Session: 11-13-01 Digitalization of Subsurface, Well Systems, Subsea Systems and Operations

Paper Number: 80314

80314 - Design and Demonstration of Autonomous Directional Drilling With a Miniature Scale Rig 

Drillbotics, an international student competition hosted by SPE/DSATS, directed the 2020/2021 competitors to design, build and implement a miniature, fully autonomous drilling rig capable of intersecting one or multiple pre-set targets within a rock sample with up to 30-degree inclination and 15-degree azimuth adjustments from the KOP. Hole size was limited to 1.5” (3.8cm). The wellplan was calculated autonomously when the targets were revealed during the final test. This paper presents the 5th generation autonomous miniature drilling rig by a team of four students from the Norwegian University of Science and Technology (NTNU), who won the 2020/2021 Drillbotics competition.

The rig features a sophisticated control system implemented in Simulink. The steering concept relies on orientating the fixed bent BHA to control the well path trajectory. The control system uses a nonlinear Model Predictive Controller (MPC) to simulate future movement with different BHA azimuth orientations before applying the optimal orientation to minimize deviation from a pre-planned Bezier curve well path. A closed-loop Kalman filtered BHA orientation estimated from downhole sensor measurements is used in combination with a movement model to estimate bit position. To simulate a mud-motor stator, a 4 mm cylindrical titanium rod inside the drillpipe transmits rotation from a top drive motor to the bit. The drill pipe orients the toolface. The novel BHA allows building inclination while transmitting rotational torque from the titanium rod to the drilling bit, custom-made and designed by the NTNU team. The drilling rig system avoids twist-offs from downhole torque spikes and drilling vibrations by increasing RPM and implementing a more stable drill bit.

53 deviated wells were successfully drilled prior to the competition for testing and tuning the rig systems to meet the objectives and requirements in the final competition run. On the day of the competition, the miniature rig calculated an optimized well path based on the Bezier curve method and drilled successfully while steering towards the targets in a total of 23 minutes. The maximum potential of the rig was demonstrated to the Drillbotics committee in an extra run, drilling through the rock in 6 minutes with an inclination of 37 degrees. The team has successfully designed, built, and implemented a functional miniature rig to autonomously drill deviated wells through a rock sample with pre-set targets in a safe manner. Results indicate nonlinear MPC shows promise as a potential option for accurately steering a fixed bent sub system.

Special design considerations were required to adapt the drilling concept to the limited hole size. The new bit design proved to provide improved ROP. Work processes were adjusted to accommodate disruption to lab and workshop access and face-to-face meetings due to pandemic restrictions.

Presenting Author: Magnus Steinstø NTNU

Authors:

Magnus Steinstø NTNU
Gaute Hånsnar NTNU
Benedicte Gjersdal NTNU
Trygve Mikal Viga Skretting NTNU
Alexey Pavlov NTNU
Fred Florence Rig Operations, LLC