Proactive Geosteering in Thin Reservoir Bounded by Anhydrite in Saudi Arabia

Thin reservoirs of a few feet in thickness present a clear challenge to well placement. Drilling out of the target is a real<br>possibility, and plugging back and reentry can be extremely difficult. Clearly, the best solution is to avoid exiting the target<br>reservoir by detecting approaching boundaries as early as possible and by remaining at an optimal distance from the<br>boundaries. This practice is known as “proactive geosteering.” In recent developments, wave resistivity LWD and azimuthal<br>wave resistivity sensors have been shown to effectively facilitate proactive geosteering. Their abilities to scan laterally several<br>feet, up to more than 10 ft, around the wellbore and to identify the relative azimuth of approaching boundaries have been<br>instrumental in recent successes.