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Real-time, downhole, multiphase flow rate data is widely acknowledged to be of significant value for production optimization. This is particularly the case for high-cost deepwater developments and in complex multi-lateral wells. Applications of downhole flow data include zonal production allocation, identifying and localizing production anomalies, direct determination of well productivity index, ability to commingle production from multiple zones, and reduction in surface well testing and facilities requirements. However, despite the potential value of this data, in the past reliable continuous measurements of downhole flow rates in producing wells have not generally been available because of difficulties in designing and deploying measurement devices for hostile in-well environments. This paper discusses the design, operating principles, and flow loop testing of the world's first all-fiber optic multiphase flowmeter for downhole deployment. The flowmeter provides real-time measurement of flow rate, phase fraction, pressure and temperature. It is deployed with the production tubing and is rated to 125°C and 15,000 psi. It is full-bore, non-intrusive, has no moving parts, is electrically passive, and overcomes the design limitations imposed by downhole environments. Thus, it has the potential for providing highly reliable downhole measurements. The flowmeter has been extensively tested in Shell's multiphase flow loop in Rijswijk, The Netherlands over a wide range of oil and brine compositions and phase fractions, flow rates, and meter inclinations. Results from the testing have demonstrated the ability of the flowmeter to measure flow rates and water fractions in oil-water systems to within ±5% over the entire range of water cuts. These results have been validated by data from several field deployments. |
