In oil and gas production operations, wellbore instability is primarily caused by shale hydration. Thus, a thermally stable inhibitor is essential to prevent shale hydration. This research focuses on synthesizing a copolymer of maleic acid and acrylic acid/graphene oxide (poly-(AAMA)-GO) via free radical polymerization as an effective and low-cost inhibitor. The combination of the copolymer and graphene oxide aims to produce a fluid inhibitor with high thermal stability. Additionally, the unmodified copolymer of acrylic acid and maleic acid poly-(AAMA) was synthesized for comparative analysis. The inhibitory properties of both compounds were evaluated using anti-swelling, immersion, and shale recovery tests, with potassium chloride (KCl) serving as the industry benchmark. Poly-(AAMA) and poly-(AAMA)-GO effectively inhibited sodium bentonite swelling, achieving anti-swelling ratios of 75% and 78%, respectively, compared to 58% for KCl. Characterization revealed that poly-(AAMA) and poly-(AAMA)-GO adhered to sodium bentonite particles through electrostatic interactions and hydrogen bonding, forming a thin film that enhanced hydrophobicity and limited water penetration into the interlayers. Poly-(AAMA)-GO exhibited excellent thermal stability up to 250 ℃, demonstrating its potential for high-temperature well fluid. Despite their structural differences, both compounds exhibited similar inhibitory effectiveness due to their shared chemical characteristics.