控压钻井停止循环期间垂直环空连续气侵机理研究

RESEARCH ON VERTICAL ANNULUS CONTINUOUS GAS CUTTING DURING STOPPING MANAGED PRESSURE DRILLING CIRCULATION

为了提高控压钻井精度、反馈速度,确保井筒物质平衡及钻井安全性,有必要深入开展停止循环工况下的气液两相瞬态流动规律研究。基于计算流体动力学方法,应用VOF方法对停止循环期间垂直环空连续气侵的机理进行了数值模拟研究,得出了气侵发生后环空流体的运动特性。结果表明,气侵量越大,被顶出的钻井液体积越多、井底压力越小,但当气相的能量不足以将剩余的钻井液携带出井口时,井筒混相流体的流动由瞬态变为拟稳态的零液量流动,与常规气液两相流动一般性规律不同,零液量流动摩阻压降为负值。

In order to improve the control accuracy and feedback speed of managed pressure drilling and ensure material balance and drilling security,gas- liquid transient flow law should be further studied under the condition of non- circulating. Based on computational fluid dynamics method,VOF model was applied to simulate the mechanism of vertical annular continuous gas kicks during non- circulating condition and annular fluid flow behavior finally was obtained after gas kicks. Results indicate that the more volumes of drilling fluid are ejected and bottom hole pressure is lower as the gas kick volumes are higher.However,wellbore miscible fluids flow change from transient into pseudo steady state zero- net liquid flow( ZNLF) when the gas phase energy are not enough to carry the rest of drilling fluid. In contrast with conventional general laws of gas- liquid two phase flow,the frictional pressure drop of ZNLF is negative.