Using corrosion-resistant materials such as high-chromium–nickel alloy for tubulars helps to protect well completions from corrosive fluids. But these alloys present a serious challenge for conventional electromagnetic pipe inspection systems.

This ADNOC survey took place in a high-temperature sour well. The flow-wetted areas of the well had been completed with chrome-resistant alloy (CRA) tubulars. The diagnostic system, particularly the data acquisition and interpretation process required for the corrosion assessment of CRA tubulars, is much more complex than for conventional steel tubulars. In this case, the corrosion study was a high-temperature environment where the produced gas contained hydrogen sulphide (30%) and carbon dioxide (10%).

The operator, ADNOC Sour Gas, selected TGT’s Chrome Tube Integrity product to provide an accurate barrier-by-barrier assessment of the corrosion-resistant alloy tubulars in the well.

Powered by the True Integrity system using the Pulse electromagnetic platform, Chrome Tube Integrity delivers accurate wall thickness data for CRA tubulars and can differentiate between internal and external defects, when complemented with the calliper data. TGT has conducted detailed tests on machined defects to calibrate the Chrome Tube Integrity product for this
purpose. The assessment of low-magnetic tubulars such as CRA is possible without compromising on quality if the fast-response Pulse sensor is used.

The Chrome Tube Integrity measurements were made in memory mode with the sensors being run on slickline. This was an industry first for through-barrier integrity diagnostics in highly corrosive gas wells completed with high-chromium–nickel tubing.

The survey provided a quantitative assessment of corrosion across three barriers: tubing, production casing and intermediate casing. The survey also updated and confirmed the depths for casing collars and centralisers. A fourth barrier (surface casing) was identified and qualitative assessment made.

Chrome Tube Integrity showed that all the CRA tubulars complied with the manufacturing standard; no corroded intervals were detected (See logplot). This new approach provided the operator with an integrity baseline and enabled optimisation of future assessment and intervention plans.

This project confirmed the value of Chrome Tube Integrity as an effective product for a targeted investigation of specific integrity breaches or as routine surveillance support for ongoing integrity management programmes. It also demonstrated the suitability of Chrome Tube Integrity for conducting multi-barrier assessments in wells that contain corrosion-resistant alloy (CRA) tubulars.