Liquid loading is a common production problem in mature gas wells. As the formation pressure decreases and gas flow rate also decreases, the gas kinetic energy is unable to lift the liquid phase completely to the surface. Liquid starts to accumulate at the bottom of the well, which increases the back pressure of the reservoir. This is reflected in a fluctuated production of liquid and gas rates. At the same time, it significantly reduces the production rate and eventually kills the well. Correct prediction of critical gas velocity at which the well starts to load is very important to the operators since they could take appropriate measures to prevent liquid loading and extend the well production life. In the past, most studies on liquid loading focused on vertical wells. Only recently have a few studies been conducted to deal with the liquid loading for deviated and horizontal wells. To date, there are few published studies discussing how to predict the critical gas velocity across a wide deviation angle range. In fact, there are contradictory conclusions made by different researchers. In this paper a database related to the critical gas velocity is compiled with data from published literature. A new model is developed and evaluated with the experimental data. The gaps in the previous studies and modeling are also discussed.
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