ABSTRACT
F(s)= Fτ(s)τ0 + Fn(s)n0 + Fb(s)b0, M (s)= Mτ(s)τ0 + Mn(s)n0 + Mb(s)b0.
2. Distribution external force vector f (s)ds for the tubular string differential element: (1) Tubular string deadweight qk (2) Normal contact pressure of the curved tubular string and well wall N =N (cos θ n0,
−sin θ b0) (3) Tubular string internal and external flowing fluid viscous friction force ( fuo + fui)τ0 (4) Axial friction force ff1 =−f1N τ0 (5) Circumferential hoop friction force ff2 =−f2N (sin θ n0 + cos θ b0) Thus, the whole external force vector can be represented as follows:
f (s)= ( fui + fuo − f1N )τ0 + N cos θ n0 − N sin θ b0 − f2N (sin θ n0 + cos θ b0) + qk , where, f1 represents the axial friction coefficient between the tubular string and well wall; f2 represents the circumferential hoop friction coefficient between the tubular string and well wall; fui, fuo represents the viscous friction coefficient of the external and internal fluid acting on the tubular string.
