Effect of nozzle-to-throat spacing on water-jet gas pump performance

Implementation of water alternating gas (WAG) injection on a reservoir, with simultaneous water and gas injection, provided with liquid-jet gas (LJG) pumps utilization. These devices are designed to prepare a water-gas mixture by mixing the active liquid phase with high pressure and a passive gas medium. Several unsolved problems remain in the LJG pumps performance, including the optimal distances from the edge of the nozzle to the entrance to the mixing throat (nozzle-to-throat spacing). According to the analysis of previous studies, it was identified that the results were obtained chiefly for low-head LJG pumps, conical nozzles were used in the investigations, gas pressures at the LJG pumps gas intake were near to atmospheric, and there was a wide variation in the recommended nozzle-to-throat spacing. However, the implementation of the WAG injection under field conditions is meant to be used associated petroleum gas with excess pressure, high-pressure LJG pumps, and the diaphragm nozzles. Due to this, the aim of this paper was a comprehensive study of the nozzle-to-throat spacing effect on LJG pumps performance, with diaphragm nozzles application. As well as, excess gas pressure at the intake of LJG pump was necessary to approach the oil and gas field conditions. The studies were carried out on the test-bench, which is designed to investigate LJG pumps performance. Water was used as an operating fluid, and air was used as a gas phase. The test-bench has cyclic system of operation which made it possible to obtain stable excess gas pressures at the LJG pumps intake. To evaluate the performance of the jet apparatus, the pressure-energy characteristics were used. As a result of experimental studies, it was identified that the ratios of mixing throat diameter dthroat to the nozzle diameter dnozzle range from 1.26 to 2.21, the nozzle-tothroat spacing varies in the range of (0.75-1.53)dthroat, and the greatest value of 1.53dthroat is achieved with the dthroat/dnozzle = 1,55. As well as, optimization of nozzle-to-throat spacing leads to enhance the pressure-energy characteristics and the injection coefficient by an average of 10%. © 2020, Neftyanoe Khozyaistvo. All rights reserved.