2007 25th International North Sea Flow Measurement Workshop
Wet Gas Metering Using Sonar-based Flow Meters and Piping Pressure Loss Gradients
Convenient and accurate measurement of gas and liquid rates of wet gas mixtures represents a long standing challenge within the oil and gas industry. Recently, sonar-based flow meters have been demonstrated to provide accurate measurement of the mixture flow rate of wet gas mixtures on a clamp-on basis. This paper describes an approach which combines sonar-based flow meters with the measured pressure drop across a section of pipe to provide gas and liquid flow rates. The approach leverages recognition that variations in the pressure gradient along a given section of pipe containing a wet gas mixture are primarily determined by the flow rate and liquid content of the mixture. In this approach, a sonar-based flow meter provides the mixture flow rate, and the measured pressure drop across a section of fixed geometry piping provides a basis to determine the liquid loading. The interpretation of the measured quantities in terms of gas and liquid flow rates is performed using either empirical data-based model or with the assistance of a multiphase flow model. The approach is of particular interest in applications in which pressure gradient measurements either exist, or can be installed without requiring a process shutdown. Two data sets are provided demonstrating the utility of this approach: 1) a laboratory test with data spanning range of flow rates and pressures with wetness levels predominately in range of 0 to 2.0 Liquid Gas Mass Ratio, and 2) a field test in which the measured produced gas and liquid rates from a wet gas well are compared to test separator measurement over a range of flow rates and wetnesses ranging from 0.08 to 0.15 Liquid to Gas Mass Ratio.