Petrography Analysis

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Exploration Technique: Petrography 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: Provides detailed information about rock composition and morphology
Stratigraphic/Structural:
Hydrological:
Thermal:
Cost Information
Low-End Estimate (USD): 275.0027,500 centUSD
0.275 kUSD
2.75e-4 MUSD
2.75e-7 TUSD
/ sample
Median Estimate (USD): 420.0042,000 centUSD
0.42 kUSD
4.2e-4 MUSD
4.2e-7 TUSD
/ sample
High-End Estimate (USD): 625.0062,500 centUSD
0.625 kUSD
6.25e-4 MUSD
6.25e-7 TUSD
/ sample
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Petrography Analysis:
Petrology is the study of rocks. A petrographic analysis is an in depth investigation of the chemical and physical features of a particular rock sample. A complete analysis should include macroscopic to microscopic investigations of the rock sample.
Other definitions:Wikipedia Reegle


 
Introduction
A petrographic analysis is critical when trying to learn about a rock, reservoir, or formation of interest. The scale of investigation depends on the importance of the particular sample of interest. To fully describe and characterize a rock takes varying stages of analysis beginning with an outcrop or hand sample.
 
Use in Geothermal Exploration
When investigating a geothermal resource the petrographic analysis plays a critical role in determining the resource potential. A petrographic analysis can be describing core samples from an exploration well, looking at thin sections of the reservoir or reservoir boundary, using a scanning electron microscope (SEM) to characterize the fracture surfaces from microstructures, doing X-ray diffraction (XRD) to identify exact mineral assemblages of a rock, or some other useful petrographic technique that can be used to identify the chemical or physical features of a specific rock. A well rounded investigation needs to account for both macroscopic and microscopic features.



 
Data Access and Acquisition
Data acquisition begins with a rock sample from outcrop, drill core, or cuttings. Once macroscopic details about the formation or rock sample have been determined by visually inspecting an outcrop or hand sample, a petrographic thin section is typically made to characterize the microscopic features. Thin sections are great for identifying the minerals present, porosity, inter-granualr volume (IGV), alteration, microstructures, and provenance. However, thin sections are only two dimensional, to get a three dimensional understanding of the micro-features a scanning electron microscope (SEM) is typically used. SEM’s can reveal micron scale surface features of a rock sample. One of the consequences of a rock interacting with an electron beam in an SEM is that characteristic X-rays are released, which can be measured to determine a relatively qualitative elemental composition of the specific grain being investigated. This process is called energy dispersive X-ray spectrometry, or EDS, and can be very helpful in providing basic elemental composition of a sample. To acquire quantitative bulk rock compositions XRD is a common technique. 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.






 
References


Page Area Activity Start Date Activity End Date Reference Material
Petrography Analysis At Fenton Hill HDR Geothermal Area (Laughlin, Et Al., 1983) Fenton Hill HDR Geothermal Area 1983


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


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


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


Petrography Analysis At Raft River Geothermal Area (1980) Raft River Geothermal Area 1980 1980


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


Petrography Analysis At Roosevelt Hot Springs Geothermal Area (Petersen, 1975) Roosevelt Hot Springs Geothermal Area 1975 1975


Petrography Analysis At U.S. West Region (Krohn, Et Al., 1993) U.S. West Region


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



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