Fine-grained clay fraction (,0.2 {mu}m) [electronic resource] : An interesting tool to approach the present thermal and permeability state in active geothermal systems
- Published:
- Washington, D.C. : United States. Dept. of Energy, 1992. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Physical Description:
- 13-18 : digital, PDF file
- Additional Creators:
- United States. Department of Energy and United States. Department of Energy. Office of Scientific and Technical Information
- Access Online:
- www.osti.gov
- Summary:
- We have investigated by X-ray diffraction the very fine grained secondary minerals (< 0.2 {micro}m) developed in geothermal systems, in relation with their present thermal and permeability state. Because the smallest particles are the most reactive part of a rock, they are the youngest mineral phases of the geothermal fields. This study has been performed on two active geothermal fields: Milos field, Greece (130 < T < 320 C) and Chipilapa field, Salvador (90 < T < 215 C). In the Milos field, the mineralogical composition of the < 0.2 {micro}m clay fraction observed in the reservoir strongly differs from the overlying altered metamorphic schists in the presence of abundant quantities of saponite and talc/saponite interstratified minerals at unusually high temperature. These phases are considered to be kinetically control-led ''metastable'' minerals which rapidly evolve towards actinolite and talc for present temperatures higher than 300 C. Their occurrence is a good indicator of discharge in highly permeable zones. In the geothermal field of Chipilapa, the mineralogical composition of the < 0.2 {micro}m clay fractions fairly agrees with the temperatures presently measured in the wells, whereas several discrepancies may be pointed out from the compositions of coarser clay fractions (< 5 {micro}m) which contain minerals inherited from higher temperature stages. Permeable zones may be evidenced from an increase of expandable components in the interstratified minerals and a decrease of the coherent domain of the unexpandable clay particles (chlorite).
- Subject(s):
- Note:
- Published through SciTech Connect., 01/01/1992., "sgp-tr-141-3", Seventeenth Workshop on Geothermal Reservoir Engineering: Proceedings, Stanford University, Stanford, CA, January 29-31, 1992., Patrier, P.; Papapanagiotou, P.; Beaufort, D.; Traineau, H.; Bril, H., ERM-BP, Civaux, FR, Lab. Petrologie des Alterations Hydrothermales, Pointers Cedex, FR, IMRG-BRGM-BP, Orleans Cedex 2, FR, and Lab. Geologie, Univ. Limoges, Limoges, FR
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