Core Holes At Long Valley Caldera Geothermal Area (Chu, Et Al., 1990)

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Exploration Activity: Core Holes At Long Valley Caldera Geothermal Area (Chu, Et Al., 1990)

Exploration Activity Details
Location Long Valley Caldera Geothermal Area
Exploration Technique Core Holes
Activity Date - 1989

Usefulness useful
DOE-funding Unknown

 
Exploration Basis
Phase I drilling of the LVEW (formerly known as the LVF 51-20 core hole) was completed on the Resurgent Dome in the summer of 1989 by Oxy Santa Fe and Unocal in cooperation with Sandia National Laboratories, as part of a DOE-funded project attempting to reach high predicted temperatures up to 500°C at about 6 km depth north of Casa Diablo.[1][2]
 
Notes
Temperature gradients measured in LVF 51-20 were 50°C /km following completion of the well, and indicate that recharge of cool meteoric water occurs within the upper 750 m of the Resurgent Dome. This well also provided high-quality lithologic and structural data within the Resurgent Dome, which were previously unavailable.[3] The measured thermal conductivity of core from well LVF 51-20 of 2.3 W/m°C was applied to a thermal gradient of 40°C /km in CP-1 to extrapolate a conductive heat flow estimate of 90 mW/m^2 for the Resurgent Dome.[4] This heat flow estimate is similar to the 120 mW/m^2 measured in the cored section of LVF 51-20.[4] These conductive heat flow measurements are somewhat lower than the values predicted to exist beneath the Resurgent Dome. At the time, a heat flow value of 250 mW/m^2 was expected under the hypotheses that a steady-state magma body exists beneath the center of the caldera at 5-8 km depth or that periodic reinjection of new magma into this magma chamber sustains the heat flow through the caldera. These results suggest either that a shallow magma body no longer exists below the caldera's Resurgent Dome, as was previously predicted, or that deep non-thermal groundwater circulation along extensional faults influences measured heat flow values in the overlying formations.

 
References

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Additional References
  1. John B. Rundle,Charles R. Carrigan,Harry C. Hardee,William C. Luth. 1986. Deep Drilling to the Magmatic Environment in Long Valley Caldera. EOS, Transactions American Geophysical Union. 67(21):490-491.
  2. T.Y. Chu,J.C. Dunn,John T. Finger,John B. Rundle,H.R. Westrich. 1990. The Magma Energy Program. Geothermal Resources Council Bulletin. 19(2):42-52.
  3. John T. Finger,John C. Eichelberger. 1990. The Magma Energy Exploratory Well. Geothermal Resources Council Bulletin. 19(2):36-41.
  4. 4.0 4.1 Heat Flow from DOE's Magma-energy Well at Long Valley, California [Abstract]