An Optimal Combination Method of Injection Interval Based on Seepage Resistance

Abstract

Separate layer water injection is an effective way to alleviate the contradiction between layers. During the extra high water cut stage, the oil-water percolation capacity changed significantly, which leads to the increase of seepage difference in various oil layers. The interlayer interference is more prominent. The method of combining water injection intervals according to static parameters such as permeability and small layer thickness is difficult to meet the need of accurate water injection in the period of extremely high water cut. Therefore, the characteristic of seepage resistance in different water-cut stages is analyzed based on the oil-water two-phase relative permeability curve. The idea of water injection interval combination is changed from similar permeability in the middle and high water cut period to similar percolation resistance in the extremely high water cut period. The influencing factors of seepage resistance between oil and water wells are analyzed. Based on the principle of water and electricity similarity, the calculation method of seepage resistance in each small layer of injection well is established. The boundary of variable coefficient of seepage resistance is determined by numerical simulation. A new method of interval combination with the aim of minimizing the coefficient of variation of seepage resistance is established. The application effect of this method shows that the potential number of interval combination adjustment wells can be increased more than 30% in the water control and efficiency improvement test area of Daqing Changyuan Oilfield. After implementing the optimal combination of 10 injection wells, the water cut of the connected production wells decreased 0.2% and the production increased 606t, achieving a good effect of oil increase and water control in the context of 96% water cut. This method provides an effective method to control water cut rise and production decline in extra high water cut old oilfield.