In this study, boundary element method was used to model sea wave propagation on a hemisphere shape under water tank and oil-water common surface oscillation in the tank. Also, kinematic and dynamic oundary conditions of free surface and common surface of oil and water were discritized by Finite difference method. There were some singularities in BEM method, which were removed by applying zoning method. The wave specifications and water depths, which were entered in numerical model, were extracted from Geographic and climatic profiles of Abuzar oil field region in Persian Gulf. The results show an acceptable accordance with ther researches. Also, the results illustrated that, using open ended storage tanks near our offshore platforms has not any problem and it can be a good proposal for oil storing by considering their advantages.