New perspective on gas-well liquid loading and unloading

This paper discusses the multiphase flow mechanism responsible for gas-well liquid loading. It shows that the conventional idea of droplet flow reversal (Turner et al. (1969)) does not capture reality and that actual observations are better described by film flow reversal. This paper subsequently explores how film flow reversal changed views on existing gas-well liquid unloading techniques such as continuous foam injection, and discusses new manners of gas well deliquification that specifically aim to delay film flow reversal. The benefits of different types of tubing wall modification have been evaluated via small-scale lab testing. Most promising, hydrophobic coating of tubing reduces the gas rate below which liquid loading occurs by about 50%. The benefits of hydrophobic coating are translated to representative field conditions. Copyright 2010, Society of Petroleum Engineers.