Fluid-structure coupling effect on the setting process of expansive downhole emergency packer

A downhole emergency packer is prepared to seal the drill pipe-casing annulus when the high-pressure overflow and kicks occur during offshore drilling. When there exists fluid in the annulus, the increase in fluid pressure during setting increases the difficulty of working and even results in sealing failure. The primary objective of this research is to investigate the influence mechanism of downhole fluid on the setting efficiency, and provide theoretical support for solving such problems under hydrodynamic conditions. In this work, the hyperelastic constitutive model of the rubber cylinder was established through uniaxial tension and uniaxial compression tests. The fluid-structure coupling model was developed by finite element method, to simulate the setting process of the downhole emergency packer and quantitatively evaluate the impact of downhole fluids on setting efficacy. The results revealed that the fluid velocity and pressure increased throughout the setting process while the annular area shrank, raising the setting difficulty. The existence of fluid flow considerably diminished the setting efficacy of the rubber cylinders. The sealing coefficient, K decreased by 7.15%, 11.06%, and 14.41% when the flow velocities from the inlet were 5 m/s, 6 m/s, and 7 m/s, respectively. Therefore, the setting pressure could be increased according to the actual downhole conditions to achieve the actual setting effect safely.