重力稳定气驱判别模型和试验

Gravity assisted gas injection: assessment model and experimental study

通过室内试验,研究储层倾角、注入速率和原油黏度等因素对重力稳定注气提高驱油效率的影响,根据注采数据和管内残余油砂分布,分析其提高采收率原理。通过理论推导,建立简易量化的顶部注气重力稳定判别模型NGAGI,综合考虑储层倾角、渗透率、驱替液与被驱替液密度差异、原油黏度和注气速率等因素的影响。结果表明:增大地层倾角、减小注气速率和降低原油黏度,可延长重力稳定高效驱油时间,提高采收率,气驱后管内残余油砂分布显示,排除端部效应导致模型两端效果不好,模型中部重力稳定气驱后残余油饱和度低于10%;当NGAGI>1时,可实现重力稳定气驱模式,并通过室内和矿场试验验证,可有效评价重力稳定气驱前缘稳定性,为油田矿场应用提供一定的决策依据。

In this study,laboratory experiments were conducted to investigate the displacement efficiency and mechanisms of GAGI,and the effects of dip angle,injection rate and oil viscosity on oil recovery were tested. The residual oil distribution after gas displacement and overall oil production were analyzed to reveal the EOR mechanisms of GAGI. A quantified GAGI assessment model（ the NGAGInumber） was proposed,in which the geological and operational parameters were considered,such as dip angle,the density defference between the displacement and displaced fluids,oil layer permeability,crude oil viscosity and injection rate. The experimental results show that large dip angle,low injection rate and low oil viscosity can stabilize the gas/oil contact and improve oil recovery,and the residual oil saturation can be less than 10% after gas displacement. The experimental and field data indicate that gravity stablized gas injection can be realized when the NGAGInumber is greater than 1. The proposed NGAGImodel can be used as a creterion to assess the stablity and efficiency of GAGI for field project design and operation.