Abstract
Many pumping systems tend to lose pressure boosting capability at high intake gas volume fractions (GVF) resulting in gas-lock. Delaying occurrence of gas-lock is beneficial to extending the operating envelope of these pumping systems. This study presents the results of operating a multiphase pump at speeds higher than typical, conventional field applications, in addition to incorporating a flow-conditioning device at pump inlet. These attributes delayed occurrence of multiphase gas-lock to intake GVFs up to 98%.
The multiphase pump tested had a 5.38-inch housing outer diameter and shaft rotational speed of 6000 revolutions per minute (RPM). A nozzle was installed at the pump inlet to facilitate homogenization. The range of total volume flow rate of air and water at pump intake was between about 4900 to 7600 barrels per day (BPD), with intake pressures approximately 50 psig. The total intake volume flow rates were varied and the pump pressure boost was measured until the pump gas-locked.
The results showed that for the total volume flow rates tested, the multiphase pump was able to provide pressure boost of about 55psi at an intake GVF of 91%. For other flow conditions when the intake GVF was increased to 98%, the multiphase pump provided a 10 psi pressure boost. An observation during the test was the gas-liquid mixture flow through a nozzle resulted in a very fine spray mist. With the nozzle installed at the pump intake, a more stable pump operation was achieved throughout the tests. In conclusion, operating the pump at speeds of 6000 RPM facilitated extension of the operating condition when gas-lock occurred in the multiphase pump. Installing a nozzle device was beneficial in conditioning the flow at entry to the pump to ensure stable operating conditions. These findings are being incorporated in a field prototype version of the pump to handle higher volumes of gas and liquid in the field.
This study mainly highlights the method used to delay gas-lock in a multiphase pump. Operating the pump at higher than conventional speeds and installing components at the pump inlet to condition the flow are beneficial to ensure the pump continues to deliver pressure boost for intake GVFs up to 98%. Extending multiphase pump operating envelope is desirable for field operators to produce more continuously and economically from wells with very high gas content.
