Investigation of alcohol-based deep eutectic solvents for inhibiting hydration in shale formations

Abstract

When drilling with water-based drilling fluids, the principal causes of wellbore instability are shale hydration and swelling. There exists an imminent necessity for the development of high-performance hydration inhibitors to effectively address this issue. Within the scope of this work, four alcohol-based deep eutectic solvents (DES) derived from choline chloride were prepared as efficient hydration inhibitors. The inhibitory capabilities of these alcohol-based DES, along with traditional inhibitors such as potassium chloride and polyetheramine, were compared through tests including linear swelling, hot-rolling dispersion, capillary suction timer, and sedimentation experiments. In the alcohol-based DES solutions, the expansion heights of bentonite decreased from 7.65 mm to 3.65, 3.96, 3.89, and 4.10 mm, respectively. After hot-rolling at 80 °C, the recovery rates of shale cuttings increased from 33.62 % to 91.33 %, 84.68 %, 88.38 %, and 81.24 %, respectively. All of the alcohol-based DES demonstrated superior hydration inhibition effects. The inhibition mechanism of alcohol-based DES was drawn from a comprehensive assessments encompassing zeta potential, particle size distribution, optical microscope observation, surface tension, and X-ray diffraction measurements. The predominant mechanism responsible for the inhibition of shale hydration resided in the electrostatic and hydrogen bonding interactions between the DES and clay. Additionally, the alcohol-based DES exerted a supplementary effect by reducing water intrusion via lowering the liquid surface tension. Due to their outstanding inhibitory performance, the prepared alcohol-based DES exhibited substantial promise as high-performance hydration inhibitors in shale drilling applications.