Adam Walker reports on the latest work by a key player in specialist remote visual inspection technology.
An eight-year partnership on well integrity has proved extremely frutiful for all players and aptly demonstrates the merits of camera-based well inspection technology.
The partnership has involved Inspectahire working with Shell Global Solutions and RTD in developing visual and pulsed eddy current (PEC) inspections of production wells in the UK North Sea sector. Using small camera systems, Inspectahire has managed to get into the D annulus in several wells and find a path to the highest astronomical tide (HAT) and lowest astronomical tide (LAT). These areas of the surface casing and conductor have historically had the greatest wall loss.
A five-year rolling programme has just been successfully completed in all Shell North Sea assets - and without any accidents or injury to personnel. Further work is now planned for TAQA and Chevron throughout 2014 as well as ongoing monitoring for Shell EPE.
Inspectahire believes detailed planning will result in a successful and efficient inspection, which is why a strict procedure is followed with regards to D annulus inspections.
First, a thorough access survey is carried out to see if there is a sufficient gap at the top of the well between the surface casing and conductor (D annulus). This is done using small bullet cameras to fluid/grout level. If no access is available due to the starter head sitting on the conductor, a hole cutting (100mm) into the conductor is required at two locations. A PEC probe can then be deployed down the D annulus to measure wall thickness of the surface casing and conductor if required.
A further test was developed over the years to check the integrity of the surface casing. Pressure was induced in the C annulus and cameras were lowered down the D annulus fluid level to observe. Lots of bubbles indicated large communication between annulus. Fewer bubbles indicated less communication. No bubbles and pressure build up in the C annulus indicated no communication.
Inspectahire conducted a remote CCTV inspection of damaged conductors on a number of wells on-board a large offshore platform. The inspection was performed during normal production conditions.
All three conductors were found to be completely sheared at the -10 support level at approximately -42m from the top of them. The top and bottom pieces were off-set and interlocked with themselves or part of the support structure. Pieces of the support structure and tulip style guide assembly appeared to be trapped between the upper and lower conductor parts. Significant wear was evident on the casing of DA-03 but could not be seen on DA-11 or DA-06 due to the casing leaning against the conductor.
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Adam Walker is with Inspectahire Instrument Company, Aberdeen, UK.
