注氮气改善稠油蒸汽吞吐后期开采效果

蒸汽吞吐后期随着地层能量枯竭和井筒周围含油饱和度减少，周期含水升高，油气比下降，开采效益变差。注氮气是改善稠油蒸汽吞吐后期开采效果的有效途径，其主要增产机理是增加蒸汽波及体积，补充驱动能量，进一步降低残余油饱和度和提高回采水率。模拟研究表明，在吞吐后期宜采取先注氮气，后注蒸汽的注入方式，并且存在一个优化的周期注氮量。

Improve Steam Soaking Performance by Injecting Nitrogen

At the late stage of steam soaking, the reservoir pressure is low, so is the oil saturation within the wellbore area, while the water cut is high and the ratio of oil to gas low, which means the reservoir production get worse. Nitrogen injection is an effective way to improve oil recovery at late stage of steam soaking, which increases the steam soaking volume and provides displacement energy to reduce residual oil saturation and enhance recovery. The results from reservoir simulation indicated that it is reasonable to inject nitrogen first and then steam at late steam soaking, and there exists an optimum nitrogen volume in a injection cycle.