Abstract: A system and method that include receiving a well plan and determining a plurality of sections of the well plan and receiving data from surface and downhole to determine a current location of a drill bit. The system and method also include analyzing the well plan to automatically derive trajectory constraints that are associated with each of the plurality of sections of the well plan and determining a plurality of trajectory candidates that pertain to respective paths from the current location of the drill bit to respective targets based on a consideration of the trajectory constraints. The system and method further include determining costs according to at least one cost function to rank the plurality of trajectory candidates to determine a working plan that includes an optimal path from the current location of the drill bit to reach a final target.

Abstract: A method can include receiving data for a bottom hole assembly of a drillstring and a drill plan; generating candidate trajectories using at least a portion of the data; generating drill command schedules for the candidate trajectories; ranking the candidate trajectories based at least in part on the drill command schedules; and outputting at least a top ranked candidate trajectory and its corresponding drill command schedule.

Abstract: The present invention is a method of establishing a geographical model of a wellbore that includes receiving a first geographical model of the wellbore and receiving measured log data and a trajectory of the wellbore. A first simulated tool response is simulated along the trajectory based on the first geographical model. A measured tool response is determined based on measured log data. A first portion of the first simulated tool response corresponding to a second portion of the measured tool response is found wherein the first portion and the second portion have substantially a same interval of length along the trajectory. The first portion and the second portion are compared to generate a second geographical model. The second geographical model can be used to geosteer a bottom hole assembly.