Well type
Oil producer
Max. downhole pressure
2,020 psi
Max. downhole temperature
125°F
Challenge
Precision cut to enable straddle retrieval
Custom solution
Well Cutter 238 fitted with custom 1.7” cutting head
4-week timeframe
Designed, manufactured, tested, and deployed
After attempting a coiled tubing operation to retrieve a straddle from across a downhole safety valve (DHSV), a client in Denmark concluded that the straddle could not actually be pulled through the tubing hanger due to a slight discrepancy in inner diameter, i.e. the tubing hanger was marginally smaller than the tubing.
Despite a successful milling operation in which Welltec® increased the ID of the tubing hanger to enable access, the subsequent fishing operation resulted in recovery of the GS fishneck only, which had apparently backed-off, emerging without the straddle.
Welltec developed a proposal to perform a cut from within the 1.811” inner mandrel, the main technical challenge of which was the need for a precise correlation to cut 975 mm into the mandrel.
In order to meet the client’s timeline for further operations, this proposal required the accelerated design, manufacture, and validation of a custom 1.7” cutting head within a four-week period, engineered as an add-on to be run in hole with a Well Cutter® 238.
Planning and design
The operation was planned as a cut-and-fish sequence, with the cutting head designed to leave the upper section of the straddle free for recovery and the lower section retrievable on the follow-up runs.
The custom cutting tool featured a ‘no-go’ mechanism, designed to allow entry precisely 975 mm into the mandrel, ensuring the correct cutting location. Grinding pads were selected to minimize the creation of shavings and maintain a controlled, low torque on the mandrel.
Three full-scale test runs were completed to validate tool performance and confirm functional reliability ahead of the deployment.
Intervention
Following several drift runs and an initial run in hole proper, the bullnose was modified (offshore) with welded guide fins to improve entry. The custom cutter subsequently reached the required depth, and with the correct position confirmed by the no-go, completed the cut through the 1.811” ID (2.3” outer diameter) mandrel in five hours. The crew monitored surface readout data throughout, tracking progress and confirming when the end position was reached.
Fishing progressed in stages utilizing the Wellgrab™ fishing and mechanical services platform: the top section of the straddle was freed and recovered via 77,000 lbs of force. A reconfigured run removed the next weak point via 70,000 lbs of force.
A downhole camera was deployed between runs to inspect the fish top and assess conditions. Real-time collaboration between onshore and offshore teams guided decision-making throughout.
Final recovery employed a push/pull technique to free the remaining straddle using up to 20,000 lbs down stroke, and 70,000 lbs upstroke.
First and foremost, the operation enabled the client to gain access beyond the original straddle setting, and subsequently perform critical maintenance.
Welltec’s ability to design, manufacture, test, and deploy a custom solution through in-house organization within just four weeks was crucial to meeting the client’s timeline.
The use of e-line conveyed tools (Well Cutter with a custom-made 1.7” head, and Wellgrab fishing and mechanical services platform) delivered high precision and control throughout, from a surgically accurate cut to the staged fishing operation.
Furthermore, the intervention was completed without resorting to high-risk contingency methods such as explosive cutters, maintaining a strong safety profile while achieving all objectives.
