Synthesis and Properties of a Novel Hydrophobic Nano‐Activated Carbon Based Shale Inhibitor for Water‐Based Drilling Fluids

ABSTRACT To address the limitations of traditional polymer‐based shale inhibitors, including susceptibility to hydrolysis and degradation under high‐temperature conditions, insufficient plugging performance, and difficulty in sealing micro‐fractures due to oversized molecular dimensions, this study innovatively employed an aqueous free‐radical copolymerization approach to synthesize a cationic nano‐shale inhibitor, designated as HNAC@AM‐DMDAAC‐MAH‐β‐CD. The structure, thermal stability, shale inhibition efficacy, and underlying mechanism of the inhibitor were comprehensively evaluated using characterization techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and contact angle measurement, complemented by performance tests including relative inhibition rate, linear expansion rate, cuttings rolling recovery, and mud‐making inhibition. Experimental results demonstrate that the inhibitor exhibits exceptional thermal resistance and inhibition performance. At elevated temperatures of 160°C and 200°C, the thermal rolling recovery rates of cuttings reached 91.83% and 89.83%, respectively, while the linear expansion rate was as low as 11.07%. Furthermore, it effectively suppressed the hydration dispersion and mud‐making behavior of bentonite. Notably, leveraging its nanoscale structural attributes, the inhibitor enabled efficient sealing of micro‐nano pores and throats, offering an innovative solution to the challenge of wellbore stability in deep and ultra‐deep drilling operations.