One of the limitations of an ESP system is the inability to handle fluid with a high presence of free gas at the pump intake. Even when a gas separator and a gas-handler pump are used downhole, the excessive amount of free gas exceeds the capability of these components and negatively affects the performance of the total system. This is, an unstable pump operation, limitations to achieve the full potential of the well, inaccurate production tests, unstable electrical power consumption, low pump efficiency, poor motor cooling and low reliability and increased operation costs because of premature equipment failure.
Due to the high bubble pressure point of the fluids in some gassy wells, it is necessary to install the ESP equipment as deep as possible in order to gain the highest pump intake pressure and so, reducing the amount of free gas at this point. For the ESP provider and the operator it is very important to maintain stable operation of the equipment; however, sometimes for the operator it is necessary to produce as much free gas to the surface as possible due to its capability to generate electrical power for self-supply.
The need of Apiay Field (Ecopetrol – Colombia) to increase the gas production rate and simultaneously the oil production rate, led to AlKhorayef Petroleum to design a shrouded ESP downhole system with a double stage of gas separation in order to reactivate a very gassy well (depleted) where none of the artificial lift systems at the field (Sucker Rod lift, PCP and ESP) could operate with good results. The first stage of gas separation consisted of a configuration of different equipment to separate free gas used on Sucker Rod Lift systems. The second one consisted of the using of a vortex ESP gas separator and a gas-handler pump in the ESP string.
This paper discusses the benefits of a newly-designed shrouded ESP system and its adaptation for using some downhole equipment for gas separation commonly used in rod lift systems.