What is "geosteering"

Geosteering is the intentional directional control of a wellbore based on the results of downhole geological logging measurements rather than three-dimensional targets in space, usually to keep a directional wellbore within a pay zone. In mature areas, geosteering may be used to keep a wellbore in a particular section of a reservoir to minimize gas or water breakthrough and maximize economic production from the well. In the process of drilling a borehole, geosteering is the act of adjusting the borehole position ( inclination and azimuth angles) on the fly to reach one or more geological targets. These changes are based on geological information gathered while drilling.