Optimization of Flushing Fluid Plugging Theory Based on Plugging Experiments and Simulations

During sand cleanout operations in shale oil horizontal wells, severe wellbore leakage occurs due to incompatibility between plugging particles and the formation, resulting in a failure to establish circulation. This study determined the optimal plugging theory for the target formation characteristics through laboratory leakage sealing tests and numerical simulations such as fluid–discrete element coupling (CFD-DEM). The results show the following: Plugging experiments indicated that the Vickers criterion achieved the best performance, with an invasion depth of 9 mm, followed by the Ideal Packing Theory, at 12 mm, while the D90 rule performed the worst, with an invasion depth of 13 mm. The simulations results from the CFD-DEM coupling model demonstrated that the Vickers criterion achieves the most effective plugging performance, followed by the Ideal Packing Theory, with the D90 rule exhibiting the least effectiveness. This indirectly validates the rationality and effectiveness of the Vickers criterion in configuring particle sizes for plugging materials. Finally, sand-packed-tube displacement experiments demonstrate that the Vickers criterion yields the lowest permeability and optimal plugging performance, further validating its rationality and effectiveness in configuring particle sizes for plugging materials. This research provides crucial technical support for the safe and efficient development of shale oil horizontal wells, effectively reduces operational costs, and holds significant importance for advancing technological progress in shale oil extraction.