Investigation on downhole gas-liquid two phase separation and mixing transportation characteristics with high gas fraction

Abstract

Produced fluids in oilfields usually contains water, natural gas and other substances. With development of oilfields, formation energy decreases and oil reservoir degases, therefore high gas content wells increase. When the produced liquid is lifted by the Electric Submersible Pump (ESP), high gas content will impact pump working performance, and even leads to cavitation and gas lock, which greatly impact lifting efficiency and interrupt well production. To solve the problems caused by high gas content, this paper puts forward an idea of “separating - mixed transporting”, in which the separating is conducted by a flat deflector, and the mixed transporting is achieved by an ejector. According to this idea, an indoor experimental device and a numerical model were established. Laboratory experiments and numerical simulations were carried out simultaneously. The Euler-Euler multiphase flow model and Reynolds stress turbulence model (RSM) are used in the numerical simulation. It is found that a stable gas core formed by the guide vane appears near the swirl field center, and the gas core width decreases with the gas-liquid mixing flow rate increases. With the increase of inlet void fraction, the gas core width increases gradually. When the inlet gas fraction increases to 70%, the gas core can be taken out by the air pipe to achieve the purpose of complete separation. The distribution of the gas-liquid two-phase in the swirl field and the pressure drop during gas-liquid mixed transportation are compared and analyzed by numerical simulation and experimental testing, it is found that the numerical simulation results are in good agreement with the experimental results, which verifies the rationality of the selection of numerical simulation model. The research results are of great significance to broaden the application scope of ESP in high gas fraction oil wells.