Predicting Thermal Breakthrough from Tracer Tests: Simulations and Observations in a Low-Temperature Field Laboratory

Abstract

Inert and adsorbing tracer tests were conducted in a 10 x 10 meter five-spot well pattern to ascertain parameters required to predict thermal breakthrough from computer simulations. These predictions were then compared to observed thermal breakthrough of hot water injected into a cold reservoir. The field site, referred to as “Altona Flat Rocks”, is not a geothermal reservoir but was developed as an inexpensive, well characterized field laboratory in fractured rock for testing reservoir characterization methods relevant to geothermal fields. Thermal breakthrough was predicted, a priori, based on the fracture surface area swept determined by both the sorbing tracer breakthrough and by interpretation of the conservative tracer. Heat transfer surface area predictions based on the sorbing tracer test interpretation correlated reasonably well with observed thermal breakthrough in the field whereas surface areas derived from conservative tracer measurements were generally worse.