https://doi.org/10.15255/KUI.2005.024
Published: Kem. Ind. 56 (1) (2007) 9–20
Paper reference number: KUI-24/2005
Paper type: Review
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Polymeric flow Improver Additives for Crude Oils and Gas Condensates

A. Erceg Kuzmić, M. Radošević, G. Bogdanić, J. Jelić-Balta and R. Vuković+

Abstract

This paper describes the problem of paraffin deposition during production, transportation and processing of crude oil and gas condensate. The troublesome paraffin stands for normal hydrocarbons ranging from approximately C18–C38, mixed with small amounts of branched paraffin, monocyclic paraffin, polycyclic paraffin, and aromatics. The amount of paraffin found in crude oils as described in the literature, varies from less than 1 to more than 50 percent. The solubility of paraffin depends on chemical composition, temperature and pressure. Paraffin precipitates at an equilibrium temperature and pressure defined as the cloud point. The paraffin deposits often begin on surfaces cooler than the liquid. The viscosity is increased by the presence of paraffin crystals and if the temperature is reduced sufficiently, the crude oil/gas condensate will become very viscous (pour point). The crude oil/gas condensate viscosity behaves in a Newtonian manner until wax crystals begin to form and, after lowering the temperature, behaves in a non-Newtonian manner. Many options are available to counter the problems caused by paraffin wax deposition. These include various mechanical, thermal and chemical means (for example, steam heating, blending with lighter cutter stocks and treating with chemical additives). A preferred option would be to use wax modifier additives, commonly known as pour point depressants. Crystal modifiers are copolymers from these groups: copolymers of ethylene vinyl acetate, poly -olefins, alkyl fumarate- vinyl acetate copolymers of C18-through C22 methacrylates and copolymers of maleic anhydride esters. The mechanism of paraffin deposition and prevention is described. The additives modify the size and shape of the crystal and inhibit the formation of large wax crystal lattices. With efficient additives, crude oil/gas condensate behaves in a Newtonian manner at low temperature. A section of the paper describes the influence of chemical structure and molecular weight of the flow improver additives for crude oils and gas condensates prepared by the authors of this review article. The additives are based on methacrylic long chain alkyl ester homopolymers or copolymers with vinyl carboxylic acids or vinyl aromatic monomers. The quality of the prepared additives as pour point depressants and rheology improvers was proved by applying them to crude oil from INA fields Števkovica, Obod and Ðeletovci as well as gas condensate fields Molve, Kalinovac, Stari Gradac, Gola, and Hungarian gas condensate field Barcs. The best results were obtained with the copolymers of methacrylic long-chain alkyl esters with functional monomers.

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Keywords

polymer additives, crude oil, gas condensate, pour point, rheological properties