Large-Scale Application of Wet-Gas Metering at the Oman Upstream LNG Project

Abstract This paper describes the application of wet gas flow measurement to over 35 wells in the Oman Upstream LNG project. This multiphase metering process uses permanently installed wet gas Venturi meters at each well location in combination with a tracer dilution technique. Standard single phase venturi flow rate calculations are corrected for the mixed phase flow by published correlations. The tracer dilution technique, which involves the injection of suitable tracers into the flow line followed by sampling of the liquids, is applied periodically to enable the liquid to gas ratios to be determined. In the present case, wells are involved with condensate/gas ratios ranging from 350 m3/million sm3 to 800 m3/million sm3. Unique experience has been gained in implementing the wet gas metering process in a large scale installation, including the incorporation of the wet gas Venturi correction algorithm in the DCS system, the understanding of fluid PVT behavior and its effects on the calculations, and the optimal installation of venturi, tracer injection and fluid sampling hardware. To date the technique has provided results with an error of less than 10% for the gas phase. This continues to improve as more experience is gained and empirical data is collected. This paper describes the wet gas flow rate calculations, the sample production data supporting the validity of the technique, as well as a number of practical issues to be considered before applying this technique to continuous gas/condensate metering. The current application demonstrates that wet gas flow measurement has been applied successfully to large scale multiphase metering of individual gas/condensate wells, thereby providing continuous production data for reservoir surveillance whilst eliminating the need for expensive test separators and associated manifolds.