Impedance-based flowline water cut measurement system

A water cut measurement system comprising:

• an elongated tubular section configured to flow a multiphase fluid comprising water and hydrocarbons, the elongated tubular section comprising:
• a first portion having a first diameter,
• a second portion axially coupled to the first portion and having a second diameter less than the first diameter, and
• a third portion axially coupled to the second portion and having a third diameter greater than the second diameter;
• and
• an electrode sub-system positioned in the second portion of the elongated tubular section, the electrode sub-system comprising a first electrode and a second electrode configured to flow a current;
• and
• a controller coupled to the electrode sub-system, the controller configured to determine a ratio of hydrocarbons to water in the multiphase fluid flowed through the elongated tubular section based on an impedance measured by the electrode sub-system responsive to the current flowed through the electrode sub-system.