SPE DUPTS Webinar Automated Trajectory Drilling for Rotary Steerable Systems
Summary
Dr. Christian Hansen presented on the topic of automated directional drilling with rotary steerable systems. He explained that directional drilling today is still a manual process characterized by monitoring drilling parameters and trends, predicting the future wellbore trajectory and adjusting steering parameters as required. When drilling with a rotary steerable system (RSS) in the bottom-hole assembly (BHA), the trajectory control system is distributed between surface and downhole. The surface control makes use of downhole measurements and capabilities of the rotary steerable BHA, and in turn is used to control the downhole components, forming a ‘directional drilling control loop’ and allowing the efficient drilling of a quality wellbore. Traditionally, the directional driller assumes the surface control, whereas downhole control is performed by the RSS-BHA allowing drilling certain parts of a section automatically.
Christian explained that an automated trajectory drilling system closes the loop at surface to achieve fully automated control and shared his experiences when implementing such an automated system. Like a human directional driller, the automated system continuously monitors actual versus planned well path, including positional offset, inclination and azimuthal deviations and achieved versus planned dogleg severity. This information is used to predict the wellbore trajectory. Christian pointed out that in case of falling behind the well plan significantly, the trajectory drilling system automatically initiates a course correction to steer back to plan smoothly within the prediction horizon by keeping all hard constraints. Due to the build-in trajectory optimization and consideration of wellbore construction constraints, the controller avoids hefty steering back to plan.
In the webinar operational considerations as well as sensor and actuator influencing factors had been discussed. The concept of embedding the driller and directional driller in the decision-making workflow was outlined, too. Furthermore, the importance of interoperability and an open software architecture to allow automatic data flow at rig site was pointed out. Finally, the performance of the automated trajectory drilling system was assessed, and two case studies had been presented, where up to 98 % of a single wellbore has been drilled automatically. It was found that the amount if steering downlinks while drilling a wellbore automatically is very similar to the number of downlinks a human directional driller would have sent. In addition, the trajectory predictions from the automated trajectory drilling system helped the directional driller to perform its anti-collision scans effectively.
All in all it can be said that complex wellbores can be drilled automatically – onshore and offshore – when the critical success factors such as “Inclusion of Driller and Directional Driller in the Control Loop”, “Automated data flow”, “Accurate sensor data”, “Availability of actuators”, and “Control Models, Disturbance Models, and Estimators” are considered.
The webinar was concluded with a Q&A session.