Scientific core hole Valles caldera No. 2b (VC-2b), New Mexico

Conference · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5621984

Garner, J N; Hulen, J B; Lysne, P; Jacobson, R; Goff, F; Nielson, D L; Pisto, L; Criswell, C W; Gribble, R ^[1]; Alamo, Los

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1. Los Alamos National Lab., NM (USA)

Research core hole was continuously cored to 1.762 km on the western flank of the caldera's resurgent dome in 1988. Bottom hole temperature is about 295{degree}C within Precambrian (1.5 Ga) quartz monzonite, deep within the liquid-dominated portions of the Sulphur Springs hydrothermal system. VC-2b may be the deepest, hottest, continuously cored hole in North America. Core recovery was 99.2%. The only major drilling problems encountered were when temperatures at the bit exceeded 225{degree}C below depths of about 1000 m. The result of these conditions was loss of viscosity and/or lubricity in the mud, apparently caused by breakdown of the high temperature polymers. Lithologies in caldera-fill indicate the drill site may be proximal to ignimbrite vents and that an intracaldera lake with temperatures approaching boiling formed soon after the caldera itself. Structural correlations between VC-2b and the 528-m-deep companion hole VC-2a indicate the earlier Toledo caldera (1.45 Ma; Otowi Member tuffs) and even older Lower Tuffs caldera experienced no structural resurgence similar to the 1.12 million year old Valles caldera. The hydrothermal system penetrated by these bores, consists of a shallow vapor-rich cap, which has evolved from an earlier 200{degree}C liquid-dominated system, overlying stacked, liquid-dominated zones up to about 300{degree}C. Geochemistry of mud returns collected during drilling suggests chloride-rich geothermal fluids were entering the bore and mixing with the drilling fluids in the fractured lower Paleozoic and Precambrian sections. 23 refs., 5 figs., 1 tab.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5621984
• Report Number(s): LA-UR-89-2025; CONF-891031--2; ON: DE89014316
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
BOREHOLES
CALDERAS
CAVITIES
DRILL CORES
ENERGY SYSTEMS
EVALUATION
FEDERAL REGION VI
FLUIDS
GEOLOGY
GEOPHYSICAL SURVEYS
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
Geothermal Legacy
HYDROTHERMAL SYSTEMS
NEW MEXICO
NORTH AMERICA
RESERVOIR TEMPERATURE
SURVEYS
TEMPERATURE MEASUREMENT
TEMPERATURE SURVEYS
USA
WELL TEMPERATURE