Research on the Mechanism and Prevention Countermeasures of Stuck Coiled Tubing During Coiled Tubing Fracturing in the Junggar Basin

The coiled tubing (CT) fracturing technology offers advantages such as pressurized dragging operation and maintaining a large borehole diameter after fracturing. However, during fracturing in the conglomerate and volcanic rock reservoirs of the Junggar Basin, CT stuck during retrieval occurs frequently. In this study, a model simulating the variation in the in situ stress field during CT hydraulic fracturing is established based on elastic mechanics and the displacement discontinuity method (DDM). Based on the geological characteristics of conglomerate and volcanic rock reservoirs in the Junggar Basin, and considering engineering parameters such as fracture length and fracture count in CT hydraulic fracturing, this study investigates the variation in the in situ stress during CT hydraulic fracturing and explores the stuck mechanism of CT. An index for fracturing completion is constructed to evaluate the stuck of CT during the fracturing process. With the goal of full stimulation of the horizontal section, a quantitative optimization design is conducted for the fracturing stage spacing and number of stages under different geological conditions, resulting in corresponding charts. The results indicate that the stuck mechanism during CT fracturing is caused by the continuous accumulation of stress induced by hydraulic fractures, leading to stress inversion. The fracturing completion increases with the stage spacing and the original horizontal stress difference. The length of the fractured section first increases and then decreases with the increase in stage spacing, while it increases with the original horizontal stress difference. The research findings can be applied to the optimization design of stage spacing and number of stages for CT hydraulic fracturing in conglomerate and volcanic rock reservoirs of the Junggar Basin, effectively preventing and controlling stuck coiled tubing in CT fracturing.