Numerical modeling on the sensitivity of directional dependent interface heat transfer on thermal transport in a coupled fracture-matrix system

Abstract

The conventional dual-porosity model has been modified by considering the heat exchange term at the fracture-matrix interface in the governing equation for thermal transport within the low permeable rock-matrix as against its conventional consideration within the high permeable fracture. A finite volume numerical model has been developed in order to analyze the influence of the source/sink term which defines the heat transfer at the fracturematrix interface. The comparison of the spatial distribution for temperature within the fracture and within the reservoir matrix for two different models, (1) conventional model in which the source/sink heat transfer term included in the equation for thermal transport within the fracture; (2) proposed model in which the source/sink heat transfer term included in the equation for thermal transport within the rock-matrix, have been performed. In addition, the sensitivity of the reservoir matrix thermal conductivities, both horizontal and vertical, on thermal energy extraction from the reservoir matrix has also been analyzed using the proposed model. Numerical results suggest that the estimation of temperature distribution in the fracture and rock-matrix and thus quantifying the heat extraction from the reservoir matrix is underestimated in a fracture-matrix system by using the conventional thermal transport model. It has been also observed that the temperature distribution obtained in the fracture and the rock-matrix by considering the heat transfer term in the thermal transport equation within the fracture shows significant variation from the temperature distribution obtained by considering the heat transfer term in the equation for thermal transport within the rock-matrix.