泡沫油衰竭开采后续水驱提高采收率实验研究

Experimental study on enhanced foamy oil recovery after solution gas drive by waterflooding

通过物理模拟实验研究转驱压力和水驱速度对泡沫油衰竭开采后续水驱开发效果的影响,考察泡沫油水驱机制。结果表明:泡沫油流阶段是稠油溶解气驱过程中的主要产油阶段,在这一阶段的采出程度占最终一次采收率的90.91%;衰竭开采后续水驱中,溶解气驱采收率随转驱压力的降低而逐渐增大,水驱采收率随转驱压力的降低而呈阶梯式规律逐渐减小,总采收率在拟泡点压力3.1 MPa附近的开发效果最好,可达35.71%;转驱压力可能通过影响泡沫油流中油气两相在孔隙介质中的分布影响水驱稳定性,并且这种影响在高含水期前较为明显,对高含水期影响较小;水的渗吸作用是水湿性多孔介质中见水后水驱泡沫油的主要动力,水驱速度越小,渗吸作用相对越强,水驱采收率越高,水驱速度由2.5降为0.01 mL/min时水驱采收率可提高13.11%。

The influences of pressure at injection timing and injection rate on the waterflooding were investigated through physical simulation experiment,and the mechanisms of foamy oil recovery by waterflooding were explored.The results show that the foam oil stream is the main recovery phase during the dissolved gas drive in heavy oil,which dominates 90.91％ of the primary recovery rate.In the waterflooding of the natural depletion,the primary recovery gradually increases and the waterflood recovery decreases in a stepped law with the pressure at injection timing decreasing.The ultimate recovery reaches the maximum of 35.71％ at the pseudo-bubble point of 3.1 MPa approximately.The stability of waterflooding is possibly influenced by the varying distribution of oil and gas in porous medium aroused from the difference of core pressure.And the in fluence is significant only before the water cut is high.Water imbibition is the main mechanism of displacement after water breakthrough in water wet medium.The effect of water imbibition relatively increases with the decrease of injection rate,which leads to a higher recovery.The waterflooding recovery can be improved by 13.11％ when changing the injection rate from 2.5 mL/min to 0.01 mL/min.