In tracer tests in oil reservoirs, a fluid (water) with a radioactive substance pulse is injected into the porous medium and it is monitoring until its arrival in neighboring extraction wells. From the observations of each extraction well, a tracer breakthrough curve is generated (time vs. tracer concentration). These curves are used to determine the existence of communication channels in underground formations and to characterize the porous medium properties, such as porosity, dispersivity, thickness of the production layer and residual oil saturation, among other applications. In this talk we will present the numerical modeling of the dynamics of the tracers, when the injection/extraction tests are performed in a single-well. We will show results for bipolar flow and a study for the injection phase in partially penetrating wells. Numerical simulations are generated by finite element with bilinear elements. Bibliography [1] J. Cosler: Effect of rate-limited Mass-Transfer on Water Sampling with Partially Penetrating Wells. Ground Water, 42(2) (2004), pp. 203--222 . [2] J.-Sh Chen, Ch.-L. Wu and Ch.-W. Liu: Analysis of contaminant transport towards a partially penetrating extraction well in an anisotropic aquifer. Hydrological Processes, 44 (2010), pp. 2125--2136. [3] J.S. Chen, C.W. Liu. Effect of transverse dispersion on solute transport in a vertical dipole flow test with a tracer. Journal of Hydrology, (2011), pp. 1--11. [4] Coronado M., Sandoval M. L., Escobar-Alfaro G. S. Modeling fluid flow and tracer transport in partially penetrating injection wells. Corrections are submitted to Journal of Petroleum Science and Engineering. March 5, 2018. [5] Sandoval M. L., Coronado M., Grande-Sánchez S. Dynamics of vertical dipole tracer tests in a sandy-clay reservoir. Paper in preparation.