Prediction of the Critical Gas Velocity of Liquid Unloading in a Horizontal Gas Well
- Zhibin Wang (Southwest Petroleum University and Xi'an Jiaotong University) | Liejin Guo (Xi'an Jiaotong University) | Suyang Zhu (Southwest Petroleum University) | Ole Jørgen Nydal (Norwegian University of Science and Technology)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- April 2018
- Document Type
- Journal Paper
- 328 - 345
- 2018.Society of Petroleum Engineers
- horizontal gas well, liquid-loading, liquid-film thickness, inclined annular flow
- 1 in the last 30 days
- 438 since 2007
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Analysis of the experimental data for liquid-entrainment rate, forces exerted on liquid droplet, and secondary flow occurring in the gas core show that the liquid is mainly carried in the form of film in the inclined annular flow. Therefore, it is more reasonable to establish a mathematical model from the bottom-film reversal than from the droplet reversal.
In this study, a new analytical model is developed from force balance of the bottom film of the inclined tubing after studying the bottom-film thickness and gas/liquid interfacial friction factor to reveal the liquid-loading mechanism. Furthermore, a new Belfroid-like empirical model is proposed that is based on the calculation results of a wide range of flowing parameters from the new analytical model to predict the liquid-loading status of gas wells. The new empirical model introduces a coefficient Cd,p,uSL,T to consider how the fluid properties under downhole flow condition affect the critical gas velocity. Cd,p,uSL,T in the new empirical model increases with the pipe diameter, liquid velocity, and flowing pressure, and decreases with the flowing temperature.
The new analytical model, having an average error of 8.45%, agrees well with the published experimental data, and it also performs well in predicting the pressure gradient at liquid unloading condition. The new empirical model could be applied for the prediction of real field operations and has been validated with an accuracy rate of 95% against data newly collected from 60 horizontal wells. The new work can accurately and easily judge the liquid-loading status, and it also reveals how the fluid properties under downhole flowing condition affect the liquid loading.
|File Size||1 MB||Number of Pages||18|
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