Research On The Oil-water Distribution Pattern And Production Decline Model Of The Low Permeability Reservoir

MD block of Wenmi oil field is a low permeability sandstone reservoir. In the process of waterflooding, interlayer contradictions, planar conflicts and inner contradictions are very prominent, the water rises fastly, and recovery degree is low. In order to improve the water injection effect of this block, this thesis studies the block development effect and development characteristics, reservoir oil-water movement rules and its influencing factors using statistics and reservoir engineering methods. It also analyzes the production decline rule of MD blocks and the affecting factors of production decline rule from theory. And according to the characteristics of reservoir, this thesis optimizes the model of prediction production. The paper obtains the following major understanding and achievements.First, the paper analyses the adaptability of the MD block development way. Although the block production pressure differential is basically stable, formation pressure is above of the reasonable formation pressure levels, natural or artificial injection water energy has not been fully used. Pressure coefficient keeps rising and the local pressure is seriously high. The degree of the water flooding reserves control and producing is poor.Second, the rate of water increasing of the MD block initial development is basically according with Tong’s theoretical curves and flow tube method’s theoretical curves, but it deviates seriously from the prediction of those methods when the water rate is high stage.Third, MD block development characteristics shows that the carry water rate begins to drop when the recovery degree is higher than3.86%.with the recovery degree increasing, the carry water rate is fast diminishing, and the utilization rate of the injection water is smaller and smaller. Water consumption index rises slowly in the early stage of development, but it obviously increase when the reservoir is into medium water cut stage, after taking a lot of blocking water measures, water flooding development effect has been improved, and the injected water utilization is improved. Therefore blocking water measures is the effective ways to improve development effect.Fourth, the thesis shows that the water breakthrough time of MD block is2.5times of the effective time; Wells response and breakthrough are given priority to single sand layer. The production of wells declines after water breakthrough. The main factors of influence oil-water movement are injection-production patterns nets, sedimentary microfacies, formation coefficient, water injection intensity, etc.Fifth, the production of MD block declines mainly for index descending. The factors of influence production decline are water rate, driving mode, recovery mode, etcSixth, the productions of MD block suit to use Weng-Model when it started diminishing, and use Decline Curve to predict production when it is high water cut stage. Arps production decline model is used to forecast the average annual single-well.