苏丹M盆地高酸值原油有机酸的组成与分布

Component and distribution of organic acid oil with high TAN,M Basin,Sudan

苏丹M盆地是苏丹乃至整个中、西非剪切带最富含油气的盆地之一，发现的原油主要为中质油（重度为20～34°APD，其次为重质油（重度小于20°API），普遍高含沥青质、高含蜡、高凝固点、高酸值、低含硫。为了给高酸值原油的储运及加工利用提供科学依据，选择M盆地Fula North-3井Bentiu组产出的典型高酸值原油样品，进行不同馏分有机酸成分解剖。结果表明，高酸值原油的有机酸主要由环烷酸组成，且主要分布在300℃以上的重质馏分中；环烷酸的分子量分布情况与馏分的沸程趋势相一致，随着馏分变重、酸值增加，环烷酸的平均分子量增大、分布变宽、碳数范围增大；环烷酸结构以一环、二环、三环为主。

M Basin has the most prolific hydrocarbons in central Sudan, even in the whole shear zone of the middle and western Africa. The effective hydrocarbon source rocks of the basin are believed to be the Lower Cretaceous lacustrine shales deposited during the synrift stage of the basin evolution. Most of the oils are normal oil with 20-34°API; the others are heavy oil with 〈20°API. All oils are with a low sulfur content, high asphaltene, high wax, high pour point, and high total acid number, especially in Bentiu reservoirs. The primary geochemical analyses indicate that biodegradation is the key genetic factor for high TAN crudes. Organic acid from high TAN crudes is mainly composed of naphthenic acid which is mainly distributed in the more than 300℃ fractions with mono-, bi-, tri- cycles. As fraction becomes heavier and acid value increases, the average molecular weight of naphthenic acid increases, its distribution gets wider and the carbon number range increases. The research results will be useful to crude transportation and processing.