Experimental study on the mechanical responses of downhole tools in highly-deviated waterflooding well

摘要

The complexity of the well structure of highly-deviated wells causes complicated and changeable mechanical response of the downhole tools under the operation conditions such as waterflooding, packer seating, circulation well cleanup and packer unlocking. To investigate the mechanical response mechanism of downhole tools in highly-deviated wells during different operation stages, a force test instrument is developed and used to test the axial forces of downhole tools in two typical highly-deviated wells in Jidong oil field in China. It has been found that reverse circulation well cleanup has little influence on the axial forces in downhole tools due to the small bulging effect caused by the pressure difference between the inner and outer of the tubing. Whereas, the packer seating operation has the biggest effect on the change of axial force in tubing string due to the piston effect. In case of no anchor, the maximum axial force imposed on the packer can reach 125 kN which is far more than the maximum static friction force (30 kN) that a packer can bear. In the waterflooding stage, due to the temperature effect, the tubing section close to the packer sustains compression force and is likely to produce sinusoidal buckling and helical buckling. Mechanical response analysis on the whole construction period also shows that the different combination scheme of downhole tools has great influence on the forces in them.