Overcoming Offshore Inspection Challenges
By: Lilly Darnell, Senior Marketing Specialist, Quest Integrity Group
As seen in the September 2012 issue of Pipelines International Magazine. Download the PDF version here.
Offshore pipelines can be challenging to inspect due to limited launcher/receiver facilities or limited accessibility. Quest Integrity Group offers a solution for these historically difficult to inspect or unpiggable pipelines with its InVista™ in-line inspection tool.
Recently Quest Integrity Group was contracted to inspect a 6 inch, 2.5 km offshore pipeline using its InVista™ tool. The line had limited access on the wellhead and production platform for traditional inspection tools and had no pig traps. In addition, the line had not been in use for approximately two-and-a-half years and the client needed to reinstate it quickly due to a planned drilling expansion. Quest Integrity was able to quickly mobilise to deliver the inspection and assessment results for the client.
Using the InVista tool, Quest Integrity overcame challenges faced in this inspection project, including no available access for a receiver and special spool arrangements to connect to the flange on the vertical section of the riser. The launcher connection was also located at an unbarred tee.
Because the tool is lightweight at 25 kg and 1,200 mm in length, temporary traps were installed in the limited space available. This meant no hot work or permanent alterations were needed. This benefit, as well as the geometry and wall-thickness data being provided in a single run, resulted in a significant cost saving for the operator.
The InVista tool has superior navigational capabilities, such as short radius back-to-back bends, which also aided the ease of access (reducing the space needed for traps), unbarred off-takes and pipe schedule changes including heavy wall.
The tool is bi-directional and can run in low-flow/low-pressure environments. The total project turnaround was three days; however the actual run time was only a few hours. Due to a high tool tolerance, 99.6 percent of wall-thickness data were collected after only two foam cleaning runs.
The inspection included a fully integrated API579 compliant Level 2 fitness-for-service assessment as a standard deliverable. InVista identified the actual wall-thickness measurement as 10.3 mm (as-built drawing indicated 104.3 mm). There were also two external defects with 41 per cent wall loss and three internal corrosion points ”" the maximum at 25.9 per cent wall loss. In addition, three dents were identified with a maximum of 3.2 percent of the outside diameter of the pipe.