Abstract
Continuous flow gas-lift wells are susceptible to hydrodynamic instability (heading), which may cause cyclic variations of the wellhead pressure, oil and gas flow rates. Gas-lift instability is a reason of many operational problems, for example, compressor shutdowns caused by pressure and liquid flow rate surges, difficulties in the operation of low pressure separators, and excessive gas consumption. Stability problems in complex multiphase systems can be solved using stability maps. A stability map is a plane (2D) diagram that shows the regions of stable and unstable operation of the system, as well as its operating limits. In this paper theoretical and experimental stability maps for gas-lift wells are presented. Fild test were conducted to investigate the flow stability in a deep offshore gas-lift well. Different gas-lift stability criteria proposed in the literature are compared. Based on this study, recommendations on the selection of gas-lift stability criteria were developed. Examples of gas-lift stability map applications are also given.