First oil production from a deep-water oil field is to be achieived by the installation of an initial development system (IDS). Well testing is required for field development and reservoir management. The well testing system requires high-accuracy oil and water rates to provide the data needed for decision analysis in ongoing drilling programs. The well testing system must also be integrated with other platform operations, such as well cleanup after drilling. We introduce here, the concept of a multiphase meter in series with conventional separation technology for improved process control. This feedback control loop configuration is simulated in MATLAB and shown to extend the capabilities of both technologies. The principle of gas volume fraction control in two-phase separator liquid lines is shown to be supplementary to conventional level control systems for performance enhancement of oil field well testing. Concepts demonstrated here can also be easily applied as retrofits to existing separation facilities, which show accuracy or upset problems.