Geosteering: Continuous Surface Model Updates Using Gamma Log

Abstract Logging-while-drilling (LWD) tools transmit formation data in real-time to the surface as the drill bit moves through the subsurface. LWD is particularly valuable in horizontal wells where it minimizes the risk of getting off course and drilling into undesired formations. The introduction of ultra-deep azimuthal resistivity (UDAR) technology has improved the process of drilling horizontal wells (Antonsen et al. 2022), but its value is limited to reservoirs where important resistivity contrasts are observed. When this is not the case, a classical LWD measure like gamma ray, becomes crucial for well placement. The interpretation of well logs is difficult, however, and error prone whenever manual work is involved. In this paper, we present a method for consistently integrating the structural model with LWD measurements while drilling. This approach enables estimation of the distance between the drill bit and nearby constraining zone boundaries, allowing for continuous updates of the surface model during drilling operations. By avoiding manual operations, the risk of getting a structural model that has diverged from real-time measurements is reduced.