Fracture propagation law of shale gas horizontal wells under the influence of production stress disturbance in refracturing

During shale gas production, old wells often experience rapid capacity decline and difficulty in effectively utilizing the reservoir after the initial fracturing stimulation, which severely impacts production. The refracturing technology can reactivate low-producing wells to a certain extent through the secondary reconstruction of the residual reserve area. However, due to changes in the stress field after reservoir production, the fracture propagation law is often unclear. Therefore, this study uses a fully coupled flow-geomechanics model combined with the extended finite element method to numerically simulate the stress disturbance and refracturing fracture propagation under single- and double-fracture production scenarios. The results show that after production, the stress field near the fractures changes direction, causing the refracturing fractures to deviate significantly after initiation. As production time increases, the amplitude and range of stress deviation first increase rapidly, then decrease slowly. The fracture deviation amplitude and range follow the same trend, and the fracture pressure increases accordingly. When moving away from the production fracture, the stress deviation gradually slows down, weakening its influence on fracture propagation, and the fracture pressure increases steadily. Furthermore, during double-fracture production, as the distance between production fractures decreases, the area unaffected by stress deviation gradually shrinks. When the distance between production fractures is less than 15 m, the central region will still experience the influence of stress deviation during refracturing. In conclusion, to avoid intersection with the primary fracture during refracturing, it is recommended to choose areas far from the production fractures and with longer production times for fracturing stimulation. The simulation results can provide theoretical guidance to some extent for selecting the location and timing of perforations in field refracturing operations.