Erosion characteristics and parameter optimization for casing eroded by abrasive water jet under confining pressure: An integrated experimental–numerical–data-driven study

In unconventional natural gas development, abrasive water jet (AWJ) technology is constrained by high downhole confining pressure, while critical operational parameters are still largely extrapolated from surface testing. This study investigates the casing erosion behavior of AWJ on 140-grade casing under confining pressure through an integrated experimental–numerical–data-driven framework. Erosion tests with and without confining pressure were performed to evaluate the effects of pump pressure, target distance, and jetting time on drilling depth and diameter. To capture fluid–particle–structure interactions, a coupled Arbitrary Lagrangian–Eulerian–Discrete Element–Finite Element Method (ALE–DEM–FEM) model was established and quantitatively validated against experimental data (e.g., erosion depth). In parallel, a Whale Optimization Algorithm–tuned Support Vector Regression (WOA–SVR) model was trained on a dataset expanded via data augmentation (for the studied pressure/distance parameters) to predict drilling depth rate (DepthRate) and drilling diameter rate (DiameterRate). Current experimental results showed that confining pressure markedly reduced drilling efficiency at larger target distances, identifying an effective distance near 11 nozzle diameters—a critical threshold significantly compressed compared to atmospheric conditions. Simulations revealed that confining pressure shortened the jet core, lowered peak abrasive-particle velocity, and induced a sand-cushion effect that dissipated momentum, consistent with the observed shallow–wide erosion-pit morphology. The WOA–SVR models indicated high predictive accuracy (R² 0.95) with low root mean squared error (RMSE) and mean absolute error (MAE). These findings suggest that enhancing performance under confining pressure requires an optimization strategy that balances operational trade-offs (e.g., tool wear, energy cost), offering a useful reference for optimizing AWJ technology in unconventional gas development.