A Comparative Study on Drag Reduction Methods for Continental Shale Drilling in the Fuxing Block, Southeastern Sichuan Basin

Extended-reach horizontal wells in continental shale formations of the Fuxing Block, southeastern Sichuan Basin, face prominent challenges, including drag and torque exceeding 50 metric tons and difficulties in weight-on-bit (WOB) transfer. Continental shale is characterized by high porosity, high permeability, distinct amphiphilic properties, and rapid performance degradation of oil-based drilling fluids (OBDF). These features lead to the formation of thick filter cakes and compacted cuttings beds, which further exacerbate abnormal drag. Existing research often focuses on single technical aspects, lacking integrated, full-cycle multi-factor coupling analysis. Based on field data from 14 drilled wells in the block, this study standardizes key factors through data preprocessing, quantifies process weights using the Analytic Hierarchy Process (AHP) model, and fits censored drag data via the Reliability Analysis model. Results indicate that design optimization contributes most significantly to drag reduction (weight: 0.5499). The critical failure drag for encapsulated lubricants is identified as 61.74 t. For wells with horizontal sections exceeding 2500 m, the application of floating casing technology enhances drag control reliability.