An investigation into shale swelling inhibition properties of dodecyltrimethylammonium chloride (DTAC) for water-based drilling fluids

Shale formations adsorb water and swell when they are in contact with water-based drilling fluids due to the content of active clay minerals. Shale swelling in the well wall is one of the main challenges of drilling operations and causes many problems and damages. Modifying drilling mud with shale swelling inhibitors is one of the solutions to this challenge. Recently, amines and their derivatives have been considered by researchers due to their ability to control the swelling of shale layers and the range of properties that can be adapted to any drilling conditions. In this study, Dodecyltrimethylammonium Chloride (DTAC) was investigated as a new shale stabi-lizer and swelling inhibitor. Various tests such as bentonite sedimentation, bentonite inhibition, shale sample recovery and dynamic linear swelling were used for this study. Wettability, zeta potential, isothermal water adsorption and thermogravimetric analysis (TGA) tests were performed to evaluate the mechanism of action of this amine-based shale swelling inhibitor. Based on the results, DTAC shows good inhibition power in controlling and reducing the swelling of shale and bentonite samples at both low and high temperatures, even at low concentrations. DTAC is well-compatible with other common additives in drilling fluids. On the other hand, this amine shows a relatively stronger function than Cetyltrimethyl Ammonium Bromide (CTAB) and Ammonium Chloride (NH4Cl). Adsorption of DTAC molecules on the surface of charged plates of bentonite particles reduces the negative charges of these plates, makes inaccessible places available on the plates of water molecules, in-creases their hydrophobicity and finally reduces the sensitivity of surfaces to adsorption of water molecules, which leads to stabilization of shale samples and bentonite particles against contact with aqueous media.