The Science and Art Behind the Development of Intelligent Downhole Trajectory Automation with Minimal Surface Intervention
Authors: Ignova M. , Brovko K. , Mantle K. , Jones M. , Abe V. , Gorodnov A. 
Published: April 2024

Abstract
A vision that that will become a reality in the near future is that a drilling well plan can be programmed to rotary steerable tool and the tool will drill autonomously to a geometrical or geological target with minimal intervention from surface. The autonomy of the downhole trajectory control is important due to reasons such as distortion caused by the turnaround time of the communication between tool and channels being uplinked to the surface; this communication operates downhole in a closed loop with high and medium sampling frequencies (e.g., in seconds and sub-second levels) and the delay in terms of closing the loop via the surface and the reaction time of these controllers. The current state of downhole automation is that the rotary steerable tool can drill vertical, tangent/horizontal, and curve sections of the well plan. Application of already developed modes demonstrated that downhole automation could minimize formation effects and follow the plan more closely compared to manual drilling and interventions from surface due to faster reaction in the closed loop system. Automation minimizes drilling risks of not hitting the target or colliding with another well, and it can reduce the number of personnel on the rig, reducing health, safety, and environment risks. It has also been proved that by minimizing the number of surface interventions, the rate of penetration increases and wells are drilled faster. This work involves the next step of reaching the vision of drilling well autonomously downhole, which is the ongoing development of automatic kick-off and auto-landing.
Rotary steerable system (RSS) tools appeared in the 1990s, and the dogleg severity (DLS) and direction (gravity or magnetic) were controlled by sending a set of downlinks/corrections from the surface by directional drillers (DD) to the tool to drill to predefined targets (see Fig. 1). In terms of the level of automation of the RSS tools with respect to the drilling with motors, RSS tools are one step higher and arguably mapped to Level 1 downhole automation, with Level 0 being no downhole automation and Level 5 being an autonomous downhole system. Additional layers of automation have been incorporated downhole in the RSS tools over the years, with the main driver being more precise control of the trajectory with less interaction from the surface. Other objectives are minimizing the disturbances such as formation push and changes in the drilling parameters, bottomhole assembly (BHA) configurations, and bit properties and minimizing the effects of the vibration during the steering. One of these advances is dividing the segments of the planned trajectory (see Fig. 2 for segmentation of a 2D planned trajectory). Another advance is automating different segments with different levels of automation. For example, using the same scale mentioned above with Level 5 an autonomous downhole system, auto-vertical, auto-tangent drilling could be mapped to Level 2, and auto-curve drilling could be mapped to Level 3 downhole automation as it requires additional information such as rate-of-penetration and drilling state detection and also acts as an outer loop to the auto-tangent control system. What is left of the segmented trajectory plan (see Fig. 2) is auto-kickoff mode, which can be used from low inclination before auto-curve is engaged, and auto-landing, going from any initial DLS to DLS of zero for any inclination (except starting from inclination close to zero). Auto-landing is seen as a special case for controlling the change in the DLS between two points in space.