Directional drilling

Lore & Background

The history of directional drilling began with the slow realization that wells need not be vertical, spurred by late-1920s lawsuits over boundary-crossing wells. Early survey tools included simple pendulums for inclination and magnetic compasses for azimuth, but magnetic readings were affected by metalwork. The Sperry Corporation modified small gyroscopic compasses for Sun Oil, leading to the spin-off Sperry Sun (now part of Halliburton). A survey measures depth, inclination, and magnetic azimuth at a point; consecutive surveys track the wellbore's path.

In 1934, H. John Eastman, Roman W. Hines, and George Failing saved the Conroe, Texas, oil field by drilling slanted relief wells to relieve gas pressure from a fire. Failing had patented a portable drilling truck in 1931. Eastman Whipstock, Inc., became the world's largest directional company in 1973. The next major advance came in the 1970s with downhole drilling motors (mud motors) and bent subs, allowing direction changes without pulling drill pipe. Measurement while drilling tools using mud pulse telemetry, wired pipe, or electromagnetism enabled real-time data transmission.

Rotary steerable systems (RSS) later allowed directional control while rotating the drill pipe, improving access in difficult formations. Directional drilling serves multiple purposes: increasing reservoir exposure, accessing reservoirs under towns or lakes, grouping wellheads on one surface location (e.g., offshore platforms), drilling along fault undersides, and creating relief wells for blowouts. Surveys are taken every 10–150 meters, with MWD tools used during critical angle changes.

Reader's Guide

Directional drilling transformed resource extraction by enabling non-vertical bores for oil, gas, water, and coal bed methane. Its significance lies in solving legal and practical challenges: early lawsuits over boundary-crossing wells drove development of survey tools, while the 1934 Conroe fire demonstrated the life-saving potential of relief wells. The technology allowed drilling under towns, lakes, and difficult formations, and reduced surface disturbance by grouping multiple wellheads on one pad—critical for offshore platforms and land operations. Advances like downhole mud motors and rotary steerable systems made directional drilling more efficient and accessible, though sliding with a motor remains slower and costlier than rotating. The legacy includes the formation of Sperry Sun and Eastman Whipstock, and the ongoing refinement of MWD and RSS tools. Directional drilling remains essential for maximizing reservoir contact, managing blowouts, and minimizing environmental footprint.

Did You Know?

• The first major use of directional drilling was in 1934 to extinguish the Conroe, Texas, oil field fire using slanted relief wells.
• The Sperry Corporation modified small gyroscopic compasses for Sun Oil, leading to the spin-off Sperry Sun, now part of Halliburton.
• A survey in directional drilling measures three components: measured depth, inclination, and magnetic azimuth.
• Rotary steerable systems allow directional control while the drill pipe rotates, unlike sliding with a downhole motor.