Optimal Method Of Reasonable Pressure System For Partial Pressure Water Injection

Most water-cut or high water-cut oilfields in China have always adopted stratified quantitative water injection technology to solve and realize the problems to achieve the purpose of stable production and low consumption.However,due to certain limitations of stratified quantitative water injection technology,it is bound to fail to realize the injection-production balance of the target reservoir,therefore,it is difficult to achieve the expected purpose.Stratified quantitative water injection cannot realize real quantitative water injection.If we want to ensure the long-term stability of bottom hole pressure and realize stratified effective drive,we must carry out optimal design of reasonable pressure system for partial pressure water injection,and establish a technological process that can not only overcome the influence of water injection starting pressure gradient,but also realize dynamic monitoring of seepage pressure.Constant pressure water injection technology combines the purpose of water injection with water injection measures,which not only dynamically monitors the water injection pressure and water distribution speed,but also effectively avoids a large number of ineffective injection-production cycles,so that all layers in the well are balanced and the effect of water-drive oil production is remarkable,but there are few researches on this aspect at present.Based on the production background and the geological situation of a test block,a 3D geological model is established in this paper,which quantitatively characterizes the static characteristics of the target reservoir,and establishes data volumes such as effective formation thickness and main seepage physical properties.The distribution of remaining oil in the study area is quantified,and the flow distribution law in all directions of each layer is clarified.Based on the test well of the test block X-1.Combined with the dynamic index and static data of the oil well,the high value area of movable oil saturation and the horizon with large permeability increase of the test well are defined considering the distribution law of remaining oil and the effect of oil well linkage.Through the analysis of typical horizons,the direction and horizon of possible dominant channels in X-1 test well are implemented.Therefore,the measure types of horizon of the test well are finally determined.In this paper,the starting pressure of each layer in X-1 test well is measured by preset cable intelligent injection measurement and adjustment system for the first time.Based on the calculation formula of plane radial abortion energy in seepage mechanics,the starting pressure gradient corresponding to each layer in water injection well is calculated,and thecalculation model of stratified reasonable water injection pressure gradient in each layer is established.Three kinds of water-drive experiments with three-pipe parallel artificial cores under different conditions are designed according to the basic physical parameters of square cores.The experimental results show that the average recovery ratio corresponding to water-drive by pressure control-pressure increasing technology is 56.29%.Experiments show that for multi-layer reservoirs developed by long-term water injection.After forming a dominant seepage channel in the reservoir,the water absorption profile of different strata can be adjusted and controlled by controlling the injection pressure of high permeability layer and increasing the injection pressure of low permeability layer,so as to fundamentally realize the purpose of improving the overall production degree and water injection qualification rate of the reservoir by layered constant pressure water injection.Through the above research,it is concluded that constant pressure water injection can improve the injection pressure of low permeability layer and control the injection pressure of high permeability layer to a greater extent on the basis of geological injection allocation,thus alleviating the contradiction between layers and adjusting the water absorption profile to the greatest extent,and finally realizing the purpose of improving the utilization rate of water injection and the vertical production degree of reservoir.While enriching and developing the optimal design method of reasonable pressure system,this paper has certain theoretical and practical significance for adjusting the development measures of layered constant pressure water injection technology.