On the thermoporoelastic properties of fractured reservoir rocks

This paper presents both analytical and experimental studies on the properties of fractured reservoir rocks subject to thermoporoelastic effects. The analytical study focuses on identifying the thermoporoelastic effects near the wellbore during production. In the analysis, the thermal field is initially determined from the thermoelastic solution. The derived temperature is then cast into the fluid governing equations where explicit coupling between the fluid pressure and the temperature is expressed. The naturally-fractured reservoirs are represented by overlapping a porous and a fractured systems, or via a dual-porosity medium. The fluid and thermal interchange between the rock matrix and the fractures are conditioned by functions which are proportional to the respective pressure and thermal gradients. The objective of the subsequent experimental study is to determine the practical scales of some of the key thermoporoelastic parameters such as the fracture stiffness required as input to the given analytical model. Experimental determination of these factors depends on the sensitivity achieved in measuring thermal strains for both saturated or unsaturated rock samples subject to either thermal or fluid pressure loads, or both. The laboratory tests were performed on both intact rock samples and samples containing single vertical (radial) and horizontal fractures.