The gas-lift producer in this case study had been shut-in due to sustained annulus pressure (200 bar) and excessive volumes of H2S that could not be handled by the production facilities. The operator wanted to assess primary barrier integrity and guide a workover programme. Traditional diagnostics methods, such as production logging tools (PLT) and temperature logs, were deemed inefficient because they could scan only the production tubing and were unable to confirm the integrity of the packer and production casing. Identifying and shutting off the source of the water with high H2S content would protect the environment and deliver a production gain of 2,050 barrels of oil per day (BPD). Eliminating the production of highly toxic H2S and ensuring its containment within the well system would also deliver important environmental and safety benefits.

TGT’s True Integrity system with Chorus technology uses spectral acoustic methods to assess barrier sealing performance. The system offers a large scanning radius and the sensitivity to detect even small leaks. The ability to indicate failures in the tubing, in the casing behind the tubing, and in key completion components such as the production packer and gas-lift mandrels makes this technology highly effective at establishing the best approach for remediation when barrier failures occur.

High precision surveys across the reservoir zone characterised the flow and its content, thereby guiding operations for shutting off the water zone with high H2S content. Traditional PLT methods would not have been enough to make this identification as the water source may be above or below the perforated interval. The diagnostics also revealed the effectiveness of cement sealing across the reservoir zones.