海上油田水驱开发注水压力优化

渤海B油田经过长期注水开发,注水压力逐渐上升,注水量不断下降,同时,酸化解堵效果变差,有效期变短,导致油田长期欠注,地层压降大,产量递减快。在实际注水过程中,注水井近井地带会形成一定污染,造成额外的附加压降,目前执行的注水压力界限是早期注水开发时的设计值,已不能满足当前的注水需要,亟需开展注水压力优化研究。因此,引入附加压降理论,运用流体力学原理计算实际注水压差,推导出理论无因次吸水指数,进而求得理论注水压差,并通过压降试井及酸化解堵效果来验证附加压降计算值的准确性,最终得到合理的注水压力,为油田提压注水提供依据。结合现场设备条件,在渤海B油田实施了23井次提压注水,在节省酸化解堵费用的同时,也取得了较好的增注稳油效果,为提高油田最终采收率提供保障。

Optimization of Water Injection Pressure in Developing Offshore Oil Reservoirs

Over years of waterflooding development, the water injection pressure has been increasing and the water injection pressure has been decreasing while the effect of acidizing treatment becomes worse, resulting in long-term insufficient injection, large formation pressure drop and rapid production decline in Bohai B oilfield. In actual water injection process, near-borehole pollution may occur and cause additional pressure drop. The injection pressure limit available at present was designed at the early waterflooding development stage, which cannot adapt to the current conditions, so it is urgent to research how to optimize the injection pressure. In this study, after introducing the theory of additional pressure drop, the actual water injection pressure differential was calculated based on fluid mechanics, the theoretical dimensionless water injectivity index was derived, and finally the theoretical water injection pressure differential was obtained. The accuracy of the calculated additional pressure drop was tested in wells with the results of pressure-drop well testing and acidization, and the reasonable water injection pressure was optimized. The result provides basic data for later water injection while increasing pressure. Depending on field equipment conditions, 23 well-time of water injection while increasing pressure have been implemented in B oilfield, which on the one hand, has saved acidization cost, and on the other hand, maintained oil production. It is helpful to improve the ultimate recovery in the oilfield.