In MultiPhase mode, the meter performs accurate measurements at high speed, to enable detecting and compensating for variations and changes in the flow regime. In Wetgas mode the MPM meter benefits from the more stable flow regimes and conditions, to focus on sensitivity rather than speed.
The Dual Mode functionality offers unique user benefits:
- The meter works well in slug flow; when flow conditions are constantly changing between wetgas (gas part of slug) and multiphase (liquid part of slug).
- No need to replace multiphase with wetgas meter, or vice versa, if well characteristics change over time
- Can be combined with MPM Droplet Count; enabling very accurate measurements at ultra high GVF’s typically in the range from 99 % and above.
Wetgas is a form of multiphase flow where the gas is the dominant constituent (typically 95+ % GVF, Lochart Martinelli parameter < 0,3). For practical purposes, it is defined as a flow where the gas has enough momentum to carry the liquid in a stable flow, with no slugging. The main challenge for high GVF applications is to be able to measure correctly the small liquid quantities as well as the watercut, to split the liquid into water and condensate.
Slug flow conditions have traditionally been considered difficult for multiphase meters. Most conventional meters require well mixed or homogeneous flow, both in the cross section of the pipe (assuming no gas concentration) and in the longitudinal direction. Slug conditions are, however, quite normal in real world applications.
In applications where the flow is slugging, the automatic selection mode offered by the MPM meter can be essential to obtaining reliable results. As seen in multiple field examples, even if the average GVF is at moderate levels and one expects multiphase flow conditions, the Gas Volume Fraction (GVF) might vary over the full range from almost zero to hundred percent within seconds.