Research On Adaptability Of Enhanced Oil Recovery Technology In High Permeability And Low Permeability Strong Water Channeling Reservoirs

In strong heterogeneity high-permeability reservoirs and long-term water injection or fractured low-permeability reservoirs,the injected water flows rapidly and ineffectively along the water channel,resulting violent water flooding.This kind of common strong water channeling reservoirs are taken as objects.Physical simulation experiment methods are used to study the particularity of the mining performance and the distribution of remaining / residual oil and the special difficulties in enhancing recovery factor for exploring suitable methods to improve recovery factor.A physical model with extra-high permeability bands between injection-production wells was developed to simulate strong heterogeneous high-permeability reservoirs.The distribution of water saturation shows that during the waterless production period,the front edge of the waterflood advances rapidly towards the well;the water swpet area after the breakthrough of the waterflood front does not expand significantly.The main potential of EOR in such reservoirs is continuous remaining oil of the unswept area.The experiments show that even if there are no extreme special conditions,high-permeability reservoirs will form strong water due to long-term water injection erosion and the water saturation distribution is severely uneven.After the formation of strong water channeling,the medium / weak water washing area is huge and the distribution of remaining oil is highly dispersed.In the strongly heterogeneous high permeability reservoir,polymer flooding is effective,but limited after the formation of strong water channeling.The remaining oil can be displaced by the combination method of high concentration polymer slug and well pattern adjustment.This paper puts forward a method of EOR,which combines the whole profile control-oil displacement and well pattern adjustment after strong water breakthrough.The experiments show that once a strong water channeling is formed,no matter how long water or surfactant flooding lasts,it can only drive out the residual oil in the strong water washing area and the remaining oil production situation is basically not improved.Polymer flooding can improve the displacement efficiency of residual oil in medium / weak water washing area,but the plugging ability and scope are limited.The strong emulsified system has the dual functions of oil washing and medium profile control,which can effectively displace the residual oil and the polymer colloid particle(PCP)can effectively adjust the deep displacement profile.PCP-strong emulsified system which has the synergistic effect is proposed to enhance oil recovery in strong water channeling and high permeability reservoir.According to the oil saturation distribution,the water breakthrough is formed more rapidly in low-permeability reservoir than in high-permeability reservoir,even in the low-permeability homogeneous model under the ideal condition of uniform injection.The proportion of strong water washing area in low permeability model is far less than that of high permeability model.The remaining oil in low permeability reservoir is mainly a large number of contiguous matrix crude oil.Invalid circulating water rate is defined to express the characteristics of water breakthrough.Based on the curve of invalid circulating water rate,water breakthrough coefficient is caculated to evaluate of water breakthrough strength in different reservoirs.The water breakthrough coefficient increases with the decrease of permeability.The strong water breakthrough that is easier to form in the low permeability reservoir than in the high permeability reservoir can be expressed as the quantitative law.The potential of EOR in low permeability reservoir after waterflooding is continuous residual oil in the unswept area.Compared with the experimental results of different chemical oil displacement agent in low permeability model,polymer flooding is not suitable due to injection problem.Ultra-low interfacial tension system is not suitable for heterogeneous(fracture)low permeability reservoir model.The strong emulsion flooding agent flooding not only flood the residual oil in the areas of weak and medium water washing,but also significantly expands the swepted area.Aiming at the special difficulties in low permeability reservoir,a EOR method of sectional plugging and local driving is proposed,which uses PCP to block strong water channeling,strong emulsifier to assist plugging and low viscosity oil displacement agent to locally drive matrix remaining oil.