| Reservoir heterogeneity in X block of Shengli Oilfield is serious,resulting the poor waterflooding development effect and difficulties in stable development.However,X block still has great development potential.Technical study on improving the development effect of water flooding is a key to improve development economic benefits of Shengli Oilfield.The stratified waterflooding is an effective measure to improve water flooding development effect and oil recovery factor in reservoirs at later stage of high water cut,which can reduce the development contradiction between layers,but the contradictions within the layer cannot be solved.Profile control in water injection wells is one of the important measures to achieve balanced flooding and reduce the development contradiction within the layer at later stage of high water cut period.In order to maximize the development effect of waterflooding,the water distribution can be adjusted in different layers and within one layer.Therefore,the combination of stratified waterflooding and water shutoff and profile control should be brought into full play to maximize the water injection utilization factor and improve the waterflooding development effect.Through the analysis of the geological characteristics of the X block and the big pore plugging technology,three-phase foam was selected for profile control.In this paper,in view of the poor development effect of reservoirs at the high water cut stage in X block,the combination of stratified waterflooding and three-phase foam profile control is used to maximize the water injection efficiency.The entropy weight algorithm and gravity center clustering analysis method are used to divide the water injection interval of the X block,and 4 sets of optimal interval combination schemes are formed.Based on the analysis of the calculation method of interval injection allocation,it is proposed to combine the gray correlation method,fuzzy math method and comprehensive division coefficient method to construct the enthalpy coefficient formula to calculate the sizing amount interval of each layer.According to the geological development characteristics of block X,the X-block geological model was established and numerical simulation was carried out.By comparing the development effects of stratified waterflooding and general waterflooding,the preferred scheme 2 is the optimal water injection scheme;in order to evaluate the deep profile control system suitable for the geological characteristics of high-water-bearing reservoirs and the physical properties of crude oil in the X-block,three-phase foam is selected through laboratory experiments.The composition of the system is:0.5%GD-1+0.6%CMC+400 mesh,5%bentonite,the adaptability of system is evaluated through a series of physical model experiments.The experiment results showed that this system has good performance in deep profile control,selective plugging,seepage capacity,liquid flow diversion and erosion resistance.When the reservoir heterogeneity is 4,it is best to inject 0.4PV three-phase foam,the injection pressure difference and the ultimate recovery factor of the reservoir can be significantly improved.This three-phase foam has a good profile control effect on the formation with permeability difference of 8,and the comprehensive recovery rate can be increased to 72.8%.Finally,the combination of stratified waterflooding and profile control is carried out for numerical simulation.When combined with profile control,the production effect is better than that of applying stratified waterflooding alone.The cumulative oil increase is 6.92×10~4 m~3 higher than that of applying stratified waterflooding.The oil recovery factor is 3.18%higher than that of applying stratified waterflooding alone.Combination of stratified waterflooding and profile control further improves the water injection utilization factor and waterflooding development effect. |
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