Geothermal chemistry activities at LASL. Progress report, January--December 1975
The nature of rock-fluid interactions in the LASL Hot Dry Rock Geothermal System is being studied using both new and standard hydrothermal systems. Permeability measurements using a newly developed technique to allow measurements at elevated temperature and pressure (up to 200/sup 0/C and 0.4 kb confining pressure) show GT-2 granite has a minimum in situ permeability of a few tenths of a microdarcy. Noncirculating systems, rocking vessels and static vessels are used to approximate the steady state reactions found in a slow moving geothermal system. Solutions in these systems approach steady state equilibrium in a matter of hours. Correlation of single mineral + solution reactions in static vessels have shown only slight agreement with existing PATHCALC modeling. New circulating systems are operating which allow recirulation of the working fluid. Felsic rocks (granitoid) are more reactive than crystallized mafic rocks (amphibolite) but less reactive than glassy mafic rocks (kileaua basalt). The sequence of mineral reactivity is quartz greater than feldspar much greater than mafic minerals for all solutions used. Solution composition reached a steady state in a few days in the temperature range 200/sup 0/C to 300/sup 0/C. Working fluids such as distilled water and San Antonio river water, once reacted, yielded a total solute inventory of at most 500 to 1000 ppM showing the dilute nature of these working fluids (i.e., they are not brines). Rock dissolution was enhanced compared to distilled water when using 0.1 N Na/sub 2/CO/sub 3/ as a working fluid. The preferential and prompt removal of quartz from the rock matrix in these experiments indicates Na/sub 2/CO/sub 3/ solutions may be used to decrease impedance in the geothermal well. Trace elements are being examined as possible tracers for dissolution of minerals.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 7138526
- Report Number(s):
- LA-6448-PR
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GRANITES
DISSOLUTION
PERMEABILITY
ROCK-FLUID INTERACTIONS
HOT-DRY-ROCK SYSTEMS
AQUEOUS SOLUTIONS
EQUILIBRIUM
HIGH PRESSURE
HIGH TEMPERATURE
MATHEMATICAL MODELS
ROCKS
TRACE AMOUNTS
DISPERSIONS
GEOTHERMAL SYSTEMS
IGNEOUS ROCKS
MIXTURES
SOLUTIONS
152002* - Geothermal Data & Theory- Properties of Minerals & Rocks
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