Reza Falahat - Assistant Professor at Sahand University of Technology, Tabriz, Iran

Since 2000, 4D seismic has significantly improved production recovery factor of oil and gas reservoirs. To getthe impact of fluid on 4D seismic signals, during the simulation to seismic modelling, black oil modellingconcepts is routinely used. The accuracy of black oil modelling below the bubble point pressure has been takeninto consideration in this research. Since gas is liberated by pressure drop below the bubble point pressure, thesignificant compositional change were observed on both gas and oil phases by reservoir pressure drop. Theeffect of this compositional change were investigated on the seismic properties of the oil and gas and also onthe saturated rock. We observe that, although there is significant compositional change, black oil modelling isstill valid enough below bubble point pressure for 4D seismic analysis, because the compositional change issimulated using Solution Gas Oil Ratio (Rs). It is, however, recommended to investigate the accuracy ofempirical relationship to calculate solution gas oil ratio Rs for the 4D seismic analysis purposes.

4D seismic, Reservoir monitoring, Black oil modelling, Compositional change, Gas come out of solution