Pre- Field Trial Testing of a Twin Screw Multiphase Pump

Abstract

Abstract Performance tests were conducted on a twin screw multiphase pump in a large-scale flow loop prior to its first trial in an oil field in the Middle East. The main objectives of these tests were (1) confirmation of the pump’s hydrodynamic performance by examining the flow rate-head (Q–H) curves and the efficiency-head (η–H) plots, (2) checking the integrity of the design and construction, and (3) obtaining operational experience with the complete system. The pump was installed at the exit of a 82 m long, 106.3 mm ID pipeline and upstream of a three phase high pressure separator. The fluids used were nitrogen and water. A total of 76 flow tests were executed under the following experimental conditions; gas volume fraction (GVF) at the suction: 0 – 95 %; pump speed: 1200 – 1800 revolutions/minute; and differential pressure: 142 – 350 psig. These ranges covered most of the operating conditions to be expected during the field trial. The pump operated successfully in the flow loop for a total of 150 hours. The Q-H curves showed an increase in volumetric efficiency with an increase in GVF. At high GVF, above 80%, an almost critical flow situation was attained, where the total flow rate was independent of the differential pressure. The η–H plots showed that the pump efficiency decreases with an increase in GVF. These characteristics are consistent with the results of tests conducted by other manufacturers on similar pumps. During the tests, no leaks were obtained through the mechanical seals and there were no problems with the quenching unit and cooling at the bearings. A maximum rise in temperature of 13 °C occurred when the GVF was 95%. Scratches seen on the external face of the screw and the internal face of the sleeve were attributed to scales in the pipeline. As a result of these data, the pre-field trial tests on the twin screw pump were considered successful and ready for testing in an oil field.