LOW TEMPERATURE FLOW CHARACTERISTICS OF SOME WAXY CRUDE OILS IN RELATION TO THEIR COMPOSITION : PART II EFFECT OF WAX COMPOSITION AND CONCENTRATION ON THE DEW AXED CRUDE OILS WITH / WITHOUT ADDITIVES

In this part of the work the effect of wax concentrations on the rheologica! properties of the dewaxed Duliajan (Assam) and Lingaia crude oils have been studied. The dewaxing of the crude oil was done by removing n-paraffins from the crude oil by urea adduction. The urea adducted n-paraffins concentrate-the wax- was characterized by its carbon number distribution. The urea non adducted oil portion - the denormalized crude oil (DNO)- was characterized for its pour point. The wax in different concentration was then added in the DNO and the change in the rheological properties like pour point, yield stress and plastic viscosity were studied using a Haake Rota Viscometer. The effect of carbon number distribution, i.e. the composition of the wax, on these rheological properties was also investigated. Four different commercial pour point depressanl additives have been used to study their effects on the pour point, yield stress and plastic viscosity of the reconstituted (wax mixed DNO) crude oils.

From this study it has been found that wax concentration and its composition are primarily responsible for the variation in the pour point of the DNO, and the DNO composition has a small effect. However, as seen in the Part I of this paper, the response of the pour point depressant additive in effecting the change in the pour point is primarily governed by the composition of the DNO. The additives have shown better response in the DNO having more aromatic concentrate, as has been found in the case of Duliajan (Assam) DNO.