Numerical Viscoelastic Simulation of Wellbore Shrinkage in Non-uniform In-situ Stress

The effect of density of drilling mud and expansion coefficient hole on wellbore shrinkage was analyzed assuming that the creep of salt rock is three element rheological model adopted ANSYS finite element software.A numerical example demonstrates that wellbore is ellipse rather than circle on the condition that non-uniform in-situ stress;The largest values of wellbore shrinkage are obtained at the X direction,but the minimum values locate at the Y direction;The values of wellbore shrinkage at the X direction is decrease with the increase of density of drilling mud and increase with the increase of expansion coefficient hole.The values of wellbore shrinkage at the Y direction is mainly affected by density of drilling mud compared with expansion coefficient hole.The wellbore of the Y direction will be narrow when density of drilling mud less than 1.6g/cm3 and will be enlarge when density of drilling mud greater than or equal to1.8g/cm3.