Assuring the Mechanical Integrity of Expandable Sand Screens
Authors: Willson Stephen , Crook Tony , Yu Jian Guo , Stenebråten Jørn , Gilchrist John , Tiffin David 
Published: October 2008

Expandable sand screens have the potential to revolutionize sand control in weak reservoirs. However, by the very fact that plastic expansion of the screen is necessary to deploy it, concerns have been raised as to how these completions will perform if run in very deformable reservoirs.

This paper presents the results of an extensive mechanical characterization testing and analysis program designed to assure the mechanical integrity of expandable screens when deployed in weak, compacting reservoirs undergoing significant reservoir depletion. The expanded screens are inherently weak when tested using conventional crush testing. However, traditional crush testing does not correctly simulate the loading imparted onto the screens under actual reservoir conditions. To address these concerns the results of extensive laboratory crush and buckling tests performed on sections of expanded screens are reported. The tests are designed to mimic potential failure modes when screens are deployed in both vertical and horizontal wells. The laboratory results have been analyzed in detail using advanced numerical finite element modeling techniques. Important features of the numerical modeling are described; importantly, the paper discusses the relative merits of 2-dimensional versus 3- dimensional finite element representations of the screens, and the extent to which unequal slot opening and initial imperfections influence the collapse resistance.

Numerical simulations of expandable screen performance in compacting reservoirs are then presented and discussed.

Introduction

Expandable sand screens are an exciting new completions technology that has the potential to revolutionize sand control in weak reservoirs. However, by the very fact that plastic expansion of the screen is necessary to deploy it within the reservoir borehole, legitimate concerns have been raised as to what might be the long-term response of these completions if run in very deformable reservoirs. In BP.s portfolio of recently developed and undeveloped fields, weak sands are in the majority. These developments will require some form of sand control. Expandable sand screens offer a very cost effective, high productivity completion option that could enhance production. However, with any new technology, there is a pressing need to assure long-term performance in order to avoid well multiple failures at some point in the future. Over the past three years, BP has embarked upon a program of work to provide this high level of assurance to field development groups.

This work has enabled BP to deploy world-record lengths of expandable sand screens in North Sea fields. In 2000, a 566m length of 5½. screen was expanded to 8½. in BP.s first application of this technology in a horizontal well. More recently in 2001, 4 screens were successfully expanded to 6". in 275m and 510m legs of a Level 6 multilateral completion. Here the formation strength and stiffness were lower than previous applications of this technology-essentially 0 psi to 700 psi unconfined strength and ca. 0.5×106 Young's modulus.