Experimental and Finite Element Analysis of the Stanford Hydrothermal Reservoir Model

Abstract

Initial results are available from the first experiment to calibrate the heat extraction history of a physically simulated fractured hydrothermal reservoir using a rock loading of large, regular-shaped granite blocks. Thermocouples embedded in a set of the rock blocks and in water at various locations in the model provide heat extraction data. The data are also used to evaluate the effects of thermal stressing on heat transfer properties.

The results of the first experiment show a surprisingly uniform cross-sectional water temperature throughout the physical model indicating effective cross mixing between fracture channels. The temperature difference between rock centers and surrounding fluid reached lOOOF during the cooling process, decreasing to smaller values by the end of the experiment, indicating that the rock energy extraction was relatively complete, with a high, constant temperature of the produced water.

For analysis of this and future experiments, a finite element method has been developed so that individual blocks can be represented as single elements. This approach allows less restraints on element shapes compared to finite difference models and provides possible application to full size reservoirs.