Gravity separator for a multi-phase effluent

A method of separating a hydrocarbon multiphase fluid mixture, the hydrocarbon fluid mixture (E) comprising an oil phase, a water phase and a gas phase, the method comprising:

• an application step in which the hydrocarbon fluid mixture (E) is applied to a separator that separates by gravity the hydrocarbon fluid mixture (E) into a liquid layer and a gas layer, the liquid layer being constituted by a water-enriched layer and an oil-enriched layer, the liquid layer being separated from the gas layer by a gas/liquid interface (GLI) having a liquid level (LL) in the separator,
• wherein the method further comprises:
• a) an extraction step in which the oil-enriched liquid (O) is extracted from the oil-enriched layer at an oil flow rate (Qo), and in which the water-enriched liquid (W) is extracted from the water-enriched layer at a water flow rate (Qw),
• b) a liquid-level measurement step in which the liquid level (LL) is measured,
• c) a level-based adjustment step in which one of the flow rate (Qo, Qw) is adjusted so that the liquid level is maintained at a pre-set liquid level value (LLSP),
• d) a parameter measurement step in which a parameter representative of an impurity ratio present in one of the extracted liquid (O, W) is measured, and
• e) a parameter-based adjustment step in which the other flow rate is adjusted so that the parameter representative of an impurity ratio is maintained at a pre-set parameter value.