Study On Water Flooding Characteristics And Remaining Oil Distribution Pattern Of Reservoir With Bottom Water

The oil-rich low permeability bottom-water reservoirs in China have a great potential for exploitation.Along with long-term natural energy development of oil wells,reservoir energy reduction is inevitable.Waterflooding is one of the development ways to supplement the formation energy and improve the recovery of such reservoirs.Reservoir heterogeneity,microfracture development,distribution differences of bottom water and interlayer,the complex of water channeling characteristics of oil wells in the late stage and the confused distribution mode of remaining oil always lead to great difficulties for the treatment of water channeling and the development of remaining oil in such reservoirs.Taking the BLC Chang2 reservoir of Ordos Basin(i.e.,typical bottom-water reservoir)as an example,this paper uses the “point-line-plane” method to finely describe the geological characteristics of the study area and determine the reservoir properties.Furthermore,we use the feature induction method to classify the production performance characteristics of oil wells,and uses the gray correlation method to clarify the different water breakthrough models of oil wells in the late stage of water injection development.On this basis,we use eclipse software and BP neural network method to investigate the water breakthrough law of low permeability bottom-water reservoir and prediction model of water breakthrough mode of oil well.More importantly,the water channeling characteristics and remaining oil distribution mode of oil well under different water flooded modes are investigated through the reservoir numerical method(i.e.,the study of water phase streamline and remaining oil saturation distribution).The results show that:(1)BLC Chang2 reservoir belongs to low porosity,low permeability and weak bottom-water reservoir.(2)The production performance characteristics of oil wells in the late stage of waterflooding development can be summarized into three categories: bottom water influence type,composite influence type and water injection influence type.And the production performance characteristics could be further divided into six categories: consistent high water-cut,composite influence bottom water breakthrough,composite influence water injection breakthrough type and composite influence type.(3)The main factors affecting the waterflooding development of bottom-water reservoir are: the thickness of bottom-water layer,the distance of water and bottom-hole,the length of interlayer and the velocity of water injection.(4)Clarifying the main control factors of water breakthrough characteristics of oil wells in bottom-water reservoir.(5)The prediction model of water supplement is established,and the characteristics of water channeling and distribution pattern of remaining oil are defined in different flooding modes of oil wells.The above results provide theoretical guidance for the water channeling treatment and remaining oil development in bottom-water reservior.