A survey on mathematical modelling of deposition in waxy crude oils

Abstract

Waxy Crude Oils (WCO's) are characterized by the presence of heavy paraffins in sufficiently large concentrations. They exhibit quite complex thermodynamical and rheological behaviour and present the peculiar property of giving rise to the formation of segregated wax deposits, when temperature falls down the so called WAT, or Wax Appearance Temperature. In extreme cases, segregated waxes may lead to pipeline occlusion due to deposition on cold walls. In this paper we review the mathematical models formulated to describe: (i) wax cystallization or thawing in cooling/heating cycles; (ii) the mechanisms of mass transport in saturated non-isothermal solutions; (iii) the experimental device used to measure wax solubility and wax diffusivity; (iv) wax deposition in pipelines carrying a warm, wax-saturated WCO through cold regions; (v) wax deposition accompanied by gelification during the cooling of a WCO under a thermal gradient. © EDP Sciences, 2011.