控压钻井井下气侵工况的自适应参数及状态估计

Adaptive parameter and state estimation of managed pressure drilling while downhole gas kick

针对控压钻井过程中井下可能发生气侵的特殊工况,提出一种可在异常工况下估计井底压力,并借此判断异常工况的方法.首先,基于简化的漂移通量模型,在传统控压钻井水力学模型中添加气体膨胀项,建立控压钻井气液两相流模型;其次,将井下环空摩擦积分和井底气侵量视为未知参数,将井底流量视为未知状态,设计一种可对未知参数以及未知状态进行联合估计的自适应观测器,并以此为基础估计井底压力;最后,通过仿真实验验证所提方法的有效性.仿真结果表明,所建气液两相流模型可在井下发生气侵时模拟井底压力变化,且所提观测器能实时准确地跟踪井底流量及压力变化.

This paper proposes an estimating bottom-hole pressure under abnormal conditions and judge abnormal working conditions method for the special conditions where gas invasion may occur downhole in the process of managed pressure drilling.Firstly,based on the simplified drift flux model,the gas-liquid two-phase flow model of managed pressure drilling is established by adding the gas expansion term to the traditional hydraulic model.Then,considering the downhole annular friction integral and bottom-hole gas influx as unknown parameters,and the bottom-hole flow as unknown state.An adaptive observer that can jointly estimate unknown parameters and unknown state is designed,and the bottom-hole pressure is estimated based on the obsever.Simulation experiments verify the effectiveness of the proposed control method.The simulation results show that the gas-liquid two-phase flow model can simulate the change of bottom-hole pressure when gas kick occurs downhole,and the observer can accurately track the changes of bottom-hole flow and pressure in real time.