Real-time quadrupole mass spectrometer analysis of gas in boreholefluid samples acquired using the U-Tube sampling methodology
Description: Sampling of fluids in deep boreholes is challenging becauseof the necessity to minimize external contamination and maintain sampleintegrity during recovery. The U-tube sampling methodology was developedto collect large volume, multiphase samples at in situ pressures. As apermanent or semi-permanent installation, the U-tube can be used forrapidly acquiring multiple samples or it may be installed for long-termmonitoring applications. The U-tube was first deployed in Liberty County,TX to monitor crosswell CO2 injection as part of the Frio CO2sequestration experiment. Analysis of gases (dissolved or separate phase)was performed in the field using a quadrupole mass spectrometer, whichserved as the basis for determining the arrival of the CO2 plume. Thepresence of oxygen and argon in elevated concentrations, along withreduced methane concentration, indicate sample alteration caused by theintroduction of surface fluids during borehole completion. Despiteproducing the well to eliminate non-native fluids, measurementsdemonstrate that contamination persists until the immiscible CO2injection swept formation fluid into the observationwellbore.
Date: January 11, 2006
Creator: Freifeld, Barry M. & Trautz, Robert C.
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