Core Analysis

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Exploration Technique: Core Analysis

Exploration Technique Information
Exploration Group: Lab Analysis Techniques
Exploration Sub Group: Rock Lab Analysis
Parent Exploration Technique: Rock Lab Analysis
Information Provided by Technique
Lithology: Core analysis is done to define lithology.
Stratigraphic/Structural: Core analysis can locate faults or fracture networks.

Oriented core can give additional important information on anisotropy.

Hydrological:
Thermal: Thermal conductivity can be measured from core samples.
Cost Information
Low-End Estimate (USD): 2,000.00200,000 centUSD
2 kUSD
0.002 MUSD
2.0e-6 TUSD
/ 30 foot core
Median Estimate (USD): 10,000.001,000,000 centUSD
10 kUSD
0.01 MUSD
1.0e-5 TUSD
/ 30 foot core
High-End Estimate (USD): 25,000.002,500,000 centUSD
25 kUSD
0.025 MUSD
2.5e-5 TUSD
/ 30 foot core
Time Required
Low-End Estimate: 1 weeks0.0192 years
168 hours
7 days
0.23 months
/ job
Median Estimate: 4 weeks0.0767 years
672 hours
28 days
0.92 months
/ job
High-End Estimate: 8 weeks0.153 years
1,344 hours
56 days
1.84 months
/ job
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Core Analysis:
Core samples are obtained from drilling a well, typically using a synthetic diamond coated bit that has a hollow center so cylindrical rock samples (“core”) can be extracted. Core samples successfully recovered are visually inspected to determine rock type, mineralization, and fracture networks, then certain laboratory analyses may ensue to acquire detailed rock properties.
Other definitions:Wikipedia Reegle


 
Introduction
Core drilling is an exploration technique that has potential to identify the reservoir and determine where further drilling should take place. This drilling technique is also referred to as “slim-hole drilling.”[1] The actual rock analysis begins with identifying general characteristics of the sample, then select samples are sent to labs for a more detailed investigation. This is a very common exploration technique to identify or “prove” a geothermal resource and costs can range widely. Costs typically depend on drilling conditions and depth of the well.

A box of rock core samples obtained from a diamond core drilling rig. Photo from [1], contributed under GNU licensing on June 5, 2006.

 
Use in Geothermal Exploration
Core analysis is a standard technique that is a major aspect of defining the geothermal resource at depth. An abundance of information about the geothermal resource is gathered from core analysis, which has the potential to physically “prove” the amount of thermal energy a given resource is able to produce.
 
Related Techniques
Core analysis may include Differential Strain Curve Analysis (DSCA) and/or Anelastic Strain Analysis (ASR), in addition to the following techniques:



 
Physical Properties
In-situ stress magnitude and orientation.
 
Data Access and Acquisition
Drilling is conducted at a targeted location based on preliminary exploration techniques. The time it takes to complete a cored well depends on difficulty of drilling and depth of the well. A cored well cannot usually reach a depth much greater than 2.5 km.[1] Preliminary core analysis can either be done at the drill site by a geologist, or after the well has been drilled and the core has been transported to a laboratory or a repository. Other common analysis techniques are thin section, X-Ray diffraction, and/or scanning electron microscope.[2] The goal is to characterize the rock, both chemically and physically, to determine if the host rock has sufficient properties to sustain a geothermal power or heat utilization facility.

Typical Core Analysis Techniques:
Thin Section - Petrographic thin sections are very thin (~30 microns) slices of a rock mounted on a glass slide which can be viewed under a petrographic microscope to determine microscopic rock textures, mineral assemblages, provenance, porosity, and possibly reservoir quality.
X-Ray Diffraction (XRD) - This technique is used to quantitatively characterize the mineralogical composition of a rock sample. There are various XRD machines and techniques, but typically a rock sample is crushed into a fine powder which is packed and mounted onto a stage that is analyzed by X-rays. The X-ray detector captures this information which gets plotted onto a diffractogram where characteristic peaks can be identified as specific minerals.
Scanning Electron Microscope (SEM) - To investigate 3-D micro-morphology of a rock sample or fracture surface the SEM is a common technique to use. The SEM uses an electron beam to generate a 3-D image that can zoom from 20X to 20,000X (0.05 micron scale range). The SEM also provides semi-qualitative elemental composition of the material under investigation using an energy dispersive spectrometer (EDS).
Electrical Resistivity - Core samples can be used to generate electrical impedance maps which can provide details about the heterogeneity and petrographic controls on electrical properties.[3]
Ultrasonic compressional and shear velocities - Velocities are sensitive to rock type and porosity, but there are also other variables that can influence velocity, such as textural and mineralogical variations.[3]
Reflectance Spectroscopy - A portable Analytical Spectral Device (ASD) spectrometer can be a fast way to analyze core at the well site and determine the general mineral composition of logged core. This technique is not as robust as thin section, XRD, or SEM, but can be a valuable tool to rapidly characterize a core sample and identify which sections need a more detailed analysis.[2]












Page Area Activity Start Date Activity End Date Reference Material
Core Analysis At Alum Area (DOE GTP) Alum Geothermal Area


Core Analysis At Black Warrior Area (DOE GTP) Black Warrior Area


Core Analysis At Blue Mountain Geothermal Area (U.S. Geological Survey, 2009) Blue Mountain Geothermal Area 2008 2008


Core Analysis At Colrado Area (DOE GTP) Colado Geothermal Area


Core Analysis At Coso Geothermal Area (1979) Coso Geothermal Area 1979 1979


Core Analysis At Coso Geothermal Area (1980) Coso Geothermal Area 1980 1980


Core Analysis At Desert Peak Area (Laney, 2005) Desert Peak Area


Core Analysis At Dunes Geothermal Area (1976) Dunes Geothermal Area 1976 1976


Core Analysis At Fenton Hill HDR Geothermal Area (Brookins & Laughlin, 1983) Fenton Hill HDR Geothermal Area 1983


Core Analysis At Fenton Hill HDR Geothermal Area (Laughlin, Et Al., 1983) Fenton Hill HDR Geothermal Area 1983


Core Analysis At Fish Lake Valley Area (DOE GTP) Fish Lake Valley Area


Core Analysis At Flint Geothermal Area (DOE GTP) Flint Geothermal Area


Core Analysis At Fort Bliss Area (Combs, Et Al., 1999) Fort Bliss Area


Core Analysis At Fort Bliss Area (DOE GTP) Fort Bliss Area


Core Analysis At Gabbs Valley Area (DOE GTP) Gabbs Valley Area


Core Analysis At Geysers Area (Boitnott, 2003) Geysers Area


Core Analysis At Geysers Area (Lambert & Epstein, 1992) Geysers Area


Core Analysis At International Geothermal Area, Indonesia (Boitnott, 2003) International Geothermal Area Indonesia


Core Analysis At International Geothermal Area, Indonesia (Laney, 2005) International Geothermal Area Indonesia


Core Analysis At International Geothermal Area, Philippines (Laney, 2005) International Geothermal Area Philippines


Core Analysis At Jemez Mountain Area (Eichelberger & Koch, 1979) Jemez Mountain Area


Core Analysis At Kilauea East Rift Geothermal Area (Quane, Et Al., 2003) Kilauea East Rift Geothermal Area 1989 2000


Core Analysis At Kilauea Summit Area (Keller, Et Al., 1979) Kilauea Summit Area


Core Analysis At Lake City Hot Springs Area (Benoit Et Al., 2005) Lake City Hot Springs Area


Core Analysis At Long Valley Caldera Geothermal Area (Pribnow, Et Al., 2003) Long Valley Caldera Geothermal Area 2003


Core Analysis At Long Valley Caldera Geothermal Area (Smith & Suemnicht, 1991) Long Valley Caldera Geothermal Area 1985 1988


Core Analysis At Long Valley Caldera Geothermal Area (Sorey, Et Al., 1991) Long Valley Caldera Geothermal Area 1985 1988


Core Analysis At Mcgee Mountain Area (DOE GTP) Mcgee Mountain Area


Core Analysis At Medicine Lake Area (Clausen Et Al, 2006) Medicine Lake Area


Core Analysis At Newberry Caldera Area (Carothers, Et Al., 1987) Newberry Caldera Area


Core Analysis At Raft River Geothermal Area (1976) Raft River Geothermal Area 1976 1976


Core Analysis At Raft River Geothermal Area (1979) Raft River Geothermal Area 1979 1979


Core Analysis At Raft River Geothermal Area (1981) Raft River Geothermal Area 1981 1981


Core Analysis At Raft River Geothermal Area (2011) Raft River Geothermal Area 2011 2011


Core Analysis At Silver Peak Area (DOE GTP) Silver Peak Area


Core Analysis At Snake River Plain Region (DOE GTP) Snake River Plain Geothermal Region


Core Analysis At U.S. West Region (Laney, 2005) U.S. West Region


Core Analysis At Valles Caldera - Sulphur Springs Geothermal Area (Armstrong, Et Al., 1995) Valles Caldera - Sulphur Springs Geothermal Area 1988 1992


Core Analysis At Valles Caldera - Sulphur Springs Geothermal Area (Ito & Tanaka, 1995) Valles Caldera - Sulphur Springs Geothermal Area 1995


Core Analysis At Valles Caldera - Sulphur Springs Geothermal Area (Morgan, Et Al., 1996) Valles Caldera - Sulphur Springs Geothermal Area 1996


Core Analysis At Valles Caldera - Sulphur Springs Geothermal Area (WoldeGabriel & Goff, 1992) Valles Caldera - Sulphur Springs Geothermal Area 1992


Core Analysis At Yellowstone Region (Dobson, Et Al., 2003) Yellowstone Caldera Geothermal Region


Core Analysis At Yellowstone Region (Sturchio, Et Al., 1990) Yellowstone Caldera Geothermal Region


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