Multiphase vortex flowmeter system

A method for measuring the flow of co-mingled gas and liquid produced from a well, said method comprising:

• providing a vortex flowmeter measuring fluid velocity and having a flow passageway for co-mingled gas and liquid containing a bluff body inducing turbulent vortices in the fluid flow through the passageway;
• detecting the frequency of the vortices;
• detecting the amplitude of the vortices;
• and
• determining the phase of the fluid flow by the following steps:
• (a) if the absolute value of the change in the frequency of the vortices with respect to time is greater than a first predetermined value, the fluid is multiphase;
• (b) if the absolute value of the change in the frequency of the vortices with respect to time is less than the first predetermined value and the amplitude of the vortices is greater than a second predetermined value, the fluid is liquid phase;
• and
• (c) if the absolute value of the change in the frequency of the vortices with respect to time is less than the first predetermined value and the amplitude of the vortices is less than the second predetermined value, the fluid is gas phase;
• if the fluid phase is liquid or gas, calculating the flow based on the fluid velocity measured by the vortex flowmeter;
• and
• if the fluid is multiphase, calculating the liquid and fluid flows based on the frequency and amplitude of the vortices to determine the proportion of liquid-to-gas in the flow, and the fluid velocity measured by the vortex flowmeter.