Development of CO2-responsive gels for CO2 conformance control in high-permeability reservoirs using the Taguchi optimization method

• Published in: Separation and purification technology Vol. 377; p. 134312
• Main Authors: Ricky, Emanuel X., Kawamala, Martin, Liu, Shuai, Liu, Jiang, Mmbuji, Athumani O., Nyakilla, Edwin E., Myers, Matthew, Xu, Xingguang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 19.12.2025
• Subjects: CO2 channelling; CO2 conformance control; CO2-responsive gel; Enhanced oil recovery; High-permeability reservoir; the Taguchi method; CO2-responsive gel; the Taguchi method; CO2 conformance control; Enhanced oil recovery; CO2 channelling; High-permeability reservoir
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2025.134312

(a) CO2 channelling through high permeability zones and (b) CO2 channelling plugging mechanism. [Display omitted] •Novel PDEA-co-DMAP was formulated for CO2 conformance control in heterogeneous reservoirs.•The Taguchi method has systematically optimized the gel formulation parameters.•Optimized PDEA-co-DMAP exhibited high gel strength, thermal stability, and plugging efficiency.•CO2 plugging efficiency of PDEA-co-DMAP was confirmed through core flooding experiments.•The thermodynamic compatibility of the optimized gel formulation was verified using MD simulation. CO2-responsive polymer gels have attracted the interest of many researchers due to their potential applications in CO2-EOR operations and CO2 sequestration. Traditional approaches to optimizing monomer combinations and ratios for synthesizing CO2-responsive gels are time-consuming and expensive, limiting the rapid development and effective formulation of CO2-responsive polymer gels. This work utilizes the Taguchi method to optimize the CO2 swelling characteristics of a novel cross-linked copolymer gel using 2-(diethylamino)ethylmethacrylate/DEA as a base monomer and varying the relative amounts of acrylamide/AM, 2-(dimethylamino)ethylmethacrylate/DMA, 1-vinyl-2-pyrrolidinone/VPD, and N-[3-(dimethylamino)propyl]methacrylamide/DMAP. Through systematic optimization, it was discovered that the AM and VPD monomers used in previous studies to synthesize CO2-responsive gels do not exhibit good CO2-responsiveness properties, while DEA, DMA, and DMAP were more effective. Thus, in designing CO2-responsive polymer gels, more efforts should be put into screening tertiary amine monomers. Based on the optimization results, poly(DEA-co-DMAP) gel formulation was found to exhibit better performance. Molecular dynamics (MD) simulation results confirmed that the optimized poly(DEA-co-DMAP) gel exhibits significant thermodynamic compatibility and stronger intermolecular interactions with the CO2 molecules at the molecular level. The swelling ratio and rheological tests of the optimized gel in 1 % NaCl solution with CO2 at 25 °C indicated that poly(DEA-co-DMAP) exhibited a swelling ratio of 30 and a gel strength of 980 Pa, signifying that it possesses remarkable CO2 responsiveness and mechanical stability which are crucial for its plugging role in subsurface geological CO2 environments. Thermogravimetric analysis (TGA) of poly(DEA-co-DMAP) revealed an initial decomposition temperature of 267 °C, indicating that it exhibits remarkable thermal stability, which enables its use over a wide range of reservoir temperatures. The CO2 plugging efficiency test of the optimized gel in 1 % NaCl solution at 60 °C showed that poly(DEA-co-DMAP) achieved a plugging efficiency of 95 %, indicating that it can significantly reduce CO2 channelling in high-permeability sandstone reservoirs. This research work is expected to provide theoretical value and practical guidance concerning the formulation of CO2-responsive gels, hence accelerating the advancement of CO2-responsive gels from laboratory scale to practical field applications, and ultimately contributing to efficient oil recovery from heterogeneous reservoirs.