Abstract: A self-regulating apparatus and method for measuring the components of a multiphase petroleum stream includes initially stratifying an incoming petroleum stream into substantially liquid and gas streams. The initial fluid stratification allows a flow-splitting separation to occur as the streams first enter a vertical separation tube. By positioning the inflow line eccentric to the vertical separation tube, a liquid vortex is created by the incoming liquid component to further enhance the liquid/gas separation. The liquid component is then drawn off by a liquid flow line also eccentrically positioned on the vertical separator, thereby minimizing the energy dissipation of the liquid vortex. Both the gas and liquid components can then be individually measured before being recombined at a common outflow port for discharge.