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Title: Thermal and petrologic constraints on lower crustal melt accumulation under the Salton Sea Geothermal Field

Authors:
; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G)
OSTI Identifier:
1416608
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Earth and Planetary Science Letters
Additional Journal Information:
Journal Volume: 467; Journal Issue: C; Related Information: CHORUS Timestamp: 2018-01-11 07:48:34; Journal ID: ISSN 0012-821X
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Karakas, Ozge, Dufek, Josef, Mangan, Margaret T., Wright, Heather M., and Bachmann, Olivier. Thermal and petrologic constraints on lower crustal melt accumulation under the Salton Sea Geothermal Field. Netherlands: N. p., 2017. Web. doi:10.1016/j.epsl.2017.02.027.
Karakas, Ozge, Dufek, Josef, Mangan, Margaret T., Wright, Heather M., & Bachmann, Olivier. Thermal and petrologic constraints on lower crustal melt accumulation under the Salton Sea Geothermal Field. Netherlands. doi:10.1016/j.epsl.2017.02.027.
Karakas, Ozge, Dufek, Josef, Mangan, Margaret T., Wright, Heather M., and Bachmann, Olivier. 2017. "Thermal and petrologic constraints on lower crustal melt accumulation under the Salton Sea Geothermal Field". Netherlands. doi:10.1016/j.epsl.2017.02.027.
@article{osti_1416608,
title = {Thermal and petrologic constraints on lower crustal melt accumulation under the Salton Sea Geothermal Field},
author = {Karakas, Ozge and Dufek, Josef and Mangan, Margaret T. and Wright, Heather M. and Bachmann, Olivier},
abstractNote = {},
doi = {10.1016/j.epsl.2017.02.027},
journal = {Earth and Planetary Science Letters},
number = C,
volume = 467,
place = {Netherlands},
year = 2017,
month = 6
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on March 30, 2018
Publisher's Accepted Manuscript

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  • The Salton Sea Geothermal Field is the largest water-dominated geothermal field in the Salton Trough in Southern California. Within the trough, local zones of extension among active right-stepping right-lateral strike-slip faults allow mantle-derived magmas to intrude the sedimentary sequence. The intrusions serves as heat sources to drive hydrothermal systems. We can characterize the field in detail because we have an extensive geological and geophysical data base. The sediments are relatively undeformed and can be divided into three categories as a function of depth: (1) low-permeability cap rock, (2) upper reservoir rocks consisting of sandstones, siltstones, and shales that were subjectmore » to minor alterations, and (3) lower reservoir rocks that were extensively altered. Because of the alteration, intergranular porosity and permeability are reduced with depth. permeability is enhanced by renewable fractures, i.e., fractures that can be reactivated by faulting or natural hydraulic fracturing subsequent to being sealed by mineral deposition. In the central portion of the field, temperature gradients are high near the surface and lower below 700 m. Surface gradients in this elliptically shaped region are fairly constant and define a thermal cap, which does not necessarily correspond to the lithologic cap. At the margin of the field, a narrow transition region, with a low near-surface gradient and an increasing gradient at greater depths, separates the high temperature resource from areas of normal regional gradient. Geophysical and geochemical evidence suggest that vertical convective motion in the reservoir beneath the thermal cap is confined to small units, and small-scale convection is superimposed on large-scale lateral flow of pore fluid. Interpretation of magnetic, resistivity, and gravity anomalies help to establish the relationship between the inferred heat source, the hydrothermal system, and the observed alteration patterns. A simple hydrothermal model is supported by interpreting the combined geological, geophysical, and thermal data. In the model, heat is transferred from an area of intrusion by lateral spreading of hot water in a reservoir beneath an impermeable cap rock.« less
  • Naturally occurring U and Th series radionuclides have been analyzed in high temperature brines ({approximately} 300{degree}C, 25 wt% dissolved solids) and associated rocks from two deep geothermal wells located on the northeastern margin of the Salton Sea Geothermal Field (SSGF). These data are part of a study of the SSGF as a natural analog of possible radionuclide behavior near a nuclear waste repository constructed in salt beds, and permit evaluation of some characteristics of water-rock interaction in the SSGF.
  • Using empirical matched field processing (MFP), we compare 4 yr of continuous seismic data to a set of 195 master templates from within an active geothermal field and identify over 140 per cent more events than were identified using traditional detection and location techniques alone. In managed underground reservoirs, a substantial fraction of seismic events can be excluded from the official catalogue due to an inability to clearly identify seismic-phase onsets. Empirical MFP can improve the effectiveness of current seismic detection and location methodologies by using conventionally located events with higher signal-to-noise ratios as master events to define wavefield templatesmore » that could then be used to map normally discarded indistinct seismicity. Since MFP does not require picking, it can be carried out automatically and rapidly once suitable templates are defined. In this application, we extend MFP by constructing local-distance empirical master templates using Southern California Earthquake Data Center archived waveform data of events originating within the Salton Sea Geothermal Field. We compare the empirical templates to continuous seismic data collected between 1 January 2008 and 31 December 2011. The empirical MFP method successfully identifies 6249 additional events, while the original catalogue reported 4352 events. The majority of these new events are lower-magnitude events with magnitudes between M0.2–M0.8. Here, the increased spatial-temporal resolution of the microseismicity map within the geothermal field illustrates how empirical MFP, when combined with conventional methods, can significantly improve seismic network detection capabilities, which can aid in long-term sustainability and monitoring of managed underground reservoirs.« less
  • A pilot-size brine handling system was operated from Magmamax Well 1 in southern California to study the characteristics of siliceous scale deposition and to evaluate the possibility of treating the brine with chemical additives to control scaling. The rates of formation, chemical constitution, and morphology of the scales were examined as functions of temperature, brine salinity, substrate material, and antiscalant additive activity. The most active classes of compounds were those containing polymeric chains of oxyethylene and polymeric nitrogen compounds that are cationic in character. The best single compound was Corcat P-18. 30 refs.