Autonomous Restriction Navigation Through Wellbore in Wireline and Slickline Operations

Abstract

A novel technique of autonomous restriction navigation that significantly increases efficiency and safety is presented. New algorithms orchestrate the automated winch control system to prevent over-speeding when passing through restrictions, which diminishes incidents of unintentional pull-off and toolstring damage caused by entering wellbore obstructions at high speed. Every pull-off incident would significantly reduce the production of the well because the toolstring and cable must be recovered. This new dynamic speed scheduling system optimizes restriction navigation, showing an order of magnitude improvement over industry-standard human-driven winch operation. A new forward-looking algorithm analyzes restrictions in the direction of conveyance to predict the time and distance to future encounters with restrictions. It uses toolstring length, current depth, cable speed, and the winch controller's deceleration rate to maintain the maximum allowed speed until the exact moment deceleration must occur for the toolstring to enter a restriction at the proper speed. Finally, it maintains a higher winch gear even at low speeds when passing through restrictions except in those situations when extra-low speed is required. The new technique has been extensively tested in intervention campaigns in the North Sea, allowing comparison against manual operation and previous-generation automated conveyance. Winch operators would often fail to slow down at restrictions or would slow down too early or too late. Previous-generation automation, due to its lack of forward-looking algorithms, would not decelerate until the toolstring encountered the restriction and could accelerate with the toolstring still in the restriction. To prevent this, the wellsite supervisor would need to spend extra time manually calculating top and bottom restriction depths for each conveyance direction, often leading to overestimation or miscalculation of the restriction declarations. In case studies from field trials, the new technique consistently uses the correct restriction speed for the entire toolstring length. Users only need to declare wellbore speed restrictions as they appear on the well diagram. In manual operation, an experienced user will retain high winch gear through a restriction, whereas previous automation would stop and change gear. The new technique digitalizes winch driving competency by incorporating high-gear retention. After a year of field trials with zero incidents, several case studies with multiple restrictions in the well confirm the greater efficiency of the new navigation technique over previous generations. The developed comprehensive automated speed-control logic and restriction navigation technique maximizes conveyance speed while eliminating risk and costly errors. Its intrinsic value increases when operations are performed in highly sophisticated well completions and tortuous wells, which are becoming more common.