Topside and Subsea Experience with the Multiphase Flow Meter
Authors: Letton Winsor , Svaeren Jon A. , Conort Gilbert 
Published: December 2007

Multiphase flow meters (MPFM) are finding increasing acceptance offshore, where operators are achieving some level of comfort after several years of familiarization with the technology. Meters are being applied in well testing, well management, and allocation of production. Since first deliveries of the Framo meter in 1993, significant experience has been gained in both topside and subsea application of the devices. For topside applications, the principal advantage of the meter remains the elimination of the test separator and all its associated hardware and maintenance. For subsea applications, the advantage is even greater, viz, the elimination of the platform.

Combining the Framo fluid mixer and Venturi with a multiple-energy gamma ray absorption composition measurement provides the optimum in precise estimation of gas, oil, and water flow rates, while at the same time solving many of the operational problems which plague alternative methods.

Operational experience with Framo multiphase meters installed around the World, both topside and subsea, will be reviewed. Special attention will be paid to the difficult issues peculiar to subsea meters, such as their remote installation, retrieval, calibration, and maintenance.

Finally, future trends in multiphase metering will be explored. One of the most significant of these will be the migration of this methodology into areas of application where today it is not economically feasible. What must be done to apply multiphase metering in more routine applications, such as in onshore fields? The answer, as with any other standard oilfield measurement, lies in the evolution of the technology from an experimental domain on one of routine usage. This and other future directions in this discipline will be addressed.

Purpose of Multiphase Flow Measurement Before considering in detail the descriptions and experiences of multiphase meters, it is useful to list the reasons why a producer might want to use them.

Elimination of Test Separator, Manifold and/or Flow Line. This is ordinarily the single most important reason for choosing to use a multiphase meter (Fig. 1). Not only are test separators and their associated metering equipment expensive, but their bulk requires additional platform space in offshore topside installations. In the case of satellite fields, running a test line back to a test separator on a platform is also a non-negligible expense.

Continuous or Near-Continuous Monitoring. With a meter on each producing well, as shown in Fig. 1b, the measurement of production will be complete and continuous - obviously a very desirable condition. Even if only a single meter is used downstream of the manifold, as shown in Fig. 1c, the frequency of testing is considerably greater than with conventional test system of Fig. 1a. In addition, whereas a conventional testing system might take hours to become stable for measurement, the system in Fig. 1c could yield good test results minutes after a well is switched in.

Reduction of Maintenance. Because well-designed multiphase meters must be virtually maintenance-free if they are to be used subsea or on unmanned platforms, their application will significantly reduce operational expenditures (OPEX) over conventional test separation systems.

Numerous other advantages of multiphase measurement could be listed, but what is shown above should be sufficient to convince any potential user that they deserve consideration. Having crossed this threshold, whether through one's own experience or that of others, it is apparent that if one chooses to use a multiphase meter, then a test separator is no longer needed - having both "belt and braces" is not required. Unfortunately there are those in the industry who would suggest otherwise.

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