On the Reliability of the Numerical Models for Oil Industry Applications

Abstract

Establishing manufacturing tolerances for steel pipes to be used in the oil industry, such as amplitude of the out-of-roundness, specially its second mode in Fourier decomposition, eccentricity, residual stresses, etc., is an involved issue that should balance production cost with expected performance. Finite element simulations are nowadays a standard industrial tool for exploring the effect of those tolerances on the structural behavior as well as on the performance of tubular goods, and to study the technological windows (the locus in the space of the process control variables that defines a given process set-up) of the pipes production process that will render products within the expected tolerances. Hence, it is of the utmost importance that sound computational techniques are used and that the model results are validated using experimental results. Regarding the modeling of steel pipes collapse and post-collapse behavior, in this paper we propose some guidelines for the development of finite element models that simulate collapse tests. Some of the aspects that we discuss are: applicability of 2D models, shell elements for the 3D models, nonlinearities to include in the models, material modeling, residual stresses modeling, boundary conditions for simulating different pressure tests, code verification and results validation. Regarding the link between production process and manufacturing tolerances we briefly review some results that we obtained for the case of the UOE process and threaded connections for OCTG (oil country tubular goods).