Insights into the interaction between lowsal-alkali formulation: Debunking the effect of alkali and lowsal-alkali formulation on the wettability alteration of the quartz substrate

Abstract

The role of salts in altering the interfacial tension (IFT) and wettability of the rock towards oil recovery is evident through low salinity (lowsal) water flooding. On the other hand, alkali flooding is a well-established method of chemical enhanced oil recovery, which works by reducing the IFT of liquid–liquid system, alters the wettability of rock, and emulsifies the oil–water. Despite having sound knowledge on the applicability of alkali in EOR, the synergistic effect between salts and alkali towards the oil recovery still needs more investigation. In this work, the interaction of salts such as (NaCl and CaCl2) and alkali (NaOH, Na2CO3) on the IFT and wettability of the quartz substrate is investigated. To understand the effect of individual components of crude oil on the IFT and wettability, two different model oils, an aliphatic hydrocarbon (decane), and also actual crude oil from oilfield are employed. It is observed that the lowsal (NaCl)-alkali (NaOH, Na2CO3) formulation effectively reduces the IFT of basic model oil–water and aliphatic-water system than the individual effect of alkali and salts. The lowsal (NaCl)-alkali formulation completely swept the hydrocarbon from the quartz substrate by imparting Marangoni force. Thereby a complete removal of the crude oil droplet from the quartz surface is visually reported for the first time using lowsal (NaCl)-alkali system. These results are further validated by a new approach of Petri dish based static experimental technique which confirms the saponification reaction between acidic and the basic components in the crude oil. Further, the attraction of anionic surfactant (sodium stearate) by cations (Na+) in the NaCl is also validated. We also conclusively show that the increase in contact angle of crude oil and acidic model oil in wettability experiments is primarily due to neutralization reaction and it is not an indicator of oil-wet.