Study On Enhanced Oil Recovery By Combination Of Profile Control With Fine Water Flooding In Extra-High Water Cut Oilfield

L reservoir is a multilayer edge water reservoir.It has been in the stage of high water cut,while the oil recovery is only 37.9%.There are still a large amount of remaining oil in the water-flooded zones,which is difficult to be exploited.Based on the study of oil and water distribution under the current development stage,the key technologies to improve the effect of water flooding have been studied,such as well pattern modification,injection and production parameters adjustment and water flooding profile controling.In this paper,the L reservoir is used as an example to establish the geological model,and the remaining oil distribution is studied by numerical simulation.The results show that the remaining oil distribution in the L reservoir is scattered,mainly in the form of flakes.In the vertical direction,the water flooding in zone TI~3 is effective,and the remaining oil is mainly storged in zone TI~2.Furthermore,using modified formula of production potential to evaluate the remaining oil.Based on the theory of streamline numerical simulation,the relationship between injectors and producers,water injection efficiency,predominant flow field and water sweep efficiency of L reservoir are evaluated respectively.Due to the dominant channels between injectors and producers,water injected in one direction break through seriously,resulting in poor sweep efficiency.Because a large amount of water recycling underground,the average water injection efficiency is only 6.5%.Considering of remaining oil distribution,the fine water flooding technology,such as adjustment of well pattern,the subdivision of strata and the optimization of injection and production parameters is studied in this paper.The results show that the water injection efficiency can be optimized by adjusting the injection and production volumes,and accumulative oil is 1.4×10~4t after forecasting for three years.The separate injection technicology is used to realize the subdivision and reorganization of the waterflooding section,the decreasing rate of the daily oil production is finally slow down.Water injected for 30 days and stop for 20 days are the optimization results of cyclic water injection system.The injection-production coupling system are as follows:zone TI~2 intermittent injection and production for 30 days,and zone TI3 is 15 days.Five infill wells are selected using the remaining oil potential method.After changing some inefficient producters to injectors,the oil production of some producers are improved.In the aspect of flooding profile control,the simulation results of parallel double cores show that the weak gel flooding is more effective than the polymer flooding.On the basis of fine water flooding adjustment,three kinds of profile control with fine water flooding technical methods are proposed,and the effect of each method is forecasted by numerical simulation.The results show that the water sweep efficiency will become higher after combination of well pattern modification with deep profile control.When the water cut curve after deep profile control is picking up again,the following adjustment of water injection or liquid production can make a further water cut decline,and enhance the effect of deep profile control.