Multiphase flowmeters (MPFM)
MPFMs are in-line meters designed to measure the relative flows of gas, oil and water in a flowline, without requiring prior separation of the phases. However, some MPFMs do require some form of flow conditioning upstream of the meter. Measurements of the flowstream are made by two or more sensors, and the resultant data are processed to yield the individual phase flowrates.
Source: API RP 17A, Design and Operation of Subsea Production Systems—General Requirements and Recommendations, Fourth Edition, Reaffirmed 2011. Global Standards