Advanced leak detection in oil and gas pipelines using a nonlinear observer and OLGA models
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An adaptive Luenberger-type observer with the purpose of locating and quantifying leakages is presented. The observer only needs measurements of velocity and temperature at the inlet and pressure at the outlet to function. The beneficial effect of output injection in form of boundary conditions is utilized to ensure fast convergence of the observer error. This approach is different from the usual practice where output injection might appear as a part of the PDE s. This makes it possible to employ OLGA, which is a state of the art computational fluid dynamics simulator, to govern the one-phase fluid flow of the observer. Using OLGA as a base for the simulations introduces the possibility to incorporate temperature dynamics in the simulations which in previous work was impossible. The observer is tested with both a straight, horizontal pipeline and an actual, long pipeline with difference in altitude. Both simulations with oil and gas are carried out and verification of the robustness of the observer is emphasized. In order to cope with modelling errors and biased measurements, estimation of roughness in the monitored pipeline is introduced.