Due to the concerns about the effect of greenhouse gases on the climate, Geologic CO2 storage is a very active area of research. One of the biggest risks associated with such projects is the possibility of leakage. Detrimental environmental consequences present a need to study potential leakage scenarios. Stored CO2 may leak if possible leakage pathways are available and favorable. Pressure and temperature decrease from the leakage source to the surface. Below the CO2 saturation pressure, liquid condensation of the CO2 occurs. At even lower temperatures and pressures, in the presence of water, hydrate formation occurs. CO2-hydrate forms when free water is available and the temperature is below 283 K and pressure is below 647 psi. During leakage, decreases in the temperature and pressure results in a CO2 phase change that affects the leakage flux. The purpose of this study is to estimate the leakage flux for different scenarios taking thermodynamic phase changes into account. A numerical model with coupled mass and energy balances was developed and used to estimate the flux as a function of time. Due to wide temperature and pressure changes over the course of the simulation, an accurate fluid properties model is required to reduce fluid properties related errors. Multi-parameter Span-Wagner equation of state for CO2 is used to achieve this. The numerical model allows for CO2 to exist in gas, liquid and hydrate phases. Hydrate formation was modelled using the van der Waals-Platteeuw model. Heat flux from the surroundings play an important role in effecting a phase change. Example calculations indicate a cyclical nature of the leakage flux under certain conditions. These calculations indicate the importance pressure of the leakage source (aquifer), the amount of water in the pathway (fracture/faults), the geothermal gradient and the surface temperature besides the thickness and the permeability of the fracture.
|Original language||English (US)|
|Number of pages||9|
|State||Published - 2017|
|Event||13th International Conference on Greenhouse Gas Control Technologies, GHGT 2016 - Lausanne, Switzerland|
Duration: Nov 14 2016 → Nov 18 2016
All Science Journal Classification (ASJC) codes