<p>Global warming is an important environmental concern and among the different emerging technologies the Carbon Capture and Storage (CCS) comes off as a very promising one. In the CCS process, CO2 can be stored in aquifers under cap-rocks and the leakage of the gas due to natural fractures for example may cause harm to the environment if it happens. As a possible solution to avoid gas leakage the natural formation of CO2 hydrate is considered. Gas hydrates are ice-like structures where a gas molecule is englobed by a cage of water molecules. Hydrates, in general, are formed under conditions of high pressure and low temperature and may work as a new cap-rock to suppress unexpected leakage of CO2. In this work, a numerical study was conducted to simulate the microscopic formation of CO2 hydrate in the pore of sand grains. Our previous work had reported the importance of hydrate morphology to the permeability under no flow conditions. This work focused on identifying the changes in the morphology and consequently in permeability caused by hydrate formation with gas flow. The numerical domain was created using the particle growth method using real grain shapes, which had been taken digitally from the Toyoura sand. The initial condition of the simulation consisted of having residual water after an initial passage of gas through the microscale domain. CO2-water two-phase flow was simulated using the lattice Boltzmann method. The initial positions of hydrate nuclei were defined using the classical nucleation theory and hydrate growth was simulated using the phase field method. The two-phase flow was forced by various pressure gradients and hydrates were formed within sand-grain pores under different temperature and porosity conditions. It was found that hydrate morphology and consequent relative permeability in the flow-coexisting case are different from those under no flow condition.</p>

Numerical Simulation of Microscopic Formation of Carbon Dioxide Hydrate in Two-Phase Flow

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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