辽河超稠油的化学组成特征及其致黏因素探讨

INVESTIGATION ON THE COMPOSITION OF THE EXTRAHEAVY OIL IN LIAOHE OILFIELD AND THE CAUSE OF ITS HIGH VISCOSITY

基于对辽河油田2个超稠油化学组成的系统剖析,研究了辽河油田超稠油的致黏因素,以及化学成分的结构类型、极性和相对分子质量大小对稠油黏度的影响。结果表明,辽河盆地曙光油田超稠油具有成熟度低,胶质、沥青质含量特别高,低相对分子质量组分特别少,并且遭受过严重生物降解等特征。胶质和沥青质的总质量分数接近70%,尤其是沥青质质量分数在40%以上,明显高于国内一般稠油。气相色谱可检测物的总质量分数在饱和烃、芳烃馏分中低于22%,在酸性非烃和中性非烃馏分中分别低于15%和1%。饱和烃中正构烷烃及支链、直链烷烃接近消耗殆尽,GC-MS检测到的几乎全部是孕甾烷、重排甾烷和降藿烷系列化合物。低成熟度和强烈的次生降解作用是其形成的石油地球化学条件,极高含量的大分子组分和极性非烃组分是其具有高黏度的化学组成基础。

Based on a systematic analysis of the chemical composition of two extraheavy oils from Liaohe oilfield,China,together with investigations on the influence of class,polarity and molecular mass of components to the viscosity,chemical character and causes of the high viscosity of the oil were discussed.The results showed that the heavy oils contained mainly polar hetero-components and high molecular mass components due to that their organic matter was low mature and had suffered from extreme biodegradation.The content of resin and asphaltene in the oil was as high as 70% together and reached 40% for asphaltene fraction alone,which was much higher than that in heavy oils from other oil reservoirs of China,while the content of GC amenable components was very low,which was accounted less than 22% of the aliphatic and aromatic hydrocarbon fractions,and less than 15% and 1% of the acidic and neutral hetero-component fraction respectively.Only trace acyclic alkanes were detected by GC-MS in the aliphatic hydrocarbon fractions,while compound serials of pregnanes,diasteranes and norhopanes dominated.It was concluded that low maturity and microbial,chemical,as well as physical alteration of the composition of the oil were the main petrogeochemical conditions for the formation of extraheavy oils,and the extremely high content of high molecular mass components and hetero-components in the oil was the chemical basis of its high viscosity.