摘要：The effective way to enhance water flooding recovery for the reservoir with low permeability and strong vertical heterogeneities is separated layer water flooding.In this paper,a new nodal analysis model for separated layer water injection well was established,and the data collected from a well from the G8 oil field in Changqing low-permeable reservoir was taken as an example,then the influence factors of the injection rate and pressure for separated layer water injection and the application boundary of separated layer water injection process were calculated and analysed.The results show that: the trial method based on the method of step by step searching approach in the numerical solution for nonlinear equation set can rapidly and accurately solve the nodal analysis model for separated layer water injection,especially separated multi-layer water injection well; For separated layer water injection in low-permeability reservoir,appropriately increasing wellhead injection pressure can significantly improve the injection rate of the under layer with lower permeability.The larger the permeability contrast and the larger interlayer pressure difference in reservoir,the smaller the injection rate of under layer with lower permeability,comparing to the upper layer with high permeability,and the larger the change of bottom hole injection pressure for the under layer; In order to achieve well displacement efficiency in separated layer water injection to low-permeability reservoir,it is necessary to determine the process applicable boundary.For field G8,the boundaries are the formation pressure has to be lower than 28~30MPa,the permeability needs to be greater than 0.4-0.5 x 10"3pm2,and the minimum wellhead injection pressure must to be 17MPa.This study provides a corresponding theoretical basis for clarifying the characteristics and laws of separated layer water flooding in low-permeable reservoir,as well as improving the effect of the fractional process.
关键词：Low-permeability reservoir;separated layer water injection;nodal analysis;permeability contrast;interlayer pressure difference
