Preparation and mechanism of environmentally friendly poly-citrulline as shale inhibitor for water-based drilling fluids

Shale inhibitors is a treatment agent in mud, but most inhibitors cannot balance the relationship between inhibition performance and environmental protection performance. In this paper, poly-citrulline was synthesized using citrulline. Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis and toxicity tests were used to characterize the PCCP, and linear expansion tests, rolling recovery tests and sodium bentonite dispersion tests were utilized to measure the inhibitory performance of the PCCP. Its mechanism of action was studied through zeta potential tests, X-ray diffraction and laser particle size. The experimental results revealed that PCCP is a low-molecular-weight nontoxic polymer with excellent inhibitory properties. When 1.5 wt% PCCP was added, the linear expansion rate was 26.4%, the rolling recovery rate was 78.4%, and the Na-Bent dispersion was inhibited by 16%. PCCP is adsorbed on clay particles, compressing the electric double layer and reducing the negative charge. At the same time, the molecules are partially intercalated into the crystal layer space of the clay but more so by wrapping the clay particles, hindering the water molecules from contacting the clay particles and inhibiting the hydration and dispersion of the clay minerals. This article provides environmentally friendly and efficient design ideas for shale inhibitors.