Chapter 12 - Intermittent gas lift troubleshooting

Abstract

Many of the operational and analytical tools that are available for troubleshooting wells on intermittent gas lift are presented in the chapter. Cases for which some, or all, of the troubleshooting techniques for intermittent gas lift do not apply are identified. A list of the required data for troubleshooting wells on intermittent gas lift is presented. An in-depth description of wells that should not be analyzed as intermittent gas lift wells is described (using injection-gas mass balance equations among other techniques). Calculations procedures for wells that should be analyzed as intermittent gas lift wells are derived in detail to find: the productivity index, liquid fallback losses, optimum cycle time, assessment of the working condition of the operating valve, and required volume of gas that should be injected per cycle (several problems are solved to show how these techniques can be applied). These analytical techniques are separately described for valves in good working conditions, damaged gas lift valve with its internal check valve in good working condition, intermittent gas injection through an orifice valve, and unwanted casing–tubing communications. The procedures to perform and analyze downhole pressure and temperature surveys for intermittent gas lift are presented and several surveys (from actual wells) are analyzed to find the true liquid pressure gradient in the production tubing, the production pressure and temperature at the operating valve’s depth just before this valve opens, gas lift valve’s opening and closing pressures, the liquid fallback, productivity index, and the optimum cycle time. Many examples of wellhead pressure charts are presented and analyzed to show how different operational conditions can be identified. Finally, several complete troubleshooting analyses of wells producing on intermittent gas lift with different kinds of problems are presented.