A process train for a floating production storage and offloading installation includes a crude oil storage tank equipped with at least one set of electrostatic internals. The set of electrostatic internals are arranged to provide a treatment flow path within the crude oil storage tank oblique to a longitudinal centerline of the crude oil storage tank and through an electric field provided by the set of electrostatic internals. Employing these electrostatic internals within the tank permits an allowable inlet water content into the tank of up to 80%, significantly reducing the required topside processing equipment. The process and system also includes, upstream of the tank, two separator vessels arranged in parallel so each receives a portion of an incoming oil-and-water stream, a flash vessel arranged downstream of the two separator vessels, and a degasser vessel. Downstream of the crude oil storage tank is an electrostatic treater.