Through May of 1993, a sequence of reservoir flow tests has been conducted at our Fenton Hill Hot Dry Rock (HDR) test site as part of the Long-Term Flow Testing (LTFT) program. This testing, which extended over an aggregate period of about 8 months, has demonstrated several significant features concerning HDR reservoirs that taken together reflect very positively on the future development of the HDR concept into a viable commercial reality. Of most significance is the demonstrated self-regulating nature of the flow through such a reservoir. Both temperature and tracer data indicate that the flow, rather than concentrating in a few potential direct flow paths, progressively shifted towards more indirect flow paths as the test proceeded. This self-regulating mechanism may be related to the strongly temperature-dependent viscosity of water. Measurements have shown that the reservoir flow impedance is concentrated in the near-wellbore region surrounding the production well. This situation may well be a blessing in disguise since this suggests that the distance between injection and production wells can be significantly increased, with a greatly enhanced access to fractured hot rock, without an undue impedance penalty. However, since the multiply interconnected joints within the HDR reservoir are held open by fluid pressure (pressurepropping), a higher mean reservoir pressure is the obvious path to increased productivity while still retaining the distributed nature of the flow. Other significant observations include a very small rate of reservoir water loss that was still declining at the end of the flow testing, and a set of temperature measurements in the production well that show no significant temperature drawdown during the period of testing.

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

Copyright 1994, 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.