The purpose of this work is to present the results of the phase behavior study for a live heavy oil during a pressure depletion process using magnetic resonance imaging (MRI) as a tool to characterize foamy oil phenomena. The experiments were carried out in the pressure range of 13.1 to 1.4 MPa. Signal intensity images were obtained at each pressure and with respect to time, that is, approximately for a total time of 3 h after each pressure change. It is possible to see a variation in intensity across the sample. These changes can be associated with changes in mobility as well as segregation of the oil. It was also possible to observe that what we trust is the formation of gas channels at the last two pressure values, as it comes out of solution. A correlation between the transverse relaxation time T-2 and temperature was established with the aim of producing one between T-2 and viscosity. In this way viscosity maps for the live oil were obtained as a function of pressure and time. It was observed that above the bubble point, the viscosity maps varied from low to high to low with respect to time for the same pressure. Below the bubble point the situation is reverse. The viscosity map changes from high to low to high with respect to time for the same pressure. The study shows the potential use of MRI to follow viscosity changes during pressure depletion test in a PVT MRI cell.