horizontal drilling — Oil & Gas Glossary

What Is Horizontal Drilling?

Horizontal drilling steers a wellbore from vertical to a near-horizontal trajectory, typically exceeding 80 degrees from vertical, to intersect and produce from geological formations along their lateral extent rather than through their thickness. Combined with hydraulic fracturing, horizontal drilling has transformed the global energy industry by unlocking vast reserves in unconventional formations including Canada's Montney, the US Permian Basin, Australia's Cooper Basin, and Saudi Arabia's Ghawar field.

Key Takeaways

Horizontal wells produce three to five times more hydrocarbons than vertical wells by exposing significantly more reservoir rock to the wellbore, with lateral sections commonly extending 2,000 to 5,000 metres (6,562 to 16,404 feet).
The technique depends on mud motors, rotary steerable systems (RSS), and measurement-while-drilling (MWD) tools that allow real-time trajectory control while drilling.
Lateral lengths in the Permian Basin now exceed 4,600 metres (15,000 feet), with operators like ExxonMobil and Chevron routinely drilling multi-mile laterals from single pad locations.
Canada's Montney formation, spanning Alberta and British Columbia, is one of the world's most prolific horizontal drilling plays, with over 10,000 horizontal wells drilled since 2005.
Horizontal drilling reduces surface disturbance by allowing multiple wells to be drilled from a single pad, a significant environmental advantage regulated by the AER, BCER, and BLM.

How Horizontal Drilling Works

A horizontal well begins as a conventional vertical well, drilled straight down through surface formations to the "kickoff point" (KOP), the depth at which the directional drilling assembly begins building angle. The KOP is typically set 100 to 300 metres (328 to 984 feet) above the target formation, depending on the build rate and formation geometry.

From the KOP, the wellbore curves gradually from vertical toward horizontal using either a mud motor with a bent housing or a rotary steerable system. The build rate, measured in degrees per 30 metres (degrees per 100 feet), determines how sharply the well turns. Standard build rates range from 4 to 12 degrees per 30 metres, with medium-radius builds (8 to 20 degrees per 30 metres) preferred in most unconventional completions. Once the wellbore reaches the target angle within the producing formation, the drill bit continues laterally through the pay zone.

Real-time directional control relies on measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools positioned behind the drill bit in the bottom-hole assembly (BHA). These instruments transmit inclination, azimuth, gamma ray, and resistivity data to surface via mud pulse telemetry or electromagnetic signals, allowing the directional driller to steer the bit within a target zone as thin as 3 to 5 metres (10 to 16 feet) over lateral distances exceeding 3,000 metres (9,843 feet).

Horizontal Drilling Across International Jurisdictions

Horizontal drilling techniques are applied globally, though formation geology, regulatory requirements, and operational practices vary by region.

Canada

The Montney formation, extending across northeastern British Columbia and northwestern Alberta, hosts the densest concentration of horizontal drilling activity in Canada. Operators including Canadian Natural Resources, Tourmaline Oil, and ARC Resources drill horizontal laterals of 2,000 to 3,500 metres (6,562 to 11,483 feet) into the Montney's tight siltstone and dolostone reservoir. The AER regulates well spacing (typically 200 to 400 metres between laterals on a stacked pad) and requires directional surveys filed under Directive 056. The Duvernay formation in west-central Alberta and the Viking formation in Saskatchewan represent additional major horizontal drilling targets. The BCER oversees operations in BC's Montney region, with emphasis on induced seismicity monitoring associated with horizontal drilling and completions.

United States

The Permian Basin (Texas and New Mexico) is the world's most active horizontal drilling province, with over 350 horizontal rigs operating simultaneously at peak activity. The stacked pay concept, where operators target multiple formations (Wolfcamp A, B, C, D; Bone Spring; Spraberry) from a single pad, maximises recovery per surface acre. The EIA reports that horizontal wells in the Permian averaged initial production rates of approximately 1,000 barrels of oil equivalent per day in 2023. The Eagle Ford (south Texas), Bakken (North Dakota), and Marcellus (Appalachia) are additional major horizontal plays, regulated by their respective state agencies.

Australia

Horizontal drilling in Australia targets both conventional and unconventional reservoirs. The Cooper Basin in South Australia and Queensland, operated by Santos and Beach Energy, employs horizontal wells in tight gas and oil formations. NOPSEMA regulates offshore horizontal drilling on the Northwest Shelf and in the Browse Basin. Australia's coal seam gas (CSG) industry in Queensland's Surat and Bowen basins uses horizontal drilling to access coal seams at relatively shallow depths of 200 to 1,000 metres (656 to 3,281 feet).

Middle East

Saudi Aramco pioneered maximum reservoir contact (MRC) wells in the Ghawar field, the world's largest conventional oil field. MRC wells use multilateral horizontal drilling to create multiple lateral branches from a single wellbore, with total lateral exposure exceeding 10,000 metres (32,808 feet) per well. ADNOC applies similar multilateral horizontal techniques in Abu Dhabi's offshore fields, including Upper Zakum and SARB, to maintain production from mature carbonate reservoirs.

Norway and the North Sea

Extended-reach horizontal drilling from fixed platforms is standard practice on the Norwegian Continental Shelf. Equinor's Johan Sverdrup field uses horizontal producers with lateral lengths of 2,000 to 4,000 metres (6,562 to 13,123 feet). The Troll field, one of Europe's largest gas fields, employs extremely long horizontal wells to access its thin oil column (12 to 26 metres thick) spread over a massive areal extent. Sodir's regulations under the Activities Regulations require detailed well path planning and anti-collision analysis for all directional and horizontal wells.

Tip: For investors, the key metric in horizontal drilling is lateral length versus initial production rate. Longer laterals generally deliver higher IPs, but capital costs increase with each additional metre drilled and completed. The optimal lateral length depends on rock quality, completion design, and commodity prices. In 2024, breakeven costs for three-mile laterals in the Midland Basin dropped below USD $40 per barrel WTI, while shorter one-mile laterals in less productive formations may require USD $55 or more to break even.

Fast Facts

In 2017, ExxonMobil's Sakhalin-1 project in Russia's Far East drilled the Odoptu OP-11 well to a measured depth of 15,000 metres (49,212 feet), setting the world record for the longest extended-reach well. The horizontal departure exceeded 14,100 metres (46,260 feet). In the North Sea, BP's M-16Z well at Wytch Farm (UK) held the extended-reach record for over a decade at 11,278 metres (37,001 feet) measured depth with a horizontal departure of 10,728 metres (35,196 feet), demonstrating that onshore wells can access offshore reservoirs kilometres from the drill site.

Horizontal drilling is referenced by several related terms:

Horizontal Well: the completed wellbore resulting from horizontal drilling
Lateral: the horizontal section of the wellbore within the target formation
Extended-Reach Drilling (ERD): horizontal or high-angle wells with exceptionally long horizontal departures, typically exceeding twice the true vertical depth
Multilateral Well: a well with multiple horizontal branches originating from a single vertical or deviated parent wellbore
Maximum Reservoir Contact (MRC) Well: Saudi Aramco's term for multilateral horizontal wells designed to maximise formation exposure in the Ghawar field
Pad Drilling: drilling multiple horizontal wells from a single surface location, reducing surface footprint and rig move costs
Unconventional Well: commonly refers to horizontal wells completed with multistage hydraulic fracturing in tight rock formations

Frequently Asked Questions

What is horizontal drilling in oil and gas?

Horizontal drilling is a technique that steers a wellbore from vertical to near-horizontal within a target formation, allowing the well to produce from a much greater length of reservoir rock than a vertical well. The lateral section typically extends 1,000 to 5,000 metres (3,281 to 16,404 feet) through the pay zone. Combined with multistage hydraulic fracturing, horizontal drilling has unlocked production from tight formations across Canada, the US, Australia, and the Middle East.

How deep does horizontal drilling go?

True vertical depths (TVD) for horizontal wells range from 200 metres (656 feet) for shallow coal seam gas in Queensland to over 4,000 metres (13,123 feet) in deep formations like the Duvernay or Wolfcamp D. Measured depth (the total drilled length) is significantly greater due to the horizontal lateral, with total well lengths commonly reaching 5,000 to 8,000 metres (16,404 to 26,247 feet). Extended-reach wells have exceeded 15,000 metres (49,212 feet) measured depth.

Why is horizontal drilling better than vertical drilling?

Horizontal wells expose far more reservoir rock to the wellbore. A vertical well through a 30-metre (98-foot) thick formation contacts only 30 metres of pay zone. A horizontal well in the same formation with a 3,000-metre (9,843-foot) lateral contacts 100 times more rock, dramatically increasing production rates and ultimate recovery. Pad drilling also reduces the number of surface locations needed, minimising environmental disturbance and access road construction costs.

Why Horizontal Drilling Matters in Oil and Gas

Horizontal drilling, combined with multistage hydraulic fracturing, ranks among the most transformative technologies in the history of the petroleum industry. It converted trillions of cubic feet of gas and billions of barrels of oil from "technically unrecoverable" geological curiosities into commercially viable reserves, reshaping global energy markets and geopolitics. From the Montney and Duvernay formations powering Canadian LNG exports to the Permian Basin sustaining US energy independence, from Saudi Aramco's maximum reservoir contact wells maintaining Ghawar's output to Equinor's extended-reach producers in the North Sea, horizontal drilling remains the enabling technology behind the majority of new oil and gas production brought online worldwide each year.

Horizontal Drilling: Definition, Process, and Global Applications