Assessing Axial Load Effects on Downhole Tool Structural Integrity

Abstract This paper evaluates the impact of axial forces on drilling tool integrity during drilling, underreaming, and underreaming-only operations. It aims to verify the effects of axial forces on equipment through real runs with the goal of reducing tool damage and enhancing operational efficiency. The use of under-reamers has become a common approach to address wellbore quality and casing running challenges. This analysis employs detailed 4D simulations of drilling dynamics using real-time data to examine force distributions on the actual Bottom Hole Assembly (BHA). The focus is on lateral and axial vibrations of the cutting structure to determine optimal drilling parameters. Axial forces impacting the tool body within the BHA may be masked by stable parameters, necessitating additional outputs to identify potential axial force fluctuations and guide final drilling parameters. The paper identified significant concerns arising from the fluctuation of the neutral point during drilling at different Weight on Bit (WOB) and well trajectories, leading to high-frequency axial force variations. This phenomenon can transform the reamer body into a jackhammer-like action, causing high stress concentrations and damage to cutter blocks, the cutting structure, and other internal mechanisms. Over the past five years, statistics show that nearly 17% of Service Quality (SQ) issues are due to underreamer body damage during underreaming operations, making it the second highest cause of tool damage. Understanding axial force distribution dynamics is crucial for minimizing equipment damage and optimizing operational efficiency. This paper presents novel insights into optimizing reamer placement based on axial force distribution on the BHA. It highlights precautionary measures in parameter selection to enhance drilling dynamics, prevent tool failure, and reduce repair costs.