Long tube flooding tests for investigating salt precipitation induced by CO₂ injection

Capturing a large amount of CO₂ from industry, energy production, or incineration plants and storing it in the subsurface such as depleted hydrocarbon reservoirs or saline aquifers can fundamentally reduce the footprint of atmospheric greenhouse gasses. Injection of CO₂ in a saline aquifer zone or depleted hydrocarbon reservoir will vaporize formation water and lead to potential salt precipitation in porous rock, thus increasing the risk of formation damage near the wellbore area and reducing the injectivity of CO₂ in the reservoir. Previous experimental studies on salt precipitation have focused on core flooding, including micro-core flooding, ordinary single-plug flooding, and composite core flooding. The length of the core plugs limits these flooding tests. They usually suffer from serious end effects, and it is generally challenging to investigate the variation along the flooding direction, especially after large pore volumes of injection. In this study (Project Greensand), we have researched and developed new equipment termed “long tube apparatus” to improve the understanding of salt precipitation and gage the effects of formation damage in detail for a North Sea depleted oil field reservoir (Nini West) under investigation, while injecting CO₂. The main aim of the experiment was to determine two properties such as salt and water content, which are used to evaluate the formation damage due to salt precipitation. Finally, a numerical simulation was carried out using CMG GEM in both 1D homogeneous model and another heterogeneous model honoring the channeling at the inlet. Results with qualitative agreement were achieved, especially with the heterogeneous model.