Estimation of volume fraction and flow regime identification in inclined pipes based on gamma measurements and multivariate calibration

Abstract

A combination of gamma measurements and multivariate calibration was applied to estimate multiphase flow mixture density and to identify flow regime. The experiments were conducted using recombined hydrocarbon fluids sampled from an onshore receiving terminal including hydrate thermodynamic inhibitors (monoethylene glycol and methanol (MeOH)). These hydrate inhibitors were added to deionised water at 60% concentration by volume. The experiments were conducted at a temperature of 0 °C and a 75‐bar pressure, comparable with deep water production on the Norwegian continental shelf. Two angles of inclination (1° and 5°) and two water cuts (15% and 85%) were investigated. A single‐energy gamma densitometer was installed on the test facility for measuring the mixture density, whereas the dual‐energy gamma densitometer was traversed linearly from the bottom to the top of the pipe for multivariate calibration and prediction. Seventy partial least square prediction models were calibrated based on single‐phase experimental data. These models were used in estimating the mixture density and identifying the flow regime in all the experiments. The estimated mixture densities were accurate as compared with those from the single‐energy gamma densitometer with the root mean square error of prediction of 13.6 and 9.7 kg/m3 for 1° angle of inclination and 17 and 26.6 kg/m3 for 5° pipe inclination. The models were also able to identify the flow regimes investigated for both 1° and 5° angles of inclination. Copyright © 2012 John Wiley & Sons, Ltd.