准噶尔盆地南缘凝析油、蜡质油与稠油的形成机理

发布时间：2018-04-26 12:14

本文选题：凝析油 + 蜡质油　；参考：《中国科学:地球科学》2017年05期

【摘要】：对于发育多套不同成熟度烃源岩、存在多种类型原油及天然气的复杂含油气区,如何准确判断油气来源与成因一直是非常困难的事情.准噶尔盆地南缘中部地区存在正常原油、轻质油、凝析油、蜡质油和稠油,同时也发现了大量天然气,长期以来对该地区凝析油的来源与成因一直存在很大争议,而对于蜡质油与稠油的形成则几乎没有研究.本文以该地区为研究实例,探讨复杂油气区凝析油、蜡质油与稠油成因判识地质地球化学方法,揭示该地区多种类型原油并存的原因与地球化学过程.南缘中部地区40多个原油、轻质油、凝析油和稠油化学组成及其变化特征精细分析对比表明,该区凝析油以低碳数正构烷烃为主,含有丰富的环己烷、甲基环己烷等环烷烃和苯、甲苯、二甲苯等低碳数芳烃,庚烷值在19~21%,异庚烷值在1.9~2.1,甲苯/正庚烷比值在1.5~2.0之间,其烷烃的分布与高密度蜡质原油和稠油呈镜像关系.结合该区原油、凝析油油源及天然气气源对比结果认为,该区凝析油是白垩系湖相烃源岩生成的成熟原油油藏,在后期遭受了侏罗系生成的高成熟天然气气侵改造的产物,为蒸发分馏/相控运移分馏作用形成的凝析油.蜡质油是蒸发分馏/相控运移分馏作用过程的中间产物或阶段产物,稠油是蒸发/相控运移分馏作用的残留物.蒸发/相控运移分馏作用是南缘凝析油、蜡质油、稠油形成的主要成因机理,其导致油藏原油及凝析油的正庚烷、甲基环己烷、甲苯等轻烃化合物含量发生很大变化,使凝析油的甲苯/正庚烷等比值具有很大的不确定性.因此,不能依据凝析油中甲苯/正庚烷与正庚烷/甲基环己烷比值简单地套用Thompson图版判识其成因,而必须从研究区地质条件、烃源岩成烃演化与生烃历史、各种类型油气分子组成与分布特征、不同物理化学性质油气在纵向及区域上分布等方面综合分析判识凝析油的成因.
[Abstract]:For the development of multiple sets of source rocks with different maturity and the existence of complex oil-bearing regions with various types of crude oil and natural gas, it has been very difficult to accurately judge the source and origin of oil and gas. There are normal crude oil, light oil, condensate oil, waxy oil and heavy oil in the central area of the southern margin of Junggar Basin. At the same time, a large amount of natural gas has also been discovered. For a long time, the origin and origin of condensate oil in this area has been very controversial. The formation of waxy oil and heavy oil is hardly studied. In this paper, taking this area as an example, the origin of condensate, waxy oil and heavy oil in complex oil area is discussed, and the reason and geochemical process of the coexistence of various types of crude oil in this area are revealed. The fine analysis and comparison of the chemical composition and variation characteristics of more than 40 crude oil, light oil, condensate oil and heavy oil in the central part of the southern margin show that the condensate oil in this area is dominated by low carbon number n-alkanes and rich in cyclohexane. Low carbon aromatic hydrocarbons such as methylcyclohexane and benzene, toluene, xylene, etc., the heptane number is 1921, the isoheptane number is 1.9 ~ 2.1, and the ratio of toluene to n-heptane is 1.5 ~ 2.0. The distribution of alkanes is mirrored with high density waxy crude oil and heavy oil. Combined with the correlation of crude oil, condensate oil source and natural gas source, it is concluded that the condensate oil is a mature crude oil reservoir generated by lacustrine source rocks of the Cretaceous system, and has been the product of gas invasion and transformation of highly mature natural gas generated by Jurassic system in the late stage. Condensate formed by evaporative fractionation / phase controlled migration fractionation. Wax oil is the intermediate product or stage product of evaporative fractionation / phase controlled migration fractionation process, and heavy oil is the residue of evaporation / phase controlled migration fractionation process. Evaporation / phase-controlled migration fractionation is the main mechanism of formation of condensate, waxy oil and heavy oil in the southern margin, which leads to great changes in the contents of light hydrocarbons such as n-heptane, methylcyclohexane and toluene in crude oil and condensate. The ratio of toluene to n-heptane of condensate oil is uncertain. Therefore, based on the ratio of toluene / n-heptane to n-heptane and n-heptane / methylcyclohexane in condensate oil, we can not simply apply the Thompson chart plate to judge its origin, but must base on the geological conditions, hydrocarbon generation evolution and hydrocarbon generation history of source rock in the study area. The molecular composition and distribution of various types of oil and gas, as well as their physical and chemical properties, the vertical and regional distribution of oil and gas, etc., are comprehensively analyzed to identify the origin of condensate oil.
【作者单位】：中国石油勘探开发研究院;提高石油采收率国家重点实验室;中国石油天然气集团公司油气地球化学重点实验室;中国石油新疆油田公司;浙江大学地球科学系;
【基金】：中国石油天然气股份有限公司科学研究与技术开发项目(编号:06-01A-01-02,2011A-0201,2014A-0211,2016A-0202)资助
【分类号】：P618.13

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