Determination of Wax Precipitation Tendency Using Sara Analysis

Abstract Separation of crude oil into hydrocarbon fractions such as saturate, aromatic, resin and asphaltene (SARA) fractions is needed in order to obtain the concentration of each group. This chemical analysis of crude oil is necessary for upstream, midstream and downstream operations; as it yields information such as crude oil stability (asphaltenic stability), fouling propensity and the blending compatibility of the crude oil. Since SARA analysis can give information on asphaltenic stability, there is need to investigate the use of this analysis for wax precipitation tendency or wax instability. In this work, thirteen samples collected from three different fields in the Niger Delta region were studied. The modified ASTM D2549–02 was employed to separate the crude oil samples into their various chemical species. Wax Appearance Temperature (WAT), pour point and wax content were measured on the samples as well to determine whether they were waxy crude oils or non-waxy crude oils. Out of the thirteen samples studied, seven were confirmed waxy samples while six were non-waxy from the WAT, pour point and wax content measurements. The SARA analysis carried out on twelve of the samples on the other hand, showed the samples had a high percentage of saturates ranging from 40.97 wt% to 67.60 wt%. Samples C11 and C12 which were non-waxy crude oils even had saturates of 62.56% and 55.56% respectively. Thus, SARA analysis data on its own might not be a tool to distinguish waxy crude oils from non-waxy crude oils.