Frontier Application | NMR Characterization of Interaction Mechanisms Between CO₂, Core Samples, and Formation Water During Geological Carbon Sequestration

Injecting carbon dioxide (CO₂) into core samples for Enhanced Oil Recovery (EOR) is a cutting-edge petroleum extraction technique. This method emerges in response to the dual challenges of rising global energy demand and increasing environmental concerns. As conventional oil reserves continue to deplete, improving the recovery rate of existing reservoirs has become a crucial objective in the energy sector. CO₂ injection enhances oil mobility by dissolving into crude oil, causing it to expand and lowering its viscosity—thereby significantly boosting recovery efficiency^[1].

Extensive research has been conducted on CO₂ sequestration and its EOR mechanisms. With technological advancements and reduced costs, CO₂ core flooding is increasingly recognised as a viable method for boosting oil recovery^[2]. However, when CO₂ is injected into reservoirs, it disrupts the equilibrium system and triggers chemical reactions among the CO₂, formation water, and reservoir rocks. These interactions can alter various geochemical and physicochemical properties of the target reservoir. Particularly under in-situ reservoir conditions, such reactions are still poorly quantified at the pore scale. This case study addresses that gap.

Schematic diagram of CO₂-enhanced oil recovery (EOR)

In this case study, low-field NMR equipment from Niumag was used to monitor core sample changes before and after CO₂ injection, including porosity, permeability, and mass. Additionally, T₂ spectra were analysed under different conditions across four core samples. The study focused on the interaction mechanisms of CO₂–water–rock, providing valuable insights for similar reservoirs in both CO₂-EOR and CO₂ sequestration applications^[3].

Figure 1: Porosity/permeability increment (a) and mass loss (b) in CO₂, water, and rock interaction.

Figure 2: T₂ values under CO₂–rock and CO₂–rock–water interactions for different core samples.

 

This case study investigated the interaction mechanisms of CO₂, water, and core samples at the pore scale during carbon sequestration, leading to the following conclusions:

1) Figure 1 shows that after CO₂ sequestration, the permeability and porosity of the core samples increased, but their mass decreased.

2) Figure 2 shows that, due to dissolution reactions, the amplitude increase of CO₂–water–rock was larger than CO₂–rock alone, and the amplitude change correlated with the type of minerals and porosity in the samples.

3) This study demonstrated that the interaction of CO₂, brine, and core samples caused significant changes in reservoir properties (increase in porosity), which is favorable for the development of reservoir pores.

For more details, see reference^[3].

If you are interested in the above applications, feel free to contact us: 15618820062

 

References

[1] Abdelaal A, Gajbhiye R, Alshehri D, et al. Improvement of supercritical carbon dioxide foam performance for EOR in sandstone reservoirs: An experimental and optimization study[J]. Gas Science and Engineering, 2022.

[2] Shiyi Y, Desheng M A, Junshi L I , et al. Progress and prospects of carbon dioxide capture, EOR-utilization and storage industrialization[J]. Petroleum Exploration and Development, 2022, 49(4):955-962.

[3] Zhang Y, Shi L, Ye Z, et al. Experimental Investigation of Supercritical CO2 –Rock–Water Interactions in a Tight Formation with the Pore Scale during CO2 –EOR and Sequestration[J]. ACS Omega, 2022, 7, 27291−27299.