Selecting The Optimal Logging Suite For Geothermal Reservoir Evaluation- Results From The Alum 25-29 Well, Nevada

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Conference Paper: Selecting The Optimal Logging Suite For Geothermal Reservoir Evaluation- Results From The Alum 25-29 Well, Nevada

Abstract
This paper presents the results of analysis of a state of the art set of wireline petrophysical and wellbore image logs recorded in the Alum 25-29 well, southwestern Nevada. The Alum well penetrated nearly 2000 ft (610 m) of volcano-clastic rocks and more than 1000 ft of basement, separated from the sediments by a shallowly dipping detachment fault. The logs were acquired both to characterize the site and also to select the most effective set of logs to acquire in future wells. The results revealed that acoustic images are superior to electrical images to detect structurally important natural fractures and stress-induced wellbore breakouts and tensile wall fractures, and were adequate to detect stratigraphic features. Density, photo-electric factor (PEF), neutron, and gamma ray (GR) logs provided sufficient information to clearly delineate basement lithologic variations, suggesting that pulsed neutron logs may not in many cases be needed, and density and electrical resistivity data were important to calibrate structural models based on surface surveys. A crossed-dipole acoustic log detected stressinduced anisotropy in the sediments, and also appeared to be able to identify and orient steeply dipping, compliant and therefore possibly conductive fractures in basement rocks. Because the shear-wave velocity was extremely low throughout most of the sedimentary section dipole data was required for its determination. The analysis results, which included a stress determination based on an extended leakoff test to determine Shmin and observations of intermittent breakouts and tensile fractures, revealed a normalfaulting environment, with SHmax oriented in the strike direction of the fault and of the dipping sediments. Fluid flow appeared to be concentrated beneath the detachment within an interval in which some mud losses occurred while drilling, and shallow-reading resistivity logs recorded much lower values than deeper-reading logs suggesting that resistivity log separation may be useful to identify permeable zones.

Authors 
Daniel Moos and Joel Ronne








Published 
GRC, 2010





DOI 
Not Provided
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Citation

Daniel Moos,Joel Ronne. 2010. Selecting The Optimal Logging Suite For Geothermal Reservoir Evaluation- Results From The Alum 25-29 Well, Nevada. In: (!) ; (!) ; (!) . (!) : GRC; p. (!)