Intersecting faults and sandstone stratigraphy at the Cerro Prieto geothermal field

Conference · Fri Feb 01 04:00:00 EST 1980

OSTI ID:5226832

Vonder Haar, S; Howard, J H

The northwest-southeast trending Cerro Prieto fault is part of a major regional lineament that extends into Sonaro and has characteristics of both a wrench fault and an oceanic transform fault. The distribution of lithologies and temperature within the field was studied by comparing data from well cuttings, cores, well logs, and geochemical analyses. Across the earliest developed portion of the field, in particular along a 1.25-km northeast-southwest section from well M-9 to M-10, interesting correlations emerge that indicate a relationship among lithology, microfracturing, and temperature distribution. In the upper portion of Reservoir A of this stratigraphic section, between 1200 and 1400 m, the percentage of sandstones ranges from 20 to 55. Temperatures are 225/sup 0/ to 275/sup 0/C based on well logs, calcite isotope maxima, and Na-K-Ca indices. The study shows that an isothermal high in this vicinity corresponds to the lowest total percentage of sandstones. Scanning electron microphotographs of well cores and cuttings from sandstone and shale units reveal clogging, mineral dissolution, and mineral precipitation along microfractures. The working hypothesis is that these sandy shale and siltstone facies are most amenable to increased microfracturing and, in turn, such microfracturing allows for higher temperature fluid to rise to shallower depths in the reservoir.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5226832
• Report Number(s): LBL-9546; CONF-7910166-11
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150202* -- Geology & Hydrology of Geothermal Systems-- Non-USA-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATES
CERRO PRIETO GEOTHERMAL FIELD
DRILL CORES
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
GEOLOGY
GEOTHERMAL FIELDS
Geothermal Legacy
LITHOLOGY
OXYGEN COMPOUNDS
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SHALES
STRATIGRAPHY
TEMPERATURE DISTRIBUTION