LOW-TEMPERATURE RHEOLOGICAL BEHAVIOR OF UMBARKA WAXY CRUDE AND INFLUENCE OF FLOW IMPROVER

The low temperature flow properties (pour point and rheological parame ters) have been determined for untreated and additive-treated Umbarka waxy crude. The rheological characteristics of the crude showed non-Ne wtonian yield-pseudoplastic flow behavior and a pronounced thixotropic effect. Viscometric data are fitted to Bingham, Casson and Herschel-B ulkley plastic flow models using linear and non-linear computer regres sion analysis. Herschel parameters showed inconsistent results, wherea s the Casson equation fitted the data reasonably well. Treatment of th e crude with flow improver ameliorated both rheological properties and pour point, but in a different manner. The influence of the additive on the rheology of the crude is affected greatly by shear rate. The th ixotropic phenomenon of the crude is likely to be temperature-dependen t in addition to the other controlling factors. (C) 1998 Elsevier Scie nce B.V.