(431g) Chitosan-Based Sustainable Preformed Polymeric Gel for Conformance Control in Oil and Gas Reservoirs

Oil and gas extraction usually produces relatively large amounts of produced water, which causes a number of mechanical and environmental problems. Chemical treatments, such as in-situ crosslinked polymer gel and preformed particle gel (PPG), are recently applied and proven more effective than mechanical treatment. A sustainable PPG made of chitosan and polyacrylamide (PAM) has been newly developed and examined in several petroleum environments for conformance control. The crosslinking mechanism between chitosan and PAM has been confirmed by FTIR spectroscopy and validated by scanning electron microscopy observations. Numerous concentrations of the base polymer of PAM and the chitosan crosslinker have been screened to select the best system that provides optimum swelling and strength behavior. Various rheological experiments and swelling ratio measurements have been conducted on the PPG to test their performance in different reservoir conditions, such as pH, temperature, and salinity. The experiments are extended to cover the long-term thermal and ionic behavior of the PPGs. In addition, the theoretical approach has been used to calculate the gel particle sizes in different salinity conditions to examine their capture behavior in the reservoir's pore throats. The outcomes revealed that the best amounts of PAM with 0.5 wt% chitosan were between 5 and 9 wt%, while the best amounts of chitosan with 6.5 wt% PAM were between 0.25 and 0.5 wt%. These concentrations may create PPG formulations with a high degree of swellability and enough mechanical strength. Regarding salinity factor, the swelling ratios were lower in saline water with a TDS of 67297.6 mg/L compared to deionized water, which reached 80.00 g/g in deionized water and dropped to 19.00 g/g in saline water. In contrast, the storage modules were higher in saline water than in deionized water, having ranges between 2053-5989 Pa and 1695-5000 Pa, respectively. This behavior was mainly due to the salt shielding effect, which causes the PPGs to shrink. The swelling ratios were lower, and the storage modules were higher in neutral conditions with a pH of 6 compared to acidic and alkaline mediums, mainly due to the ionization of functional groups of COO^– and NH₃⁺ in PPG structure, causing electrostatic repulsions. The temperature effect causes the swelling ratios to increase and the PPG structure to expand and accommodate more water, which is owed to the amide group’s hydrolysis to carboxylate groups. Moreover, as the swollen particles in this investigation are planned to be 0.63–1.62 mm in deionized water and 0.86–1.00 mm in saline water, their sizes may be controlled. FTIR analysis showed an interaction between the amide groups in PAM with both the hydroxyl groups and amine groups in chitosan, demonstrating the crosslinking mechanism. Finally, the PPG of PAM and chitosan demonstrated long-term thermal and hydrolytic stability in high-temperature and high-salinity environments while displaying good swelling and rheological qualities. This PPG system is deemed promising and will help replace other PPGs currently utilized in the industry by mitigating their toxicity.