Unconventional energy resources are being intensely researched given the pivoting global attention towards sustainable energy, energy transitioning, and NETZERO. In this regard, repurposing the Abandoned Oil and Gas Wells, AOGWs seems to be a panacea for untapping the huge potential of subsurface geothermal energy. However, the extraction of geothermal energy from the AOWGs will require a comprehensive understanding of the subsurface characteristics of the Porous Sedimentary Oil Reservoir, PSOR, formations. Incidentally, estimation of the geothermal potential of AOGWs will particularly depend on developing a representative computational model that can integrate the effect of spatial heterogeneity of the PSOR into it. Hence, a methodology has been proposed, to determine the geothermal potential of a PSOR by using the processed well-log data of an onshore oil reservoir in the Upper Assam Shelf Basin, India. The basic log data, including bulk density, effective porosity, the volume fraction of the minerals, and the saturation of the pore fluids, have been used to estimate the thermal properties of the PSOR. Further, PETREL® has been employed for spatial extrapolation of all the fundamental thermo-hydro-petrophysical characteristics of the PSOR by using the geostatistical analysis.