casing swage

A casing swage is a solid steel mandrel with a tapered or rounded leading nose and a cylindrical body machined to a specific outside diameter that is run into a deformed, buckled, or collapsed casing string on a workstring or drill string and driven through the restriction by the weight of the string above to plastically deform the damaged casing section outward, restoring a portion of the original inside diameter and allowing wireline tools, completion equipment, and production tubing to pass through the previously impassable restriction. The swage operates on the principle of cold plastic deformation: when the steel casing wall is driven beyond its elastic limit by the wedging action of the tapered swage nose, the casing steel yields and deforms permanently outward to accommodate the swage OD, and because steel has work-hardening properties, the deformed section retains most of the restored diameter after the swage is withdrawn, unlike purely elastic deformation that would spring back when the tool is removed. In Western Canada Sedimentary Basin well intervention programs, casing swaging addresses three principal damage modes: mechanical deformation from formation subsidence or compaction in WCSB heavy oil and oil sands wells (Cold Lake, Athabasca, and Peace River areas) where overburden compaction of 0.3 to 1.5 m over the producing life of a SAGD or CSS well creates inward radial loading on the casing that produces buckling or ovalization; parting or partial collapse from corrosion wall thinning that allows external formation stress to deform the pipe inward at the thinned section; and mechanical impact damage from dropped objects, stuck tools that required jarring, or landing string impacts during completion equipment running operations. The swage is sized to the target restored ID rather than the nominal casing ID, because a swage that exceeds the yield strength of the casing at the undamaged wall sections would damage good pipe rather than restoring the damaged section; typical WCSB swage designs target 90 to 97 percent of the nominal API drift diameter of the casing string, restoring enough bore to pass the required completion tools without attempting to fully restore the original ID which would require forces exceeding the pipe body tensile capacity in severe deformation cases. Multiple swage passes are often required for significantly deformed casing sections, beginning with a smaller diameter swage that passes through the restriction at lower force and opening the bore progressively with successively larger diameter swages until the target drift diameter is achieved, with each pass expanding the casing by 3 to 6 mm in diameter and requiring careful monitoring of the workstring weight indicator to ensure the applied force does not exceed the connection or pipe body tensile capacity. The decision to swage versus section-mill and patch a damaged WCSB casing section depends on the deformation severity (swaging is effective for ovalization and partial collapse where the casing wall is intact; section milling is required for perforations, splits, or severe folding where the wall is breached), the available wellbore clearance (the swage must fit through the restriction, which requires the restriction to have at least a small remaining bore), and the depth and economic life remaining in the well (swaging at $15,000 to $40,000 is preferred over a casing patch at $80,000 to $250,000 when the restoration need is marginal bore clearance rather than pressure containment). Understanding casing swage design, the plastic deformation mechanism that makes the bore restoration permanent, the multi-pass swaging technique for severely ovalized casing, the decision criteria for swage versus section mill in WCSB well intervention programs, and the force limits that prevent damaging undamaged casing sections gives production engineers, workover planners, and coiled tubing and workstring supervisors the technical framework to restore casing integrity and intervention access efficiently in WCSB mature well operations.

• Cold plastic deformation and work hardening in casing swaging: The casing swage nose applies a radial expansion force to the deformed casing wall that exceeds the yield strength of the steel (typically 380 to 758 MPa for J-55 to P-110 casing grades), causing permanent plastic deformation. The work-hardening that accompanies plastic deformation increases the local yield strength of the deformed zone by 5 to 15 percent above the original value, providing some compensation for the reduced wall thickness that results from thinning during expansion. For WCSB J-55 or K-55 surface casing deformed by formation subsidence, the work-hardened swaged section typically retains the restored bore within 1 to 2 mm over subsequent thermal and pressure cycles.
• Progressive swaging sequence for severe WCSB oil sands deformation: Cold Lake and Peace River SAGD well casing damaged by 0.5 to 1.0 m of cumulative formation compaction may have casing OD reduced by 20 to 40 mm from nominal, requiring progressive swaging over 3 to 6 passes. The typical sequence begins with a swage sized to the measured minimum bore (confirmed by multi-finger caliper) and increases by 5 to 8 mm OD per pass. Swage running weight (the compressive load applied to drive the swage through the restriction) is monitored against the workstring connection makeup torque-to-yield limit; forces above 200 to 400 kN (depending on workstring OD) indicate the swage is at the restriction face and is deforming the casing rather than advancing through it, signaling that the correct swage size has been reached for that pass.
• Swage sizing relative to casing drift diameter: The target swage OD is set at 90 to 97 percent of the API drift diameter for the casing grade and weight being swaged, ensuring that the restored bore passes the required drift ring for subsequent completion operations. For 139.7 mm J-55 production casing with an API drift of 122.2 mm, a target swage OD of 115 to 119 mm is typical for a first-pass operation through a collapse restriction, with subsequent passes increasing toward 121 mm if the deformed section has sufficient remaining wall thickness to accept further expansion without splitting or buckling the pipe body.
• Swage versus section mill decision for WCSB casing damage: Swaging is the preferred first intervention for ovalized or partially collapsed casing where the pipe wall is intact and bore clearance is the primary issue; it requires only a workstring or coiled tubing run with the swage tool at bottom, no milling debris or cement requirements, and costs $15,000 to $40,000. Section milling followed by casing patch installation is required when the casing has corrosion perforations, longitudinal splits, or irreparably folded sections that swaging cannot open without breaching or further damaging the pipe wall; section milling typically costs $80,000 to $180,000 plus casing patch material. A caliper log showing minimum wall thickness below 60 percent of nominal adjacent to the deformation zone is a common criterion for selecting section mill over swage, because the thin wall would rupture under swaging loads.
• Swaging in WCSB SAGD steam injection wells: In Cold Lake and Peace River SAGD horizontal producer and injector pairs, casing deformation from overburden compaction and thermal cycling under steam injection at 200 to 240 degrees Celsius creates both geometric restrictions (ovalization reducing the bore) and wall damage (weld seam cracking from repeated thermal expansion and contraction cycles). Swaging the horizontal section of a SAGD producer requires a flexible swage body or a jointed swage assembly on coiled tubing that can navigate the 6 to 9 degree dogleg at the heel of the horizontal well while transmitting sufficient compressive force to expand the deformed casing in the lateral section where the deformation is most severe.

Progressive Swaging Restoring SAGD Producer Access in a Cold Lake Well

A Cold Lake SAGD producer operating for 12 years at steam temperatures of 220 degrees Celsius developed a 31 mm reduction in inside diameter at 480 m depth in the vertical section, reducing the 139.7 mm J-55 production casing bore from a nominal 122.2 mm to 91 mm minimum (measured by multi-finger caliper). The restriction prevented the electric submersible pump from being pulled for replacement on the planned workover. A progressive swaging program was designed using a workstring with swage subs: first pass at 95 mm OD, second pass at 103 mm OD, third pass at 111 mm OD, fourth pass at 118 mm OD (96.5% of the 122.2 mm API drift). Maximum workstring compression loads were 185 kN on passes 1 and 2, increasing to 290 kN on pass 3, and requiring 380 kN on pass 4. All loads remained below the 420 kN limit for the workstring connections. After four passes over 16 hours of rig time, the gauge ring confirmed 118 mm clear bore through the swaged interval. The ESP was pulled, replaced, and re-run without restriction. Total swaging operation cost: $62,000. Alternative cost of a casing patch and ESP retrieval via section mill: estimated $210,000 with 4 additional days of rig time.

Related Terms

Casing patch is the alternative to swaging for WCSB casing damage where the pipe wall has been breached by corrosion, splits, or irreparable folding; while swaging restores bore access by plastic expansion of an intact wall, casing patches restore pressure containment by bypassing the damaged interval with a new liner section sealed above and below the damage zone. Section mill is used in WCSB well intervention when casing damage is too severe for swaging (wall perforations, severe folding, or wall thickness below 60% of nominal), cutting away the deformed casing section to create an open-hole interval that accepts a cemented casing patch liner. Multi-finger caliper is the diagnostic tool run before swage design in WCSB damaged casing wells, measuring the inside diameter profile of the deformed interval to determine the minimum bore, the ovalization geometry, and the wall thickness at the deformation zone, all of which are required inputs for selecting the initial swage diameter and the progressive swaging sequence. Casing inspection log (multi-finger caliper, electromagnetic inspection, or ultrasonic imaging) is the prerequisite survey before swage design in WCSB deformed casing wells, quantifying the bore reduction, ovalization geometry, and remaining wall thickness at the damage zone to confirm that swaging is mechanically feasible and to determine the starting swage diameter and the number of progressive passes required. Formation subsidence in WCSB Cold Lake, Peace River, and Athabasca heavy oil reservoirs is the primary driver of casing deformation requiring swage intervention, with cumulative overburden compaction of 0.3 to 1.5 m over the producing life of SAGD and CSS operations creating inward radial casing loading that progressively reduces the bore at the depths of maximum compaction until wireline and workover access is blocked.