Evaluation of Commercially Available Virtual Flow Meters (VFMs)

Abstract

This report documents a project to improve subsea flow measurements to allow the flowrates of individual wells to be known more accurately. Because production revenues are determined from flowrates, improved flow measurement reduces the financial risk to stakeholders, including producers and the U.S. government. Improved measurement also helps to improve reservoir recovery. In this study, commercially available flow models were evaluated for their suitability as virtual flow meters (VFM). Virtual flow meters use input from sensors installed at various measurement points (nodes) in the wellbore, on the seabed and in surface facilities. The evaluation of this approach to flowrate metering is particularly meaningful in deepwater subsea applications to complement and backup physical measurements robustly and in a cost effective manner. The soft implementation of this modeling approach leverages already existing information from various measurement devices in the in the wellbore and subsea infrastructure. The study aimed at assessing the implementation and performance of commercially available VFM software packages using real production data from a subsea well equipped with a subsea multiphase flowmeter (MPFM). The study consisted of three evaluation rounds involving five commercial VFM products. The models were tuned incrementally using the subsea multiphase meter elemental computing parameters consisting of total mass flowrate, gas volume fraction (GVF), and water-liquid ratio (WLR). The results from a series of ‘blind’ tests were compared to actual flowrates with the objective to establish the sensitivity of the models' results to the measurement devices, the parameters used in the tuning, and measurement devices and fluids properties inconsistencies. Compared to other evaluations, the study is based on existing production data from a live well in which extensive data quality checks were necessary prior to sharing the data with VFM suppliers. Such effort led to consistent and conclusive results from at least three VFM packages that completed all three study rounds. The findings from the study using this data set confirm the robustness of VFM techniques in estimating production flowrates with adequate tuning. It was also established that VFM can be a cost effective and reliable backup measurement instrument to an ailing subsea multiphase meter where partial meter measurement and VFM can restore functionality to the combined flow measurement system.