Analysis Clarifies Failures of Gas Lift Valves in Subsea Wells
Authors: Carpenter Chris 
Published: October 2024

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215010, “Failure Analyses of Gas Lift Valves That Caused Improper Tubing/Annular Communication in Subsea Wells,” by Sebastião T.X. Bastos, Galileu P.H. Oliveira, and Tatiana Sanomya, Petrobras, et al. The paper has not been peer reviewed.

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This work presents the results of several failure analyses of gas lift valves (GLVs) retrieved from the operator’s subsea wells. These valves were unable to prevent backflow from tubing to annulus, thereby compromising well integrity. These investigations allow a more-precise diagnosis of GLV failures that tends to reduce the risk of problem recurrence and can guide the correction of fragilities in current designs. They also can contribute to better planning and definitions in future well completions, resulting in increased reliability for this method of artificial lift.

Failure-Analysis Procedure
Usually, GLV failures are detected in tubing-integrity tests. Every time a leak rate above the limits for surface-controlled subsurface safety valves is registered in such an integrity test, a procedure is performed to try to restore the sealing capacity of the GLV by flushing the valve with diesel. Then, another tubing integrity test is performed.
When removing a supposedly failed GLV from a well, special care must be taken at the rig to preserve the equipment, retaining its condition inside the well as much as possible. For this reason, the following recommendations are prescribed:
- The GLV, and any material adhered to any part of its body, must not be washed.
- If parts of the valve, debris, or any material adhered to the valve detach from its body, they shall be collected, placed inside clean plastic bags, and shipped along with the valve for failure analysis.
- Equipment packaging requires placement in a proper box for transportation after bubble-wrapping the valve’s body and detached parts.
- Equipment storage and transportation shall preserve its original conditions.
- Mechanical shocks must be avoided.
The failure analysis itself occurs at the valve’s manufacturing shop and must be witnessed by at least two specialists from the operator. A database on GLV failures is kept and provides statistical data and general information on these incidents.
This procedure constantly has been subject to changes as new lessons learned point to the incorporation of improvements. For instance, the requisite for not cleaning the GLV at the rig came after observing that deposits could have been removed in the process. Also, more recently, some questions have been raised regarding the execution of the leakage test at the beginning of the inspection at the shop, because such tests could interfere with the position of the GLV’s internals or displace or disarray any deposited material. Thus, this step has been discontinued unless a good reason exists to suppose that the valve internal seals are functional.

Failure-Analysis Excerpts
The complete paper presents seven cases of failure analysis (four are included in this synopsis) for GLVs retrieved from subsea wells in recent years, accompanied by a short description of the facts of the case. Ordinary actions and events are omitted for brevity.