating-with-gas process is widely applied in oil recovery but faces challenges such as gas channeling and clay swelling that significantly reduce efficiency. To address these issues, a CO₂-responsive liquid–solid transformation profile control agent (MA–D230) was designed. This agent was synthesized from myristic acid (MA) and O,O′-bis(2-aminopropyl)polypropyleneglycol (D230) with a molar ratio of 2:1. MA was transferred from the solid to the liquid phase in D230 solution by electrostatic self-assembly. Upon CO₂ injection, MA was precipitated from the MA–D230 aqueous solution as a solid particle profile control agent, while D230 was protonated as a clay swelling inhibitor. The mechanisms of MA precipitation and D230 protonation were confirmed by the ¹H NMR analysis. After CO₂ injection, RE-MA precipitated from the MA–D230 aqueous solution, exhibiting the same crystal structure, structural features, and melting point as its original state. Furthermore, RE-MA can form in environments with salinity levels ranging from 0 to 2000 ppm, while particle sizes in the micrometer range are generated upon CO₂ injection. Moreover, the core flooding experiments further demonstrated that MA–D230 had an excellent ability to enhance oil recovery. In short, a new method was proposed to solve the problems of gas channeling and clay swelling in CO₂ flooding during the WAG process.