Packer-to-Tubing Forces for Intermediate Packers

Abstract

Changes in temperature and pressure during pump-in and production usually result in changes in tubing length or tubing and packer forces, depending on whether the tubing is free to move. Earlier papers presented means for calculating these effects for a completion containing one packer. This paper briefly summarizes those papers and generalize, the calculation to paper briefly summarizes those papers and generalize, the calculation to completions with more than one packer. Introduction This paper presents a means of calculating the forces that occur at intermediate packers as a result of changes in temperature and pressure. Intermediate packers are those within the tubing string, such as packers are those within the tubing string, such as dual packers or selective completion packers. The intermediate packer-to-tubing force is needed to design multi- and selective-well completions so that the well can be treated through the completion assembly. Without a proper design, it is possible to shear the release mechanism in the intermediate packer(s), which can result in a costly failure of the packer(s), which can result in a costly failure of the completion assembly.This paper is an extension of papers by Lubinski et al. and Hammerlindl. To eliminate much cross-referencing, the basic equations of Refs. 1 and 2 are presented with a brief review of the theory. presented with a brief review of the theory. This paper also develops the theory required to solve intermediate packer-to-tubing forces, illustrates solutions to typical problems, and develops the initial packer-to-tubing forces that result when the packer-to-tubing forces that result when the intermediate packer is set hydraulically.The calculation procedure requires working the problem from the lowest packer to the surface in problem from the lowest packer to the surface in stages. The first stage is the tubing between the first and second packers; the second stage is the tubing between the second and third packers (or the surface if there is no third packer), etc. The procedures are the standard ones used in Refs. 1 and 2. The only changes are in the procedures used to determine the actual and fictitious forces and the changes in length due to applied forces at the intermediate packers.The text pertains to uniform completions unless otherwise stated. A uniform completion is one with a single-size tubing string containing only one fluid and a constant-ID casing string where the annulus contains only one fluid, which may or may not be the same fluid as contained in the tubing. Compendium of Movement and Forces Applied Forces With No Fluid If a tubing string is suspended freely in a cased well containing no fluid and a tensile force is applied to the lower end in the axial direction, the tubing elongates. If a compressive force is applied, the tubing shortens and buckles.The elongation due to a tensile force is determined from Hooke's law. The e nation for Hooke's law in terms of length change is(1) JPT P. 515