Systems and methods for subsea fluid phase separation

A method for subsea fluid phase separation, comprising:

• configuring a horizontal vessel in series with a vertical gas-liquid separation vessel;
• producing a liquid output stream from the vertical gas-liquid separation vessel;
• flowing the liquid output stream from the vertical gas-liquid separation vessel into the horizontal vessel;
• flowing an oil-water mixture stream from the horizontal vessel to a first oil-water separation vessel;
• flowing a separated oil stream from the first oil-water separation vessel to a second oil-water separation vessel;
• receiving an indication of a level or a pressure of the horizontal vessel and the vertical gas-liquid separation vessel;
• and
• performing, based on the indication, a processing operation that:
• generates a control signal to control operation of a pump that provides fluid flow into and/or out of the vessels;
• or
• generates a control signal to control operation of at least one valve associated with the vessels.

A system comprising:

• a configuration of multi-stage hydrocyclones, including a liquid-liquid hydrocyclone in series with a solid-liquid hydrocyclone in series with another liquid-liquid hydrocyclone, for produced water treatment in a subsea environment to enable water re-injection;
• and
• a control system comprising a dynamic multiphase flow simulation model coupled with a dynamic process simulation model;
• wherein the configuration of multi-stage hydrocyclones causes breaking of solids-stabilized emulsion particles in the water and solids removal from the water prior to water re-injection.