Maintaining Wellbore Safety: Closed-Loop Limit Control of Tripping Operations

Abstract

A significant part of well construction is invested in tripping drill pipe. This type of operation is considered not productive in terms of drilled wellbore but is however necessary for the well construction process. The associated cost of tripping operations can be as high as 30% of the overall well CAPEX and poses an attractive optimization case to reduce spending by means of increasing efficiency. Furthermore, a byproduct of increased efficiency is a cleaner operation in terms of carbon emissions. Increasing efficiency for tripping operations concerns two main components: reducing connection time and optimizing the motion of the string while tripping in and out of the wellbore. The connection time can be reduced by means of machine automation to deliver repetable and safer handling of the drill pipe during connections. Optimizing the tripping parameters to move the string requires a more complex approach, where physics-based modeling plays a key role in determining a safe operating envelope (SOE) to move the string without harming the formation or the surface equipment in the process. The system described in this paper touches upon this problem and includes the concept of interfacing to automated drilling control systems (ADCS) to achieve closed-loop control of tripping operations. The solution proposed deploys a hydraulic digital twin of the wellbore that estimates the permissible axial velocities and accelerations to use when running drillstring in and out the wellbore. The same digital twin is used during pre-job modeling to verify proposed tripping plans, and later on in real-time to update the tripping limits for velocity and acceleration for every stand as the tripping process continues. The results produced in real-time are published to a data aggregation layer to serve as input for a tripping automation application to refine fit-for-purpose monitoring and control algorithms. The automation system finds optimum proposals of tripping limits and updates them directly in the rig control system in real-time. The trip monitoring system automatically and continuously publishes optimum velocity and acceleration tripping limits per stand and transmits them as set points to the ADCS to define a safe operating envelope (SOE). This approach can greatly reduce the overall tripping time in comparison to non-automated deployments. Furthermore, the reduction of invisible lost time (ILT) takes place while maintaining the integrity of the formation, and the integrity of the surface equipment. A set of case studies confirm the effectiveness of the approach and illustrate its benefits. A case study from the Middle East addresses the topic of adoption of drilling automation applications such as the tripping advisor. Another case presents the concept of interoperability using as example a deployment on a rig simulator setup in Europe to perform closed-loop control using the tripping application to write velocity and acceleration limits continuously to the ADCS.