A Calculation Model for Liquid CO₂ Injection into Shallow Sub‐Seabed Aquifer

Abstract

This study provided a model for calculating the aquifer transmissibility, the CO2 injection rate, the inner diameter of the injection well, and the number of wells for liquid CO2 disposal in the aquifer. The possibility of disposing liquid CO2 in an aquifer just beneath the sea floor was shown, based on the equilibrium lines in the pressure and temperature map. Our study focused on the feasibility of liquid CO2 disposal below the critical temperature because CO2 can be denser in the low‐pressure range (below the critical temperature) than above the critical temperature. An aquifer about 200 m under the sea floor, at a water depth of around 500 m (700 m below the sea surface), will serve for liquid CO2 disposal. In the aquifer the absolute pressure is approximately 7.3 MPa, sea‐floor temperature is about 4–6°C, and aquifer temperature is about 15–20°C. Therefore, it can be assumed that CO2 dissolves in the aquifer water, and liquid CO2 replaces the water. This means that under the previous conditions, more CO2 can be injected into the aquifer compared to supercritical conditions. Furthermore, by forming a cap of CO2 hydrates, the sediment between the sea floor and the aquifer, prevents CO2 leakage to the sea. Even without the cap, liquid CO2 and CO2 hydrates form at the sea floor, so the CO2 exerts no large environmental impact.

Critical Review on Carbon Dioxide Sequestration Potentiality in Methane Hydrate Reservoirs via CO2–CH4 Exchange: Experiments, Simulations, and Pilot Test Applications

“…This implies that even a smaller and thinner caprock is enough to prevent carbon dioxide from escaping due to the increase in the viscosity of CO 2 due to the cooling conditions. This increase in viscosity and the density of liquid carbon dioxide slow vertical migration compared to warm (supercritical) carbon dioxide; hence, carbon dioxide is stored efficiently in existing caprock or a secondary hydrate layer. , …”

“…This increase in viscosity and the density of liquid carbon dioxide slow vertical migration compared to warm (supercritical) carbon dioxide; hence, carbon dioxide is stored efficiently in existing caprock or a secondary hydrate layer. 47,48 2.2. Solubility Trapping Mechanism.…”

Experimental Studies on Gas Hydrate‐Based CO2 Storage: State‐of‐the‐Art and Future Research Directions

“…In addition, it eventually forms a "hydrate cap" above the gas or liquid "CO 2 pool." [16,[74][75][76] The schematic diagram of this CO 2 storage method is shown in Figure 7. The "hydrate cap" seals the CO 2 in the sediments.…”

Two Phase Flow, Phase Change and Numerical Modeling

“…The reservoir with radius R and thickness h R , is saturated with water and open with constant pressure at its outer boundary. Assume omitting well pressure loss, the initial CO 2 mass flow rate , M(0), at time t = 0, that is injected into the reservoir from its bottom hole, is equal to radial water flow rate in the reservoir [Michael et al (2008) and Sasaki & Akibayashi (1999)],…”