Investigation of analogy between thermal and electrical properties of some reservoir rocks

Although there is an analogy between electrical and thermal conductivities, rock electrical parameters are mostly related to the pore system, whereas thermophysical properties mostly affected by the solid part. It seems that using the mentioned analogy and simultaneous consideration of the electrical and thermophysical properties lead to a better description of the rocks. In this paper, a solid part of rock was considered as a bundle of cylindrical rods. The formation thermal factor (FT) was defined as a parameter based on thermal conductivities of evacuated rock and its solid part and using the analogy with the definition of formation resistivity factor (FR). Also, a combination of electrical and thermophysical properties was used to describe rock permeability. Two datasets of dolomite and sandstone were used to confirm the analogy between FT and FR. Results revealed that there is a power relation between FT and rock solidity similar to the power relationship between FR and porosity, i.e., Archie’s equation. Determination coefficients (R2) of FT versus solidity for sandstone and dolomite samples were 0.97 and 0.99, respectively. Furthermore, it was concluded that permeability and FR × FT have a power relationship with high R2 for sandstone (R2 = 0.92) and dolomite samples (R2 = 0.93). Moreover, the relationship between permeability and FR × FT was proven using the Kozeny-Carman model. Finally, the electrical quality index (EQI) and thermal quality index (TQI) were defined based on the analogy with reservoir quality index (RQI). It is believed that simultaneous consideration of RQI, EQI, TQI, FR × FT , and their correlations with well-log data lead to a more accurate characterization of the reservoir rock.