Auto, Natural or In-Situ Gas Lift Systems Explained

Abstract The terms auto, natural or in-situ gas-lift all refer to artificial lift systems that use gas from a gas bearing formation to gas-lift a well. The gas-lift gas is produced downhole and bled into the production tubing via an auto gas-lift valve designed for gas operations. The value of auto gas-lift is probably easier to demonstrate than for other types of intelligent well because it provides a direct replacement for conventional gas-lift equipment, compressors, pipelines and the ancillary equipment they require. An estimated 60 auto gas-lift systems have been installed at the time of writing this paper, most of them in the Scandinavian sector of the North Sea. Several papers have discussed this technology but, so far, none have presented a rigorous analysis or solution of the wells’ production from a gas-lift perspective. This paper presents the basic theory behind auto gas-lift and how to apply it. The components of the theory are well known and commonly used in Nodal analysis and conventional gas-lift design. Properly combining these components allows an auto gas-lifted well's performance to be calculated and downhole equipment to be correctly sized and located.