Patent ID: 7412368

Claim:
A method of determining design parameters for oil well casing and tubing to prevent buckling in a deviated wellbore, comprising: receiving well parameter data comprising at least one of tubing size, tubing weight, well depth, and well geometry; calculating a first parameter used in predicting movement of the tubing near at least one boundary condition in the deviated wellbore based on the received well parameter data, wherein calculating a first parameter used in predicting movement of the tubing near at least one boundary condition in the deviated wellbore based on the received well parameter data comprises calculating a parameter used in predicting the movement of the tubing near a packer in the deviated wellbore using the formula: θ ⁢ ⁢ ( ξ ) = ln [ cosh ⁢ ⁢ ( 2 2 ⁢ Δ ⁢ ⁢ ξ + ϕ s ) cosh ⁢ ⁢ ( ϕ s ) ] where θ(ξ) is a buckling parameter for a beam-column solution for tubing located near the packer in the deviated wellbore; Δξ is the change in dimensionless length associated with the tubing where ξ is given by the relationship: ξ = s ⁢ P EI where s is the measured depth of the tubing; P is the axial buckling force of the tubing; and EI is the bending stiffness of the tubing; and φ s is a numerical constant; calculating a second parameter used in predicting a total bending moment near the at least one boundary condition based on the received well parameter data; calculating a third parameter used in predicting a maximum bending stress near the at least one boundary condition in the deviated wellbore based on the total bending moment; and calculating a fourth parameter used in predicting a minimum axial force necessary to initiate buckling based on the received well parameter data, wherein the first, second, third, and fourth parameters are utilized in a design of the oil well casing and tubing to prevent buckling in the deviated wellbore.