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U.S. Department of Energy
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Clay-mineral fabrics and chemistry in Salton Trough geothermal fields

Conference ·
OSTI ID:5372635
Fluid production from, and hence the economic viability of, a geothermal field is related to the amount of clay minerals in the caprock and in the reservoir rocks. In both the East Mesa and Cerro Prieto fields in the Salton Trough of southern California, United States, and Baja California, Mexico, scanning electron micrography (SEM) has vividly documented the role of clay fabrics in deltaic quartz-sandstone reservoirs. For example, in East Mesa well 78-30 at 1630 m depth in a zone of quartz dissolution, the clay present in pores exhibits an irregular, crenulate, honeycomb fabric and has the following composition from energy dispersive x-ray analysis (EDAX): Si 61%, Al 25%, Fe 20%, Na 6%, K 2%, and Mg 1%. Platy clusters of clay (kaolinite) in Cerro Prieto well T-366 at 2522 m in a 300/sup 0/C geothermal aquifer were analyzed as: Si 62%, Al 25%, Mg 6%, and Fe 1%. In other samples, illite takes the form of wispy fibers whose intertwined ends form bridges across pores. These clay fabrics appear to reduce permeability significantly by clogging the pore throats, even though dissolution porosity ranges from 25 to 35%. Nineteen wells have been studied to date.
Research Organization:
Lawrence Berkeley Lab., CA (USA); Terra Tek, Inc., Salt Lake City, UT (USA)
DOE Contract Number:
W-7405-ENG-48
OSTI ID:
5372635
Report Number(s):
LBL-12348; CONF-8010260-1; ON: DE82008925
Country of Publication:
United States
Language:
English