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Title: (Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California)

Abstract

Our studies involved petrographic, fluid inclusion, geochemical and stable isotopic studies of drillcores and fluids from the Salton Sea geothermal system. Our initial studies revealed the presence of previously-unrecognized evaporitic anhydrite at depth throughout the geothermal system. The high salinity of the Salton Sea geothermal brines previously had been attributed to low-temperature dissolution of surficial evaporitic deposits by meteoric waters. Our microthermometric studies of halite--containing fluid inclusions in the meta-evaporites indicated that the high salinity of the geothermal brines is derived in part from the hydrothermal metamorphism of relatively deeply-buried salt and evaporites. In addition, our research concentrated on mineralized fractures in drillcores.

Authors:
Publication Date:
Research Org.:
California Univ., Riverside, CA (USA). Inst. of Geophysics and Planetary Physics
Sponsoring Org.:
DOE/ER
OSTI Identifier:
6993946
Report Number(s):
DOE/ER/13408-1; UCR/IGPP-88/27
ON: DE90012891
DOE Contract Number:
FG03-85ER13408
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; 58 GEOSCIENCES; SALTON SEA GEOTHERMAL FIELD; GEOCHEMISTRY; ANHYDRITE; BRINES; CALIFORNIA; CHEMICAL ANALYSIS; CHEMICAL COMPOSITION; DRILL CORES; GEOTHERMAL FLUIDS; GEOTHERMAL WELLS; HYDROTHERMAL SYSTEMS; ISOTOPE RATIO; PROGRESS REPORT; ROCK-FLUID INTERACTIONS; ALKALINE EARTH METAL COMPOUNDS; CALCIUM COMPOUNDS; CALCIUM SULFATES; CHEMISTRY; DOCUMENT TYPES; ENERGY SYSTEMS; FEDERAL REGION IX; FLUIDS; GEOTHERMAL FIELDS; GEOTHERMAL SYSTEMS; MINERALS; NORTH AMERICA; OXYGEN COMPOUNDS; SULFATE MINERALS; SULFATES; SULFUR COMPOUNDS; USA; WELLS; Geothermal Legacy; 152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions; 580000 - Geosciences

Citation Formats

McKibben, M.A. (Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California). United States: N. p., 1988. Web. doi:10.2172/6993946.
McKibben, M.A. (Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California). United States. doi:10.2172/6993946.
McKibben, M.A. Wed . "(Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California)". United States. doi:10.2172/6993946. https://www.osti.gov/servlets/purl/6993946.
@article{osti_6993946,
title = {(Sulfide-oxide-silicate phase equilibria and associated fluid inclusion properties in the Salton Sea geothermal system, California)},
author = {McKibben, M.A.},
abstractNote = {Our studies involved petrographic, fluid inclusion, geochemical and stable isotopic studies of drillcores and fluids from the Salton Sea geothermal system. Our initial studies revealed the presence of previously-unrecognized evaporitic anhydrite at depth throughout the geothermal system. The high salinity of the Salton Sea geothermal brines previously had been attributed to low-temperature dissolution of surficial evaporitic deposits by meteoric waters. Our microthermometric studies of halite--containing fluid inclusions in the meta-evaporites indicated that the high salinity of the geothermal brines is derived in part from the hydrothermal metamorphism of relatively deeply-buried salt and evaporites. In addition, our research concentrated on mineralized fractures in drillcores.},
doi = {10.2172/6993946},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jun 01 00:00:00 EDT 1988},
month = {Wed Jun 01 00:00:00 EDT 1988}
}

Technical Report:

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  • The Salton Sea geothermal system (SSGS) occurs in Plio-Pleistocene deltaic-lacustrine-evaporite sediments deposited in the Salton Trough, an active continental rift zone. Temperatures up to 365{degree}C and hypersaline brines with up to 26 wt.% TDS are encountered at 1-3 km depth in the sediments, which are undergoing active greenschist facies hydrothermal metamorphism. Previous models for the origins of the Na-Ca-K-Cl brines have assumed that the high salinities were derived mainly from the downward percolation of cold, dense brines formed by low-temperature dissolution of shallow non-marine evaporites. New drillcores from the central part of the geothermal field contain metamorphosed, bedded evaporites atmore » 1 km depth consisting largely of hornfelsic anhydrite interbedded with anhydrite-cemented solution-collapse shale breccias. Fluid inclusions trapped within the bedded and breccia-cementing anhydrite homogenize at 300{degree}C and contain saline Na-Ca-K-Cl brines. Some of the inclusions contain up to 50 vol.% halite, sylvite and carbonate crystals at room temperature, and some halite crystals persist to above 300{degree}C upon laboratory heating. The data are consistent with the trapping of halite-saturated Na-Ca-K-Cl fluids during hydrothermal metamorphism of the evaporites and accompanying solution collapse of interbedded shales. The authors conclude that many of the slat crystals in inclusions are the residuum of bedded evaporitic salt that was dissolved during metamorphism by heated connate fluids.« less
  • In situ fluid sampling activities were conducted at the Salton Sea Scientific Drilling Project (SSSDP) well during late December 1985 and late March 1986 to obtain unflashed samples of Salton Sea brine. In late December, three sampling runs were made to depths of approximately 1800 m and temperatures of 300/sup 0/C. In late March, 10 sampling runs were made to depths of approximately 3150 m and temperatures of 350/sup 0/C. In brief, the Los Alamos tool obtained samples from four of eight runs; the Lawrence Berkeley tool obtained samples from one of one run; the Leutert Instruments, Inc., tool obtainedmore » samples from zero of three runs; and the USGS quartz crystal experiment was lost in the well. The most complete sample was obtained from run No. 11, using the Los Alamos sampler and Sandia battery pack/controller on a wireline. About 1635 ml of brine, two noble gas samples, and two bulk gas samples were collected from this run. Samples of brine and gas from productive runs have been distributed to about 15 researchers for various types of analyses. Chemical analyses by the Los Alamos and US Geological Survey analytical teams are presented in this report, although they are not corrected for flashing and precipitation.« less
  • A detailed study of wireline logs from 11 wells in the Salton Sea and Westmorland geothermal systems was undertaken in order to determine the effects of hydrothermal alteration on the response of electrical and gamma-gamma density well logs. For the Salton Sea geothermal field, definite correspondence between log responses and hydrothermal mineralogy is evident, which in turn is related to the physical properties of the rocks. Three hydrothermal and one unaltered zone can be identified from log data on shales. These are: (1) the unaltered montmorillonite zone (<100/sup 0/ to 190/sup 0/C); (2) the illite zone (100/sup 0/ to 190/supmore » 0/C to 230/sup 0/ to 250/sup 0/C); (3) the chlorite zone (230/sup 0/ to 250/sup 0/C to 290/sup 0/ to 300/sup 0/C); and (4) the feldspar zone (>290/sup 0/ to 300/sup 0/C). The characteristic responses on well logs by which these zones are identified result primarily from changes in clay mineralogy of the shales and increases in density with progressive hydrothermal metamorphism. In the Westmorland geothermal field, differentiating mineral zones from log responses was only partially successful. However, analyses of both well log and petrologic data for wells Landers 1 and Kalin Farms 1 suggest that the former is heating up and the latter is cooling.« less
  • A Demonstration Reaction Clarifier - Gravity Filtration System with a 1600 GPM throughput capability was in operation at the joint DOE-SDG and E-MAGMA test facility located in the Salton Sea Geothermal Field, southern California, during the summer of 1979. The system, which was designed to condition spent effluent from a 10 MWe-size geothermal power plant, removes supersaturated dissolved species and residual suspended solids from brine prior to subsurface brine disposal via injection wells. The post-processing chemical stability of conditioned effluents was established by means of anaerobic incubation tests at 90/sup 0/C. The effect of residual dissolved polymer, that might bemore » used for the purpose of scale control in upstream power plant components on the efficiency of reaction clarification, was also evaluated. Membrane filtration and core tests were used to assess the injectability of processed brine. It was found that the clarifier-filter operational procedures and system design permitted oxygenation of the brine by air intrusion. This resulted in partial stabilization of dissolved silica and precipitation of oxides of iron. As a consequence, conditioned brine injectability was poor. However, elimination of the air intrusion problem would result in a substantial improvement in brine quality. Residual amounts of dissolved polyaminoethylene (20 ppm, by weight), a powerful antisilica precipitant, in brine was shown by means of bench-scale tests carried out at approx. 90/sup 0/C to improve the efficiency of the clarification process where the additive appears to function as a flocculant.« less
  • Two brine production methods were compared with respect to available power at the wellhead: self flowing (brine lifted by steam from vaporization of the brine), and pumped (brine lifted by a mechanical pump and kept in the liquid state). Five conversion processes were compared with respect to fraction of available power converted to electric power: flash steam (steam turbines operating on steam from flash vaporization of the brine), dual steam (flash steam with two-phase expanders to recover the flash vaporization mechanical energy), total flow (two-phase expanders only), binary (heat transferred from the brine to a secondary working fluid), and flashmore » binary (heat transferred from flashed steam to a secondary working fluid). The conclusions of this study are: (1) The flow rate from a self-flowing well can be substantially increased by increasing well bore diameter at and above the flashing level. (2) Self-flowing stepped diameter wells provide more wellhead power than pumped wells (for equal production zone diameters) at nearly all reservoir conditions. (3) Multi-stage flash steam systems using steam turbines provide more output power than binary systems at all reservoir temperatures, using reasonable values for component performance. (4) Total flow machines, used alone, offer no performance advantage as compared to multi-stage direct flash steam, unless efficiency of total flow devices can be increased above current projections. (5) Two-phase expanders in combination with steam turbines provide the highest output power.« less