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通过对哈拉阿拉特山地区不同地质单元不同层系原油(油砂)色谱、色质等地球化学分析,系统解剖了原油的地球化学特征。根据原油的母质类型、沉积环境、成熟度和C20、C21、C23三环二萜烷分布特征,划分为3种成因类型:Ⅰ类原油分布在浅层超剥带和逆冲推覆带浅部,为风城组烃源岩生成的低熟—成熟油,强烈生物降解,正构烷烃分布不完整,三环二萜烷呈上升型,高伽马蜡烷,富含β-胡萝卜烷;Ⅱ类原油分布在逆冲推覆带中深部,为风城组烃源岩早期生成的低成熟油,未(或轻微)遭受生物降解,具有明显的植烷优势;Ⅲ类原油集中分布在哈浅20井区超剥带西山窑组,主要为乌尔禾组烃源岩生成的高成熟油,混有少量风城组烃源岩生成的原油,具有姥鲛烷优势,低伽马蜡烷,低β-胡萝卜烷,三环二萜烷呈山峰型。通过山前带地质建模和构造变形分析,提出哈山石炭系逆冲推覆体下发育厚层的风城组烃源岩,其向北可延伸至达尔布特断裂附近,使研究区烃源岩分布扩大了近1 000km2,该认识无疑扩大了研究区的找油范围,对拓展准北缘地区的油气勘探领域具有重要意义。
The geochemical characteristics of the crude oil were dissected systematically through the geochemical analysis of the chromatograms and chromatism of crude oil (oil sands) in different layers of different geological units in the Halaalatang area. According to the type of parent material, sedimentary environment, maturity and the distribution characteristics of tricyclic diterpenes C20, C21, C23, it is divided into three types of genesis: Type Ⅰ crude oil is distributed in shallow super-stripping zone and shallow thrust zone , Low maturity-mature oil generated from source rocks of Fengcheng Formation, strongly biodegradable, incomplete distribution of n-alkanes, tricyclic diterpenes ascending type, high gamma-alkanes and beta-carrot rich Class Ⅲ crude oil distributes deep in the thrust nappe belt and is not (or slightly) biodegraded by the source rocks of the Fengcheng Formation in the early stage. It has obvious phytase advantages. Class Ⅲ crude oil is mainly distributed in the shallow 20 well zone Xishanyao Formation, mainly composed of high-mature oil from the Wuerhe Formation source rock, mixed with a small amount of crude oil from the source rocks of the Fengcheng Formation, has the advantages of pristane, low gamma-alkane, Low β-carotene, tricyclic diterpanes peaked. According to the geological modeling and tectonic deformation analysis in the piedmont belt, the source rocks of the Fengcheng Formation with thick strata under the thrust crust of the Ha-Shan Carboniferous are suggested to extend northward to the vicinity of the Darbott fault, The distribution of source rocks has expanded by nearly 1000 km2. This understanding undoubtedly expanded the oil-finding area in the study area and is of great significance to the exploration of oil and gas exploration in the quasi-north margin.