Study On Water Flooding Law And Flow Field Evolution Characteristics Of Heterogeneous Reservoirs With Different Interlayers

Water injection development is the main technology in developing oilfields.While obtaining significantly effective results,it also left most oilfields in the high water-cut stage,even the extremely high one.Due to the inefficiency of injection water cycles,to conserve oil and control water content as well has become the focus of developing high water-cut oilfield.The fluid displacement law,seepage field evolution characteristics,and characteristics of dominant seepage channel development in the water injection of heterogeneous reservoirs have always been the focal points in the oilfield research.Therefore,recognizing the water drive law and flow field evolution characteristics clearly matters a lot for guiding practical reservoir development and adjustment.This paper firstly carries out water-flooding experiments with four types of heterogeneous reservoirs,namely,thick homogeneous reservoirs,heterogeneous reservoirs with undeveloped interlayers,heterogeneous reservoirs with developed interlayers and heterogeneous reservoirs with partly-developed interlayers,which clarified the influence of reservoir physical properties and interlayer characteristics on the fluid migration in reservoirs.Then,the inter well the displacement law and the development position and process of the dominant seepage channel are revealed on the basis of the numerical inversion of the experimental process,combined with streamline and Lorentz curve research methods.They present the quantitative characterization of the development volume.In addition,studies on permeability ratio,oil-water viscosity ratio and the influence of displacement speed on the dominant seepage channel have contributed to the improvements in researching water flooding and practical applications of typical well groups in mines as well.The results show that: 1)Water flooding in the development of heterogeneous reservoirs performs best;partially connected interlayers provide migration channels for interlayer fluid flow within the reservoir,as a result of which,heterogeneous reservoirs with partly-developed interlayers contact water easily so that it demonstrates the worst the water flooding effect.2)In plane,the streamline is spindle-shaped,narrow on the top and wide on the bottom,and the distribution of the streamline on the lower part is more dense.The heterogeneous reservoirs with underdeveloped interlayers have the greatest difference in distribution on the streamline.Apart from heterogeneous reservoirs,the high-speed reservoir areas are located near the connection of the oil and water wells in the lower part of the reservoir and near the well.Vertically,under the influence of gravity,the flow lines of different characteristics of reservoirs show a downward trend.Among them,the partly-developed reservoirs drop most obviously and most complicatedly,and the reservoirs with developed interlayers fall most slightly;3)The interlayers can effectively block the vertical migration of fluid.After blocking high permeability layers,the dominant seepage channels in the upper and middle of reservoirs increase most obviously.The connecting layers provide channels for fluid inside the reservoirs.Although the development scale of the dominant seepage channels in the upper and middle of the reservoir increased,the interlayer interference intensified,which is not conducive to water flooding;4)The volume of the dominant seepage channels decreases with the increase of the permeability difference.And without interlayers,the dominant seepage channels in the upper and middle developed heterogeneous reservoirs decrease fastest,the heterogeneous reservoirs with partly-developed interlayers drop slowest.With displacement rate going up,the dominant seepage flow volume increases and then remains at a certain stable value.At a low speed,the displacement rate increases,the coefficient of variation of cumulative fluid production per unit thickness increases,and the difference between layers becomes larger.At a high speed,the displacement coefficient increases,the coefficient of variation of cumulative fluid production per unit thickness decreases,and the difference between layers narrows;5)Wells with complex structures can improve the range and efficiency of water flooding.A complete interlayer is conducive to the adjustment of the development layer system of high water cut in the later stage.And soaking is not able to improve the waterflood recovery efficiency of the heterogeneous reservoir obviously.