Effect of gas-lift on liquefied petroleum gas (LPG) product yield: A case study of Chinarevskoe gas treatment unit (Kazakhstan)

More than expected increase of LPG yield was observed at the gas treatment unit after continuous gas-lift start up on Chinarevskoe oil field in western Kazakhstan. This paper studies the influence of gas-lift gas on fluid composition changes at separator conditions, and further, on LPG yield at the gas treatment unit. Gas-lift well operation and process plants simulations were carried out using Aspen HYSYS software and matched with real data from the field. Process simulation at constant separator pressure, varying temperatures, gas-lift gas flow rates and water cut indicated increase in LPG yield up to 4%. It was proofed that the increase of LPG yield did not come from propane and butanes from the gas-lift gas. It was concluded that increase of LPG yield is the consequence of mass transfer of components dissolved in oil, liquid, to the vapor phase, i. e. stripping of oil components by gas-lift gas as stripping medium took place. The amount of stripped components, and resulting LPG yield increase, at constant separator pressure on oil treatment plant depended on gas lift gas flow rate, temperatures and gas-lift gas composition. Presence of water had low impact on amounts of hydrocarbon components stripped from oil.