Due to the high viscosity and poor mobility

it's difficult to measure the viscous oil well accurately with traditional test separator. Besides

viscous oil wells have a wide range of flow rates

often from several to thousand barrels per day

while the GVF varies from 0 to 80%. So few measuring devices are able to test viscous wells. To address this issue

this paper proposes a method for oil-water-gas measurements in heavy oil applications

which covers a wide flow range. It includes a Venturi meter

a dual gamma sensor and a mini separator equipped with a differential pressure transmitter(DPT). When the viscous oil flow rates are in the measuring range of Venturi

a proper-sized Venturi and a dual gamma sensor are used to measure the flow rates of oil

water and gas

respectively. Since the viscous oil is flowing with low Reynolds number

a suitable model was established to calculate the discharge coefficient of the Venturi. When the multiphase flow rate falls outside the low limit of the Venturi meter or it is an intermittent flow

the liquid mass flow rate can be obtained through a mini separator

where the liquid accumulates and generates differential pressure across the separator. Combing with gamma sensor

we can get the flow rates of oil

water and gas respectively. In this method

gamma rays technology is used to conduct the phase fraction measurement more accurately. This technology is independent of viscous oil flow patterns such as emulsion. Coupling with the weighing method through the mini separator

a full range on-line measurement of oil

water and gas in viscous oil can be realized. The experiments on a prototype meter(2 inch Venturi and DN50 piping)made by this method were carried out in a multiphase test loop. The test results indicate that the measurement standard deviations of liquid flow rate

WLR(water to liquid ratio)and gas flow rate are 4.2%

1.5% and 6.3%

respectively.