控压钻井系统井下不确定参数与未知状态估计

Estimation of downhole uncertain parameters and unknown state of managed pressure drilling

针对控压钻井过程中井下信息获取难度大的问题,本文设计了一种可以同时估计井下不确定参数与未知状态的自适应观测器.首先,针对未知状态中含有不确定参数的控压钻井系统,提出了一种可解耦不确定参数的观测器匹配条件.其次,根据此观测器匹配条件设计自适应观测器估计井下参数与状态,并通过李雅普诺夫稳定性理论证明了估计误差的渐近稳定性.最后,基于线性矩阵不等式方法求解观测器增益,提高观测器的鲁棒性.仿真分析表明:与已有针对控压钻井系统设计的自适应观测器相比,本文所设计的观测器对井下环空摩擦积分和井底流量的估计具有更好的收敛性以及鲁棒性.

Aiming at the difficulty of obtaining downhole information in the process of managed pressure drilling,this paper designs an adaptive observer that can simultaneously estimate the downhole uncertain parameters and the unknown state.First of all,an observer matching condition that can decouple uncertain parameters is proposed for managed pressure drilling systems that contain uncertain parameters in the unknown state.Then,an adaptive observer is designed based on the observer matching condition to estimate downhole parameters and state,and the asymptotic stability of the estimation error is proved based on the Lyapunov stability theorem.Finally,the observer gain is obtained based on linear matrix inequality(LMI)method to improve the robustness of the observer.Simulation analysis shows that compared with the existing adaptive observer for managed pressure drilling system,the proposed observer has better convergence and robustness for the estimation of downhole annular friction integral and bottom-hole flow.