A TRACER TEST USING ETHANOL AS A TWOPHASE TRACER AND 2NAPHTHALENE SULFONATE AS A LIQUIDPHASE TRACER

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A TRACER TEST USING ETHANOL AS A TWO-PHASE TRACER
AND 2-NAPHTHALENE SULFONATE AS A LIQUID-PHASE
TRACER AT THE COSO GEOTHERMAL FIELD

• Michael Mella1, Peter Rose1, Jess McCulloch2, and
  Cliff Buck2
• 1Energy and Geoscience Institute at the
  University of Utah
• 2Coso Operating Company, LLC
• GRC 2006
• SAN DIEGO

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Objective

• To evaluate the use of a novel two-phase tracer,
  ethanol, in combination with an established
  liquid-phase tracer, 2-naphthalene sulfonate to
  determine liquid-phase and vapor-phase flow
  patterns within a hot, fluid-depleted section of
  the Coso geothermal field

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Background of Alcohol Tracing in Geothermal
Reservoirs

• Adams and coworkers (1992-2005)
• Adams, M.C. (1995) Vapor, Liquid, and Two-Phase
  Tracers in Geothermal Reservoirs, Proc. World
  Geothermal Congress, pp. 1875-1880.
• Adams, M.C., Yamada, Y., Yagi, M., Kondo, T., and
  Wada, T. (2000) Solubility of Methanol,
  Propanol, and SF6 as High-Temperature Tracers,
  Proc. World Geothermal Congress, pp. 3015-3019.
• Adams, M.C., Yamada, Y., Yagi, M., Kasteler, C.,
  Kilbourn, P., and Dahdah, N. (2004), Alcohols as
  Two-Phase Tracers, Proceedings, Twenty-Ninth
  Workshop on Geothermal Reservoir Engineering,
  Stanford, California.
• Fukuda and coworkers (2000-2003) methanol,
  ethanol, isopropanol, and n-propanol
• Fukuda, D., Asanuma, M., Hishi, Y., Kotanaka, K.
  (2005), Alcohol Tracer Testing at the Matsukawa
  Vapor-Dominated Geothermal Field, Northeast
  Japan, Proceedings, Thirtieth Workshop on
  Geothermal Reservoir Engineering, Stanford
  University, SGP-TR-176.
• Mella and coworkers (2005) n-propanol
• Mella, M.J., Rose, P.E., Adams, M.C., Dahdah,
  N.F., McCulloch, J., Buck, C. (2006), The Use of
  n-Propanol at the Site of the Coso Engineered
  Geothermal System, Proceedings, Thirty-First
  Workshop on Geothermal Reservoir Engineering,
  Stanford University, SGP-TR-179.

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Analytical Approach

• SPME
• Gas chromatography

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SPME Method

• A syringe needle that is coated with an 85-µm
  thick layer of adsorbent Carboxen/PDMS is exposed
  to the head space of a liquid (brine or steam
  condensate) solution containing an alcohol,
  allowing the alcohol analyte to adsorb
  quantitatively onto the needle fiber.
• The syringe is used to inject the adsorbed
  alcohol into a gas chromatograph for analysis.
• The result is a reduction in the detection limit
  to approximately 1 ppb (a reduction below
  conventional methods by a factor of about 30)

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SPME Syringe in Place During Headspace Adsorption
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Gas Chromatogram Showing N-Propanol Response
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The Tracer Test

• 790 kg of denatured ethanol injected into Coso
  well 68-20 on January 8, 2006
• 100 kg of 2-naphthalene sulfonate injected into
  68-20 on January 13, 2006
• Neighboring production wells sampled over the
  subsequent months

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The Southwest Portion of the Coso Geothermal Field
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Returns of Liquid-Phase Tracer 2-Naphthalene
Sulfonate
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Returns of Two-Phase Tracer Ethanol
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Locations and Trajectories of Wells Showing
Liquid and Vapor Tracer Returns
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Ethanol and 2-NS Returns from 68-20
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Normalized Vapor- and Liquid-Phase Tracer Return
Patterns
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Plan View of Northeast Coso Wells
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Vapor- and Liquid-Tracer Return Patterns Differ
Significantly
Well 34-9RD2 in Northeast region
Well 68-20 in Southwest region
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Conclusions

• A laboratory method was developed for the
  analysis of ethanol that resulted in
  approximately a 30-fold reduction in detection
  limit.
• Ethanol was shown to be an effective tracer for
  determining fluid-flow patterns in a field
  experiment at the Coso geothermal field.
• Striking differences were shown to exist between
  liquid- and vapor-phase tracer responses in two
  field tests at Coso.

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Acknowledgments

• This work was supported by the Department of
  Energy under grants DE-FC07-00ID13986 and
  DE-FG36-04GO14295, which does not constitute an
  endorsement of this paper.
• The authors thank Jess McCullough of Coso
  Operating Company, LLC and Frank Monastero of the
  Naval Weapons Center Geothermal Program Office
  for their support in conducting the field
  experiments at Coso.