Acid-Modified Biochar/poly(arginyl-Lysine) Composite as an Environmentally Friendly High-Temperature Shale Inhibitor

Abstract

High-temperature shale oil and gas drilling calls for effective and environmentally friendly additives capable of control clay hydration, shale dispersion, and wellbore instability in water-based drilling fluids. In this study, we prepared an acid-modified biochar (BC)/poly(arginyl-lysine) (JL) composite, designated JL-BC, via physical blending, and then evaluated its inhibition performance by means of linear swelling and hot-rolling recovery tests. Under treatment withJL-BC solution, the sodium bentonite (Na-BT) swelling height decreased to 4.49 mm at 150 °C for 16 h, while shale cuttings recovery reached 92.1% after aging at 220 °C for 16 h, results that outperforming those of potassium chloride (KCl), polyetheramine (PEA), 2,3-epoxypropyltrimethylammonium chloride (EPTAC), and dopamine (DA). Furthermore, the water-based drilling fluid supplemented with JL-BC maintained good rheological behavior, fluid loss control and inhibition performance after aging at 180 °C for 16 h. Mechanistic analyses revealed that JL-BC adsorbed strongly onto clay surfaces via electrostatic interactions and hydrogen bonding, thereby weakening the electrostatic repulsion between clay particles and reducing the amount of hydration-related water associated with Na-BT, which contributed to the inhibition of clay hydration and swelling. An environmental friendliness assessment showed that JL-BC was nontoxic and readily biodegradable, that it did not significantly increase soil heavy metal concentrations and promoted nutrient accumulation in wheat seedlings. Collectively, these findings indicate that JL-BC is a promising environmentally friendly shale inhibitor for high-temperature applications.