Thermodynamic Modeling of Naphthenate Formation and Related pH Change Experiments
- Murtala A. Mohammed (Heriot-Watt University) | Kenneth S. Sorbie (Heriot-Watt University) | A.G. Shepherd (Shell Global Solutions International B.V.)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- August 2009
- Document Type
- Journal Paper
- 466 - 472
- 2009. Society of Petroleum Engineers
- 4.3.4 Scale, 4.3 Flow Assurance
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- 447 since 2007
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The prediction and prevention of both sodium and calcium naphthenate "scales" is an important issue in oil production. A broad description of how these scales form has been available for some time, although most experimental findings are still of a qualitative nature. In this paper, an equilibrium thermodynamic model is presented for predicting naphthenate partitioning and precipitation in an oil/brine immiscible system from some chosen initial conditions (i.e., naphthenate initial concentration in oil, brine pH, [Ca2+], etc.). This model has, with some assumptions, been applied to both model and real naphthenate system.
This model describes two types of naphthenate experiment: 1) full naphthenate precipitation, and 2) simpler "pH change" experiments in which no precipitation occurs. To predict naphthenate precipitation, the theory suggests knowing: 1) the partition coefficient of the naphthenic acid, HA, between the oil and the water phases, Kow; 2) the pKa of the naphthenic acid in water; and 3) the solubility product, KCaA2 (or other similar solubility parameter), of the naphthenate deposit. In the simpler pH change experiments, only the first two of these parameters (i.e., Kow and pKa) are required. Using the naphthenate model without precipitation, the effect of varying parameters on the degree of pH change predicted at equilibrium in the oil/naphthenic acid/brine system was studied. Also, the model was used to examine the sensitivities of the various parameters on the final pH was also applied. The comparison between the model predictions and experiment at a higher brine pH value is overall satisfactory.
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Dyer, S.J., Graham, G.M., and Arnott, C. 2003. Naphthenate ScaleFormation--Examinations of Molecular Controls in Idealized Systems. PaperSPE 80395 presented at the International Symposium on Oilfield Scale, Aberdeen,29-30 January. doi: 10.2118/80395-MS.
Ese, M.-H. and Kilpatrick, P.K. 2004. Stabilization of water-in-oilemulsions by naphthenic acids and their salts: Model compounds, role of pH, andsoap: Acid ratio. Journal of Dispersion Science and Technology25 (3): 253-261. doi:10.1081/DIS-120038634.
Fan, T.P. 1991. Characterization of naphthenicacids in petroleum by fast atom bombardment mass spectrometry. Energy& Fuels 5 (3): 371-375. doi:10.1021/ef00027a003.
Gaikar, V.G. and Maiti, D. 1996. Adsorptive recovery ofnaphthenic acids using ion-exchange resins. Reactive and FunctionalPolymers 31 (2): 155-164.doi:10.1016/1381-5148(96)00054-5.
Gallup, D.L., Smith, P.C., Chipponeri, J., Abuyazid, A., and Mulyono, D.2002. Formation and Mitigation of"Metallic Soap" Sludge, Attaka, Indonesia Field. Paper SPE 73960presented at the SPE International Conference on Health, Safety and Environmentin Oil and Gas Exploration and Production, Kuala Lumpur, 20-22 March. doi:10.2118/73960-MS.
Goldszal, A., Hurtevent, C., and Rousseau, G. 2002. Scale and Naphthenate Inhibition inDeep-Offshore Fields. Paper SPE 74661 presented at the InternationalSymposium on Oilfield Scale, Aberdeen, 30-31 January. doi:10.2118/74661-MS.
Havre, T. E. 2002. Formation of Calcium Naphthenate in Water/Oil System,Naphthenic Acid Chemistry and Emulsion stability. PhD thesis, Department ofChemical Engineering, Norwegian University of Science and Technology,Trondheim, Norway (October 2002).
Havre, T.E., Sjöblom, J., and Vindstad, J.E. 2003. Oil/Water-Partitioning andInterfacial Behavior of Naphthenic Acids. Journal of Dispersion Scienceand Technology 24 (6): 789-801. doi:10.1081/DIS-120025547.
Laredo, G.C., López, C.R., Álvarez, R.E., Cano, J.L. 2004. Naphthenic acids, totalacid number and sulfur content profile characterization in Isthmus and Mayacrude oils. Fuel 83 (11-12): 1689-1695.doi:10.1016/j.fuel.2004.02.004.
Mohammed, M.A. and Sorbie, K.S. Forthcoming publication: Naphthenic AcidExtraction and Characterization From Naphthenate Field Deposits and Crude OilsUsing ESMS and APCI-MS.
Robbins, W.K. 1998. Challenges in the Characterization of Naphthenic Acidsin Petroleum. ACS Petrol. Chem. Div.( pre-print ) 43 (1):137-140.
Rousseau, G., Zhou, H., and Hurtevent, C. 2001. Calcium Carbonate and NaphthenateMixed Scale in Deep-Offshore Fields. Paper SPE 68307 presented at theInternational Symposium on Oilfield Scale, Aberdeen, 30-31 January. doi:10.2118/68307-MS.
Shepherd, A.G., Thomson, G., Westacott, R., Neville, A., and Sorbie, K.S.2005. A Mechanistic Study ofNaphthenate Scale Formation. Paper SPE 93407 presented at the SPEInternational Symposium on Oilfield Chemistry, The Woodlands, Texas, USA, 2-4February. doi: 10.2118/93407-MS.
Shepherd, A.G., Thomson, G., Westacott, R., Sorbie, K.S., Turner, M., andSmith, P.C. 2006. Analysis ofOrganic Field Deposits: New Types of Calcium Naphthenate Scale or the Effect ofChemical Treatment. Paper SPE 100517 presented at the SPE InternationalOilfield Scale Symposium, Aberdeen, 30 May-1 June. doi: 10.2118/100517-MS.
Sorbie, K.S., Shepherd, A.G., Turner, M., Smith, P.C., and Westacott, R.E.2005. Naphthenate Formation in Oil Production: General Theories and FieldObservations. Proc., Chemistry in the Oil Industry IX, Manchester, UK,31 October-2 November.
Vindstad, J.E., Bye, A.S., Grande, K.V., Hustad, B.M., Hustvedt, E., andNergård, B. 2003. FightingNaphthenate Deposition at the Heidrun Field. Paper SPE 80375 presented atthe International Symposium on Oilfield Scale, Aberdeen, 29-30 January. doi:10.2118/80375-MS.