Research On Oil Displacement Law And Parameter Optimization Of Surfactant Flooding In Carbonate Reservoirs

The complex lithologic carbonate reservoirs developed in the Middle East are one of the main types of overseas oil and gas rights blocks of our country and an important area to ensure country’s energy security.Some achievements have been obtained in enhancing the oil recovery of carbonate reservoirs with surfactants,but the understanding of the oil displacement laws of surfactants is not unified.It is of critical significance for developing such reservoirs to clarify the law of surfactant flooding in complex lithologic carbonate reservoirs.In this thesis,the laws of surfactant flooding and reasonable development parameters in complex lithologic carbonate reservoirs are studied by means of physical experiments,reservoir engineering and numerical simulation.It mainly includes four parts:(1)The influence of the concentration of surfactant and the ratio of calcite and dolomite in carbonate on wettability is studied qualitatively and quantitatively by conducting contact angle experiment,and then establish the constitutive equation of the variation of rock average wetting angle.The results of the contact angle experiment show that the variation of the average wetting angle increases first and then tends to be stable with the increase of the cationic surfactant concentration,and increases with the increase of the proportion of calcite in the rock slice;(2)Using flooding experiments and reservoir engineering methods,the effects of surfactant concentration and mineral components on the oil-water relative permeability are analyzed qualitatively and quantitatively,and establish the constitutive equation of two-phase relative permeability.The experimental results show that with the increase of surfactant concentration,two-phase flow area increases significantly,the relative permeability of the oil phase increases while the water phase decreases,and the point that oil relative permeability is equal to water relative permeability moves to the right,the change of two-phase relative permeability tends to be stable with the concentration of surfactant continues to increase With the increase of the proportion of calcite in the core,the relative permeability of oil phase increases while the water phase decreases,and the residual oil saturation decreases;(3)Combined with the results of experiments and reservoir engineering methods,the oil-water relative permeability and capillary force interpolation scaling factors in the numerical simulation of surfactant flooding in complex lithologic carbonate reservoirs are improved,and establish a flooding numerical model to verify the effect of the improved interpolation scaling factor.The results show that the improved interpolation scaling factor is more suitable for the actual flooding process,and the interpolation scaling factor improved by oil-water relative permeability constitutive equation has the best effect;(4)Using the improved interpolation scaling factor,combined with the properties of typical complex lithologic carbonate reservoirs in the Middle East to carry out numerical simulation research,then optimize the parameters in the development process,such as surfactant concentration,slug volume,injection rate,and injection timing,and the influence of complex lithology on the development effect during the surfactant flooding process was analyzed.