气侵期间岩屑运移规律研究

基于井筒多相流、传热学原理,综合考虑高温高压下天然气和钻井液物性参数变化,建立了环空气液固多相流数学模型,并采用多相流流动和井筒-地层传热耦合方法进行数值求解,着重进行气侵期间岩屑运移规律和敏感性参数分析。计算结果表明:相比泡状流,段塞流携岩能力较差,不利于维持井眼清洁;随着井口回压/循环排量的增加,气相体积分数逐渐减小,岩屑体积分数逐渐增加,而当流型发展为段塞流时,岩屑体积分数随井口回压/循环排量的增加而减小,而气侵量对其的影响正好相反;钻井液塑性黏度、机械钻速、岩屑粒径以及岩屑颗粒球形系数对气相体积分数基本没有影响,而对岩屑体积分数影响较大。

The research of Cuttings migration during gas invasion

Based on wellbore multiphase flow and heat transfer theory, a mathematic model for annular gas liquid solid multiphase flow is built considering the property parameter changes of gas and mud in high temperature high pressure (HTHP). The model has been solved by multiphase flow and wellbore-formation transmission coupling methods. The cuttings migration law parameter sensitivity during gas cut were emphatically analyzed. The calculating results show that: slug flow has a poor cuttings carrying capacity compared with bubble flow, which will adversely affect hole cleaning; with wellhead back pressure/pump rate increasing, gas rate reduces and cuttings content increases, but when the flow pattern develops to slug flow, cuttings content would decrease with the increase of back pressure/pump rate, and amount of gas cut would increase; mud viscosity, ROP, particle size and spherical coefficient can hardly affect gas volume fraction, but have great impact to cutting volume fraction .