Laboratory investigations on upward gas-liquid transport from low-pressure reservoirs during slug-to-annular flow pattern transitions

Laboratory experiments conducted in the past to observe advantages and limitations regarding possible utilization of small diameter tubes (SDT) operating under slug or pseudo-slug flow patterns to remove liquids from low-pressure reservoirs have been extended to pipe diameters up to 3/4''.; By increasing the gas injection rate, it was possible to observe the effect of transition from slug to annular flow pattern on the liquid production rate under a broad range of reservoir pressure conditions.; Experimental results have been compared with existing mechanistic models for evaluating the flow patterns, transitions and pressure drop. A new tool for assessing the level of pressure oscillations as an indication of flow-pattern transition related instabilities was developed, calibrated and used.; Effects of pipe diameter, reservoir pressure and interfacial tension on liquid transportation were observed and quantified. In addition, local turbulence promoters have been inserted and their effect on production enhancement has been evaluated.