The U-Tube: A Novel System for Acquiring Borehole Fluid Samples from a Deep Geologic CO2 Sequestration Experiment
Skip to main content
eScholarship
Open Access Publications from the University of California

The U-Tube: A Novel System for Acquiring Borehole Fluid Samples from a Deep Geologic CO2 Sequestration Experiment

  • Author(s): Freifeld, Barry M.
  • Trautz, Robert C.
  • Kharaka, Yousif K.
  • Phelps, Tommy J.
  • Myer, Larry R.
  • Hovorka, Susan D.
  • Collins, Daniel J.
  • et al.
Abstract

A novel system has been deployed to obtain geochemical samples of water and gas, at in situ pressure, during a geologic CO2 sequestration experiment conducted in the Frio brine aquifer in Liberty County, Texas. Project goals required high-frequency recovery of representative and uncontaminated aliquots of a rapidly changing two-phase (supercritical CO2-brine) fluid from 1.5 km depth. The data sets collected, using both the liquid and gas portions of the downhole samples, provide insights into the coupled hydro-geochemical issues affecting CO2 sequestration in brine-filled formations. While the basic premise underlying the U-Tube sampler is not new, the system is unique because careful consideration was given to the processing of the recovered two-phase fluids. In particular, strain gauges mounted beneath the high-pressure surface sample cylinders measured the ratio of recovered brine to supercritical CO2. A quadrupole mass spectrometer provided real-time gas analysis for perfluorocarbon and noble gas tracers that were injected along with the CO2. The U-Tube successfully acquired frequent samples, facilitating accurate delineation of the arrival of the CO2 plume, and on-site analysis revealed rapid changes in geochemical conditions.

Main Content
Current View