Burn-Over Operations in WCSB Fishing and Wellbore Intervention: Milling Through Stuck Wireline Cable, Washover Shoe Design, and Recovery Procedures for Stuck Logging Tools and Perforating Guns in Alberta Wells
Burn-over in WCSB well intervention and fishing is a milling operation in which a hollow shoe (the burn-over shoe, also called a washover shoe or cable burn shoe) run on the bottom of a drill string or workover string is rotated over a stuck wireline cable, logging tool, or perforating gun assembly to sever the cable and release the stuck downhole equipment, allowing operations to resume in the wellbore. The term "burn-over" describes the mechanical action of the milling shoe rotating over and cutting through the wireline cable — the rotating mill burns through the cable just as a torch burns through rope — rather than any thermal burning mechanism. In WCSB horizontal and deviated well completions, wireline tool sticking is a frequent operational hazard: logging tools (formation evaluation tools, caliper tools, temperature tools) can become mechanically stuck in ledges, washouts, or casing restrictions; perforating guns can hang on casing collars or in corroded casing IDs; and in highly deviated WCSB Montney and Cardium horizontal wells, the wireline cable itself can become pinched under the weight of the tool string resting on the low side of the casing bore. When conventional wireline remediation methods (applying overpull to the cable up to the cable breaking strength, jarring down with a mechanical jar, pumping lubricant to reduce friction) fail to release the stuck tool, the wireline service company and well operator must choose between cutting the cable at surface and fishing for the stuck tool with drill string (losing the cable down the hole and requiring a separate fishing job), or running a burn-over shoe to sever the cable near the stuck point and fall-back the lower cable and tool assembly as a fish, commencing a fishing job for the mill-over fish. The burn-over operation preserves the option of fishing the tool body from the wellbore, whereas a surface cable cut leaves the full tool string and all cable below the cut as a fish that must be retrieved or sidetracked around before completion operations can continue.
Key Takeaways
- Burn-over shoe design and material selection for WCSB wireline cable severing in cased and open hole: The burn-over shoe is a short hollow milling tool (typically 150-300 mm long) with an ID slightly larger than the wireline cable OD plus a clearance for centralization, and an OD slightly smaller than the casing ID (leaving 5-10 mm annular clearance for fluid circulation and swarf removal). The milling face of the burn-over shoe can be: a flat-faced mill with tungsten carbide inserts for cutting through steel wireline cable (7-strand and 6-strand WCSB monoconductor and multiconductor cables, 0.28-0.46 inch OD) in cased hole; or a finger-mill design with multiple cutting tines that engage the cable and wrap it before the final cut, used for flexible wireline in open hole WCSB CBM and coal seam gas completions where the cable may not be taut. The preferred WCSB burn-over shoe for standard monoconductor cable (0.36-inch OD, 7 × 19 galvanized steel strands) is a tungsten carbide flat-face mill with a 0.60-inch minimum clearance ID, which when rotated at 60-80 rpm with 5-10 kN of weight-on-mill and 150-200 L/min of 1.05-sg water circulation severs a WCSB steel monoconductor cable in 15-45 minutes, depending on cable condition (new versus corroded) and wellbore fluid temperature (cable strength decreases above 80 degrees C at WCSB Montney bottomhole temperatures).
- WCSB burn-over procedure: depth determination, shoe run-in, rotation, and verification of cable severance: The burn-over procedure for a stuck WCSB logging tool begins with confirming the depth of the stuck point using the cable stretch method: total cable out minus free cable above the stuck point equals the cable length under tension, which when divided by the cable stretch coefficient (typically 0.025 m/kN-km for monoconductor cable) gives the free cable length and therefore the depth of the stuck point. The burn-over shoe is made up at the bottom of a drill collar string with the ID centered over the estimated cable path, run to 3 m above the estimated stuck point, and circulation established before rotating. The shoe is worked downward at 60-80 rpm, monitoring the WOB indicator: as the shoe contacts the cable, WOB increases by 2-5 kN and the rotating torque increases by 20-50 N-m above the free-rotation baseline. As the cable is severed (typically within 30-45 minutes in WCSB operations), the torque drops back to the free-rotation baseline and the cable tension indicator at surface (monitoring any remaining tension in the cut cable above) drops to zero. The burn-over shoe is then pulled above the stuck-tool fish depth by 5 m, and a jar or overshot is run to the fish for retrieval.
- Fishing strategy after burn-over in WCSB horizontal wells: retrieving stuck logging tools and perforating guns as a fish from the horizontal lateral: After burn-over severs the wireline cable in a WCSB horizontal well, the stuck tool and the severed lower cable become a fish that must be retrieved before completion operations can continue, particularly in WCSB Montney completions where a stuck perforating gun in the lateral blocks access to 50-80% of the planned perforation stages. The fishing strategy depends on the fish type: for logging tools (typically 1.5-3.5-inch OD, relatively short), an overshot (releasing or circulating overshot) is run on a work string to engage the top of the fish and pull it to surface; for perforating guns (2.0-5.0-inch OD, up to 12 m long for a WCSB Montney perforating assembly), a mule-shoe guide on a reverse-circulation fishing assembly is required to engage the gun OD without engaging the extended-charge ports. If the fish cannot be pulled (gun cemented in by scale or sand bridges around it), the WCSB operator may elect to drill over the fish using a dedicated mill assembly to cut the stuck gun into small swarf that circulates out of the wellbore, followed by re-running the perforating program in the milled-clean section of the lateral.
- Prevention of wireline tool sticking requiring burn-over in WCSB Montney and Cardium completions: tool selection, cable sizing, and operating practice: WCSB wireline tool sticking and burn-over events are preventable through proper tool string selection, cable sizing, and operating practice. Key prevention measures include: selecting tool OD at least 5 mm below the minimum casing ID measured by the caliper log before perforating (particularly important in WCSB Cardium wells where casing corrosion or scale deposits over 10-20 years of production reduce the nominal 5-1/2-inch ID from 124 mm to as little as 100-110 mm in the worst perforated zones); using a cable weight (lead bar) above the tool string to maintain downward tension on the tool assembly in horizontal wells where gravity cannot keep the tool against the low side of the casing (cable tension of 500-1,000 N required to prevent tool rotation and cable twist under perforating shock in horizontal WCSB Montney wells); and using a cable with a breaking strength at least 5× the maximum expected pulling force before committing to the burn-over threshold (applying overpull up to 80% of cable breaking strength before declaring the tool stuck and requesting burn-over authorization from the well operator). WCSB operators report a burn-over frequency of approximately 1 event per 150-200 wireline runs in horizontal completions versus 1 per 400-600 wireline runs in vertical or lightly deviated wells, reflecting the higher mechanical complexity of horizontal casing completions.
- Regulatory and HSE considerations for burn-over operations in WCSB wells: tool identification, radioactive source management, and well control: WCSB burn-over operations on radioactive source logging tools (natural gamma ray, litho-density, neutron porosity) require special regulatory notification under AER Directive 058 (Oilfield Waste Management) because the milling action of the burn-over shoe may damage the radioactive source housing and release radioactive material (Cs-137 from density tools, AmBe from neutron tools) into the wellbore fluid, creating a radiation contamination event that requires AER reporting, specialized wellbore decontamination, and disposal of contaminated drilling fluid through a licensed radioactive waste disposal facility. WCSB burn-over procedures for wells with radioactive logging tools require pre-authorization from the AER, a radiation monitoring protocol at surface (Geiger counter on the return flow line), a contingency plan for source release (casing patch over the burn-over interval if source is released), and a post-burn-over wellbore fluid sampling protocol to verify source integrity. Non-radioactive logging tools (induction, laterolog, sonic, caliper) carry no radioactive hazard from burn-over but require documentation of the abandoned tool assembly OD and composition (for subsequent mill-over or fishing planning) in the well abandonment record if the fish cannot be retrieved.
Burn-Over of Stuck Perforating Gun in WCSB Cardium Horizontal Well Enabling Completion Continuity
A WCSB Cardium horizontal well (2.1 km lateral, 5-1/2-inch K-55 casing, perforated with a 4-1/2-inch wireline gun assembly at 22 stages) has a perforating gun become stuck at 1,450 m from the heel during stage 14. Conventional remediation (100 kN overpull, 5,000 N mechanical jar 25 times) fails. Cable stuck-point test: 1,448 m. Burn-over authorized. Burn-over shoe (4.15-inch OD, 0.50-inch ID, TC flat-face mill) run on 3.5-inch drill collars. Burn-over initiated at 1,450 m, 70 rpm, 8 kN WOB, 180 L/min water circulation. Cable severed in 35 minutes (torque drop from 85 to 60 N-m, cable tension indicator at zero). Shoe pulled to 1,430 m. Overshot run and engages fish at 1,448 m after 3 attempts. Fish retrieved to surface with 14 m of cable still attached. Remaining 8 stages (15-22) run successfully using the same gun design, completing the well on schedule. Total NPT from stuck gun and burn-over: 18 hours. Without burn-over, abandonment of the remaining 8 stages would have reduced the anticipated 14-stage completion program to 13 stages and reduced EUR by approximately 12% based on the offset well analog for this Cardium section.
Fast Facts
Burn-over operations in the WCSB became a formal well intervention procedure in the 1960s and 1970s as wireline logging and perforating became routine in deeper, more complex Alberta wells where tool sticking was more common than in the shallower Cretaceous fields first developed in the 1940s. The modern burn-over shoe design using tungsten carbide cutting elements replaced earlier designs that used soft iron mill faces, which wore out rapidly when cutting through the harder multi-strand steel cables used in modern monoconductor wireline service.
Related Terms
The wireline logging and perforating service operations in WCSB wells that create the tool-sticking scenarios requiring burn-over intervention, including the tension and weight monitoring procedures used to detect stuck tools early and the decision criteria for escalating from overpull remediation to burn-over authorization, are described under wireline. The fishing operation conducted after burn-over to retrieve the stuck tool body, severed cable, and perforating gun assembly from the WCSB wellbore using an overshot or reverse-circulation fishing tool, including the fish description requirements for proper fishing tool selection and the milling-over contingency if the fish cannot be pulled, is described under fishing. The perforating gun system used in WCSB Montney and Cardium horizontal completions whose sticking in the horizontal lateral is the most frequent trigger for burn-over operations, including gun OD selection relative to casing ID, the shock loading at detonation that can drive the gun into a restriction, and the cable break-strength requirements for retrieving a partially stuck gun assembly before declaring it irretrievably stuck, is described under perforating gun.