Impacts of Cooling Rates on Voids in Waxy Crude Oil under Quiescent Cooling Mode

Abstract:

When waxy crude oil becomes a gel, predicting a restart pressure in pipelines has been a challenge. The formation of gas voids within the gel following sufficient cooling has an impact on the restarting pressure. This study is aimed at analyzing the effects of cooling rates on voids in waxy crude oil gel using Magnetic Resonace Imaging (MRI) technique. The flow loop rig simulating offshore oil production was designed. Waxy crude oil underwent cooling through the same temperature range to observe the effects of cooling rates on voids formed. Cooling rates were found to have different influence on the formation of voids. A maximum total voids volume of 6.96% was formed at cooling rate of 1.00°C/min. Cooling rate of 0.55°C/min produced a minimum voids volume of 5.74% near pipe wall. Higher cooling rates generally produced higher voids volume near pipe wall and in entire pipe. However, there was no definite trend observed for the voids around pipe core at which slower cooling rates were also observed forming higher voids volume.

• Periodical: Applied Mechanics and Materials (Volumes 799-800)
• Pages: 62-66
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.799-800.62
• Online since: October 2015
• Authors: Girma T. Chala*, Shaharin Anwar Sulaiman, Azuraien Japper-Jaafar, Wan Ahmad Kamil Wan Abdullah
• Keywords: Cooling Rates, Gas Voids, Waxy Crude Oil

References

[1] M. Sanjay, B. Simanta, and S. Kulwant, Paraffin Problems in Crude Oil Production And Transportation: A Review, Society of Petroleum Engineers, SPE-28181-PA, (1995).

[2] J. A. Lopes-da-Silva and J. A. P. Coutinho, Analysis of the Isothermal Structure Development in Waxy Crude Oils under Quiescent Conditions, Energy & Fuels, vol. 21, pp.3612-3617, (2007).

DOI: 10.1021/ef700357v

[3] P. D. Thuc, H. V. Bich, T. C. Son, L. D. Hoe, and V. P. Vygovskoy, The Problem in Transportation of High Waxy Crude Oils Through Submarine Pipelines at JV Vietsovpetro Oil Fields, Offshore Vietnam, Journal of canadian petroleum technology, (2003).

DOI: 10.2118/03-06-tn

[4] P. B. Smith and R. M. J. Ramsden, The Prediction Of Oil Gelation In Submarine Pipelines And The Pressure Required For Restarting Flow., Society of Petroleum Engineers, SPE-8071-MS, (1978).

DOI: 10.2118/8071-ms

[5] H. S. Lee, P. Singh, W. H. Thomason, and H. S. Fogler, Waxy Oil Gel Breaking Mechanisms: Adhesive versus Cohesive Failure, Energy & Fuels, vol. 22, pp.480-487, (2007).

DOI: 10.1021/ef700212v

[6] H. S. Lee, Computational and Rheological study of wax deposition and gelation in subsea pipelines, PhD, Chemical Engineering, University of Michigan, (2008).

[7] T. T. R. Norman, Experimental Investigation of Restarting Fully-Gelled Subsea Waxy-Oil Pipelines, Msc. dissertation, University of Oklahoma, (2010).

[8] G. Cazaux, L. Barre, and F. Brucy, Waxy Crude Cold Start: Assessment Through Gel Structural Properties, presented at the SPE-49213, SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 27-30 September, (1998).

DOI: 10.2118/49213-ms

[9] G. T. Chala, S. A. Sulaiman, A. Japper-Jaafar, W. A. Kamil Wan Abdullah, and M. M. Mior Mokhtar, Gas void formation in statically cooled waxy crude oil, International Journal of Thermal Sciences, vol. 86, pp.41-47, (2014).

DOI: 10.1016/j.ijthermalsci.2014.06.034