Speaker
Description
Carbonate reservoirs in depleted oil and gas fields are widely considered suitable candidates for geological CO₂ storage due to their high porosity and extensive subsurface distribution. In the Danish North Sea, many prospective storage formations consist predominantly of chalk and other carbonate lithologies. However, the calcite-rich composition and typically low permeability of these rocks make them highly sensitive to geochemical reactions triggered by CO₂ injection. This sensitivity is further amplified when the injected CO₂ stream contains reactive impurities such as SO₂, NO₂, and H₂S, which may be present at trace concentrations in industrial capture streams. Despite their potential importance, the coupled effects of CO₂ stream impurities on geochemical reactivity, multiphase flow behavior, and storage efficiency in carbonate porous media remain insufficiently constrained.
This contribution examines the influence of CO₂ stream composition on flow–reactivity interactions in carbonate reservoir rocks using a combined experimental and modeling approach. Dynamic core-flooding experiments are conducted on reservoir carbonate samples under representative subsurface conditions (100 bar, 35 °C). Pure methane serves as a non-reactive reference fluid, while additional experiments involve pure CO₂ and CO₂ mixtures containing CH₄, SO₂, NO₂, or H₂S. Alternating injections of gas and formation water are applied to reproduce transient multiphase flow conditions representative of advancing CO₂ plume fronts and cyclic gas–water displacement processes encountered during storage operations.
Geochemical reactions are assessed through analysis of effluent fluid compositions using ion chromatography, enabling evaluation of carbonate dissolution and potential secondary mineral reactions. To support interpretation of the experimental observations and to isolate impurity-specific effects, a one-dimensional kinetic reactive transport model is developed. The modeling framework facilitates systematic analysis of reaction pathways and their interaction with multiphase flow at the core scale, providing insight into process coupling relevant to porous media behavior.
The combined experimental–numerical framework highlights how variations in CO₂ stream composition influence both geochemical response and flow behavior in carbonate porous media. In addition to modifying carbonate reactivity, impurities affect gas–water displacement characteristics and residual gas trapping, which are critical parameters for storage efficiency and security. While geochemical reactions act at the pore scale, their short-term impact on bulk petrophysical properties remains limited under the investigated conditions, emphasizing the dominance of flow-controlled mechanisms during early stages of CO₂ storage.
Overall, this work underscores the importance of accounting for realistic CO₂ stream compositions when investigating coupled flow and reactive transport processes in carbonate CO₂ storage reservoirs and contributes to improved understanding of impurity effects in porous media relevant to carbon storage applications.
| Country | Denmark |
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