Evaluation of Kalman filters for estimation of the annular bottomhole pressure during drilling

Abstract

Estimation of the annular pressure at critical locations in the well is crucial for high-precision pressure control. Certain parameters which are important in order to determine the pressure profile of the well (in particular the friction factor, bulk modulus and density in the annulus), are encumbered with high uncertainty and are besides, continuously, but slowly changing. The objective of the thesis is to employ various Kalman filter designs estimation of the bottomhole pressure and certain important parameters/slowly varying variables, during drilling. Topics that should be addressed are: 1) Literature review of the theory of Kalman filters design 2) Design and implement an Extended Kalman filter (EKF) and possibly the Unscented Kalman filter (UKF) for a) Estimation of the annulus bottom-hole pressure b) Esimation of the friction coefficient, bulk modulus and density in the annulus 3) Analyse the performance/robustness of the observer in important cases, in particular: a) Pipe connection b) Pump ramp up/down 4) Examine observer performance to unmodeled dynamics by testing the Kalman filter against data sets from Wemod 5) Evaluate performance of the observer against experimental data from Grane.