The solid material deposited in the Minamiaga crude oil, (so-called paraffin), has distinctive characteristics: i. e., it does not totally dissolve in any organic solvents, nor disperse into the crude oil if ordinary paraffin dispersant applied. So we designated it as "paraffin" in order to distinguish it from usual paraffin whose main component is aliphatic hydrocarbon or paraffinic wax. The composition of the "paraffin" and the mechanism of its deposition were studied in the laboratory by means of analytical techniques.
At first, "paraffin" was divided into six components, i.e., oily hydrocarbon, paraffin, petrolene, asphaltene, carbene and carboid, by their selective solubility in organic solvents. Then the relative content of each component and the ratios of petrolene/carboid and carboid/paraffin were calculated for reference. Next, the same experiments were carried out with regard to several topped crude oils including Minamiaga crude oil.
As a result, it was clarified that the main component of the Minamiaga "paraffin" is carboid which is insoluble in any organic solvents, and that the petrolene/carboid ratio of the Minamiaga crude oil is far smaller than those of the other oils where paraffin problems are less serious.
Conclusively, the leading role of the "paraffin" trouble at the Minamiaga field is not paraffin but carboid, and relatively low content of petrolene in the Minamiaga crude oil seems to make the problem more difficult.
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