  PyDDC is a particle tracking reservoir simulator capable of solving
non-linear density driven convection of single phase carbon-dioxide
($\mathrm{CO_2}$)--brine fluid mixture in saturated porous media at the
continuum scale. In contrast to the sate-of-the-art Eulerian models, PyDDC uses
a Lagrangian approach to simulate the Fickian transport of single phase solute
mixtures. This introduces additional flexibility of incorporating anisotropic
dispersion and benefits from having no numerical artifacts in its
implementation. It also includes $\mathrm{CO_2}$--brine phase equilibrium
models, developed by other researchers, to study the overall dynamics in the
presence of electrolyte brine at different pressure and temperatures above the
critical point of $\mathrm{CO_2}$. We demonstrate the implementation procedure
in depth, outlining the overall structure of the numerical solver and its
different attributes that can be used for solving specific tasks.
