Method for measuring the flow rate of a multi-phase liquid

A method for measuring a flow rate of a multiphase liquid, the method comprising:

• measuring a temperature and pressure of a flow of the multiphase liquid, and measuring a density of each phase of the multiphase liquid;
• determining a speed of sound in each phase of the multiphase liquid in a working range of temperatures;
• measuring and recording amplitudes and frequencies of fluctuations of a pipe in which the multiphase liquid flows;
• dividing a range of the frequencies into portions, each portion corresponding to each phase of the multiphase liquid;
• applying fast Fourier transformation to each portion and obtaining for each portion maximal amplitudes and corresponding frequencies;
• measuring acoustic noise generated by the movement of liquid at its course through a known cross-section;
• determining a speed of flow of the liquid by the frequency of the acoustic noise caused by unevenness of the movement of liquid;
• and
• and calculating a volume flow rate of each phase of the multiphase liquid according to a formula:
• Q
• =
• π
• ·
• R
• 4
• ·
• F
• 3
• ·
• A
• ·
• K
• 4
• ·
• C
• 2
• wherein:
• Q—is a volumetric flow rate of a phase of the multiphase fluid in m3/s;
• R—is a radius of the pipe, m;
• F—is a maximal frequency of vibration in a selected range for a phase, 1/s;
• A—is a maximal amplitude of oscillation at a frequency F, m;
• K—is a dimensionless coefficient of proportionality;
• C—is a measured speed of sound in a phase of the multiphase liquid, which is experimentally determined for oil and gas, and which is tabular for water.