A good geochemical understanding of the system will require knowledge of the 'baseline' conditions of mineralogy and fluid chemistry prior to CO2 injection. Only with this information can changes due to the presence of CO2 be assessed. It is important therefore, that sample acquisition be implemented prior to CO2 injection operations.
As a minimum requirement, the first prerequisite is to have core material from a well intersecting the reservoir formation and the cap rock formation. Core and cuttings from additional wells will improve characterisation, particularly if vertical and lateral heterogeneity is suspected. The second prerequisite is to have at least one formation water sample, carefully collected from the borehole at either the surface or downhole. A special effort should be focused on obtaining both fluid and rock samples from the same location as it is essential to relate fluid chemistry to mineralogy for a good assessment of baseline conditions. Accurate measurements of reservoir temperature and pressures are also essential for accurate experimental and modelling simulations.
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