Torque & Drag Analysis Using Finite Element Method

Abstract

The calculation and analysis of torque and drag play an important role in drilling and well design. Different models (soft, stiffness, mixed and finite element) have been used to calculate the torque and drag. This paper introduces a practical FEA (Finite Element Analysis) model of the drill string which can reflect working behavior, including interaction between the drillstring and borehole wall, computational model of torque and drag, and verification with examples. The sensitivity analysis to some key input and output parameters has been conducted. The calculated hook load shows a good match to the rig recorded values. The drillstring displacements calculated by the FEA model matches those from an analytical method. The program developed and discussed in this paper can be used for torque and drag analysis, dynamic behavior analysis, and friction coefficient back-calculation. The FEA program of the drillstring presented herein will benefit in preplanning and real-time simulation of oil and gas well drilling operations.

Modeling the Energy-Saving Regimes of Curvilinear Bore-Hole Drivage

“…(19) with respect to S and correlate the result with the two first equations of system (18). ), / b(i) represent the constraint reac tions.…”

“…In this connection, the tradi tional methods of theoretical simulation of these processes based on simplified approaches should be replaced by more elaborate techniques [17][18][19]. Naturally, the process of the bore-hole drivage, the energy consumption incident to it, and the emergency situations connected with it prove to be vastly more sensitive to the mistakes admitted at the stage of the bore-hole design and necessarily occurring in its drilling.…”

“…For this reason, the technological processes of drilling curvilinear bores are associated with the necessity to determine more precisely the external and internal forces acting on curvilinear DSs at their ups, downs, and functionings (rotations). [18] accentuated: "The soft string model does not reflect the stiffness of the drill string and does not take into account the clearance between the drill string and well bore. Mitchell and Samuel [17] pointed to the necessity of application of 3D stiff-string drag and torque models for simulation of the DS motion in curvilinear bore-holes.…”

“…(18) to two Eqs (21),. it became possible to specify the majority of the unknown functions through the statement of inverse problems and only the Fx(s) and Mx(s) variables are determined on the basis of direct problem for Eq (21)…”

Comparison of Analytical and Numerical Models on Torque and Hookload Calculation

“…The element matrix or vectors must be transformed and assembled to global matrix or vectors. A numerical method, Wilson-θ method, is used to get the solution to the dynamic equations [10].…”