Mass-Balance Analysis of Tracer Breakthrough in Heterogeneous Carbonate Rock

In this work, we discuss the applicability of the existing analytic solutions for tracer step and pulse injection into a short laboratory column. We present a mass-balance analysis for four selected models. For step injection scheme, two out of four analytic models do not conserve mass at high dispersion (i.e. low Peclet numbers, see definitions below). The mass conserving solutions are presented below. However, the care should be taken to confirm that the experimental setup complies with the boundary conditions choice. For pulse injection scheme, none of the studied solutions conserve mass at high dispersion. Nevertheless, one of the solutions has a tolerable deviation from mass conservation and is recommended for use in short laboratory columns with high dispersion. Another conclusion is that using pulse injection scheme and the analytic solution for Robin/Semi-infinite boundary conditions is the most optimal way to work with short laboratory columns, such as core plugs, because such solution correctly accounts for the dispersion at the boundaries and has only negligible mass conservation issues at low Peclet numbers in comparison to other analytic solutions.