T86 Geochemistry of Geologic Sequestration of CO2: Understanding Gas-Water-Mineral Interactions over Wide Temporal and Spatial Ranges I

Monday, 1 November 2010
8:00 AM - 12:00 PM
Room 205

LABORATORY INVESTIGATION OF CO2 – ROCK – BRINE INTERACTIONS USING NATURAL SANDSTONE AND BRINE SAMPLES FROM THE SECARB TUSCALOOSA INJECTION ZONE

Paper number: T86-11
Program: Technical Sessions
Time: 10:40 AM – 10:55 AM

Authors

  • Athanasios Karamalidis Presenting Author
    National Energy Technology Lab; U.S. Department of Energy, Pittsburgh, PA
  • J. Alexandra Hakala
    National Energy Technology Lab; U.S. Department of Energy, Pittsburgh, PA
  • Craig Griffith
    National Energy Technology Lab; U.S. Department of Energy, Pittsburgh, PA
  • Sheila Hedges
    National Energy Technology Lab; U.S. Department of Energy, Pittsburgh, PA
  • Jiemin Lu
    University of Texas at Austin, Austin, TX

Abstract

The Southeast Regional Carbon Sequestration Partnership (SECARB) launched their Phase III CO2 injection into the Tuscaloosa sandstone formation at Cranfield, Mississippi. Changes in formation brine chemistry during CO2 injection were monitored in field-collected brine samples (see complementary abstract by Thordsen et al.). Our investigation focuses on laboratory-scale experiments using natural samples from the Tuscaloosa formation. Results from our work will be compared with results from the field study to determine whether laboratory-scale experiments may be used to predict changes in CO2 storage formation fluid chemistry due to CO2-water-rock interactions.

Core samples from the Tuscaloosa loose sediment injection zone were collected and preserved, and natural brines were collected via U-tube, prior to CO2 injection. XRD analysis of the sandstone showed mainly quartz, chert and feldspar with some volcanic rock and metamorphic rock fragments. Iron-chlorite (chamosite) was present at about 14 % wt. of the core sample, and only a small fraction can be attributed to carbonate minerals. The brine was a natural Na-Ca-Cl brine with 152,000 mg/L TDS. The experiment was conducted using a rocking autoclave at 350 bar pressure and 125 °C constant temperature for a reaction period of 120 days, which included 40 days of brine-rock mixing in the absence of CO2 to ensure steady-state conditions prior to CO2 injection.

After CO2 injection, solution pH decreased, and we observed increases in major cations (Ca, Mg, K). Fe(II) and total Fe increased immediately after injection; Fe(II) declined to pre-CO2 levels within 48 hours, and total Fe rose towards the end of the experiment. These data suggest a rapid reaction of Fe(II)-bearing carbonate minerals and/or iron-chlorite phases upon CO2 injection, with subsequent geochemical reactions involving Fe-bearing solid phases. Additionally, iron-chlorite dissolution in the presence of CO2 is possible since Al, Si, and Mg concentration changed over time. These results suggest a rapid initial reaction of Lower Tuscaloosa natural brine and sandstone upon CO2 injection, with subsequent precipitation and dissolution reactions occurring in the presence of CO2-charged brine.