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The intermittent gas lift (IGL) method has experimented a continuous growth due to well depletion and so is expected from its technology. IGL is a periodic transient process with two major stages: firstly, a liquid column or slug is accumulated at the bottom of the well. Secondly, the slug is displaced by pressurized gas lift to the surface. Current models estimate the height of the fluid column based on single-phase behavior due to the lack of multiphase transient models. These models underestimate dramatically the column when the operating gas lift valve is located far away from the perforations. To improve this model a study focused on a twophase flow behavior during the accumulation stage is required. In order to achieve this objective a special multiphase flow facility was assembled and more than 200 steady and transient tests were run. Continuous and transient tests were performed with flow conditions and fluid properties selected from typical fields. The collected data allowed identifying the variables that govern the phenomena and establishing a methodology to determine the mixture density, pressure gradient and column’s height. Since no previous correlation matched, a new correlation for transient hold up was generated using qualitative and dimensionless analysis. As part of the approach proposed here, time was included implicitly into the equations in order to reduce their complexity. The analysis showed that Reynolds’s number, homogeneous liquid holdup and dimensionless viscosity govern the phenomenon. The model was validated with field data . The correlation applies to slug and churn flow patterns because those are the expected patterns for typical field conditions. The accuracy obtained with field data suggests applying this approach for designing and optimizing IGL installations.

Transient Two-Phase-Flow Model for Predicting Column Formation in Intermittent Gas Lift Systems