The demand for sustainable and efficient energy solutions has driven significant interest in geothermal energy production. The successful extraction of geothermal resources relies on effective drilling techniques, which in turn depend on the properties and performance of drilling fluids. Water-based drilling fluids have gained traction due to their eco-friendliness and potential for enhanced performance. In this context, this study delves into the utilization of a novel vinyl copolymer (named TVCP) synthesized through free radical polymerization of three monomers in the formulation of next-generation water-based drilling fluids tailored for geothermal well drilling. Vinyl copolymers, characterized by their versatility and tunable properties, offer a promising avenue for addressing the challenges associated with geothermal drilling which are usually thermally induced. This investigation involves a comprehensive evaluation of the role of TVCP in enhancing various aspects of water-based drilling fluids, including rheological properties, fluid loss control, and thermal stability at 150 °C. Through a systematic approach, the study examines the influence of the varying concentrations of TVCP on the fluid's ability to maintain optimal performance under the demanding conditions encountered during geothermal well drilling. At a differential pressure of 500 psi and a temperature of 150 °C, there was a reduction of 28% in fluid loss. The viscosity profile also showed an incremental trend and lesser thermal degradation as compared to the conventional bentonite/polymer drilling fluids. The insights gained contribute to the ongoing efforts in optimizing drilling practices for geothermal energy extraction, aligning with the broader goal of sustainable energy production and minimizing environmental impact.