渗吸作用是开采基质孔隙原油的有效方法，但渗吸作用的动力问题一直没有得到很好的解决。文中应用渗流力学的基本原理，研究了渗吸作用的动力问题。渗吸作用的动力不是毛管压力，而是浮力。毛管压力是渗吸作用的阻力，加入表面活性剂可减小毛管压力，从而提高驱油效果。渗吸作用的驱油机理是重力分异，需要的时间较长，间歇注水、周期注水及低速注水均可提高开发效果。

Imbibition is an effective method to flood the oil in matrix pores of reservoirs. However, the mechanism of imbibition is not understood properly and correctly. A study was made about the mechanism of imbibition with the principles of flow in porous media. The driving force of imbibition is buoyancy rather than capillary pressure. On the contrary, capillary pressure is the resistance of imbibition. Surfactants added to injection water can reduce capillary pressure and increase the efficiency of oil recovery. The mechanismof imbibition is the gravity separation of oil and water in pores, which needs long time to finish the process. Interval water flooding, periodical water flooding and low speed water flooding are good methods to recover oil by imbibition.