Finite Element Analysis of Casing Wear in L-80 Steel: OBM vs WBM Under Varying Loads

The primary threat to well integrity in directional wells is casing wear caused by surface interaction between the casing wall and the tool joint (TJ) on the drill pipe. Unchecked casing wear can significantly reduce casing thickness, leading to failures that are costly to repair. Three main factors contribute to casing wear, directly related to the combination of casing and TJ material and the physical parameters of wear: the rotational speed of the TJ, side load on the casing wall, and the type of drilling fluid used for lubrication (oil-based mud (OBM) versus water-based mud (WBM)). This paper presents a finite element method (FEM) model developed in ANSYS Workbench LS-DYNA to predict the wear characteristics of API 5CT L-80 casing subjected to wear from a hardened steel TJ, using both OBM and WBM as lubricants. The model incorporates Archard’s wear law and experimentally determined wear coefficients, simulating a range of side loads (1000, 1200, 1400 N) and rotational speed of (115 rpm) that reflect realistic drilling conditions. To accurately represent differences between OBM and WBM, constant coefficients of friction are assigned to each type of hydraulic fluid to capture their lubrication properties. Simulation results are used to estimate wear volume, wear depth, and the specific wear rate for each combination of fluid, load, and speed. By comparing OBM and WBM directly through their operating ranges, this study demonstrates that under identical loads and speeds, WBM causes more casing wear due to its higher friction coefficient, with the difference becoming more pronounced at higher side loads and varying with speed changes. The calibrated FE model closely replicates field wear data under standard test conditions, offering a cost-effective means to assess the effects of drilling mud type and operational parameter adjustments on casing wear.