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ARPN Journal of Science and Technology >> Volume 7, Issue 1, January 2017

ARPN Journal of Science and Technology

Piston Effect and Ballooning in Horizontal SAS Completions: Challenges Encountered During Completion Integrity Test Operations

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Author Nnaemeka Ohia, Charley Anyadiegwu, Emmanuel MBA
ISSN 2225-7217
On Pages 289-294
Volume No. 4
Issue No. 4
Issue Date May 01, 2014
Publishing Date May 01, 2014
Keywords Integrity test; ballooning; piston effects; Inflow control devices; standalone sand screens.


This paper highlights the theories of piston effect and ballooning and how they can impact on the success of a completions integrity test. Piston effect caused by pressure changes induced during integrity tests in a tubing string stabbed into a packer bore can cause a reduction in the length of the tubing string. Internal pressure applied to the tubing string in the course of an integrity test can balloon the tubing string also causing a reduction in effective length. The results from this study have clearly shown that the combined effect of piston and ballooning can unseat the tubing seals from the packer bore leading to an unsuccessful integrity test. This was the case here and the (NPT) non productive time cost of this failure was over 450,000 dollars. The well cited in this study is a horizontal oil well completed with a specialized stand alone screen (SAS) capable of providing both sand control and inflow control, aimed at delaying water and gas conning, thereby optimizing production in open-hole horizontal completions. Unlike other conventional sand screen designs, this sand screen achieves inflow control by means of nozzles/inflow control devices located in the screen housing and swell packers used to achieve compartmentalization in cases of non-uniform permeability. However, these nozzles can be plugged by debris from wellbore fluids during deployment and can act as a pseudo-closed system during integrity tests thereby giving rise to substantial piston effect. This sand screen technology is relatively new and the well in this study is the second well to be completed with this sand screen design in the region. Ab-initio, conventional tubing/completion design philosophies practiced in the Niger Delta region consider piston effect and ballooning only as it affects tubing movement during production and not during deployment/installation. Going forward, these effects should be considered in the deployment program. This study has provided procedural recommendations on ways to forestall integrity test failures due to these effects.

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