The Yinggehai Basin is a key area for natural gas exploration in the western South China Sea. In recent years, commercially viable gas formations and abundant high-temperature formation water have been discovered in the Huangliu Formation of the X gasfield, indicating promising prospects for hydrothermal geothermal resource development. However, geothermal resource evaluation for this system are still lacking. Taking the X gasfield in the Yinggehai Basin as a case study, a heterogeneous 3D geothermal reservoir geological model was constructed by integrating drilling, logging, core, and seismic data. Key properties such as porosity, permeability, temperature, and water saturation were modeled and assigned in a gridded format. During the model construction, multiple stochastic simulations and seismic attribute constraints were introduced to enhance the rationality and accuracy of the spatial distribution of geological parameters. Based on this model, the volumetric method was applied to evaluate the geothermal resource potential of the Huangliu Formation, and the main geothermal resource-rich zones were identified. The results showed that the reservoir temperatures in the Huangliu Formation ranged from 167.0 ℃ to 197.6 ℃, with an average of 186.5 ℃, indicating favorable conditions for high-temperature geothermal development. The total geothermal resource was estimated to be 3.84×10¹⁶ kJ, equivalent to 1 310.5×10⁶ t of standard coal, with fine sandstone serving as the main reservoir lithology. Assuming a recovery coefficient of 8%, the recoverable resource was approximately 0.31×10¹⁶ kJ, equivalent to standard coal of 104.8×10⁶ t. The spatial distribution of resources revealed two major geothermal-rich zones, both located in the sand bodies of deepwater turbidite channels of the Huangliu Formation. These zones were characterized by high temperatures, favorable physical properties, and well-developed fine sandstone, making them preferred areas for future development. Meanwhile, water saturation model analysis indicated high water content in both the eastern and western parts of the Huangliu Formation, suggesting the presence of isolated water bodies that could serve as potential development areas. The research results provide clearer insights into the distribution characteristics and development potential of geothermal resources in the Yinggehai Basin and offer important guidance for promoting the integrated development of offshore gas fields and geothermal energy in China.