Wettability alteration of oil-wet carbonate rocks by chitosan derivatives for application in enhanced oil recovery II: High-temperature and high-pressure conditions-Core flooding tests

Biopolymers, serving as Enhanced Oil Recovery (EOR) agents, are posing challenges and opportunities within the oil industry, particularly in demanding operational conditions. The assessment of trimethyl chitosan (TMC) and its hydrophobized derivative with myristoyl chloride (TMC-C14) becomes crucial in these rigorous scenarios, presenting a significant challenge for polymer flooding. The study subjected TMC and TMC-C14 to comprehensive evaluations as EOR agents, employing contact angle measurements, interfacial tension tests using the Drop Shape Analyzer (DSA), and core flood tests under conditions of 60 degrees C, 1000 psi, and elevated salinity. Relative permeabilities were deduced from the results, while spontaneous imbibition tests provided insights into rock wettability. Amott cell tests underscored that both TMC and TMC-C14 induced accelerated spontaneous oil production within a span of 30 days. Notably, TMC-C14 exhibited superior interfacial activity compared to TMC, attributed to its hydrophobic segments. The impact on rock wettability was distinct: TMC shifted it towards water-wet, while TMC-C14 induced a neutral-wet condition. This transformation was corroborated by contact angle measurements, imbibition tests, and relative permeability curves. Capillary forces, computed from DSA data and spontaneous imbibition tests, further validated the wettability-altering tendencies of the chitosan derivatives on the rock. In core flooding tests and relative permeability curves, TMC demonstrated a notable improvement in the recovery factor (RF) compared to seawater. Specifically, RFTMC achieved 69%, surpassing RFbrine at 49%, affirming that the primary mechanism of action for chitosan derivatives lies in their ability to modify rock wettability. This study shows the potential of TMC and TMC-C14 as effective EOR agents, shedding light on their interfacial activities, impact on rock wettability, and enhanced recovery factors in challenging operational conditions.