2006 24th International North Sea Flow Measurement Workshop
Wet Gas Metering Using Combination of Differential Pressure and SONAR Flow Meters
A method to measure the gas rates and liquid rates of Type I and Type II wet gas flows is presented. The approach combines a differential pressure-based (DP) gas flow meter with a SONAR-based flow meter to provide two independent measurements of the wet gas mixtures, each with distinct and repeatable over-report characteristics due to wetness. The outputs of the two devices are then interpreted to provide gas rate and liquid rate of wet gas flows.
Experiments were conducted to validate the ability of the combination of DP and SONAR meters to measure gas and liquid rates of wet gas flows. The over-report due to wetness of a 0.6 beta ratio venturi (DP meter) and a clamp-on SONAR-based flow meter were characterized over a wide range of flow conditions broadly representative of oil and gas production and processing conditions. The experimentally determined over-report due to wetness of each was shown to be in good agreement with theoretical models predicting the over-report associated with well-mixed gas / liquid mixtures for each device.
The ability of the combination of the DP and SONAR meters to determine gas and liquid flow rates was evaluated using experimentally determined wetness sensitivity coefficients to solve for the gas and liquid rates based on the outputs of the venturi and SONAR meters installed in series on a test loop. The combination was shown to accurately measure gas flow rates to within ~+/- 2% and liquid rates to within +/-10% over a wide range of wet gas flows with gas oil ratios ranging less than 4000 scft/bbl to greater than 100,000 scft/bbl.
The results of these experiments suggest that the combination of a clamp-on SONAR-based flow meter and a differential pressure-based device is a viable means to provide both liquid and gas flow rates of type I and II wet gas flows.