Provision for oil, gas, and water surface rate measurements from every production well is one of the most required issues for effective field development control. Several types of multiphase rate measurement units are available with various principle of measurement of the total producing liquid rate and the volume cuts for gas and water. Due to oil degassing during production, gas and water breakthroughs, and subsequently high liquid rates (up to 1600 m3/day), this task has become absolutely non-trivial for the Vankor wells.

Preliminary, cyclone-based gas-separators have been considered in the field as the means for primary phase separation and consequent measurement of the each phase rate using Coriolis-based mass metering units. However, due to the narrow operating range of both the cyclone separators and Coriolis mass-metering units, correct rate measurements were failed to achieve and such obstacle was confirmed by multiple comparison measurements with a stock tank.

A mobile measurement unit with Venturi tube and using electrical principle for measuring gas and watercut has been used in the field. Due to the necessity for calibration to reference rate measurement units, use of extensive input PVT properties, and diverse relationship between electrical properties of the gas-liquid fluid and volume fractions for gas and water, the use of this unit could not help in increasing the accuracy of liquid rate measurements over 15% and covering the full production range of wells.

Another unit type for multiphase flow rate measurements uses Venturi tube and radioactive source for gas and watercut. The introduction of the unit at the field allowed one to increase the accuracy of liquid rate (within 5% for several wells), gas-oil ratio, and watercut measurements significantly. It delivered an opportunity to increase a material balance model and carrying out a full-scale dynamic model history matching of the Vankor field.

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