MATRIX-FRACTURE TRANSFER IN NON-ISOTHERMAL CONDITIONS
Abstract
A numerical and experimental study was carried out to investigate matrix-fracture transfer in fractured porous media. Film type heat flux sensors were installed in four different synthetically fractured core plugs to measure the temperature and heat flux in fracture during cold water injection. Experimental values of heat flux were used to calculate convective heat transfer coefficient. Fracture temperatures were used to calibrate numerical model developed using CMG-STARS simulator to evaluate contributing matrix thermal properties. The results show that the temperature decrease in fracture is lower when rock matrix has higher thermal properties. The variations in heat flux and temperature difference along matrix-fracture interface with respect to time necessitates the use of variable convective heat transfer coefficients for accurate analysis of matrix-fracture heat transfer.
Moreover, results of tracer experiments where Rhodamine B solution was injected at a flow rate of 1 cc/min and outer temperature of 70 °C was used to determine
dispersion coefficients using aforementioned numerical model. Sensitivity analysis of the numerical model indicated that thermal properties of matrix are effective in matrix-fracture mass transfer similar to injection rate. To illustrate, the solute penetration is higher in core plugs with larger matrix thermal properties that provide larger temperature gradient over matrix-fracture interface. This can be explained by the Soret effect that is kind of coupled heat and mass transfer at non-isothermal conditions.
Keywords: Fractured porous media, Matrix-fracture transfers, Convective heat transfer coefficient, Numerical simulation of tracer testing, Coupled heat and mass transfers
