A natural dye in water-based drilling fluids: Swelling inhibitive characteristic and side effects

The development of eco-friendly shale inhibitors is still an area which has attracted a lot of attention in the drilling industry. Henna extract is a natural dye which has recently shown considerable inhibition and weak deflocculation properties in clay-water system. This study aims to investigate swelling inhibitive feature and side effects of Henna extract in water-based drilling fluids (WBDFs). It was carried out through extensive experiments including adsorption measurements on shale by batch equilibrium, inhibition evaluation by dynamic linear swelling and cuttings dispersion, wettability alteration via contact angle measurements, compatibility by rheological properties determinations and fluid loss measurements, and lubricity. Both in natural pH and adjusted pH to 9, Linear adsorption model was more suitable for anticipating the adsorption behavior of Henna extract on the given shale sample. The results of the linear swelling and cuttings dispersion tests demonstrated that Henna extract in drilling fluid formulations diminished the swelling and dispersion characteristics of the addressed shale sample. Moreover, contact angle measurements showed that Henna extract expanded the hydrophobicity of shale formations, preventing and promoting water adsorption and shale stability respectively. This issue definitely introduces wettability alteration as a mechanism for shale stability by Henna extract. Compatibility determinations additionally uncovered that Henna extract is compatible with common WBDFs additives. As indicated by the lubricity tests, Henna extract enhanced the lubricity of WBDFs, a finding which can be of an incredible significance in directional drilling. Among others, advantages such as environmental friendliness, low cost, accessibility, and the counter corrosion property make the applicability of Henna extract in WBDFs profoundly suitable.