The Grane reservoir consists of massive turbidite sand deposits with intercalated shale bodies related to deformation of the reservoir and encasing shales. When drilled, these shales often become unstable after some time, resulting in packoff and collapsed hole, leaving planned produced intervals unrecovered. To maintain oil production from the Grane field, wells are drilled to compensate for declining production. Different strategies to stabilize the shale intervals have been unsuccessful. Real-time geological information collected while drilling are interpreted and used to understand the shape and extension of the unstable shale bodies in the context of the seismic data. This interpretation is based on azimuthal resistivity and gamma as well as extra deep reading resistivity. Using this information, the drilling system is pulled back into the sand section in front of the unstable shale and an openhole sidetrack is performed. Based on the updated interpretation of the geological data gathered while drilling through the shale, the new wellpath is designed to avoid the shale interval and penetrate reservoir intervals farther out. Openhole sidetracking is performed using the main 3D rotary steerable system (RSS) drilling bottomhole assembly (BHA). No cement plugs, ramps or kickoff BHAs are required, resulting in significant time savings. This method is proven on a number of wells and is today a part of standard well-planning on Grane. The applied method is so far the most efficient way to increase the length of the productive intervals and has proven to be a reliable and low-risk operation with a high probability for success. This paper will describe how the combination of real-time geological information and possibilities to perform openhole sidetracks are systematically used to increase the reservoir sections on Grane. Introduction The Grane oil field is located in the Norwegian North Sea, some 200 km northwest of Stavanger (Fig. 1). The field was discovered in 1991 and came on stream in September 2003, and is the first field on the Norwegian continental shelf to produce heavy (19 °API) crude oil. The oil is contained within the Heimdal Formation sands of Paleocene age. Grane has been developed with an integrated accommodation, processing and drilling platform with a fixed steel frame construction resting on the seabed at a water depth of 127 m.