A Major North Sea operator required scale-free sections of tubing to perform a plug set and tubing cut prior to pulling the completion. Calcium carbonate scale (CaCO3) forms inside the tubing and is very difficult to remove using mechanical or chemical methods. This objective was previously achieved from a jack-up rig using coiled-tubing and jetting technology (fluids & abrasives). The operator had previous success using Blue Spark’s WASP® tool (Wireline Applied Stimulation Pulsing) to remove scale from other completion hardware, so they decided to use WASP® to clean sections of the tubing.
The workover was done without a jack-up rig or coiled tubing. The WASP® tool was deployed on the operator’s preferred wireline provider’s E-Line from the platform, prior to the jack-up’s arrival. The treatment was performed at 5,800 ft. MD in a section of the wellbore that was at 30° deviation. Two 20-foot intervals were treated in one wireline run in less than 4 hours of treatment time.
A multi-finger caliper (MFC) log was performed on wireline to verify the scale removal. The caliper log (see Figure 1) confirmed that the WASP® had completely removed the CaCO3 scale from the inside of tubing over the two treated sections. Subsequently, the plug was set across the WASP® treated tubing interval and pressure tested successfully. The tubing cut was also completed successfully at the WASP® treated tubing interval, and on recovery of the tubing it was shown that all the scale had indeed been removed from this interval.
As a result of using WASP® to clean the sections of tubing:
- Coiled Tubing was not required, eliminating the cost of that service – mobilisation, rig-up, rig-down and reduced crew.
- There was a reduction of 8 days of jack-up rig time, as the WASP® operation was performed offline.
- The workover required no chemicals, explosives or controlled goods, and as such was environmentally friendly and extremely safe.
- The workover to remove scale inside tubing was completed in a very cost-effective and efficient manner.
This customer has also used WASP® to remove scale in other completion equipment, including Sub-surface Safety Valves, Side Pocket Mandrels, and Gas Lift Valves.