An innovative diagnosis method for lost circulation with unscented Kalman filter

In the simulation, the estimated pressure and outlet flow rate trace the measurements well with the evolution of pressure-loss factors and flow rate factor. Moreover, the pressure-loss factor in annulus and flow rate factor, which fluctuate to a little extent in normal drilling condition, deviate from the base value once lost circulation occurs. The simulation indicates the superior performance of the diagnosis method with the introduction of pressure-loss factors and flow rate factor, and the average error of estimated loss depth is less than 5%. In addition, the parametric sensitivity analysis illustrates the universality of the diagnosis method, which has certain ability to improve drilling safety and efficiency with lower NPT.