Multi-phase fluid flow measurement

A method of determining the gas fraction of a multiphase fluid flowstream comprising gas, and at least two liquids in the liquid phase wherein the density of the gas and the liquids is known, comprising the steps of:

• providing a Coriolis device for measuring the apparent density of the fluid flowstream and a meter for determining the fraction of one liquid in the liquid phase of the fluid flowstream;
• flowing the fluid flowstream through said meter and said device thereby measuring the apparent density and fraction of one liquid;
• and
• determining the gas fraction based on the measured apparent density of the fluid flowstream, the known densities of the gas and the liquids and the measured fraction of one liquid in the liquid phase.

A method for determining the gas fraction of a fluid mixture comprising gas and at least two liquids in a liquid phase, comprising the steps of:

• providing a flow meter characterized by a tube which is operable to be vibrated laterally with respect to the direction of flow of said fluid mixture through said tube, means for sensing the peak fluid pressure in said tube and the nominal fluid pressure in said tube, and means for measuring the frequency of vibration of said tube;
• determining the density of the fluid mixture flowing through said tube;
• vibrating said tube at a range of frequencies;
• measuring the peak pressure in sad tube in relation to the vibration of said tube to determine when sad tube is vibrating at the sloshing natural frequency of vibration of said fluid mixture;
• and
• determining the gas fraction of the fluid mixture flowing through said tube based on the nominal pressure sensed by said pressure sensing means, said natural frequency of vibration of said fluid mixture, the density of said fluid mixture flowing through said tube, the bulk compressibility of the liquid in said fluid mixture and the diameter of said tube.