Well surveillance is a key component of production optimization cycle of the gas lifted assets. Even though monitoring of the surface well parameters can give some clues on the downhole gas lift system performance of oil wells, Flowing (pressure and temperature) Gradient Surveys (FGS) in most cases is still required to check the health of the downhole gas lift system and troubleshoot the downhole inefficiencies of well gas lift operations. The FGS has certain level of risk as it involves running electronic memory gauges on wireline in the well at flowing conditions.

An emerging technology using CO2 tracer was implemented as a pilot project in eleven gas lifted wells offshore fields Dubai. The results show that this method is very effective for the quick and reliable determination of lift gas entry points in the well. The method can detect the operating lift depth, detect multiple points of injection and even detect tubing leaks.

It is true that the downhole pressure and temperature data cannot be obtained from tracer surveys. Nevertheless, the technology can be used as an alternate tool to FGS for the following advantages:

  1. Minimum equipment hook-up and no need to shut-in or choke the well, means no production loss.

  2. Less equipment required for the survey, reduces logistics issues especially in offshore locations.

  3. No wireline tools introduced into the wellbore, eliminate well intervention risk

  4. Suitable for wells where a FGS is not possible due to well slugging, significantly deviated or with downhole obstruction.

  5. Possible to run tracer survey on 3-4 wells on a day if the wells are located at the same platform.

This paper will describe the objectives of the pilot project, the well candidate selection criteria, details of the execution of the survey and interpretation of the results. Practical suggestions for getting the best results from such surveys will also be provided.

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