钻井气液两相流体溢流与分布特征研究

Research of Kick and Distribution Features of Gas-Liquid Two Phase Flow During Drilling

常规钻井返出管线敞口,钻井液在返出管线中流动为非满管流动,小气侵量时,泥浆池液面变化不明显,检测装置无法测量液面变化,钻井液返出流量无法测量或者测量误差较大,无法感知小流量差的变化。本文基于气液两相流理论建立了井筒气液两相流参数与井口溢流速度的关系模型,计算表明气侵速度越大,气泡运移距井口越近,井口溢流速度越大。并以空气和钻井液(非牛顿流体)为介质,基于VOF多相流模型,模拟了钻井液返出流量变化时气液界面变化情况,分析了纯钻井液和不同含气率钻井液在返出管线流动时液面变化特征,得出纯钻井液流动时喇叭口处液面变化最明显,优化液面检测装置安装在喇叭上,更能准确及时地检测液面变化早期发现溢流,进气速度影响返出管线钻井液液面稳定性。

Because of the opening of mud return pipe, the pipe is not full of drilling mud. When gas kick is little, the change of pit gain was indistinct, so the detection device would not be available to reflect fluid level. According the undetectable or incorrect disadvantages and default of kick detection, this paper has established the relationship between wellhead kick velocity and gas-liquid two phase flow in wellhole based on the theory of two phase flow, and the result shows that the greater of the velocity of kick, the greater of wellhead kick velocity, and the wellhead kick velocity becomes also greater with the upper movement of bubble. Based on air and mud （non-Newtonian fluids） medium and VOF method, this paper has analyzed characters of mud level of return pipe with pure mud and different void fraction. According to the results, the mud level is most obvious in the bell nipple when the fluid is pure mud. When the device is installed on the bell mouth, pit level change monitoring would be more accurate and without delay to detect early kick, and the stability of mud level in return pipe would be effected by kick velocity.