Multiphase Flow Measurement Using Tracer Technology at Dulang Oil Field, Malaysia

Abstract

Abstract Multiphase 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. Introduction Production testing of individual wells is undertaken for a number of reasons, including reservoir management, production accounting, forecasting, and well performance monitoring. Conventional testing of individual wells for oil systems and many gas condensate systems is typically achieved by use of three phase test separator vessels. Orifice meters are used to measure the gas stream and turbine or Coriolis meters are used to measure the water and liquid hydrocarbon streams. However, this equipment tends to be relatively bulky and expensive, so it is often located at production manifolds servicing several wells, each of which is individually routed through the vessel on a periodic basis. Over the last years, since June 2000, well testing services were performed using the tracer technology method MultiTrace on the Dulang and Anding fields, located offshore Malaysia (Fig.1). The objective of the tests was to obtain an accurate direct flow rate measurement of all the three flowing phases; water, oil and gas on all the monitoring wells. The gas tracer method initially started as a trial. The gas tracer technique is the complement to the well-established liquid tracer technique allowing full multiphase metering using only tracers. The technique has been developed by Petrotech to provide the possibility to in-situ verify or calibrate on-line meters like wet gas or multiphase meters. One of the reasons behind the testing campaign was the inability to perform conventional well tests due to test separator constraints in the area of metering, choke valve passing and the inability to unload low tubing head pressure wells. Where possible the results obtained from the MultiTrace technique were used as a cross reference to the results obtained from the previous well tests by using the production test separator. However, some of the low-pressure producing wells were not available since the platform was having some difficulties with the gas compressor unit. During a certain test period, a commercially available multiphase meter was installed at the test header. This allowed the tracer and multiphase meter results to be compared. The results have shown that the MultiTrace tracer testing method has been applied successfully. In total about 73 tests on 65 wells have been performed in the Dulang field. A summary of the MultiTrace measurements, results, and comparisons are presented in this paper. The MultiTrace Tracer Technique The tracer dilution technique for water and oil/condensate flow measurement was initially developed to quantify the condensate and water production in gas wells. However, the technique is also applicable for measurement of oil production.