Well type
Test well - Ullrig, Norway
Deviation
27°
Depth of operations
545 and 557 mRKB
Plug and abandonment (P&A) operations present numerous challenges, from managing time and cost efficiency to ensuring regulatory compliance and long-term environmental protection. Wells completed with control lines on the outside of the production tubing introduce additional complexity during P&A, as these lines must be properly addressed to prevent the creation of potential leak paths (micro-annuli) that could compromise the integrity of cement barriers.
Axter is a future-ready electro-mechanical solution designed to significantly expedite such P&A operations by optimizing the control line retrieval process into efficient steps: scan, mill, cut and retrieve. This technique eliminates the need to remove the production tubing, and for all intents and purposes facilitates rigless plug and abandonment operations - leaving the completion ready for cement to act as the primary well plug.
Welltec and Axter conducted a full-scale system integration test at Ullrig in Norway – a premier piloting center for drilling and well technology, systems, and methods – to validate this transformative solution with the endorsement of a leading global operator.
A full-scale integration test of the Axter system was conducted in Well U-08 at the Ullrigg test facility, targeting the retrieval of control lines from a 4-1/2" (12.6 ppf, L80) tubing set inside 9-5/8" casing. All operations were carried out at two designated depths – 545 and 557 mRKB – with a deviation of approximately 27° at that interval.
The Axter solution was deployed across two runs, each incorporating real-time scanning. In the first run, scanning was used to locate the external clamp and control line behind the tubing – essential for accurately milling the windows. In the second run, scanning was again employed, this time to identify the exact positions of the milled windows, enabling precise placement of the cast sleeves.
Stage 1 – Scan, Mill, Cut and Retrieve
In the first run, the toolstring (comprising the Axter Real-Time Scanner, -Lateral Miller, and -Line Cutter) was deployed to 557 mRKB. After scanning confirmed the position of the control line and clamp, a 200 mm (7.9") lateral window was milled into the tubing to expose the control line, which was then cut.
The toolstring was then repositioned to 545 mRKB. A second milling window was created, the control line was cut again, and this time retrieved to surface – completing the scan–mill–cut–retrieve sequence in a single run.
Stage 2 – Cast/Sleeve Installation
In the second run, two Axter Cast sleeves were deployed to cover the milled windows at 557 and 545 mRKB. Prior to installation, the Axter scanning module was used to identify the exact positions of the previously milled windows, enabling precise placement of each cast sleeve.
By bridging the milled windows, the Axter Cast sleeve helps channel cement down through the tubing and back up the annulus, promoting even cement distribution and reducing the risk of water pockets or voids in the final cement plug.
These operations validated the ability of the Axter solution to execute both precision retrieval and post-intervention cementing under representative downhole conditions.
The Ullrigg test successfully validated the Axter method as a viable, efficient, and field-ready solution for the plug and abandonment of wells with control lines on the outside of the production tubing. By executing a complete scan, mill, cut-and-retrieve sequence followed by precision bridging of milled windows, Axter demonstrated its capability to simplify one of the most complex P&A challenges – without the need to pull production tubing.
Key outcomes:
This outcome confirms readiness for field deployment, particularly in wells/fields where control lines have historically imposed high cost, complexity, and rig dependency during abandonment.
