DOT 2011: Development of an Analytical Tool to Deal with Lateral Buckling of Flowline

The following is an abstract of a presentation that will be featured at the Deep Offshore Technology International Conference & Exhibition in New Orleans, Oct. 11-13:

Alexandre Cinello, Doris Engineering

High temperatures and pressures in subsea flowlines induce large compressive axial forces in the pipe wall. With the flowline acting as a bar, its natural tendency is to relieve the resulting compressive force by buckling.

In deepwater and relatively flat seabed, non-trenched flowlines buckle horizontally. This may have consequences for the integrity of the flowline in case of an uncontrolled large buckle. This can also be an attractive solution to relieve axial compressive forces.

Today, production in deeper waters often leads to the discovery of higher temperature and pressure fields. These conditions increase the susceptibility of flowlines to lateral buckling and require the development of practical mitigation measures which adds complexity to the study of lateral buckling. Designers have access to two types of tools to analyze this phenomenon:
1) An analytical tool, the so-called Hobbs method. Due to the assumptions on which it is based, this model can be considered too conservative
2) Finite element models, which are time consuming, very sensitive to the initial assumptions and the input data, and require qualified person behind the screen.

As part of a general effort to improve oil development in offshore Angola, the Angola Deepwater Consortium (ADC) formed by Sonangol and Doris Engineering, has investigated the feasibility of developing a new analytical tool based on an improvement of the Hobbs method. This study was performed under the guidance and direction of a JIP Steering Committee composed of representatives from BP, CABGOC, Esso Exploration Angola (block 15) Ltd., Eni, Petrobras, and Total E&P Angola.

This presentation describes the objectives and the step-by-step procedure adopted for this improvement, as well as some comparisons against Finite Element models and on-site observations.

This presentation will be featured at the Deep Offshore Technology (DOT) Conference & Exhibition in New Orleans. It is scheduled for 11 a.m., Wednesday Oct. 12, in Suite C Room 15 at the Hilton Riverside.