注气体积和轻质油藏空气驱机制的关系探讨

通过细长管、填砂管氧化和驱替等一系列室内试验以及绝热条件下注空气过程的数值模拟研究注空气体积及不同注气阶段和轻质油藏注空气驱油机制的关系。根据试验和数值模拟分析结果,与其他气驱过程比较,给出典型轻质油藏空气驱替试验可能取得的原油采收率与注气体积关系理论曲线。结果表明,轻质油藏在不同注气体积条件下具有不同的驱油机制:注气体积小于0.5Vp(Vp为孔隙体积)即气体突破之前,烟道气驱为主要的驱油机制,驱油过程为一非混相气驱过程;注气体积大于0.5Vp即气体突破之后,烟道气和高温反应带共同作用的驱替作用表现为其主要机制;当反应带逐步推进至接近产出端时,反应带的热效应有可能成为重要的驱油机制。

Relationship between air volume and oil-recovery mechanism for light oil air injection process

The relationship between volume of air injected and oil-recovery mechanism for a light oil air injection process(LOAI) was studied through a series of laboratory experiments and numerical simulation including slim-tube tests,sand-pack displacement tests and numerical simulation of an adiabatic reaction process of LOAI.Based on the experimental and numerical simulation results and in comparison with other gas injection processes,a theoretical curve was given,which could be used for predicting the oil-recovery factor as a function of volume of air injected for oil displacement experiment under typical light-oil reservoir conditions.The results show that LOAI process may have different mechanisms during different injection stages related to the volumes of air injected.Up to 0.5Vp(porous volume) of air is injected(before gas breakthrough),the prevail oil recovery mechanism is flue gas driving,which is an immiscible gas flooding process.When the injected volume of air is over 0.5Vp(affter gas breakthrough),the combination of flue gas driving and the thermal effect induced by the oxidation may become an important oil recovery mechanism.Finally,thermal effect may become the dominate oil recovery mechanism when the thermal front approaches oil producers.