Characteristics Of Water Flooding Development And Adjustment Countermeasures Of Chang 3 Low-permeability Reservoir In Z Well Area

The Chang 3 low-permeability reservoir in the Z well area is located in the middle of the northern Shaanxi slope in the Ordos Basin.As of June 2018,the phenomenon of declining and accelerating production and accelerating the rise of water cuts has generally occurred.At the same time,there are also problems such as uneven formation pressure and severe flooding in some areas.In order to grasp the characteristics of water flooding development in the study area,analyze the characteristics of remaining oil,and solve the problems of injection and production contradictions,a numerical simulation study was conducted.First,the reservoir engineering method is applied to study the characteristics of water flood development in the study area and analyze the decline law of the study area.The results show that the decreasing index is more in line with the development model of the study area,and the correlation coefficient is 0.6942.As of June 2018,the overall water content of the whole area exceeded 25%,and the comprehensive water content has a further upward trend,indicating that the water content of the well area has increased rapidly,and the improvement of the water flooding development effect is not obvious.The water injection utilization rate is basically between 0.6 and 0.7.At this stage,the water flooding index growth trend has slowed down significantly.The overall effect of water flooding development in the study area has been severely limited,and it is possible to further increase the recovery factor.Through the study of the microscopic seepage mechanism in the study area,the results show that the flow field in the well group of the Z well area tends to stabilize,and the fluid forms a relatively fixed flow channel.For low-permeability areas,the injection water does not reach or has a limited scope;the heterogeneity within the layer will also have an impact,and the combined effects of multiple factors will result in residual oil enrichment.In addition,at the corners of the reservoir,the influence range of the injected water is limited,and the flow field is not significantly changed.There is also the phenomenon of residual oil enrichment in the hypertonic zone of these parts.In addition,by optimizing the development plan of the research area,it is considered that the well spacing in the Z well area is controlled at about 300 meters,which corresponds to the highest economic benefit.It is reasonable to maintain the formation pressure at about 1.0.It is recommended that the injection area in the research area be increased to 1.5 In order to increase the development efficiency of the reservoir,and at the same time control the rate of declining production within a reasonable range.