Innovative use of chitosan salt for enhanced CO₂ capture and wellbore injectivity

Creating eco-friendly stimulation fluids is still a major challenge in capturing CO₂ and improving wellbore injectivity. This study presents a dual-function approach utilizing a water-soluble chitosan–salt (CS) solution as a green additive to simultaneously enhance CO₂ uptake and generate carbonated acid for carbonate reservoir stimulation. This approach improves reservoir permeability and enables CO₂ sequestration, aligning with global sustainability goals. Chitosan, a biodegradable biopolymer, was converted into a water-soluble chitosan salt (CS) and carbonated under controlled laboratory conditions (25 °C, 508 psi) using a mixing reactor. The resulting CS–CO₂ system was injected into Indiana limestone cores to evaluate its efficiency in promoting wormhole formation and improving flow conductivity. Core-flooding experiments conducted across varying temperatures (25–75 °C), injection rates (0.5–2 cm³/min), and salinities (DI water and seawater) revealed a 250 % increase in CO₂ uptake compared to conventional carbonated water. The generated carbonated acid facilitated calcite dissolution, producing dominant wormhole structures with smoother geometries at 1000 ppm CS concentration. Pressure monitoring indicated a sharp ΔP rise exceeding 1000 psi at 5 PVBT under low-temperature conditions, confirming strong fluid–rock interactions. Compared to traditional acid systems, the CS–CO₂ formulation reduced PVBT by 60 %, increased porosity by 10 %, and doubled permeability. CT imaging validated the formation of continuous wormhole pathways, demonstrating the importance of CS–CO₂ systems as scalable, environmentally benign alternatives for carbonate reservoir stimulation.