Steering a well at a glance
- The path
- Vertical → kickoff point → build curve → lateral
- Steering tools
- Mud motors, rotary steerable systems (RSS)
- The eyes downhole
- MWD/LWD for real-time position and formation data
- Horizontal lateral
- Turn to ~90°, then run 1–3+ miles through the reservoir
- Why it matters
- Exposes far more reservoir; central to shale
Directional drilling is the practice of deliberately steering a wellbore along a planned, non-vertical path. Horizontal drilling is its most aggressive form: the hole is turned a full 90 degrees and run sideways through the target rock. Together they are the reason a single well can drain a vast area of shale that a vertical hole would barely touch.
The path: vertical, kickoff, build, lateral
A steered well follows a planned trajectory in four parts:
- Vertical section. The well starts straight down, just like a conventional hole.
- Kickoff point (KOP). At a planned depth, the crew begins to deviate the wellbore from vertical. This is where steering starts.
- Build curve. The hole bends gradually, "building angle" at a controlled rate (degrees per 100 feet) until it approaches horizontal.
- Lateral. Once near 90 degrees, the well "holds" that angle and runs horizontally through the reservoir for the full length of the lateral.
Hitting that path precisely is the job of the directional driller, who plans and steers the trajectory in coordination with the company man and the rig crew.
The tools that bend the hole
Steering a bit thousands of feet below ground requires specialized downhole tools. Two families dominate:
| Tool | How it steers |
|---|---|
| Mud motor | A bent-housing motor driven by circulating mud. To steer, the crew stops rotating the drill string and "slides" — the bent housing points the bit in the desired direction. |
| Rotary steerable system (RSS) | Steers continuously while the entire string keeps rotating, giving smoother, faster, more precise holes. More expensive, but standard on demanding wells. |
Sliding with a mud motor is cheaper but slower and produces a rougher hole; an RSS costs more per day but drills faster, cleaner laterals and is increasingly the default on long, complex wells.
MWD, LWD, and geosteering
You cannot steer what you cannot see. Two measurement systems give the directional team a real-time picture downhole:
- MWD (Measurement While Drilling) reports the bit's position and orientation — inclination, azimuth, and tool face — in near real time, so the steering can be corrected on the fly.
- LWD (Logging While Drilling) reads formation properties as the bit advances, so the team knows whether they are still inside the target rock.
Combined, they enable geosteering: actively adjusting the trajectory to keep the lateral inside the thin, most productive layer of the reservoir — sometimes only a few feet thick — for its entire length.
Why horizontal changed everything: a vertical well crosses a shale layer once, maybe 50–100 feet of pay. A horizontal lateral runs along that layer for one to three miles, exposing thousands of feet of reservoir to a single wellbore. Pair that with hydraulic fracturing and you get the modern shale well.
Extended-reach drilling (ERD)
When the lateral or the total departure from the surface location gets very long, the well enters extended-reach drilling (ERD) territory — wells that reach far horizontally relative to their vertical depth. ERD lets a rig tap reservoirs miles away from the surface location, which is invaluable offshore (draining a wide field from one platform) and on land (reaching beyond surface obstacles). It pushes equipment, hydraulics, and steering to their limits and demands the most experienced directional hands.
Need a directional hand? rigs.work maintains a reference library of directional drillers and MWD specialists available by basin and window. Open learning resources or open a reference — reference-checked and organized for fast lookup.
Common questions
Steering a complex well?
Open directional drilling, MWD, and well-planning references from the library.