an automatic well test system utilizes a coriolis flowmeter that functions as a mass flowmeter and densitometer in combination with a water - cut monitor to calculate volumetric flow rates and densities of materials draining from a test separator in a combined or two - phase production stream . an oil - phase density value is corrected to eliminate the effect of its water content , and divided into the mass flow rate reading to obtain a net oil flow rate . system operations are governed by an automated controller that utilizes a gas blanket system to prevent low pressures from liberating gas from the liquids within the test separator .