Data reconciliation in gas pipeline systems

In natural gas pipeline systems, all product transactions are based on flow rate measurements. Thus, it is essential to have good estimates of these variables. Currently, these variables are estimated using data reconciliation based exclusively on material balances. To improve these estimations, an approximate methodology that includes material balances as well as mechanical energy balances is presented. This method is based on iterations between a simplified model and a rigorous simulation model developed in SIMSCI's PRO/II 5.55 system. A new method of performing observability analysis is also developed to take into account the nonlinear mechanical energy equations and pressure measurements. Finally, because temperature measurements are used to define density, the influence of temperature measurement errors on the accuracy of the estimators is analyzed. Several examples are presented to illustrate the effectiveness of the methodology. The proposed technique proves to be very effective computationally and generates better estimates than techniques in which only material balances are used.