This paper discusses a simulation study of tracer and thermal transport in fractured geothermal reservoirs. The motivation was to explore the relationship between tracer returns and thermal breakthrough in production wells.

By employing the discrete fracture discretization method introduced by Karimi-Fard et al. (2003), we were able to run simulations with fracture grid blocks of realistic dimension. This enabled us to obtain relatively realistic models of tracer and thermal transport and investigate the sensitivity of the return profiles to various reservoir properties. Moreover, the visualization of changes in temperature, pressure and tracer concentration in the reservoir were useful to gain better insight into the behavior of these properties in the fractured systems.

The initial plan was to use the TOUGH2 code to do the simulations, but after running into a number of problems with the solver and time stepping it was decided to switch to the General Purpose Research Simulator (GPRS) developed at the Department of Energy Resources Engineering at Stanford University. The simulations were carried out using a two-dimensional thermal black-oil model, without gravity effects.

In short we found that a quantitative relationship between the tracer return profile and the thermal return profile is hard to formulate, even for relatively simple cases. The relationship will depend, for example, the flow rate through the fracture and the types of boundary conditions for the matrix surrounding the fracture. Moreover, the fracture distribution will be important, although in the case investigated here, the thermal profile was not as severely affected as anticipated.

Press the Back button in your browser, or search again.

Copyright 2010, Stanford Geothermal Program: Readers who download papers from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the original publisher.