During the completion phase of an unconventional well in Turkey, casing deformation represented a challenge to the operator and Coiled Tubing (CT) service provider due to the potential loss of almost 70% of the horizontal section. The deformation obstructed the path to continue the milling the remaining plugs. The implementation of bicentric mills and Multi-Cycling Circulation Valve (MCCV) incorporated in the milling assembly allowed efficient recovery of the horizontal section. The tubing condition analysis done by the engineering team showed that symmetric mills would not be beneficial. Conformance tubing was not an option. Bicentric milling approach was deemed the most viable solution. This approach consists of using offset mills where rotation causes the cutting head to cover an area larger than the mill's frontal face. However, this approach could lead the CT pipe getting stuck due to big junk left. The use of a MCCV, limiting the number of milled plugs, and performing a fishing run between milling runs were key to the success of the bicentric milling approach. The Turkish well was completed with ten stages isolated by nine aluminum plugs. During the fracturing of stage seven, an abnormal pressure drop was observed while keeping the same pump rate, indicating possible casing damage. After all the stages were fractured, the CT proceeded to mill the plugs using a 4.63-in Outside Diameter (OD) mill. After three plugs were milled, an obstruction was detected, indicated by frequent aggressive motor stalls at the same depth. A tapered mill was run to perform a tubing conformance, and after several hours of unsuccessful penetration, the tool was recovered. At the surface, the tool showed signs of wear around 4.268 in. A 4.0-in OD mill was used to drift this section, and it passed free. An analysis of both the plug anatomy and the casing condition was done to determine the most viable solution. A 4-in OD bicentric mill was designed to pass across the restriction with an adjusted eccentricity to allow higher contact area. Three bicentric milling runs were made with the limit of a maximum of two plugs per run to avoid a CT stuck situation due to the larger cuttings as a result of the mill's asymmetry. The sparsity of information on using bicentric mills for plug milling required research into unpublished practices for such scenarios. This paper documents bicentric milling approach, the use of offset mills, and the mitigation measurements taken during this project to avoid a stuck situation due to large debris generated.

Stuck coiled tubing (CT) is a main operational risk leading to delays, deferred production, or even loss of a well. Despite general commonalities, each CT recovery can face unique challenges including managing high pressure, working under limited spatial or lifting constraints, establishing well control, or handling a cable inside the CT. This study consolidates learnings and proposes a general workflow for a basic stuck pipe scenario, rig-up, recovery pressure control equipment and well control, CT free point evaluation, bottomhole assemblies (BHAs) and workflows for cutting and freeing the CT pipe downhole, and recovery of the CT at surface. A consolidation of published case studies provides specific examples of the hardware, workflows, and operational considerations. In addition, presentation of a recent case study extends the discussion to the challenges introduced by the presence of a cable in the stuck CT and its respective solution. This case study reviews the planning and execution of a CT recovery, including the use of decision trees to guide the decision-making process. It details fit-for-purpose hardware for safely anchoring the cable; packoffs for accessing, tensioning, and recovering it with slickline; an opening for deploying the wireline cutting BHA; and valves for pressure testing and well control. That workflow successfully freed 6,818 ft of stuck CT and allowed recovering the pipe without a workover rig on location, eliminating 11 days of rig time during subsequent tubing pulling. This is the first documented such recovery case worldwide based on a thorough literature review.

(300 words) This paper describes the lessons learned during the completion phase of an unconventional well in Argentina. Where a coiled tubing was used to perform a plug drill out campaign. The article describes the procedure of how the CT service provider followed to release a stuck pipe, the well barrier regains and its recovery. The potential solutions were analyzed by the engineering teams from both CT service provider at local and headquarter levels and the local vendors. The fact of cutting the pipe after getting stuck and unsuccessful retrieval attempts result on losing the well control barriers inside the CT pipe. There was a need to regain the well control before proceeding with the retrieval process. The use of a mechanical agents to plug the pipe was assessed, it was considered internal mechanical plugs that due to logistics will result in excessive times. Therefore, the team looked into the chemical solutions, and cement plug was also visualized but discarded due to tendency of laying down in the horizontal section of the wellbore; Finally, a high viscous resin that is fast setting time was evaluated as the optimal solution to set a plug inside the CT, which was the key to success on the safe retrieval operation. The Argentinian well was completed with 57 stages isolated by 56 dissolvable plugs over 3000 m of the horizontal section. After removing all the plugs in the horizontal section down to total depth. CT pipe was being retrieved to surface performing the final wiper trip, when it got stuck. After several unsuccessful release attempts. The decision was to cut the CT pipe at surface to allow the wireline to perform the downhole cutting. Wireline (WL) rigged up on top of the injector head and performed a tubing puncher run, 3 m below the cutting depth. Then, WL perform a second run at the free point, at a depth of 3900 m, deploying a chemical cutter to release the CT pipe. Once the CT pipe was confirmed free, the resin service company, proceed to install their high-pressure lines in the top of the injector head and proceed to pump 6.7 bbls of resin at a pump rate of 1.5 bpm, displacing it with 5 bbls of gel and 30 bbls of water leaving the bottom of the plug 500 m above of the new CT end. After the thickening time, a pressure test of the plug was done up to 8000 psi for 30 minutes followed by an inflow test of 6 hours, after the successful completion of both, the retrieval of the CT pipe was followed. This project describes the design and execution process of pumping a resin plug, without previous experience within our organization at global basis, that is suitable to regain well control on CT pipes that lost the downhole safety valves after being cut due to a stuck condition.

Coiled tubing (CT) was used to perform multistage fracturing treatments from the CT-tubing annulus in extended-reach wells of Aishwarya Field, Barmer, India. The wells were completed with chrome completion and included multiple fracturing sleeves. With peculiar challenges faced, solutions and lessons learnt are herein captured. In particular, casing deformation was observed in transverse wells, for which the workflow was developed so the wells with post-fracturing casing deformation could be completed and delivered for production. During the initial phase of the campaign. CT got stuck eight times after fracturing due to casing deformation. In three instances, the bottomhole assembly was left in the hole, and twice the CT was cut for recovery. After the workflow was implemented, no CT stuck incidents occurred due to casing deformation, and all 16 transverse wells in the campaign were delivered successfully. This study highlights the importance of differentiating between transverse and longitudinal wells while understanding their implications. In wells where casing deformation can occur, the workflow for CT-assisted multistage fracturing (MSF) operations must be adjusted. A smaller outside diameter (OD) shifting tool needs to be used without a packer assembly, and the CT cannot stay in the well during fracturing.