WorldWide Drilling Resource

How HDD Operations Use the Earth’s Magnetic Field Adapted from Information by the U.S. Geological Society For centuries mankind has relied on the earth’s magnetic field for navigation. In fact, the demands of navigators moti- vated some of the original studies of the earth's magnetic field, known as geo- magnetism today. Many drilling industries use geomagnetic information, including mineral exploration andmodern horizontal directional drilling (HDD). The main part of the planet’s magnet- ic field originates from deep within the earth. HDD technology uses that field to steer drill bits in the right direction, which reduces development costs and envi- ronmental impacts. The use of geomagnetism for nav- igation began with the use of compasses for orientation. HDD operators use a mag- netometer, which is sort of like a modern- day compass in a drill string instrument package to know which way the drill bits are going. This helps prevent collisions with other wells and maximizes oil pro- duction. The United States Geological Society (USGS) plays a unique role by monitor- ing the geomagnetic field every single second at magnetic observatories around the country. The USGS Geomagnetism Programmonitors variations in the earth’s magnetic field through a network of 14 ground-based observatories around the U.S. and its territories. Since the variable conditions of space weather can interfere with radio communication, GPS systems, electric power grids, the operation and orientation of satellites, and even air travel, there are many customers for geomag- netism data, including HDD operators. Through a process called geomag- netic referencing, measurements of the magnetic field in the drill hole are com- bined with those from magnetic obser- vatories at the surface to produce a highly accurate estimate of the drill bit position and direction. The earth’s magnetic field changes all the time across the world. This means the magnetic field on the earth's surface is different from location to location. The changes are a result of periodic daily tides or rapid magnetic storms related to the 11-year sunspot solar cycle. At high lati- tudes, like northern Alaska or the North Sea, the geomagnetic field can be very active and can change dramatically dur- ing magnetic storms, which is when we see the aurora borealis. “Drill bit positioning requires direc- tional accuracy of a fraction of a degree, and this can be accompl ished with advanced technology and expert under- standing of the earth’s dynamic mag- netic field,” said Carol A. Finn, USGS Geomagnetism group leader. “USGS 21 WorldWide Drilling Resource ® JULY 2014 operational systems measure the mag- netic field on a continuous basis. [The data is] provided to research scientists, civilian and defense government agen- cies, and customers in the private sector, including the oil and gas drilling industry.”