<p>The integration of surface and subsurface spatial data remains a fundamental challenge in geoinformatics, as conventional GIS platforms excel in three-dimensional (3D) geographical modeling but lack robust capabilities for representing complex subsurface geological structures. To bridge this gap, this paper presents a methodological framework for automated geological modeling that enables the fusion of geographical and geological models within a unified GIS environment. The framework extends ArcGIS by decomposing and reorganizing the 3D geological modeling workflow using object-oriented methods, thereby integrating geological modeling schemes into the ArcGIS platform. The methodology centers on extending ArcGIS’s basic geometric data structures to define key geological object data structures, and on designing and integrating core algorithms based on these structures for accurate positioning and high-resolution representation of geological bodies, with an emphasis on automation, reusability, and interoperability. Based on these designs, a 3D geosciences modeling software prototype was developed and implemented using ArcGIS Engine components and Visual Studio C#. The proposed framework facilitates the integrated modeling of 3D surface and subsurface data, offering a systematic solution to the longstanding challenge of multi-source spatial data integration in GIS environments. A case study of coalbed methane 3D modeling in the Qinshui Basin demonstrates the applicability of this methodology, with quantitative validation against 189 borehole measurements showing high geometric accuracy (RMSE = 0.0936&#xa0;m), pointing to its potential for broader applications in digital twins, urban planning, and natural resource management.</p>