Walking System: Pad Drilling, Types, and Rig Mobility

What Is a Walking System?

A walking system is a self-propelled hydraulic mechanism that moves a land drilling rig short distances between wellheads on a multi-well pad without rigging down the derrick or disconnecting surface equipment. Hydraulic feet or skid frames lift and advance the rig in increments, enabling pad-drilling operations in the Permian Basin, Montney, Duvernay, and other high-density play areas worldwide.

How a Walking System Works

Most walking systems use four or eight hydraulic leg assemblies bolted to the rig substructure's main beams. During a move, a control system simultaneously extends all legs downward to lift the rig clear of its pad footings by 50 to 150 mm (2 to 6 inches). Once elevated, the system shifts the entire rig body in the desired direction by a stroke length that typically ranges from 0.9 to 1.8 m (3 to 6 ft) per cycle. The legs then lower the structure back to grade, retract to their neutral position, and the cycle repeats. A standard inter-well spacing on a six-well pad may require 15 to 30 walk cycles and takes 4 to 12 hours total, compared to 3 to 7 days for a conventional move involving crane-assisted disassembly.

Crab-walk or multi-directional systems add a secondary axis of motion by mounting each leg on a rotating turntable or independent skid frame. This allows diagonal or lateral movement without realigning the entire rig, which proves critical when well spacing is irregular or surface obstructions require angled approaches. Control systems on modern units integrate load-cell feedback so the operator monitors individual leg forces in real time, preventing overload of any single substructure beam during uneven terrain moves. Hydraulic supply pressures typically operate in the 3,000 to 5,000 psi (207 to 345 bar) range, with dual redundant pump circuits for fail-safe operation under API 4F fatigue load criteria.

Longitudinal (front-to-back) walking moves the rig along the wellbore row; lateral (side-to-side) walking repositions it across rows. Some operators combine both axes to walk from one pad cluster to an adjacent cluster without substructure disassembly. Entro Industries pioneered the commercial hydraulic walking system in western Canada in the mid-2000s; the technology was later adopted by National Oilwell Varco (NOV) and Dreco, both of which integrate walking packages into their Ideal and Dreco-series substructures.

Walking Systems Across International Jurisdictions

In Alberta, Canada, the Alberta Energy Regulator (AER) requires pad development plans and surface lease agreements that accommodate walking-system footprints. The Montney and Duvernay formations see the majority of new horizontal wells drilled from multi-well pads, with AER Directive 056 governing surface and wellbore spacing. Pad counts of 6 to 16 wells per surface location are common, and walking systems are standard equipment on every contracted rig entering these plays. Substructure certification aligns with Canadian Standards Association (CSA) S37 criteria.

In the United States, the Permian Basin in Texas and New Mexico is the largest market for walking systems globally. Operators such as Coterra Energy and Diamondback Energy run walking-equipped rigs on pads of 8 to 24 wells. API Specification 4F provides the structural standard for onshore operations; BSEE governs equivalent equipment requirements on the Outer Continental Shelf. The Texas Railroad Commission and New Mexico Oil Conservation Division require substructure stability documentation but do not prescribe walking-system specifications directly.

In the Middle East, ADNOC's unconventional gas program in Abu Dhabi and Saudi Aramco's Jafurah development are driving pad-drilling adoption, with walking systems from NOV and Bentec included in long-term rig contracts. In Norway, Sodir oversees offshore development where walking systems do not apply; land rig packages exported by Norwegian contractors such as Bentec carry API 4F and NORSOK D-001 certification. In Australia, NOPSEMA regulates offshore operations; onshore rigs in the Cooper Basin and Beetaloo Sub-basin operate under state mining legislation with OEM certification as the applicable standard.

Walking System Types and Technical Specifications

The four primary configurations in commercial service are defined by leg count, motion axis, and load capacity:

Four-leg walking systems are the most compact design and suit rigs with substructure hook loads up to approximately 1,360 tonnes (1,500 short tons). Each leg assembly uses a single-stage hydraulic cylinder rated for 340 to 450 tonnes (375 to 500 short tons) of vertical load. Stroke per cycle runs 0.9 to 1.2 m (3 to 4 ft). NOV's Ideal 1200 substructure integrates a four-leg walking package as standard on many of its AC electric rig offerings. These systems walk in a single linear axis, requiring the rig to be manually pivoted or the pad to be oriented so that all wells lie along one straight row.

Eight-leg walking systems distribute load across more contact points and handle heavier substructures from 1,815 to 3,175 tonnes (2,000 to 3,500 short tons). Each cylinder carries 230 to 340 tonnes (250 to 375 short tons), and dual-axis capability is achievable by grouping legs into two independently controlled sets. Dreco's 1,500-short-ton (1,361 tonne) substructure walking package and the Entro Industries HD8 system are common examples. Eight-leg units are standard on the heaviest AC rigs deployed in the Duvernay and Montney.

Crab-walk (multi-directional) systems mount each leg on a swivel or turntable so the rig can move diagonally or laterally without rotating the entire structure. This is critical on pads where wells are not co-linear or where cellar positions deviate from a straight row. Crab-walk capability adds mechanical complexity but eliminates the need for any structural disassembly when changing pad alignment. Entro Industries' Rig Walker and NOV's Tri-Walk are the leading commercial products in this category.

Skid systems (a related but distinct technology) use steel rails or UHMWPE pads on which the substructure slides under hydraulic push-pull cylinder force, without lifting. True walking systems lift; skid systems slide. Skid systems are simpler and less expensive but require a prepared skid surface and cannot traverse uneven ground. They remain common in older pad development programs where terrain permits.

Load ratings must account for dynamic amplification during rig move (API 4F specifies a 1.1 dynamic factor for lateral moves), wind loads per ASCE 7, and setback distances for adjacent wellhead equipment. Most OEMs supply finite element analysis (FEA) reports for each installation to satisfy AER, state, or client engineering review. Walk speed ranges from 1 to 4 m per hour (3 to 13 ft per hour) over prepared ground, increasing to 6 m per hour (20 ft per hour) on engineered skid decks.

Walking System Synonyms and Related Terminology

Walking system is also known as:

• Hydraulic walking system: emphasizes the hydraulic actuation mechanism; the term used in most OEM engineering documentation
• Rig walking system: common field shorthand used by drillers and rig managers across North America and the Middle East
• Self-moving rig: informal descriptor used in operator well-program documents to distinguish pad-capable rigs from conventional move rigs
• Crab-walk system: specifically refers to multi-directional walking capability, not the broader category
• Pad-walking rig: operator procurement terminology indicating a rig contract requirement for walking capability

Related terms: pad drilling, substructure, non-productive time, multi-well pad, rig move

Frequently Asked Questions

What is a walking system in drilling?

A walking system is a hydraulic mechanism integrated into a land rig's substructure that moves the entire rig laterally or longitudinally between wellheads on a multi-well pad without disassembly. Hydraulic legs lift the rig and advance it in short strokes of 0.9 to 1.8 m (3 to 6 ft) per cycle, positioning it over the next well cellar and eliminating crane-assisted inter-well moves.

How does a walking system work?

Hydraulic cylinders extend downward from the substructure base frames, lifting the rig 50 to 150 mm (2 to 6 inches) off its pad footing. The system shifts the rig body horizontally one stroke length, lowers it back, retracts the legs, and repeats. A full inter-well move across 3 to 6 m (10 to 20 ft) typically requires 5 to 20 cycles and 4 to 12 hours.

Why is a walking system important for rig operations?

Walking systems cut inter-well move time from 3 to 7 days to 4 to 24 hours, saving USD 100,000 to USD 300,000 in non-productive time per six-well pad. They reduce personnel exposure to lifting and rigging hazards associated with full substructure disassembly, and they minimize surface disturbance by keeping the rig on a single engineered pad throughout the program.

What standards apply to walking systems?

API Specification 4F (Drilling and Well Servicing Structures) governs substructure design including walking-system load frames, with OEM-supplied FEA certifications per its fatigue criteria. In Canada, CSA S37 provides supplemental structural guidance. NORSOK D-001 and ISO 10425 apply to walking-system components in offshore-capable rig designs.

How is a walking system used on different rig types?

Walking systems are exclusively a land-rig technology; jackup, semi-submersible, and drillship rigs relocate by marine propulsion or anchor handling. Among land rigs, AC electric rigs dominate because their power infrastructure handles the hydraulic power unit (HPU) cleanly. Full four-leg and eight-leg systems are reserved for hook loads above 454 tonnes (500 short tons); simplified skid systems serve lighter workover and coil-tubing units.

Why Walking Systems Matter in Oil and Gas

Walking systems have changed the economics of multi-well pad development by turning a multi-day logistical operation into a same-shift task. The resulting reduction in non-productive time across large unconventional programs in the Permian Basin, Montney, Haynesville, and analogous plays translates directly into lower finding and development costs per barrel. As pad counts grow and well spacing tightens, repositioning a fully equipped rig in hours without disturbing wellhead equipment or surface piping delivers a concrete scheduling and cost advantage. Expanding adoption in the Middle East, Argentina's Vaca Muerta, and Australia's Beetaloo Sub-basin confirms that walking-system technology is now a standard feature of competitive land rig design worldwide.