It is possible to take advantage of nanomaterials' properties to improve water-based drilling fluids' flux and physical properties. In this paper, glycine methyl ester hydrochloride was synthesized, and the chemical structure was verified to be used as a surface modifier of graphene oxide. At the same time, graphene oxide was prepared from graphite and chlorinated with thionyl chloride, and a nucleophilic substitution reaction was performed to increase the hydrophilicity of graphene oxide. FTIR, Raman, HRTEM, and XRD techniques have identified the prepared and obtained materials from chlorinated graphene oxide's reaction with glycine methyl ester hydrochloride. The glycine-modified graphene oxide (GO) was evaluated as drilling-fluid additives at different concentrations (2.66%, 5.32%, and 10.64%) to enhancement the thermal stability of water-based drilling fluid and reducing the filtration loss. The obtained results confirmed that the successful glycine-modified graphene oxide/bentonite to enhance both thermal stability (up to 350 °F) and filtration loss.