Wash Pipe: Washover Fishing Operations, Burn Shoe Mechanics, and Stuck Pipe Recovery

A wash pipe is a relatively large internal-diameter tubular component of a fishing tool string that is used together with a burn shoe to wash over a stuck fish (drill pipe, drill collar, casing, packer, or other stranded downhole equipment) in preparation for engaging and retrieving the fish from the wellbore. The wash pipe and burn shoe together telescope down over the upper portion of the fish, simultaneously cleaning away the formation cuttings, cement, drilling mud, or other debris that has stuck or buried the equipment while presenting a fresh metal surface that an overshot, spear, or other catching tool can grip on a subsequent run. The mechanics are straightforward but unforgiving. The wash pipe is run on the bottom of the drillstring with a burn shoe (also called a rotary shoe) threaded on its bottom end. The shoe carries hard-faced cutting structure (tungsten carbide inserts, polycrystalline diamond, or simple hardfaced steel teeth depending on what is being cut) configured to mill formation, cement, or even soft metal that surrounds the fish. The shoe internal diameter is sized to clear the fish outside diameter with a typical radial clearance of 3 to 8 mm (1/8 to 5/16 inch); larger clearances reduce binding risk but reduce the ability to mill cleanly around irregular profiles such as tooljoints, stabilisers, or packer slips. Once the wash pipe and shoe assembly is run to depth, drilling fluid is circulated at high rates (typically 1,500 to 3,500 L/min, 400 to 925 gpm) through the drillstring and out through ports in the burn shoe, generating high annular velocity that lifts cuttings up the annulus between the wash pipe inside diameter and the fish outside diameter. The drillstring is rotated at 30 to 80 rpm while controlled weight (commonly 4,500 to 22,000 kg or 10,000 to 50,000 lb) is applied, advancing the assembly progressively over the fish at penetration rates of 0.3 to 3 metres per hour depending on the nature of the obstruction. Washover lengths of 30 to 90 metres (100 to 300 feet) are common in WCSB fishing operations, particularly for stuck drill collars in the Banff or Wabamun carbonates and for drill-pipe washovers in deeper Montney horizontal laterals. The wash pipe itself must combine large internal clearance over the fish with sufficient cross-sectional steel to carry torque and weight without buckling. Common WCSB wash pipe sizes include 88.9 mm (3 1/2 inch), 114.3 mm (4 1/2 inch), 139.7 mm (5 1/2 inch), and 168.3 mm (6 5/8 inch) outer diameters, with internal diameters chosen to provide 3 to 8 mm clearance over the fish. The operation is high-stakes: a successful washover typically saves a sidetrack-and-redrill expense of 1.4 to 4.5 million CAD per well, while a failed washover often forces exactly that outcome under significantly compressed timing. Washover operations in Alberta are regulated under AER Directive 037 (Service Rig Operation) and Directive 008 for any cement-related remediation that follows, with all fishing activity and associated rig time reported on the well file submitted under Directive 059 (Well Drilling and Completion Data Filing).

Washover Procedure on a Stuck Drill Collar in the Banff

A common WCSB application is washing over stuck drill collars in the Mississippian Banff or Pekisko formations of west-central Alberta, where karst fill and cavernous intervals routinely cause differential sticking or pack-off events. The fishing string is made up with a 168.3 mm (6 5/8 inch) wash pipe and a matching burn shoe sized 13 mm larger than the 158.8 mm (6 1/4 inch) drill collar OD. The shoe is dressed with tungsten carbide teeth for cutting cemented limestone debris. Circulation begins at 2,200 L/min and rotation at 45 rpm; weight is gradually increased from 6,800 to 13,600 kg until steady penetration is established at 1.2 metres per hour. After 32 metres of washover (28 hours of operating time), the fish top is fully exposed and a 158.8 mm overshot is run on the next trip to retrieve the collar string.

High-Pressure Wash Pipe for Hot Duvernay Fishing Jobs

Modern WCSB Duvernay horizontal wells reach total depths of 4,000 to 4,400 metres (13,100 to 14,430 feet) with bottomhole temperatures of 120 to 145°C (248 to 293°F) and circulating pressures during fishing exceeding 41 MPa (5,950 psi). Conventional wash pipe packing fails rapidly under these conditions, forcing frequent trips and extended rig time at cost of 35,000 to 50,000 CAD per day. Manufacturers including Baker Hughes, Halliburton, and Weatherford have developed high-pressure wash pipe systems with metal-to-metal seal packing rated for sustained 55 MPa (7,975 psi) circulating pressure and 1,200-hour service life, addressing this Duvernay fishing pain point at premium rental rates of 1,800 to 3,200 CAD per day above conventional pricing.

Related Terms

Wash pipe operations connect to several adjacent fishing and well-control concepts. Fish is the generic term for any stranded equipment that requires retrieval and defines what the wash pipe and shoe assembly is trying to expose and recover. Overshot is the most common catching tool that grips the exposed top of the fish after washover, completing the retrieval sequence by anchoring the fish to the drillstring for pullout. Stuck pipe describes the underlying failure mode (differential sticking, key seating, pack-off, or mechanical bridging) that typically necessitates a washover operation in the first place and informs the choice of cutting structure and circulation programme.

Real-World WCSB Wash Pipe Recovery Scenario

An operator drilling a 3,650 metre measured depth Duvernay horizontal well near Kaybob loses circulation in the curve section and the bottomhole assembly becomes differentially stuck at 3,180 metres after the mud column is partially lost. After two failed jarring attempts and 72 hours of fishing diagnostics costing 195,000 CAD, the decision is taken to wash over the stuck drill collar string. A 139.7 mm high-pressure wash pipe with PDC-faced burn shoe is rented at 4,800 CAD per day and run on a 41 MPa rated kelly hose system. Total fishing time including washover is 11 days at a service rig day rate of 38,000 CAD plus 6,400 CAD daily wash pipe rental and 95,000 CAD shoe redress cost.

The washover successfully exposes 47 metres of stuck drill collar; an overshot retrieves the string on the subsequent trip. Total fishing cost is 690,000 CAD versus an alternative sidetrack estimate of 2.85 million CAD plus 18 days of lost rig time. The well is back on plan within 15 days of the original stuck-pipe event, completes as a 28-stage Duvernay producer, and delivers IP30 of 920 BOE/d with payout achieved in 14 months. The wash pipe operation saved approximately 2.2 million CAD versus the sidetrack alternative.