TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMultiphase wellhead flow measurements using the tracer technology method have been successfully applied to over 65 wells in the Dulang field, located offshore Malaysia. A large range of flow conditions were covered with gas rates ranging between 943 m3/d and 165,900 sm3/d, oil rates between 20 m3/d and 319 m3/d, and water rates up to 489 m3/d. The watercut varied between 0% and 93%. The results obtained using the tracer technique was used as a cross-reference to the results obtained from conventional well tests using the test separator and to a separate multiphase meter during a trial period.The present tracer method involves injection of selected tracers for oil, gas and water at a specific injection rate into the production stream followed by subsequent sampling of the fluids at a suitable downstream location. Measurement of the tracer dilution ratios allows the accurate determination of the individual fluid flow rates.The application has proven the tracer technology method to be a robust and accurate multiphase flow measurement technique over a wide range of flow conditions. In practice the tracer method is capable of measuring over a much wider range than most test separators and multiphase flow meters making the technique very well suited for in-situ verification and calibration of installed multiphase and wet gas flow meters.

Wet gas metering technology was chosen by ExxonMobil for continuous well testing and advanced production measurement at two satellite platforms located in the South China Sea offshore Malaysia. The satellite facilities are equipped with permanently installed SmartVent wet gas venturi based meters at each well location. Special wet gas flow calculation and monitoring software have been developed and installed on a separate flow computer installation interfaced to the host platform DCS system. Prior to installation the wet gas meters have been subjected to full scale testing at a representative high pressure gas/liquid flow test facility. This has resulted in valuable measurement experience and a unique set of experimental wet gas data. After start up of the field on-site verification/calibration will be performed using the tracer technology method. As of today valuable results have been obtained from the system. The present application is a demonstration that wet gas flow measurement is increasingly gaining acceptance in replacing expensive well test separators and related infrastructure in gas/condensate field developments. Besides the significant cost savings, the availability of continuous readings of each well's production rates allows for enhanced reservoir management and production optimisation. At the same time experience has shown that successful implementation of wet gas flow measurement requires adequate attention to every aspect of the metering process. Introduction Significant cost savings related to production testing of gas/condensate wells can be realised if conventional test separators and related infrastructure are replaced by SmartVent wet gas venturi based flow meters in each well flow line, and the wetness of the flow is verified/calibrated using the non-radioactive MultiTrace tracer technique[1,2,3,4]. Accurate wellstream PVT samples can be obtained in combination with the tracer samples for EoS flash calculations and process simulation. The corrected gas flow rate can be verified via the use of the MultiTrace gas tracer technique. Prior to their installation (figure 1a and 1b) the wet gas flow meters have been subjected to full scale testing at a high pressure natural gas/condensate test facility in Norway. The first objective was to calibrate all the 15 meters in single phase flow in order to establish the actual discharge coefficients and wet gas parameters. The second objective was to test 3 out of the 4", and 3 out of the 6" meters under hydrocarbon wet gas flow conditions in order to evaluate the used wet gas measurement correlations for determining the actual gas and total liquid flow rate[1,5,6]. The tests were performed at pressures of around 35 bar and 65 bar, at different gas velocities, and with liquid fractions up to around 4–5% by volume. The latter corresponding to a Lockhart-Martinelli parameter of up to approximately 0.125. The experiments were conducted using hydrocarbon natural gas and condensate. Wet Gas Metering Principle The selected wet gas metering system consists of the installation of SmartVent wet gas venturi based flow meters at each individual wellhead providing the continuous measurement of the gas and total liquid flow rate (figure 2). The measured liquid phase will initially be split into water and condensate fractions via the use of established fluid property data and EoS flash calculations. After start-up of the field the tracer technology method will be used to measure the water and condensate flow rates independently. The wet gas flow calculations, as schematically shown in figure 2, are based on the well known De Leeuw gas correction correlation for the correction of the gas flow rate due to the free liquid content, and an additional correlation for determining the total liquid flow rate. Both correlations do not rely on homogeneous flow conditions, nor do they require the flow to be conditioned in any other way. No obstructions are placed inside the flow line other than the wet gas venturi based meter.