Key surface logging technologies in horizontal well geosteering

In the drilling of horizontal wells, the core task of surface logging is to guide geosteering while drilling by using collected data including electrical property, lithology, petrophysics, and oil/gas-bearing properties. Surface logging in the horizontal geosteering drilling have two key technologies: one is stratigraphic correlation and prediction technology before encountering the zone of interest, the other one is geological interpretation and geosteering technology after encountering the zone of interest. Based on a systematic analysis of difficult points in the two aspects, in combination with application examples, this paper deeply analyzes how to accurately drill into horizontal section by in-depth stratigraphic correlation and timely model modification in the case of inaccurate horizon depth design; and how to improve drilling-encounter ratio of oil layer and well bore quality by accurate interpretation and guidance in the case of encountering non-target zone (e.g., borehole deviates from right track, sedimentary facies changes in the target zone, faults or mudstone interlayers are encountered.).