Directional Drilling
Steering a drill bit thousands of feet underground to hit a target the size of a small room. Here's how it actually works.
Why Drill Directionally?
Vertical wells only contact a reservoir where they pass directly through it. Directional and horizontal drilling let a single wellbore travel laterally through a reservoir, dramatically increasing the surface area in contact with hydrocarbon-bearing rock. This is the technology, combined with hydraulic fracturing, that unlocked shale plays like the Permian and Eagle Ford.
Directional drilling is also used to reach reservoirs positioned under obstacles — city infrastructure, protected areas, or neighboring leases — from a surface location that wouldn't otherwise have access, and to drill multiple wells from a single offshore platform in different directions.
How the Bit Is Steered
A directional well is steered using a combination of:
- Downhole (mud) motor — a turbine-like tool near the bit that converts drilling fluid flow into rotational power, allowing the bit to turn independently of the drill string above it.
- Bent sub / bent housing — a slight mechanical bend that, combined with the motor, lets the driller build angle by "sliding" (not rotating the whole string) in a chosen direction.
- Rotary steerable systems (RSS) — modern tools that steer while continuously rotating the entire string, which improves hole cleaning and ROP compared to sliding with a motor.
MWD and LWD — Seeing Underground
MWD (Measurement While Drilling) tools sit in the BHA and continuously measure the wellbore's inclination and azimuth, transmitting that data to surface in real time — typically via mud pulse telemetry, which encodes data as pressure pulses in the drilling fluid.
LWD (Logging While Drilling) tools add formation evaluation data — resistivity, density, gamma ray — to that same real-time stream, letting the directional driller and wellsite geologist actually see what kind of rock the bit is in without waiting for a wireline log run.
The Directional Driller Role
Directional drillers are specialists, usually employed by a service company rather than the drilling contractor. They monitor the MWD data stream continuously — often from a control cabin — making steering adjustments to keep the well on its planned trajectory. It's one of the higher-paying specialist tracks in drilling; see the salary guide for current figures.