The paper presents results of an analysis of the wall waxing effect on the thermal-hydraulic parameters of oil along a non-isothermal section of a 70 km long main oil pipeline with a diameter of 1020 mm.
The paper presents the results of numerical modeling performed using the dynamic CFD simulator OLGA SIS SLB in a specialized calculation module for predicting the waxing process WAX DEPOSITION. The research is a continuation of the previously carried out studies of the influence of deposits on the inner wall of an oil pipeline on its thermal-hydraulic efficiency. Experimental confirmation of the possible positive effects of the presence of a natural protective coating on the inner surface of the pipeline in the form of a layer of asphalt-resin-paraffin deposits have already been done previously by the authors according to average indicators. In this article the results is the use of a dynamic modeling process are considered. Dynamic modeling allows to take into account not only the physics of the process in dependence on external thermobaric conditions, but also its kinetics. The results of dynamic modeling are presented in the form of temporal trends and profiles along the length. That made it possible to numerically measure the thermal-hydraulic efficiency of the near-wall sediment layer, taking into account the non-isothermality and kinetic changes of the process. In particular, the high thermal insulation properties of the sediment layer have been confirmed even with its insignificant thickness that makes it possible to significantly reduce heat transfer and significantly increase the final flow temperature (including the average along the pipeline). Thus, that led to a decrease in the average viscosity and a decrease in the rate of deposition growth. The total effect of a thin (only 2 mm) layer of deposits on the inner surface of the oil pipeline with the inner diameter of 1020 mm was expressed in a significant decrease in the pressure drop even for a short section of 70 km. It is shown the need for further study of the issue in order to develop technologies and effective methods of the waxing process to optimize the costs of in-line cleaning and inhibition of deposits. That is important both for relatively cold and hot non-isothermal sections of oil pipelines.
1. Karimov R.M., Sunagatullin R.Z., Tashbulatov R.R., Dmitriev M.E., Study of wax deposition reasons in non-isothermal main pipelines for hot pumping of high-viscosity waxy oil (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2021, no. 1, pp. 87–91.
2. Sunagatullin R.Z., Karimov R.M., Tashbulatov R.R., Mastobaev B.N., The study of the kinetics of the process of oil wax deposition in main pipeline operating conditions (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2020, no. 11, pp. 124–127.
3. Sunagatullin R.Z., Karimov R.M., Tashbulatov R.R., Mastobaev B.N., Study of the causes for wax deposition under the operating conditions of main oil pipelines (In Russ.), Nauka i tehnologii truboprovodnogo transporta nefti i nefteproduktov = Science & Technologies: Oil and Oil Products Pipeline Transportation, 2020, V. 10, no. 6, pp. 610–619.
4. Reid R.C., Prausnitz J.M., Sherwood T.K., The properties of gases and liquids, New York: McGraw-Hill, 1977.
5. Pedersen K.Sch., Skovborg P., Roenningsen H.P., Wax precipitation from North Sea crude oils. 4. Thermodynamic modeling, Energy & Fuels, 1991, V. 5(6), pp. 924–932.
6. Hansen J.H., Ronningsen H.P., Pedersen K.S., Fredenslund A.A., Thermodynamic model for predicting wax formation in crude oils, AIChE Journal, 1988, V. 34, pp. 1937–1942.
7. Lira-Galeana C., Firoozabadi A., Prausnitz J.M., Thermodynamics of wax precipitation in petroleum mixtures, AIChE, 1996, V. 42, pp. 239–248.
8. Alboudwarej H., Huo Zhongxin, Kempton E.Ch., Flow-assurance aspects of subsea systems design for production of waxy crude oils, SPE-103242-MS, 2006, https://doi.org/10.2118/103242-MS.
9. Singh A., Lee H., Singh P., Sarica C., Study of the effect of condensate tie-back on wax deposition in an Indonesian offshore crude oil pipeline, Proceedings of Offshore Technology Conference, Houston, Texas, 2014, DOI: 10.4043/25109-MS.
10. Hammani A., Ratulowski J., Countinho J.A.P., Cloud points: Can we measure or model them, Petrol. Sci. Technol, 2003, V. 21(3&4), pp. 345–358, DOI: 10.1081/lft-120018524.
11. Coutinho J.A.P., Daridon J.L., The limitations of the cloud point measurements techniques and the influence of the oil composition on its detection, Petrol. Sci. Technol., 2005, V. 23, pp. 1113–1128, DOI: 10.1081/lft-200035541.
12. Coutinho J.A.P., Pauly J., Daridon J.L., A thermodynamic model to predict wax formation in petroleum fluids, Braz. J. Chem. Eng., 2001, V. 18(4), pp. 411–422.
13. Coutinho J.A.P., Ruffier-Meray V., Experimental measurements and thermodynamic modeling of paraffinic wax formation in undercooled solutions, Ins. Eng. Chem. Res., 1997, V. 36, pp. 4977–4983.
14. Hayduk W., Minhas B.S., Wax crystallizaition for prediction of molecular diffusivities in liquids, Can. J. Chem. Eng., 1982, V. 60, pp. 295–299.
15. Wilke C.R., Chang P., Correlation of diffusion coefficients in dilute solutions, AIChE J., 1955, V. 1, pp. 264–270.
16. Matzain A., Apte A.S., Zhang H.Q. et al., Multiphase flow wax deposition modeling, Proceedings of ASME ETCE Petroleum Production Technology Symposium, 5–7 Feb. 2001, Houston, Texas, 2001.
17. Pedersen K.S., Ronningsen H.P., Effect of precipitated wax on viscosity – A model for predicting non-Newtonian viscosity of crude oils, Energy & Fuels, 2000, V. 14(1), pp. 43–51.18. Singh P., Venkatesan R., Fogler H.S., Nagarajan N., Formation and aging of incipient thin film wax-oil gels, AIChE Journal, 2000, V. 46 (5), pp. 1059–1074.