Rock Sampling

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Exploration Technique: Rock Sampling

Exploration Technique Information
Exploration Group: Field Techniques
Exploration Sub Group: Field Sampling
Parent Exploration Technique: Field Sampling
Information Provided by Technique
Lithology: Rock samples are used to define lithology. Field and lab analyses can be used to measure the chemical and isotopic constituents of rock samples.
Stratigraphic/Structural: Provides information about the time and environment which formed a particular geologic unit. Microscopic rock textures can be used to estimate the history of stress and strain, and/or faulting.
Hydrological: Isotope geochemistry can reveal fluid circulation of a geothermal system.
Thermal: Thermal conductivity of a rock sample can provide information to calculate heat flow. Hydrothermal alteration of a rock sample can indicate certain temperature or fluid compositions.
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Rock Sampling:
Systematic rock sampling can be used to characterize a geothermal reservoir. The physical and chemical properties of rock samples provide important information for determining whether a power generation or heat utilization facility can be developed. Some general rock properties can be measured by visual inspection, but detailed properties require laboratory techniques.
Other definitions:Wikipedia Reegle


 
Introduction
A rock sample belongs to a greater geologic formation, which likely has published information discussing its origin and evolution. Rock sampling is a cheap and effective way to characterize many important properties of a geothermal resource. Rock properties define a geothermal resource and are the most important factors which can yield a power generation or heat utilization facility. Rock properties determine temperature, volume, and chemistry of the fluids able to be produced, the heat source, fluid recharge, and the depth of the potential reservoir. There are dozens of techniques that can be done to measure physical and chemical properties of a single rock sample, as well as the hydrological and thermal environment of where a rock came from.
 
Use in Geothermal Exploration
A single rock sample is used to characterize a section of a well or formation, while a collection of rock samples can be used to determine if there is sufficient reservoir properties to sustain a power generation or heat utilization facility. Drilling wells and collecting drill cores is a common way to identify where a possible geothermal reservoir resides. Comprehensive characterization of a reservoir requires detailed knowledge and analysis of the rock samples collected from a well. Typically the most critical information gathered are physical properties such as; porosity, permeability, and thermal conductivity. However, there are other more detailed techniques that can reveal chemical composition, fluid circulation, temperature, etc.


 
Field Procedures
Subsurface Sampling A rock sample for geothermal exploration is typically collected from a drilled well, and initial analysis of the rock type, mineralization, composition, textures, etc. are collected in the field at the drill site or from core and cutting samples that have since been stored in a repository. However, the more in depth rock properties often require laboratory tools.

Surface Sampling
There are rock samples that can be collected on the surface, in outcrop, which may reveal important information about the geothermal resource at depth. These hand samples can be collected using a rock hammer or sledge.



 
Data Access and Acquisition
Under a detailed investigation, a systematic sampling procedure is often developed. Much of this will depend on where the wells are drilled or if there are surface manifestations present. When exploring a geothermal resource the rock samples can come from above and below the target reservoir, but the most valuable and critical samples are from the reservoir itself. There are geostatistical techniques which can be very useful for characterizing the occurrence of fractures or other specific rock properties (Babadagli & Develi, 2000; Marche, et al., 2002; Fabbri, 1997). Once a rock sample has been collected there are various procedures that can be done to measure the fluid circulation, chemical composition, porosity, permeability, thermal conductivity, formation temperature, etc.







Page Area Activity Start Date Activity End Date Reference Material
Rock Sampling At Blue Mountain Geothermal Area (U.S. Geological Survey, 2012) Blue Mountain Geothermal Area 2008 2009


Rock Sampling At Chena Geothermal Area (Kolker, 2008) Chena Geothermal Area 1973 1974


Rock Sampling At Coso Geothermal Area (1995) Coso Geothermal Area 1995 1995


Rock Sampling At Florida Mountains Area (Brookins, 1982) Florida Mountains Area


Rock Sampling At Jemez Mountain Area (Eichelberger & Koch, 1979) Jemez Mountain Area


Rock Sampling At Long Valley Caldera Geothermal Area (Goff, Et Al., 1991) Long Valley Caldera Geothermal Area 1985 1986


Rock Sampling At Mt Ranier Area (Frank, 1995) Mt Ranier Area


Rock Sampling At Neal Hot Springs Geothermal Area (Colwell, Et Al., 2012) Neal Hot Springs Geothermal Area 2011 2011


Rock Sampling At Roosevelt Hot Springs Geothermal Area (Faulder, 1991) Roosevelt Hot Springs Geothermal Area 1977 1977


Rock Sampling At Roosevelt Hot Springs Geothermal Area (Ward, Et Al., 1978) Roosevelt Hot Springs Geothermal Area 1978 1978


Rock Sampling At San Francisco Volcanic Field Area (Warpinski, Et Al., 2004) San Francisco Volcanic Field Area


Rock Sampling At San Juan Volcanic Field Area (Larson & Jr, 1986) San Juan Volcanic Field Area


Rock Sampling At Seven Mile Hole Area (Larson, Et Al., 2009) Seven Mile Hole Area


Rock Sampling At Socorro Mountain Area (Armstrong, Et Al., 1995) Socorro Mountain Area


Rock Sampling At The Needles Area (Kratt, Et Al., 2005) The Needles Area


Rock Sampling At U.S. West Region (Krohn, Et Al., 1993) U.S. West Region


Rock Sampling At Yellowstone Region (Hellman & Ramsey, 2004) Yellowstone Caldera Geothermal Region


Rock Sampling At Zuni Mountains Nm Area (Brookins, 1982) Zuni Mountains Nm Area


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