Practical Application of 3D Dubins Curve Method in Directional Well Trajectory Planning

Abstract

AbstractThis paper introduces the practical application of 3D Dubins curve in directional well trajectory planning to handle more complex downhole conditions such as consecutive targets and various constraints in the underground formation. To handle consecutive targets in a direction well, we can simply treat the whole trajectory as a combination of multiple 3D Dubins curves with the undetermined drilling directions at the targets as additional optimization variables. As for the formation constraints, practical drilling may require the well trajectory to avoid certain areas or/and control the wellbore inclination in some layers to maintain wellbore stability. To handle such a problem, we can adjust the depth of kickoff point(KOP) or use a more complex trajectory structure with more curved sections rather than a simple trajectory structure with at most two curved sections (build-up & drop or two build-ups). The optimal trajectory generated by our method is the shortest smooth path satisfying all given constraints, besides, it has a fixed curvature in the curved section so that the tool face angle does not need to change so frequently during drilling. Our method was adopted by the NTNU Drillbotics team to design the optimal trajectory for consecutive targets, contributing to the NTNU championship in the 2022 SPE Drillbotics Competition. The advantages of our method in the complex application scenarios mentioned above are demonstrated in the case studies with comparison to a previously published result and real field data provided by Equinor.