Organic alkalis as potential additives in hot water flooding for enhancing heavy oil recovery

Alkali-surfactant-polymer (ASP) flooding is a chemical enhanced oil recovery method; its working mechanisms include mobility control, wettability alteration, and in-situ emulsification. However, conventional alkalis used in the ASP flooding could cause some serious issues, including scaling, formation damage, and pipe corrosion. In this study, we investigated the feasibility of incorporating organic alkalis as chemical additives in hot water flooding to enhance heavy oil recovery. The focus was on studying the interfacial properties, that is, interfacial tension (IFT) and wettability, emulsification mechanisms, thermal stability of alkalis, and recovery efficiency through coreflooding experiments. Three organic alkalis, including diethylamine (DEA), ethanolamine (ETA), and triethlymine (TEA), were selected to evaluate their potentials in enhancing heavy oil recovery and investigate their recovery mechanisms. Coreflooding experiments were conducted at 50 degrees C and 2 MPa with sandpacks saturated with a high total-acid-number (TAN) heavy oil sample. The measurement results demonstrated that all three organic alkalis could effectively reduce the IFT between water and heavy oil from 22.7 to 1.6 mN/m and favourably alter the wettability of rock surface. ETA exhibited good thermal stability up to 100 degrees C in hot water applications. The interaction between organic alkalis and heavy oil could generate either water-in-oil or oil-in-water emulsions, depending on the water-oil ratio (WOR). The coreflooding experiments showed a significant increase (16%-17.5%) in heavy oil recovery using ETA for two distinct injection strategies. IFT reduction, wettability alteration, and emulsification were found to be the main recovery mechanisms when organic alkalis are utilized as chemical additives for hot water flooding.