Liquid loading occurs when gas production declines to a rate that is insufficient to lift the associated liquids to surface. At lower rates, gas production becomes intermittent and eventually stops entirely. However, liquid holdup in the horizontal section may impair production before loading in the production tubing becomes evident. Holdup in the horizontal section can lead to slug flow from the horizontal wellbore to the tubing and to an earlier onset of liquid loading in the tubing.

This paper presents liquid holdup data from a single onshore horizontal tight gas well, obtained through video-logging. A transient multiphase flow model is then used to match the observed conditions.

The results from the transient multiphase flow model were found to be consistent with the measured data acquired from the video-logging. Sensitivity analyses were performed with normalized trajectories representing toe-up, toe-down, undulating, and complex drilling profiles. Sensitivities to variations in the liquid-gas ratio and the distribution of the reservoir inflow were also investigated. The results of the transient multiphase flow modelling support the conclusion that complex trajectories are more prone to production losses caused by liquid holdup.

The implications of this conclusion for trajectory optimization and tubing landing depth selection are explored. Modelling liquid holdup can lead to improvements in planning new drilling projects, mitigating the impact of liquid loading on long-term performance.

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