Distribution Of Residual Oil After Chemical Flooding In Heterogeneous Formation

The target block belongs to the offshore oilfield.Due to the large reservoir thickness,both inner layer and inter layer are highly heterogeneous,leading to severe flooding in the vertical direction of the reservoir.Subsequent chemical flooding is used to improve the inner layer and inter layer flooding effect.Due to the lack of systemic cognition and summary of remaining oil distribution law,whether chemical flooding after water flooding is an effective measure or not needs further verification.This article is based on the geological data and logging data provided on site,the two-dimensional visualization model and the three-dimensional sand filling model is designed and produced on the basis of the similar criteria to study the remaining oil distribution law of water flooding and chemical flooding in the target block reservoir.The two-dimensional visualization model visually represents the vertical oil and water distribution.The three-dimensional sand-filled model can obtain the saturation distribution at each moment and position in the horizontal and vertical direction by means of resistivity monitoring.The law of residual oil distribution has been concluded by comparing the remaining oil distribution in each rhythm under water flooding and chemical flooding.The results show that polymer flooding has remarkable vertical profile control effect compared with water flooding,and the oil recovery is greatly improved.However,the improvement of oil recovery is limited applying polymer-surfactant flooding after polymer flooding.The distribution of remaining oil is affected by the reservoir rhythm,the permeability contrast,and the displacement velocity.The improvement of oil recovery is higher in positive rhythm reservoirs under chemical flooding.In the reservoir which the permeability contrast is no less than five,the residual oil in the lower permeability layer is basically not displaced after chemical flooding,and the displacement effect improves slightly by increasing the displacement velocity properly.The equalization flooding criterion is introduced to evaluate and predict the oil recovery of heterogeneous formations,providing reference for the future development of the oilfield.