Lattice Boltzmann Simulation on Reactive Transport of Calcite Dissolution by Injecting CO2-saturated Brine during Sequestration

CO2 as a kind of greenhouse gas has a greatly adverse impact on the
environment, and fixing carbon into saline aquifers effectively alleviates the
effect it brings. In the present study, the calcite dissolution during sequestration
near wellbores at different temperatures is explored to elucidate the mesoscale
mechanism of reaction transport during this process and the evaluation of
hydraulic properties with time that affects the injectivity of CO2-saturated brine.
A multi-component lattice Boltzmann method coupled fluid flow, mass
transport, heterogeneous reaction, and structure evolution is proposed to
quantitively study the reaction transport of calcite dissolution near wellbores. A
special solution included the general lattice Boltzmann concentration boundary
condition and Volume of Pixel method is utilized to model the dissolution
reaction. The influence of temperature on reaction dynamics in porous media is
analyzed by exerting the Arrhenius expression, and the concentration distribution
of H+ and Ca2+ is captured to reflect the dissolution front directly. Moreover, the
evaluated hydraulic properties characterize the effect of the dissolution reaction
on the brine injectivity.
Since the reaction rate of calcite dissolution increases with temperature, the
dissolution node of calcite is proportional to the temperature at a constant
pressure difference. And the dissolution node indicating the released volume of
Ca2+ which is a key reactant for the mineral trapping is summed to estimate the
sequestration result. Furthermore, the dissolution front observed from the porescale
simulation is heterogenous due to a higher velocity, and the dissolution
pattern of all cases is identified as the wormholing dissolution, which means that
the increasing porosity during the calcite dissolution has a great contribution to
the permeability. Admittedly, the increasing temperature during sequestration is
conducive to calcite dissolution and changes in hydraulic properties. For
sequestration operation, the high-temperature formation is recommended for both
the injectivity and the subsequent mineral trapping.
This work provides theoretical and pragmatic guidance to operators to design
CO2-saturated brine injection in saline aquifers. Furthermore, the results can also
promote cognition of the calcite dissolution for sequestration at different
temperatures