Characterization of tar from a carbonate reservoir in Saudi Arabia: Physical aspects

A detailed physical characterization of tar from a carbonate reservoir in Saudi Arabia was made to evaluate its mobility and ways of establishing contact between the lighter oil and its aquifer. Density and viscosity measurements were carried out on several tar samples, under simulated reservoir conditions of pressure and temperature. Other physical parameters such as simulated distillation, pour point and penetration index were also experimentally determined. Tar physical properties were found to vary with depth and area within the same field. The obtained experimental results showed a gradual increase in density and viscosity from the tar/oil contact towards the tar/water contact. This increase was much more pronounced in the neighborhood of the tar/water contact. Density and viscosity of tar diluted with toluene were in excellent agreement with those of pure tar. The density of non preserved tar varied between 0.956 g/cc at 200o0F and 1.008 g/cc at 76o0F while that of preserved tar varied between 0.944 g/cc at 200o0F and 0. 991 g/cc at 76o0F. The tar samples analyzed appear to behave as Newtonian fluids.