Preliminary simulations of planned experiments to study the impact of trace gases on the capacity of the Weyburn-Midale field to store carbon dioxide

Technical Report · Fri Nov 13 00:00:00 EST 2009

DOI:https://doi.org/10.2172/972125· OSTI ID:972125

Carroll, S; Hao, Y

The CO{sub 2} stream injecting into the Weyburn-Midale field can be generally classified as a reducing stream with residual H{sub 2}S and low-molecular weight hydrocarbons. The composition of the CO{sub 2} gas stream from the Dakota Gasification Company is reported to be 95% CO{sub 2}, 4% hydrocarbons, and 1% H{sub 2}S by volume (Huxley 2006). In addition to the H{sub 2}S introduced at the injection wells, significant concentrations of H{sub 2}S are thought to have been produced in-situ by sulfate reducing bacteria from previous water floods for enhanced oil production. Produced gas compositions range in H{sub 2}S concentrations from 1 to 6 volume percent. The produced gas, including the trace impurities, is re-injected into the field. Although there is no evidence for inorganic reduction of SO{sub 4}{sup 2-} to H{sub 2}S at the Weyburn-Midale field, Sitchler and Kazuba (2009) suggest that SO{sub 4}{sup 2-} can be inorganically reduced to elemental sulfur in highly reducing environments based on a natural analog study of the Madison Formation in Wyoming. They propose that elevated concentrations of CO{sub 2} dissolve anhydrite to produce the sulfate that is then reduced. Oxidizing CO{sub 2} streams with residual O{sub 2} and SO{sub 2} typical of streams captured from oxyfuel and post combustion processes are not presently an issue at the Weyburn-Midale field. However it is possible that the oxidizing CO{sub 2} streams may be injected in the future in carbonate reservoirs similar to the Weyburn-Midale field. To date there are few modeling and experimental studies that have explored the impact of impurity gases in CO{sub 2} streams targeted for geologic storage (Gale 2009). Jacquemet et al (2009) reviewed select geochemical modeling studies that explored the impact of SO{sub 2} and H{sub 2}S impurities in the waste streams (Gunter et al., 2000, Knauss et al., 2005, Xu et al., 2007). These studies collectively show that SO{sub 2} significantly reduces the pH when oxidized to H{sub 2}SO{sub 4} causing enhanced dissolution of carbonate minerals and some sulfate mineral precipitation. Low pH results in higher mineral solubility and faster dissolution rates and is thought to enhance porosity and permeability near the injection well when trace amounts of SO{sub 2} is injected with CO{sub 2}. The impact of H{sub 2}S on storage reservoir performance appears to more subtle. Knauss et al (2005) report no significant impacts of injection of CO{sub 2} gas streams with and without H{sub 2}S (1 M Pascal H{sub 2}S + 8.4 M Pascal CO{sub 2}) in simulations of CO{sub 2} storage in the Frio sandstone formation. Geochemical reactions for H{sub 2}S impurities include enhance field alkalinity and reaction with iron bearing minerals that may delay breakthrough of H{sub 2}S relative to CO{sub 2}. Emberley et al. (2005) report that half of the alkalinity measured at monitoring wells at the Weyburn-Midale field is due to HS{sup -}. Schoonen and Xu (2004) report that H{sub 2}S can be sequestered as pyrite in sandstones and carbonates by dissolving iron hydroxides and iron-bearing clays. Similarly, Gunter et al (2000) propose the that siderite converts to iron sulfides when it is reacted with H{sub 2}S. The geochemical reactions between H{sub 2}S and iron bearing minerals together with the high solubility of H{sub 2}S relative to CO{sub 2} may contribute to the delayed break though of H{sub 2}S in experiments. A few core flood experiments have shown that the injection of supercritical CO{sub 2} into carbonate aquifers has the potential to significantly alter the porosity in the absence of trace gases such as SO{sub 2} and H{sub 2}S. Luquot and Gouze (2009) documented a 2% porosity increase in carbonate cores when rock-water interactions were transport limited and solution concentrations were closer to equilibrium and a 4% porosity increase when rock-water interactions were reaction limited and solution compositions were further from equilibrium. Similarly Le Guen et al (2007) used x-ray micro-tomography and geochemistry to show that porosity significantly increases when reacted with pure CO{sub 2}. While both of these studies nicely illustrate the relationship between reaction kinetics, thermodynamics, and porosity changes using x-ray micro-tomography, actual changes in a reservoir may be significantly lower because the input brines used in these studies were significantly dilute and below mineral carbonate saturation. The objective of the simulations reported was to explore viable experimental parameters for CO{sub 2} core flood experiments designed to investigate the impact of CO{sub 2} on porosity and permeability in the Weyburn-Midale storage reservoir. We describe the simulation results for core flood experiments in which formation waters that are equilibrated with supercritical CO{sub 2} at 60 C and 14.7 M Pascals react with three different flow units within the Midale formation.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 972125
• Report Number(s): LLNL-TR-420404; TRN: US201006%%893
• Country of Publication: United States
• Language: English

Related Subjects

29 ENERGY PLANNING
POLICY AND ECONOMY
ACID NEUTRALIZING CAPACITY
CAPACITY
CARBON DIOXIDE
CARBONATE MINERALS
GASES
HYDROCARBONS
IMPURITIES
INJECTION WELLS
INTERSTITIAL WATER
IRON
IRON HYDROXIDES
IRON SULFIDES
POROSITY
REACTION KINETICS
STORAGE
SULFATE MINERALS
SULFATE-REDUCING BACTERIA
TRACE AMOUNTS
WATER