间歇生产气井关井续流阶段井筒内流体状态气液劈分模拟方法

间歇生产井大部分无封隔器,从储层产出的气水存在气液量劈分以及油管、环空内液面高度随关井时间变化等问题。常规处理办法是通过简单假设气液在管鞋处的油套管流向来确定关井阶段油套管液面变化,会产生较大的误差。采用离散井筒模型,考虑零液流两相流动规律和油套管压力平衡,建立天然气井间歇生产气液劈分模型。利用该模型可以获取气泡在零液流液柱流动过程中的压力分布、流型变化、液柱高度波动、气泡流速等关键参数。同时,搭建全尺寸井筒实验装置模拟间歇生产井关井阶段气泡上升过程,通过摄影机观察零液流液柱中流型分布,测量液柱中气泡速度和压力。研究结果表明,气泡在零液流液柱中主要分布形式是分散气泡和泰勒泡,随着气体流速增大,泰勒泡流动占主导因素。根据实验结果对所建立的模型中流体压力、流型变化和气泡速度进行验证,准确率超过95%。该模型可精确描述间歇生产气井关井续流阶段气液流动规律和压力分布。

Investigation on Liquid Holdup in Vertical Zero Net-Liquid Flow

Zero net-liquid flow (ZNLF) is a special case of upward gas-liquid two-phase flow. It is a phenomenon observed as a gas-liquid mixture flows in a conduit but the net liquid flow rate is zero. Investigation on the liquid holdup of ZNLF is conducted in a vertical ten-meter tube with diameter of 76 mm, both for Newtonian and nonNewtonian fluids. The gas phase is air. The Newtonian fluid is water and the non-Newtonian fluids are water-based guar gel solutions. The correlations developed for predicting liquid holdup on the basis of Lockhart-Martinelli parameter are not suitable to ZNLF. A constitutive correlation for the liquid holdup of vertical ZNLF was put forward by using the mass balance. It is found that the liquid holdup in ZNLF is dependent on both the gas flow rate and the flow distribution coefficient.