The interest in low salinity water injection (LSWI) compared to seawater injection or high salinity produced brine injection is increasing in both laboratory and in field tests. The single well chemical tracer test (SWCTT) is also becoming increasingly popular as an in-situ test to assess the reduction in oil saturation due to an EOR process. Hence, accurate modeling of single well chemical tracer field tests (SWCTTs) is essential. In this paper, modeling and simulation of SWCTT of low salinity water injection in a carbonate reservoir is investigated using the UTCHEM reservoir simulator. Both Radial and Cartesian grid models are setup for a field-scale pilot using measured rock and fluid data of a Middle Eastern reservoir. Tracer reactions along with the empirical LSWI model implemented in UTCHEM are used to estimate residual oil saturation as a result of low salinity water injection. Two approaches are used to estimate remaining oil saturation to LSWI including analytical and numerical methods. Results show that both approaches give consistent values for remaining oil saturation for homogeneous Radial grid model. The Cartesian grid model was used to investigate the effect of heterogeneity on SWCTT results where a new numerical approach is proposed for estimating remaining oil saturation. This finding validates the approach used and the implementation of both tracer reactions and LSWI model in UTCHEM. The proposed approach can now be used to estimate remaining oil saturation of SWCTT for reservoirs with different degrees of heterogeneity, which provides a clear insight into reservoir performance before planning multi-well demonstration pilots.