Slip Behavior of Gelled Oil and Restart-Pressure Prediction in High-Water-Cut Inclined Pipelines

In high-water-cut inclined gathering pipelines, shutdown may lead to blockage due to the flotation and wall slip of gelled crude oil. This study investigates the slip behavior and critical conditions of gelled crude oil particles on an inclined pipe wall through visualization experiments, mechanical analysis, and the Extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory and develops a method for calculating pipeline restart pressure. Experiments conducted using four crude oil samples identified three post-floating behaviors: adhesion, adhesion–slip, and bulk floating aggregation. The measured critical slip temperatures of samples 1#–4# were 33, 29, 36, and 37 °C, respectively, corresponding to 1–2 °C below their gel points. Adhesion represents a safe shutdown condition, whereas adhesion–slip and bulk floating aggregation indicate a risk of oil accumulation and blockage. When the temperature falls below the critical slip temperature, the gelled oil remains stably adhered to the pipe wall. A critical slip temperature prediction model was established using the gel point, oil–water density difference, and wax content as input parameters. The model produced absolute errors of 0.1–0.6 °C, with a mean absolute error of 0.4 °C. By coupling the Sukhov temperature-drop equation with the mechanical equilibrium equation, a restart-pressure calculation tool was developed. For two field restart cases, the predicted pressures showed relative errors of 6.45% and 7.70%, with a maximum absolute error of 0.06 MPa. The proposed method provides a preliminary quantitative tool for shutdown risk assessment, low-temperature transportation boundary determination, and restart-pressure estimation in high-water-cut inclined gathering pipelines.