Research on the Perforation Avoidance Principle for Strong Water-Flooded Layers with High Water Cut in the S Oilfield of Bohai

After long-term development by water flooding, the highly water-flooded layer number has significantly increased in the S Oilfield. In this case, the traditional classification water-flooded layer method with the corresponding perforation principle can no longer meet the needs of current development. Therefore, the dynamic interference limit triggered by the difference in displacement efficiency was analyzed by utilizing the seepage resistance coefficient and the quantitative evaluation method of low-efficiency water injection. This work was conducted on the basis of the indoor physical model test and logging interpretation results. When the displacement efficiency was greater than 30%, the interlayer interference caused by the water cut difference was small, but when the displacement efficiency was 40%–45%, inefficient and ineffective water circulation was aggravated. Considering the above dynamic interference limit, a suitable classification type was proposed for the water flooded level in the high water cut period in the S Oilfield of Bohai. On this basis, a perforation principle was established with the interference limit of displacement efficiency as the core: In the high water cut period, there was no need to avoid perforation except for engineering factors when the water flooded level was from I to V. As the water flooded level reaches VI, perforation avoidance measures should be taken. After implemented the perforation scheme made according to the proposed perforation principle in the adjustment wells in the S Oilfield, the water cut was reduced by 8 percent points on average, which indicated good results.The research results demonstrate that the perforation avoidance principle above can avoid the strong water flooded layer with ineffective circulation of injected water, and can guide the formulation of the perforation scheme for reservoir with strong water flooded level.