Method and meter for measuring the composition of a multiphase fluid

A method for measuring the composition of a multiphase fluid by radiating a photon beam therethrough and measuring the level of radiation absorption by the fluid at at least three radiation energy levels;

• and feeding the measured radiation absorption data to a data processing unit which is programmed such that it performs calculations in accordance with a phase fraction calculation scheme on the basis of said radiation absorption data and that it generates data concerning fluid composition, including its salt content, if any, on the basis of said calculations, wherein the level of radiation absorption by the fluid is measured by measuring the transmitted radiation count rate at three radiation energy levels:
• the logarithms of the measured count rates at said three energy levels are expressed as I.sub.1, I.sub.2 and I.sub.3 and the calculation scheme comprises the following matrix equation scheme:
• ##EQU5## where:
• .rho. refers to the density of a fluid fraction in kg/m.sup.3
• .mu. refers to the mass absorption coefficient in m.sup.2 /kg
• .alpha. refers to the mass fraction of a component in the fluid
• R refers to the rate of water density increase per unit increase of salinity
• .DELTA.S refers to change in salinity in kg/m.sup.3
• the subscript w refers to saline water
• the subscript s refers to salt
• the subscript o refers to crude oil
• the subscript h.sub.2 o refers to fresh water and
• the subscript ini refers to an initial state;
• and
• the data processing unit is programmed to solve said matrix equation scheme.