Analysis of Fluid-Structure Interaction during Fracturing with Supercritical CO₂

During the implementation of CO₂ fracturing for oil and gas development, the force transfer effect caused by the unsteady flow of high-pressure CO₂ fluid can lead to forced vibration of the tubing and ensuing structural fatigue. In this study, a forced vibration analysis of tubing under CO₂ fracturing conditions is carried out by taking into account the fluid-structure coupling and related interaction forces by means of the method of characteristics (MOC). The results show that for every 1 m³/min increase in pumping displacement, the fluid flow rate increases up to 3.67 m/s. The flow pressure in the pipe tends to be consistent with the pumping pressure at the initial stage and then decreases with an increase in the pump starting time. When the pumping pressure increases by 10 MPa, the additional stress in the tubing increases by 11.8%, and the peak value of the additional stress at the bottom of the well is the largest. The temperature in the tubing grows with well depth, which causes a phase change in CO₂ due to heat absorption. At this time the pressure in the tubing decreases, the fluid flow rate increases by about 1.12 m/s, and the additional stress grows by about 1.5 MPa.