6.1 Introduction

Intermittent gas lift is the default artificial lift method in gas lifted fields where formation pressures have dropped to levels where continuous flow is not sustainable any more. It is also suited for wells with relatively high formation pressures but low productivities. On average, about 10% of gas lifted wells are placed on intermittent lift, mostly in mature fields.

Chapter 6 covers all the topics necessary for the understanding of the intermittent lifting process, its control, operation, and optimization. Discussion is started with the description of the intermittent cycle and its basic mechanism. Since the proper operation of an intermittent installation highly depends on the way of controlling the injection of lift gas into the tubing string, a substantial section deals with the different control arrangements, their operation, relative advantages, and limitations. The calculation of operational parameters is demonstrated by presenting the more important calculation models available. The design of intermittent gas lift installations is detailed as follows, with illustrated examples.

In wells in their latest phase of depletion, conventional intermittent lift installations can turn out to be very inefficient, and the use of an accumulation chamber is advantageous. The application of chamber lift, although only a version of intermittent lift, can substantially increase well rates and decrease gas injection requirements. The features and operational details of chamber lift installations are described in a separate section. Finally, practical recommendations on ensuring an optimum intermittent lift operation are detailed.

6.2 Basic Features