Lab Analysis Techniques

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Exploration Technique: Lab Analysis Techniques

Exploration Technique Information
Exploration Group: Lab Analysis Techniques
Exploration Sub Group: None
Parent Exploration Technique: Exploration Techniques
Information Provided by Technique
Lithology: Water rock interaction; Rapid and unambiguous identification of unknown minerals; Bulk and trace element analysis of rocks, minerals, and sediments; Obtain detailed information about rock composition and morphology; Determine detailed information about rock composition and morphology; Cuttings are used to define lithology; Core analysis is done to define lithology
Stratigraphic/Structural: Anomalously high concentrations can indicate high permeability or conduit for fluid flow; Identify historic structure and deformation of land; Core analysis can locate faults or fracture networks.

Oriented core can give additional important information on anisotropy

Hydrological: Reconstructing the fluid circulation of a hydrothermal system; Field wide soil sampling can generate a geometrical approximation of fluid circulation; Determine origin of hydrothermal fluids; Calculate mixing ratios of hydrothermal fluids; Determine fluid composition at a point in time and space
Thermal: High mercury vapor concentration in soils can be indicative of active hydrothermal activity; Isotopic ratios can be used to characterize and locate subsurface thermal anomalies; Constrain the minimum temperature of fluid inclusion formation; certain elements exhibit high spatial correlation with high-temperature geothermal systems; Thermal conductivity can be measured from core samples
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Lab Analysis Techniques:
Lab Analysis Techniques encompass a broad array of analytical methods that can be used to characterize the chemical and physical properties of rock and fluid samples. The reliability of laboratory analyses depends strongly on both adherence to standard sampling procedures in the field when collecting materials for examination and on the application of appropriate sample preparation techniques in the lab.
Other definitions:Wikipedia Reegle


 
Introduction
Lab analyses of rock and fluid samples are crucial tools in geothermal exploration from the time of discovery of a resource through the production phase of reservoir development. Fluid lab analysis is routinely used for the characterization of liquid or gas samples, identification of contaminants, and to trace the migration of chemical species through reservoir systems. Fluid lab analysis encompasses several techniques, including isotopic analysis, major, trace element, and molecular analysis, and analysis of fluid inclusions trapped in hydrothermal minerals. Rock lab analyses are typically applied to surface samples or core recovered from wells in geothermal exploration. Analyses include measurement of the physical and chemical properties of rock samples. Physical properties include density, paleomagnetism, elastic modulus, seismic velocities, porosity and permeability. Chemical properties of rock samples are measured by XRF, XRD, and/or isotopic analyses. Application of these analyses is guided by petrographic analysis of rock samples, which provides valuable mineralogical and textural information regarding the alteration, mineralization, and deformation history of the hydrothermal system.

Researcher examining a sample on a petrographic microscope. Photo from the Sulzer Products & Services Website.

 
Use in Geothermal Exploration
Lab-based fluid analysis techniques are used throughout the lifetime of a geothermal project, from the early exploration stages through to monitoring of development wells. Fluid analysis provides data used for estimation of reservoir temperatures through various chemical and isotopic geothermometers, and allows investigators to use chemical and isotopic tracers to evaluate flow in hydrothermal systems. Gas analyses can also reveal information that can be used to distinguish the source of heat in a hydrothermal system (e.g. magmatic vs. deep subsurface conduits).

Analysis and interpretation of isotopic data in rock and fluid samples are critical techniques in geothermal exploration and resource evaluation. There are many different isotopes, but they all generally fall into two categories; radioactive or stable. Radioactive isotopes have known decay rates and half-lives, which are very useful for dating particular fluids or materials. Stable isotopes do not decay and are used to measure the ratios of the heavy isotope vs light isotope to reveal general conditions that would lead to enrichment of a particular isotope over another. There are many applications of isotope geochemistry, some which have been utilized for geothermal exploration. The uses of isotopic analysis include investigation of the thermal history of a reservoir, determination of the degree of water-rock interaction that has occurred in a system, and dating hydrothermal alteration minerals, to name a few.











 
References


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