Multiple‐Peak Response to Tracer Injection Tests in Single Fractures: A Numerical Study

Abstract

Under certain conditions, when pulse tracer injection tests are performed in a single fracture with a regional flow field, the breakthrough curves may display multiple peaks. Furthermore, the shape of these curves may change when the injection flow rate is varied. In this paper the conditions under which the breakthrough curve may present multiple peaks are analyzed numerically using stochastically generated fractures. The dispersivities of these peaks are also calculated. It is found that the dispersivity is small for each of the peaks and that the dispersivities of the different peaks in a breakthrough curve are quite similar. The results presented in this paper may be equally applied to tracer tests in a two‐dimensional strongly heterogeneous medium.