Sidetrack: Whipstock and Cement Kickoff, Stuck-Pipe Recovery, and Re-Drilling Economics
A sidetrack is a secondary wellbore deliberately drilled away from an existing hole, departing from the original path at a chosen kickoff point to reach a different bottomhole target, bypass an obstruction, or replace a damaged section of the well. It is one of the most useful tools in the drilling and well-intervention toolkit because it lets an operator reuse the upper portion of a well already drilled and cased, saving the time and cost of starting a brand-new surface hole. Sidetracks are drilled for several distinct reasons. The most common is mechanical: a drill string becomes irretrievably stuck (differential sticking, key-seating, or a twist-off leaving fish in the hole), and rather than abandon the whole well, the crew drills around the obstruction by kicking off above the stuck point. A second reason is geological or reservoir-driven: an operator re-enters an older well and drills a new lateral toward unswept oil, a better part of the reservoir, or an entirely separate zone, a practice central to the economics of mature WCSB fields. A third is geometric, correcting a wellbore that has drifted off target or building a multilateral well with several producing branches from one parent bore. The departure can be made in open hole or, more often in cased wells, through the casing using one of two main techniques. A whipstock is a long, tapered steel wedge set in the hole that deflects the bit sideways into the casing wall, where a window mill cuts an opening (a casing exit or window) through which the new hole is drilled. Alternatively, a cement (or kickoff) plug is set across the desired departure depth and the bit is used to drill off the plug at a slight angle, the directional driller building the new trajectory away from the original. Modern sidetracks are steered with measurement-while-drilling and either a mud motor with a bent housing or a rotary steerable system, allowing precise control of the new wellbore's inclination and azimuth. In the Western Canadian Sedimentary Basin, sidetracking is woven into both new-well operations and the economics of field redevelopment. On a Montney or Duvernay horizontal program, a stuck or collapsed lateral can be sidetracked to salvage the expensive surface hole, intermediate casing, and surface lease, often saving a large fraction of the multimillion-dollar well cost. In conventional Cardium, Viking, and Mannville pools, operators sidetrack old vertical wells into new horizontal legs to access bypassed pay without the cost and regulatory effort of a fresh surface location, an approach that fits AER Directive 040 well-identification and Directive 020 well-abandonment frameworks for re-entries. The decision to sidetrack rather than drill new, or to plug and abandon, is fundamentally an economic one, weighing the salvage value of the existing wellbore against the cost and risk of the kickoff and the productivity of the new target.
Key Takeaways
- It reuses the existing upper hole: A sidetrack departs from an existing wellbore at a chosen kickoff point to reach a new target, letting the operator keep the already-drilled and cased surface and intermediate sections. This salvage of prior investment is the core reason sidetracking is so much cheaper than drilling a fresh well from surface.
- Three main drivers: Sidetracks are drilled to bypass an irretrievable mechanical obstruction such as stuck pipe or a fish, to re-enter a well and reach bypassed reserves or a new zone, or to correct a wellbore that has drifted off target. A single well can host multiple sidetracks, each kicked off for a different purpose.
- Whipstock or cement kickoff: In cased holes a whipstock sets a steel wedge that deflects a window mill to cut a casing exit, while in open or cased holes a cement kickoff plug can be drilled off at an angle. Both establish the departure point; a mud motor or rotary steerable system then builds the new trajectory.
- Steered with MWD and directional tools: Modern sidetracks use measurement-while-drilling for real-time position plus a bent-housing mud motor or rotary steerable assembly to control inclination and azimuth. This precision lets operators land a new Montney or Duvernay lateral accurately even when departing from an existing bore.
- It is an economic decision: Choosing to sidetrack rather than drill new or plug and abandon weighs the salvage value of the existing wellbore against kickoff cost, risk, and the productivity of the new target. In WCSB redevelopment, sidetracking old wells into horizontal legs unlocks bypassed pay at a fraction of new-well cost.
Whipstock Sidetracks Through Casing
When a sidetrack must exit through casing, a whipstock assembly is set and anchored at the kickoff depth, its tapered face oriented to the desired azimuth using gyro or MWD survey data. A starting mill cuts into the casing along the whipstock ramp, followed by a window mill and watermelon mills that enlarge the casing exit into a smooth window. The new bottomhole assembly then drills out into formation. A clean casing window is critical: a ragged or short window snags subsequent trips and completion strings. WCSB service companies routinely run single-trip whipstock systems that set the anchor, orient, and mill the window in one run, cutting rig time on Cardium and Mannville re-entries.
Sidetracking to Recover from Stuck Pipe
Stuck pipe is one of drilling's most expensive non-productive events, and when freeing attempts (jarring, spotting acid or freeing agents, backing off) fail, sidetracking around the fish is often the cheapest path forward. The crew backs off above the stuck point, sets a cement plug to provide a firm kickoff foundation, and drills off the plug to build a new trajectory clear of the obstruction. On a deep Montney horizontal where the lateral has cost several million CAD to reach, sidetracking to salvage the cased vertical and curve sections can preserve a large share of the well investment versus abandoning and re-drilling from surface.
Fast Facts
The whipstock predates rotary directional drilling by decades. The first practical removable whipstock was developed by John Eastman and H. John Eastman in the late 1920s and used in California to deflect crooked holes back to vertical, the same tool that within a few years enabled the first deliberate directional and relief wells. The 1934 Conroe field blowout in Texas was killed by a directional relief well drilled with a whipstock, the technique that established directional drilling, and by extension sidetracking, as a mainstream oilfield capability rather than a last-ditch curiosity.
Related Terms
A sidetrack is set up by a whipstock, the deflection wedge that creates the casing exit, and it is a form of directional drilling, since the new bore must be steered along a planned trajectory. It is frequently the chosen response to stuck pipe, drilling around an immovable obstruction, and the abandoned section left behind is the fish, the equipment or pipe in the original hole that the sidetrack bypasses.
WCSB Field Scenario: Sidetracking a Collapsed Duvernay Lateral
A CNRL Duvernay horizontal near Kaybob suffered a wellbore collapse in the lateral after a twist-off left a fish at about 4,200 m measured depth, with the bottomhole assembly irretrievably stuck. Fishing attempts over three days added roughly 450,000 CAD in rig time without recovering the tools, and the formation was sloughing further with each trip. Drilling a replacement well from a new surface lease would have cost on the order of 9 million CAD plus several weeks of permitting and lease construction.
The operator instead set a cement kickoff plug above the fish at about 3,900 m, drilled off the plug, and steered a fresh lateral with a rotary steerable system into the target Duvernay interval, reusing the entire cased vertical and curve. The sidetrack reached total depth in under two weeks for roughly 2.5 million CAD, preserving the surface investment and bringing the well on production at the planned rate, a small fraction of the cost of a brand-new well.