Page Header

Influence of Hydrostatic Pressure on the Formation of Voids in Gelled Crude Oil

Girma T. Chala, Shaharin A. Sulaiman, Azuraien Japper-Jaafar, Wan Ahmad Kamil Wan Abdullah


Production of waxy crude oil from offshore fields has increased in the last decade. However, the operation is being challenged with the high wax content of crude oil that tends to precipitate at lower temperature. This paper presents the effects of hydrostatic pressure on the voids formed in waxy crude oil gel. A flow loop rig that simulates offshore waxy crude oil transportation was used to produce the gel. A Magnetic Resonance Imaging of 3-Tesla system was used to scan the gelled samples in horizontal and vertical pipes. The hydrostatic pressure effect was found to be most significant near the pipe wall as a change in percent voids volume of 0.53% was observed at that region. In particular, the voids volume reduction was more pronounced in the lower half side of the pipe. The total volume of voids in the vertical pipe was lower than that in the horizontal pipe, and this suggests that the gel in the vertical pipe became denser due to the effects from the hydrostatic pressure. Conversely, the voids volume around the pipe core in the vertical pipe was higher when compared to that in the horizontal pipe. The change in voids volume near the pipe core and wall shrunk to a minimum and converged to 0.18% voids volume at larger duration of the hydrostatic effect. Further, hydrostatic pressure was observed to have significant influences for higher duration making the void size to be distributed across and along the pipeline; however, it was found to have insignificant effects on voids size distribution for smaller duration. The findings of this study can help for better understanding of voids formation in vertical pipelines that would further assist in developing a model predicting restart pressure accurately.


[1] M. Seyyedattar, S. Zendehboudi, and S. Butt, “Technical and non-technical challenges of development of offshore petroleum reservoirs: Characterization and production,” Natural Resources Research, vol. 29, no. 3, pp. 2147– 2189, 2020.

[2] A. K. Mehrotra, S. Ehsani, S. Haj‐Shafiei, and A. S. Kasumu, “A review of heat‐transfer mechanism for solid deposition from “waxy” or paraffinic mixtures,” The Canadian Journal of Chemical Engineering, vol. 98, no. 12, pp. 2463–2488, 2020.

[3] F. Alnaimat and M. Ziauddin, “Wax deposition and prediction in petroleum pipelines,” Journal of Petroleum Science and Engineering, vol. 184, 2020, Art. no. 106385.

[4] N. Sa-ngawong, T. Kangsadan, K. Cheenkachorn, N. Inwong, and A. Mahittikul, “Study on local composition of binary n-alkane for precise estimation of wax disappearance temperature,” Applied Science and Engineering Progress, vol. 14, no. 2, pp. 271–283, 2021, doi: 10.14416/j.asep. 2020.02.002.
[5] G. T. Chala, S. A. Sulaiman, and A. Japper-Jaafar, “Flow start-up and transportation of waxy crude oil in pipelines-A review,” Journal of Non- Newtonian Fluid Mechanics, vol. 251, pp. 69–87, 2018.

[6] C. Bai and J. Zhang, “Effect of carbon number distribution of wax on the yield stress of waxy oil gels,” Industrial & Engineering Chemistry Research, vol. 52, no. 7, pp. 2732–2739, 2013.

[7] A. Japper-Jaafar, P. T. Bhaskoro, and Z. S. Mior, “A new perspective on the measurements of wax appearance temperature: Comparison between DSC, thermomicroscopy and rheometry and the cooling rate effects,” Journal of Petroleum Science and Engineering, vol. 147, pp. 672–681, 2016.

[8] Z. Liu, Y. Li, W. Wang, G. Song, Z. Lu, and Y. Ning, “Wax and wax–hydrate deposition characteristics in single-, two-, and three-phase pipelines: A review,” Energy & Fuels, vol. 34, no. 11, pp. 13350–13368, 2020.

[9] S. A. Sulaiman, B. K. Biga, and G. T. Chala, “Injection of non-reacting gas into production pipelines to ease restart pumping of waxy crude oil,” Journal of Petroleum Science and Engineering, vol. 152, pp. 549–554, 2017.

[10] H. P. Rønningsen, “Production of waxy oils on the norwegian continental shelf: Experiences, challenges, and practices,” Energy & Fuels, vol. 26, no. 7, pp. 4124–4136, 2012.

[11] J. G. Bomba, “Offshore pipeline transport of waxy crude oils,” presented at the Offshore South East Asia Show, Singapore, Jan. 28–31, 1986.

[12] B. Sarkar and A. Bhattacharya, “Transportation of waxy crude through pipeline systems: Analysis of some critical design parameters,” presented at the First International Offshore and Polar Engineering Conference, Edinburgh, The United Kingdom, Aug. 11–16, 1991.

[13] G. Ovarlez, S. Cohen-Addad, K. Krishan, J. Goyon, and P. Coussot, “On the existence of a simple yield stress fluid behavior,” Journal of Non-Newtonian Fluid Mechanics, vol. 193, pp. 68–79, 2013.

[14] M. Fossen, T. Øyangen, and O. J. Velle, “Effect of the pipe diameter on the restart pressure of a gelled waxy crude oil,” Energy & Fuels, vol. 27, no. 7, pp. 3685–3691, 2013.

[15] G. T. Chala, S. A. Sulaiman, A. Japper-Jaafar, and W. A. K. W. Abdullah, “Impacts of cooling rates on voids in waxy crude oil under quiescent cooling mode,” Applied Mechanics and Materials, vol. 799–800, pp. 62–66, 2015.

[16] T. M. Williams, J. J. C. Hsu, and H. L. Patterson, “Measurement of break away yield stress of waxy crude oil and pipeline restart system design,” presented at the Offshore Technology Conference, Texas, USA, May 6–9, 1996.

[17] J. J. Magda, A. Elmadhoun, P. Wall, M. Jemmett, M. D. Deo, K. L. Greenhill, and R. Venkatesan, “Evolution of the pressure profile during the gelation and restart of a model waxy crude oil,” Energy & Fuels, vol. 27, no. 4, pp. 1909–1913, 2013.

[18] S. Mortazavi-Manesh and J. M. Shaw, “Thixotropic rheological behavior of maya crude oil,” Energy & Fuels, vol. 28, no. 2, pp. 972–979, 2014.

[19] M. R. Davidson, Q. Dzuy Nguyen, C. Chang, and H. P. Rønningsen, “A model for restart of a pipeline with compressible gelled waxy crude oil,” Journal of Non-Newtonian Fluid Mechanics, vol. 123, no. 2–3, pp. 269–280, 2004.

[20] S. A. Sulaiman, G. T. Chala, and M. Z. Zainur, “Experimental investigation of compressibility of waxy crude oil subjected to static cooling,” Journal of Petroleum Science and Engineering, vol. 182, 2019, Art. no. 106378.

[21] G. M. De Oliveira, L. L. V. da Rocha, A. T. Franco, and C. O. Negrão, “Numerical simulation of the start-up of Bingham fluid flows in pipelines,” Journal of Non-Newtonian Fluid Mechanics, vol. 165, no. 19–20, pp. 1114–1128, 2010.

[22] G. T. Chala, S. A. Sulaiman, A. Japper-Jaafar, and W. A. K. W. Abdullah, “Effects of cooling regime on the formation of voids in statically cooled waxy crude oil,” International Journal of Multiphase Flow, vol. 77, pp. 187–195, 2015.

[23] B. Abedi, M. J. P. Miguel, P. R. de Souza Mendes, and R. Mendes, “Startup flow of gelled waxy crude oils in pipelines: The role of volume shrinkage,” Fuel, vol. 288, 2021, Art. no. 119726.

[24] A. Shafquet, I. Ismail, A. Japper-Jaafar, S. A. Sulaiman, and G. T. Chala, “Estimation of gas void formation in statically cooled waxy crude oil using online capacitance measurement,” International Journal of Multiphase Flow, vol. 75, pp. 257–266, 2015.

[25] S. Majidi and A. Ahmadpour, “Thermally assisted restart of gelled pipelines: A weakly compressible numerical study,” International Journal of Heat and Mass Transfer, vol. 118, pp. 27–39, 2018.

[26] A. Wachs, G. Vinay, and I. Frigaard, “A 1.5D numerical model for the start up of weakly compressible flow of a viscoplastic and thixotropic fluid in pipelines,” Journal of Non-Newtonian Fluid Mechanics, vol. 159, no. 1–3, pp. 81–94, 2009.

[27] G. T. Chala, S. A. Sulaiman, A. Japper-Jaafar, W. A. K. W. Abdullah, and M. M. M. Mokhtar, “Gas void formation in statically cooled waxy crude oil,” International Journal of Thermal Sciences, vol. 86, pp. 41–47, 2014.

[28] T. Defraeye, V. Lehmann, D. Gross, C. Holat, Els Herremans, P. Verboven, B. E. Verlindenb, and B. M. Nicolai, “Application of MRI for tissue characterisation of ‘Braeburn’ apple,” Postharvest Biology and Technology, vol. 75, pp. 96–105, 2013.

[29] W. Rukthong, W. Weerapakkaroon, U. Wongsiriwan, P. Piumsomboon, and B. Chalermsinsuwan, “Integration of computational fluid dynamics simulation and statistical factorial experimental design of thick-wall crude oil pipeline with heat loss,” Advances in Engineering Software, vol. 86, pp. 49–54, 2015.
[30] G. T. Chala, C. Chan, and H. Sadig, “Temperature profile and its effects on the location of lower denser substance in waxy crude oil: A numerical study,” Advanced Science Letters, vol. 24, no. 11, pp. 8880–8884, 2018.

[31] A. Tavakoli and M. Baktash, “Numerical approach for temperature development of horizontal pipe flow with thermal leakage to ambient,” International Journal of Modern Engineering Research, vol. 2, pp. 3784–3794, 2012.

[32] G. T. Chala, S. A. Sulaiman, A. Japper-Jaafar, and W. A. K. W. Abdullah, “Temporal variation of voids in waxy crude oil gel in the presence of temperature gradient,” Chemical Engineering Communications, vol. 207, no. 10, pp. 1403– 1414, 2020.

Full Text: PDF

DOI: 10.14416/j.asep.2021.10.014


  • There are currently no refbacks.