Wax precipitation in multicomponent hydrocarbon sy

Authors: I A Struchkov M K Rogachev

Publish Date: 2016/08/12

Volume: 7, Issue: 2, Pages: 543-553

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Abstract

The objective of this research is to estimate individual effect of various external parameters such as pressure cooling rate watercut and addition of mechanical impurities on change in wax appearance temperature WAT in oil In this paper complex multicomponent system like oil is replaced to simplified model solution presented by wax in kerosene solution Research methods in the study were visual method at highpressure/hightemperature conditions and rheological method under ambient pressure Experimental results shown that WAT grows with increase in concentration of wax in solution increase in pressure watercut shear rate addition of mechanical impurities and decrease in gap size of the measuring system for rheological method Numerical dependences of WAT in solution on the listed factors are received Research data are explained by the thermodynamic processes proceeding in model solution Influence of wax inhibitors addition on process of the crystal structure formation in model solutions and effective wax inhibitors is definedWAT is one of key parameters to consider when elaborating protective measures against formation of asphalteneresinparaffin deposits in oil wells WAT is temperature at which the first wax crystal appears in oil BerneAllen and Work 1938 Oil is the complex multicomponent dispersion system and the slightest change in its composition during oil production will significantly impact the change in WAT and the system properties in the whole Information about individual effect of external parameters on change in WAT in oil will allow to estimate more precisely time and potential wax formation area in the tubing to diminish the waxing process of oil wells in time and to increase the work over interval of oil wells by application of the most suitable technologiesMeasurement and prediction of wax solubility in oil and model hydrocarbon solutions were carried out by Gudmundsson and Bott 1977 AlAhmad et al 1990 Srivastava et al 1997 and Wu et al 2002 Those studies covered the wide range of wax crystallization conditions at various wax concentrationMeasurement of WAT in oil can be carried out by many research methods such as lowresolution pulsed nuclear magnetic resonance NMR lightscattering method ultrasonic method and Fouriertransform infrared spectroscopy Pedersen et al 1991 Kok et al 1996 Elsharkawy et al 2000 Karan et al 2000 Jiang et al 2001 Paso et al 2009 Jiang et al 2014 Chen et al 2014 Huang et al 2016 However only few methods are capable to determine the entrapped crude oil in the solid residue correctly The most effective methods in this context are differential scanning calorimetry DSC and proton nuclear magnetic resonance 1H NMR Coto et al 2011 These techniques allow to estimate the wax precipitation characteristics and could be used to further optimize thermodynamic models of wax depositionUnfortunately many of existing methods are expensive difficult in use and interpretation of the obtained data and require prolonged duration of the experiment whereas visual and rheological methods provide simple and rapid measurement of WAT in oil and waxcontaining solutionsMany scientists Brown et al 1994 Pauly et al 2001 2003 Li and Gong 2010 Struchkov and Rogachev 2014 shown both for live oil at constant composition and for degassed oil that WAT of waxy oil linearly increases with increase in pressure Pan et al 1997 shown composition effect on wax precipitation An increase in concentration of light components in oil leads to decrease in WATAccording to certain studies Turkulov et al 1986 Paso et al 2009 Kasumu et al 2013 Struchkov and Rogachev 2016 WAT decreases with increase in cooling rate Scientists explain this phenomenon with various kinetics of wax nucleation and crystallizationNowadays researchers find convenient to describe the whole variety of disperse systems combinations using all technologic tool available as well as to identify the role of each system element individually to change its properties So the authors modeled and investigated simplified systems that were waxcontaining solutions This paper is dedicated to study of influence of various parameters to WAT in model systems These tests were carried out via visual and rheological methods

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