Downhole Information Perception And Prediction Method Based On Ground Managed Pressure Data

In the process of managed pressure drilling(MPD),the change of bottom-hole pressure and flow is an important indicator for judging downhole working conditions.In the process of deep complex formation drilling,limited by the performance of the instrument,there is little downhole measurable information and the transmission time is long.Therefore,accurately estimate bottom-hole pressure and flow,and use the estimated information to diagnose abnormal conditions is of great significance to ensure safe and efficient drilling.To solve the above problems,this article divides the research content into the following parts:First of all,in order to overcome the problem of parameter uncertainty in the modeling of MPD system,an adaptive observer is established to adapt to the uncertain downhole friction integral and mud density,and to estimate the bottom-hole pressure and bottom-hole flow during drilling.At the same time,in view of the characteristics of modeling errors in the model and uncertain time-delay in the transmission process,a simultaneous identification algorithm of uncertain time-delay and parameters based on multi-input and single-output(MISO)system is proposed,and use the lagging bottom-hole pressure measurement data to identify and correct the modeling parameters,so as to improve the estimation accuracy of the adaptive observer.Secondly,different from the traditional method of constructing adaptive observer based on special coordinate transformation method,an observer matching condition that can decouple uncertain parameters is proposed for MPD systems that contains uncertain parameters in the unknown state.Based on the observer matching condition,an adaptive observer for jointly estimating uncertain parameters and unknown states is designed by constructive method,and the asymptotic stability of the estimation error is proved by the Lyapunov stability theory.Moreover,the observer gain is solved based on linear matrix inequality(LMI)method,which improves the robustness of the observer.Finally,a gas-liquid two-phase flow model is established based on the original hydraulic model for the special conditions that gas kick may occur downhole during the MPD process.At the same time,the downhole annular friction integral and bottom-hole gas influx are regarded as unknown parameters,and the bottom-hole flow is regarded as unknown state.An adaptive observer that can jointly estimate the unknown parameters and the unknown state is designed,and the bottom-hole pressure is estimated based on the ob sever.