Results of the Flowmeter-Injection Test in the Long Valley Exploratory Well (Phase II), Long Valley, California

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Report: Results of the Flowmeter-Injection Test in the Long Valley Exploratory Well (Phase II), Long Valley, California

Abstract
The Long Valley Exploratory Well is being drilled in the Long Valley caldera in east-central California to investigate active magmatic intrusion processes. In an effort to obtain hydrologic information concerning deep hydrothermal circulation beneath the caldera floor, a flowmeter-injection test was performed in the well. The test was designed to determine the vertical distribution of hydraulic conductivity in the lowermost section of the borehole left uncased after completion of Phase-II drilling. Total depth of the well in May 1992 was 2,313 meters, with the lower 215 meters being open hole. A total of approximately 30,000 liters of water was injected into the well over22 hours while water levels in the inner Ocean Drilling Program drill pipe and the outer-casing annulus were independently monitored and measurements of vertical fluid flow were recorded as a function of depth. Flowmeter measurements obtained in the open hole indicate no detectable fluid movement, and volumetric calculations indicate that all of the water introduced into the well can be accounted for by the attendant increases in water levels. Temperature logs obtained immediately before and after injection support the hypothesis that injected fluid simply shunted the open hole directly below the Ocean Drilling Program drill pipe and subsequently filled the outer-casing annulus above. The low hydraulic conductivity of the open hole is also manifested in the chemical analysis of fluid samples that show no evidence of formation fluids in the well.The hydraulic conductivity of the lowermost section of the Long Valley Exploratory Well after Phase-II drilling proved to be too low to quantify accurately by means of the flowmeter-injection field technique. Hydraulic communication between fluid within the inner Ocean Drilling Program drill pipe and fluid filling the outer-casing annulus further complicated the situation and introduced additional uncertainties. Nevertheless, the field data and a record of falling water levels for 6 months enable the permeability of the open hole to be constrained. An upper bound on the permeability of the formation between 2,098 and 2,313 meters is estimated to be in the microdarcy range.

Authors 
Roger H. Morin, Michael L. Sorey and Ronald D. Jacobson








Published 
U.S. Geological Survey, 1993



Report Number 
Water Resources Investigations Report 93-4127


DOI 
Not Provided
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Online 
Internet link for Results of the Flowmeter-Injection Test in the Long Valley Exploratory Well (Phase II), Long Valley, California

Citation

Roger H. Morin,Michael L. Sorey,Ronald D. Jacobson. 1993. Results of the Flowmeter-Injection Test in the Long Valley Exploratory Well (Phase II), Long Valley, California. (!) : U.S. Geological Survey. Report No.: Water Resources Investigations Report 93-4127.


Related Geothermal Exploration Activities
Activities (1)


Areas (1)
  1. Long Valley Caldera Geothermal Area
Regions (0)