Investigation of multiphase metering systems and measuring accuracy in Bibiyana gas field

Abstract

The Bibiyana gas field is the second largest gas field in Bangladesh, it has started its production on March 2007. Now it is producing about 840 MMSCF Gas and 3500 bbls condensate each day from 12 producing wells. All producing wells are located in two regions, such as North Pad and South Pad. In south pad 5 wells and gas processing facilities are situated and in North pad remaining 7 wells are located and connected to south pad process plant via common production header. Each well of North pad are comprised of individual Multiphase Flow Meter instead of conventional Test Separator system. Bibiyana Gas Filed first introduced this type of flow meter in Bangladesh to achieve better surveillance of reservoir and to apply better production allocation. Due to wrong selection of meter, fluid flow regime mismatch and due to lack of proper fluid sampling procedure this multiphase flow meter performance may also hamper. As per manufacturers’ information, this flow meters accuracy is within ±5%, while in practice it is found that this error is about 6-9%. This project work determines the fluid flow profile by using Taitel-Dukler Model, investigates the working principle of this flow meter and their sampling and calibration technique. This flow meter measures gas flow rate by using v-cone differential pressure formula, water detection by microwave technology and hydrocarbon part is analyzed by PVT Software. As per equipment data sheet, it is found that this flow meter works well for Oil density 43.5~45.1 lb/ft3 and gas density 1.15~4.46 lb/ft3 while calculated value is approximately 47.8 lb/ft3 for oil and 0.05 lb/ft3 for gases. To find out the causes, this study investigates for any phase changes from well head to separator and found no phase changes occur in individual flow line for different flow rates. All calculation including fluid pattern are done manually and phase changes are investigated by HYSYS Model. Later flow accuracy is done manually by using Field Data of the Bibiyana Gas Field. This project also analyzes the applicability and selection criteria of Multiphase Flow Meter in Bangladesh in respect to installation cost, maintenance cost, fluid property, type of meter and calibration technique. Finally this study suggests that the existing technology can be used for process parameters monitoring within limited uncertainties and not suitable for custody transfer metering.