PSI - Issue 83

Iman Onsa et al. / Procedia Structural Integrity 83 (2026) 273–279

274

1. Introduction Casing wear is a major well-integrity concern in directional drilling, where continuous contact between the rotating drill string and the casing wall can gradually remove material from the casing's inner surface. Wear commonly initiates at the tool joint (TJ), which has a larger outer diameter and higher local contact pressure than the drill pipe body. Reduction in wall thickness can lead to costly restorations or wall failure [1][2]. Casing wear is governed by a combination of operational and tribological factors, among these factors TJ rotational speed, the side load acting on the casing wall, and the lubricating performance of the drilling fluid. Drilling fluids influence wear mainly through their ability to reduce friction and modify the contact conditions at the casing-TJ interface. Oil-based mud (OBM) has lower friction than water-based mud (WBM), but the magnitude of the benefit depends on the operating conditions [3][4]. While it is true that experimental wear testing is costly and lengthy, plus it does not always take into account the range of loads and speeds normally experienced in the field, predictive numerical techniques are of interest. The use of finite element analysis (FEA) with an appropriate wear law is able to provide estimates for the contact pressure and sliding distance so they can be converted to wear depth and wear volume. This study uses a finite element wear model created in ANSYS Workbench LS-DYNA with Archard’s wear equation to evaluate the wear of an API 5CT L-80 casing due to a hardened steel trial journal bearing (TJ) and compare this to two other types of mud - oil based (OBM) and water based (WBM) - at realistic side loads, while maintaining a constant rate of rotation [5].

Nomenclature TJ

Tool joint OBM Oil-based mud WBM Water-based mud FEA/FEM

Finite element analysis/method

COF

Coefficient of friction

F N K S H

Side load (N)

Rotational speed (RPM) Wear coefficient (m 3 /N.m) Sliding distance (m)

Hardness (Pa) Wear depth (m) Wear volume (m 3 )

h

V

2. Methodology 2.1. Geometry and model description

A three-dimensional FE model was created to represent the contact interaction between an L-80 casing segment of 6 0̊ and a full geometry hardened steel TJ [4]. The casing was constrained to represent its fixed condition in the wellbore, while the TJ was assigned rotational motion to replicate the drilling rotation. A segment model was selected to reduce computational costs while maintaining an accurate description of the local contact zone where wear occurs.