Study On Main Influence Factors Of Cycle Waterflooding With A Combination Of Horizontal Well And Vertical Well In Tight Reservoir

As an important replacement resource,tight reservoir has become a hot spot of research.As the matrix permeability is very low,conventional water flooding doesn't work well in this kind of reservoir.consequently the production decrease rapidly and the energy supplement is difficult.In this paper,the XL block in Yanchang Oilfield was taken as the research area.In order to obtain the model of seepage oil production's velocity of core and check the feasibility of cycle water injection experiments,the natural cores of the XL block in Yanchang Oilfield were used as the experimental sample to launch spontaneous imbibition experiments and conventional water injection and cyclic water injection experiments.Because of imbibition effect between the artificial fractures,the natural fractures and the matrix core,the mathematical model of cycle injection of fractured tight reservoirs was established by improving the oil-water two-phase seepage flow equation.And the finite difference method is applied to solve the above cyclic water injection mathematical model.The seepage differential equation was used to simulate the injection process of indoor core,and the simulation results ware compared with the experimental results to verify the correctness of the mathematical model.In order to optimize the parameters of cycle water injection,the effect factors on the cycle water injection,including water injection speed,liquid production rate,single cycle time and cycle injection timing,were analyzed one by one.Taking into account the characteristics of planar heterogeneity in the study area,different working system of injection and production ware adopted for the high permeability and low permeability zones,and the relevant injection and production parameters for asymmetric cycle injection ware optimized.Research shows that the influence degree of that factor on the effect of cyclic water flooding is as follows:water injection rate>liquid speed>water-flooding timing>cycle time.The optimal parameters of injection and production in asymmetric periodic water flooding are as follows:for high permeable region,periodic water injection rate is 600m~3,water injection speed is 6.0 m~3/d,liquid production rate is 10 m~3/d,the time of water flooding is 100 days.for low permeable region,periodic water injection rate is 675m~3,water injection speed is 5.6 m~3/d,liquid production rate is 12.5 m~3/d,the time of water flooding is 120 days.