Process optimization and mechanism of oil-based drilling cuttings treatment based on hydrophilic deep eutectic solvent

Abstract

Oil-based drilling cuttings (OBDC) are hazardous waste, oil removal treatment must be done before they are re-utilized. Winsor I microemulsion (composed by microemulsion phase and remaining phase) cleaning is one of oil removal methods. However, there are many surfactants in the Winsor I microemulsion, which result in high cleaning cost and high possibility of surfactant contamination. In this paper, hydrophilic deep eutectic solvent (DES) and mineral oil were used to replace the microemulsion phase and remaining phase in Winsor I microemulsion, respectively, and a low-cost and surfactant-free cleaning agent was formed. The recommended DES was the mixture of choline chloride, methanol, and water with a molar ratio of 1:2.5:3, and the best cleaning agent was the mixture of DES and mineral oil with a mass ratio of 3:1. The recommended cleaning process was that added the OBDC into cleaning agent with a mass ratio of solid to liquid of 1:3, and stirred at room temperature for 100 min. At this condition, the oil content of OBDC reduced from 14.57 wt% to 1.34 wt%. In addition, the cleaning mechanism was discussed. The DES has low surface tension and good wetting property, which is similar with the microemulsion.