TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAccurate well testing is required for making intelligent decisions on oil and gas production wells. This paper reports on an effort to assess the application of multiphase metering technology to high water-cut (75+% water) and high volume production wells, as found in many North American Mid-Continent brown fields. A portable multiphase oil, water and gas production well tester was designed and field tested for these wells. Key components of the trailer mounted and battery operated tester are: a compact gas-liquid cylindrical cyclonic (GLCC) separator with control valves, GLCC bypass valving, coriolis liquid meter, infrared water-cut meter, vortex shedding gas meter and a data acquisition unit. One key finding is that separation is not needed in many such applications, thereby significantly reducing the size, weight and cost of future testers. This is due to the inherent downhole well separation and annulus venting used in most such well configurations along with specific coriolis/water-cut meter combinations allowing accurate measurements with gas content up to 10 to 20% GVF.