This paper presents new experimental data of gas/liquid flows in an annulus in the transition from annular to churn flow, which is relevant to the phenomenon of liquid loading in gas wells. The focus of the study has been on the effect of eccentricity to the onset of liquid back flow and pressure gradients. The results show that an increase in the eccentricity is triggering liquid loading already at larger gas flow rates. Pressure gradients seem to be affected most when gap bridging by waves is occurring.
Liquid loading is a well-known problem that occurs when wet gas wells approach their end-of-life. Due to the depletion of the reservoir, its pressure decreases. Consequently, the gas flow rate in the well is also reduced. When only dry gas is present in the well, the reduced gas flow rate has no further effect. However, when a liquid phase is present (condensate and/or water) the reduced gas flow rate may, at some point, no longer be effective in transporting the liquids to the well head and they will accumulate downhole; this is called liquid loading (or well liquification). The onset of liquid loading is defined here as the onset of liquid back flow.
