水驱油效率可达到 100%

水驱油之后地层中还存在大量剩余油，如何将其经济而有效地开采出来是老油田挖潜调整要解决的主要问题。 注入水的波及系数低和驱油效率低都会导致地层中存在剩余油。 残余油的存在是驱油效率低的主要表现，其往往由快速注水驱替过程中的 Jamin 效应所致。 提高注水速度可以克服 Jamin 效 应并提高驱油效率，但该方式很费水，工程条件一般不允许。 长期水洗也可以提高注入水的驱油效率，但该方式也较费水，经济效益较差。 浮力驱油也可以消除 Jamin 效应，并大幅度提高驱油效率，甚至可将驱油效率提高至 100% 。 对于中高渗透储层，可采用周期注水的方式，充分利用浮力的作用来提高驱 油效率，节省注水成本，提高油田开发效益。

The efficiency of water flooding can reach 100%

There is a large amount of remaining oil in reservoir after water flooding. How to recover remaining oil efficiently and economically is a main task in old oilfields. The remaining oil in reservoirs is by low sweep efficiency and low displacement efficiency. The low displacement efficiency of reservoirs is usually caused by residual oil in water flooded area. The residual oil is formed by Jamin effect of capillary pressure. Higher injection rate of water may overcome Jamin effect and increase the displacement efficiency of oil, however it wastes water and is not allowed by common engineering conditions. Long term water flooding can also increase the displacement efficiency of oil, but it wastes water too and has not economic benefit. Buoyance drive can increase the displacement efficiency of oil by elimination of Jamin effect, and even the displacement efficiency of oil can be raised to the final limit of 100%. For middle or high permeability reservoirs, periodical injection of water can be used to increase the displacement efficiency of oil by buoyance drive and cut down the cost of water injection for higher economic profit of oilfield development.