Systems and methods for evaluating multiphase mixtures

A method of determining salinity of a flow of a multiphase mixture flowing from a wellbore, comprising:

• during a calibration period of the flow:
• isolating a reference water phase from the multiphase mixture to identify a reference salinity value of the reference water phase;
• generating a reference oil-water line for the reference salinity value with a multiphase oil-water salinity model that relates conductivity and permittivity for multiphase oil-water mixtures;
• with a microwave sensor positioned within the wellbore, sampling the flow of the multiphase mixture to determine both a sample mixture conductivity value and a sample mixture permittivity value at a plurality of sample periods;
• generating a sample sand-water line for the flow of the multiphase mixture from the plurality of sample mixture conductivity values and sample mixture permittivity values;
• and
• updating the multiphase oil-water salinity model to generate a multiphase sand-water salinity model based on identifying a sand permittivity offset of the sample sand-water line, wherein the multiphase sand-water salinity model relates conductivity and permittivity for multiphase sand-water mixtures;
• and
• during an operational period of the flow:
• measuring, with the microwave sensor, an active mixture permittivity value and an active mixture conductivity value of the flow of the multiphase mixture;
• and
• determining an active salinity value of an active water phase of the flow of the multiphase mixture with the multiphase sand-water salinity model based on the active mixture permittivity value and the active mixture conductivity value.

A method of determining multiphase flowrates of a flow of a multiphase mixture flowing from a wellbore, comprising:

• during a calibration period of the flow:
• isolating a water phase from the multiphase mixture to identify a reference salt species composition for a reference salt species of a reference salinity of the water phase;
• and
• during an operational period of the flow:
• identifying a change in salinity of an active water phase of the multiphase mixture from the reference salinity to an active salinity;
• identifying a cause of the change in salinity based on determining an operational condition of the flow of the multiphase mixture, wherein the operational condition is associated with an additional chemical composition introduced into the multiphase mixture;
• based on the additional chemical composition and the reference salt species, determining an active salt species composition for an active salt species of the active salinity;
• updating a multiphase attenuation model including updating an initial water point to a default water point by determining a default high-energy mass attenuation coefficient and a default low-energy mass attenuation coefficient for the active water phase at the active salinity based on assuming that the active salt species consists of sodium chloride (NaCl) salt, wherein the multiphase attenuation model relates high-energy gamma ray attenuation and low-energy gamma ray attenuation to fractional compositions of multiphase mixtures;
• determining a high-energy correction factor for the default high-energy mass attenuation coefficient and a low-energy correction factor for the default low-energy mass attenuation coefficient based on the active salt species composition;
• generating an active multiphase attenuation model based on generating an active water point by applying the high-energy correction factor and the low-energy correction factor to the default water point;
• with a dual-energy gamma ray sensor, taking high- and low-energy attenuation measurements of the flow of the multiphase mixture;
• and
• determining an active phase fraction flowrate for two or more phases of the multiphase mixture based on the high- and low-energy attenuation measurements and based on the active multiphase attenuation model.