A History of Gas Lift Valve and Gas Lift Mandrel Damage and Subsequent Retrofit Gas Lift Straddle Installation in Alaska

Abstract In Alaska oilfields, non rig tubing repair has become a viable alternative to rig workovers (RWO). Tubing straddles can remediate tubing by casing ("A" annulus) communication at a tremendous savings in areas where rig workover cost is significant. This paper advances the analysis of more than 400 tubing straddles set since 1985. SPE paper 104055 showed that the majority of straddles were installed over damaged gaslift valves and gaslift mandrels. Damage to a gaslift valve can occur when it is eroded (or flow cut) due to fluid unloading of the casing by tubing annulus through the gaslift valve. This leads to tubing by "A" annulus communication which usually requires that the damaged gaslift valve be replaced. However, if the gaslift valve has been flow cut and is not replaced immediately, the gaslift mandrel itself, which is a part of the tubing completion, can be subsequently flow cut, requiring tubing replacement or tubing straddle installation. This paper will update the results of the straddle study on a large gaslifted field to quantify the signifance of the problem. It will not only discuss the history of wells that required a straddle to repair gaslift valve or mandrel damage, but will also analyze wells that only required a gaslift valve replacement to repair tubing communication due to a damaged gaslift valve. The paper will also describe the use of retrofit gaslift straddles in 3-1/2" thru 7" tubing sizes, including lessons learned. Retrofit gaslift straddles are a subset of tubing straddles. They are particularly attractive in areas where rig workover cost is significant, such as offshore, remote, or arctic locations. Most significantly, the paper will discuss a commercially available barrier gaslift valve, why it is superior to conventional gaslift valves and upcoming installation plans in Alaska to prevent gas lift valve damage and subsequent gaslift mandrel damage.