Increasing the measurability range of a gas flow rate sensor by time series measurements

In this paper we present a technique for extending the measurability range of a gas flow rate sensor (orifice meter) used for measuring the gas production in oil wells. To achieve that, we propose the use of a recursive least squares estimator whose parameters are updated in real time. A time series model is used to estimate the gas flow when it exceeds the range of the orifice meter. We tested the algorithm in a pilot plant that emulates an oil production method denominated “plunger-lift”. Since the algorithms must run in real time, to evaluate the adequacy of the model used, we had to adapt the expressions of the autocorrelation, cross-correlation, the mean and variance, in order they could be evaluated recursively. The main advantage of this approach is that the algorithm can be easily incorporated to the plant supervisory system with no need of hardware changes in the production plant.