The U-tube sampling methodology and real-time analysis of geofluids

• Main Authors: Freifeld, Barry, Perkins, Ernie, Underschultz, James, Boreham, Chris
• Language: unknown
• Published: 2009
• Subjects: 54; 58; BRINES; FREEZING; GEOCHEMISTRY; HEATING; MASS SPECTROMETERS; MONITORING; PERMAFROST; QUADRUPOLES; SAMPLING; SOLVENTS; STORAGE; WASTES; WAXES; WOOD; YUCCA MOUNTAIN; Canada; permafrost
• Online Access: http://www.osti.gov/servlets/purl/960240; https://www.osti.gov/biblio/960240

The U-tube geochemical sampling methodology, an extension of the porous cup technique proposed by Wood [1973], provides minimally contaminated aliquots of multiphase fluids from deep reservoirs and allows for accurate determination of dissolved gas composition. The initial deployment of the U-tube during the Frio Brine Pilot CO{sub 2} storage experiment, Liberty County, Texas, obtained representative samples of brine and supercritical CO{sub 2} from a depth of 1.5 km. A quadrupole mass spectrometer provided real-time analysis of dissolved gas composition. Since the initial demonstration, the U-tube has been deployed for (1) sampling of fluids down gradient of the proposed Yucca Mountain High-Level Waste Repository, Armagosa Valley, Nevada (2) acquiring fluid samples beneath permafrost in Nunuvut Territory, Canada, and (3) at a CO{sub 2} storage demonstration project within a depleted gas reservoir, Otway Basin, Victoria, Australia. The addition of in-line high-pressure pH and EC sensors allows for continuous monitoring of fluid during sample collection. Difficulties have arisen during U-tube sampling, such as blockage of sample lines from naturally occurring waxes or from freezing conditions; however, workarounds such as solvent flushing or heating have been used to address these problems. The U-tube methodology has proven to be robust, and with careful consideration of the constraints and limitations, can provide high quality geochemical samples.