A Novel Approach for Modelling Leakage through Elastomer Seals
- Harshkumar Patel (University of Oklahoma) | Saeed Salehi (University of Oklahoma)
- Document ID
- Offshore Technology Conference
- Offshore Technology Conference, 4-7 May, Houston, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2020. Offshore Technology Conference
- 7.2.1 Risk, Uncertainty and Risk Assessment, 7 Management and Information, 7.2 Risk Management and Decision-Making, 2.10 Well Integrity, 2.1 Completion Selection and Design, 2 Well completion, 2.1.3 Completion Equipment, 5.6.3 Deterministic Methods
- modelling tool, Elastomer, leakage model, well integrity, seal design
- 49 in the last 30 days
- 49 since 2007
- Show more detail
- View rights & permissions
Elastomer is a widely used seal material in oil and gas wells. Seal components in wellhead and completion equipment are important barrier elements for maintaining well integrity. In general, unlike metallic seals, it is believed that elastomer seal's performance is not highly dependent on its surface characteristics. However, there are some evidences that suggest that elastomer surface quality or defects like wear, blistering, etc. can impact fluid penetration risk and leakage.
The effect of elastomer surface quality on sealability is difficult to investigate using macroscopic (equipment level) finite element models. This paper presents a novel modelling approach that can simulate fluid penetration and predict leakage rates considering surface topography/characteristics of the elastomer sealing interface. The leakage model consists of a contact mechanics model and a fluid flow model. Deterministic contact-mechanics model can take surface topographical measurements as an input and simulate actual contact area, and microscopic gaps at different loads. This contact gap information is then used by the fluid flow model to predict flow path and calculate leakage rates.
To represent elastomer seal surface and apply the developed model, different types of rough surfaces were generated. Various operational, design, and failure scenarios were simulated to investigate the effects of surface characteristics, elastomer material properties, fluid properties, etc. on the elastomer sealability. Preliminary results demonstrate that elastomer surface characteristic such as degree of finishing can have notable influence on the seal quality as measured by contact pressure required to achieve zero leakage rate. As expected, harder elastomer seal material exhibited more sensitivity to surface quality than softer material. High fluid pressure and low viscosity were observed to increase the leakage rates for similar contact pressure distribution.
Finite element modelling based seal design is typically limited to the analysis of contact pressure distribution at the sealing interface. Presented leakage model helps further extend the design workflow by enabling consideration of surface characteristics of the seal. With further refinement and experimental validation, the model could be used to create lookup tables of contact pressures. These values can be used as target for finite element analysis of seal equipment design.
|File Size||1 MB||Number of Pages||21|
Ahmed, S., Salehi, S., Ezeakacha, C. P., and Teodoriu, C. 2019b. Experimental investigation of elastomers in downhole seal elements: Implications for safety. Polymer Testing, 76, pp.350–364. http://dx.doi.org/10.1016/j.polymertesting.2019.03.041.
Bora, C. K., Flater, E. E., Street, M. D.., 2005. Multiscale roughness and modeling of MEMS interfaces. Tribology Letters, 19(1), pp.37–48.http://dx.doi.org/10.1007/s11249-005-4263-8.
Chang W. R., Etsion, I. I., and Bogy, D. B. 1987. An Elastic-Plastic Model for the Contact of Rough Surfaces. ASME Journal of Tribology: 109(2), 257-263. http://dx.doi.org/10.1115/1.3261348.
Greenwood, J. A., and Williamson, J. B. P. 1966. Contact of nominally flat surfaces. Proc. of the Royal Society of London: A(295), 300–319. https://doi.org/10.1098/rspa.1966.0242
Greenwood, J. A., and Tripp, J. H. 1970. The contact of two nominally flat rough surfaces. Proc. of the Institution of Mechanical Engineers: 185(1), 625-634. https://doi.org/10.1243/PIME_PROC_1970_185_069_02
Mandelbrot, B., 1967. How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension. Science, 156(3775), pp.636–638. http://dx.doi.org/10.1126/science.156.3775.636.
Oil & Gas iQ. 2015. High Pressure High Temperate, High Costs, High Stakes? https://www.oilandgasiq.com/content-auto-download/5b04c1b543dfd0385d3c7c22 (Accessed 4 October 2018)
Patel, H., Hariharan, H., Bailey, G., and Jung, G. 2018. Advanced Computer Modelling for Metal-to-Metal Seal in API Flanges. Presented at SPE Annual Technical Conference and Exhibition, 24-26 September, Dallas, Texas, USA. http://dx.doi.org/10.2118/191636-ms
Patel, H., Salehi, S., Ahmed, R., & Teodoriu, C., 2019a. Review of elastomer seal assemblies in oil & gas wells: Performance evaluation, failure mechanisms, and gaps in industry standards. Journal of Petroleum Science and Engineering, 179, pp.1046–1062. Available at: http://dx.doi.org/10.1016/j.petrol.2019.05.019.
Patel, H., Salehi, S., Teodoriu, C., and Ahmed, R. 2019b. Performance evaluation and parametric study of elastomer seal in conventional hanger assembly. Journal of Petroleum Science and Engineering: 175, 246–254. http://dx.doi.org/10.1016/j.petrol.2018.12.051.
Patel, H., and Salehi, S. 2019. Investigation of Elastomer Seal Energization: Implications for Conventional and Expandable Hanger Assembly. Energies 2019: 12(4), 763; https://doi.org/10.3390/en12040763
Persson, B. N. J. 2006. Contact mechanics for randomly rough surfaces. Surface Science Reports: 61(4), 201–227. http://dx.doi.org/10.1016/j.surfrep.2006.04.001.
Salehi, S., Ezeakacha, C. P., Kwatia, G.., 2019. Performance verification of elastomer materials in corrosive gas and liquid conditions. Polymer Testing, 75, pp.48–63. http://dx.doi.org/10.1016/j.polymertesting.2019.01.015.
Whitehouse, D.J. & Archard, J.F., 1970. The Properties of Random Surfaces of Significance in their Contact. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 316(1524), pp.97–121. http://dx.doi.org/10.1098/rspa.1970.0068.
Zhao, Y., Maietta, D. M., and Chang, L. An Asperity Microcontact Model Incorporating the Transition from Elastic Deformation to Fully Plastic Flow. Journal of Tribology: 122(1), 86. http://dx.doi.org/10.1115/1.555332