Master of Science (MS)
Producing oil and gas from marginal hydrocarbon reservoirs and mature fields present particular challenges. One of the challenges for these types of fields is flow instability. Pipeline risers and artificial gas-lift systems experience instabilities, which cause significant reductions in production among others operational drawbacks. Different types of instabilities (static and dynamic) have been identified affecting those systems. However, there is still a lack of systematic investigations associated with the understanding of dynamic instabilities (periodic oscillations) and their impact in production systems. A systematic investigation of the effects of periodic forced oscillations on gas-liquid flows in a 42 m (140-ft) long, 0.04859 m (2-in) ID vertical pipe system has been carried out in the present study. The main objective of this investigation is to characterize the effect of oscillations on two-phase flow in vertical pipes to better understand this phenomenon. The time variation of liquid holdup, pressure drop and pressure gradient were analyzed under two superficial liquid velocities (Uls= 0.017 and 0.3 m/s), and three superficial gas velocities ranges of oscillation (Ugs=3-9, 9.5-14, and 8.5-21.5 m/s), as well as the impact in the flow regimes. For the range of conditions tested, it is possible to conclude that the axial variation of liquid holdup is directly affected by the periodic forced oscillations of the inlet gas flow rate, depending on the superficial liquid velocity. Additionally, experimental data under oscillatory and steady-state conditions were compared for similar superficial liquid and gas velocities. From the experimental results was observed that the pressure gradient was lower for oscillatory conditions than for steady-state conditions, for superficial gas velocity in between 4.0 and 9.0 m/s and superficial liquid velocity of 0.017 m/s. This behavior was correlated to the influence of the forced oscillated gas flow rate on the liquid holdup under those conditions. The experimental results of liquid holdup and pressure gradient were also compared with different two-phase flow models to evaluate its performance under steady-state and oscillatory conditions. Beggs and Brill (1973) was found to be the best fit for the steady-state conditions tested. Among all models tested, the empirical correlation developed in this work (which was obtained from the steady-state data) showed the best agreement for the oscillatory experiments.
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Posada, Catalina, "Effect of Forced Flow Oscillation on Churn and Annular Flow in Vertical Wellbores" (2014). LSU Master's Theses. 4194.