T204 Geologic Carbon Storage (Posters)

Tuesday, 11 October 2022
2:00 PM - 6:00 PM
Exhibit Hall F

REACTIVE TRANSPORT MODELING OF EFFECTS OF CO2 INJECTION WITH VARIABLE IMPURITIES ON DEEP SALINE RESERVOIRS

Paper number: T204-12
Program: Technical Sessions
Time: 2:00 PM – 6:00 PM

Authors

Abstract

CO2 streams from the emitters contain various impurities that upon injection into deep saline reservoirs may cause physical and chemical changes in the formation properties, and thus influence CO2 injection and geological storage capacity and dynamics. Interactions between variable CO2 stream compositions and potential host reservoirs were assessed by a reactive transport modeling to support the site selection and planning of storage strategies in Denmark. Simulations were conducted using ECO2N and TOUGHREACT. CO2 streams with oxidizing (SO2, NO2, O2) and reducing (H2S, CS, COS) impurities mix were injected into model domains representing water saturated reservoirs with various mineralogy. The models contained kinetically controlled reactions for dissolution and precipitation of minerals and oxidation and reduction of impurities, including interactions between impurities, e.g. SO2 and NO2, and impurities and water.

Effects of injection of impurities on the reservoir mineralogy and brine chemistry are more pronounced upon injection of the oxidizing mix. Simulations without rock-water interactions predict that low pH of around 1 will occur in the vicinity of the injection well and SO42- and NO3- will accumulate at the boundary between very high gas saturation and mixed saturation. When minerals are present, concentration of NO2- increases at the expense of SO42- due to the pH dependence of the reaction:

2 SO2 (aq) + 2 NO2- + H2O -> 2 SO42- + 2 H+ + N2O.

In addition, some of the SO42- precipitates as anhydrite, where calcite dissolution occurs. Negligible amount of O2 is consumed by oxidation of Fe(II) in the water. Calcite dissolution effectively buffers pH that remains close to the pH of 4.6 generated by CO2 dissolution. While the abundance of calcite varies in the formation, calculations with just siderite and K-feldspar result in minimum pH values of 3.4. Thus, the acidification from impurities where calcite is present will not pose a critical problem for the durability of infrastructure or induce reactions that could cause deterioration of the formation strength. However, the impact of impurities on the reservoir properties could scale with the amount of impurities injected, or different injection strategies (i.e., several injection/production cycles, alternating injection of oxidizing/reducing impurities).

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-377192

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