鄂尔多斯盆地长7段源内夹层型页岩油已取得勘探突破并实现规模效益开发,但泥页岩层系是否具有勘探潜力,页理型页岩油的烃类赋存状态与表征方法仍然不够明确.通过对比页岩层产出的页岩油与滞留烃性质发现,鄂尔多斯盆地延长组长7页岩层产出的页岩油具有中轻质烃类组分(nC25-)显著优势、沥青质组分很低的特征,属于轻质油,而滞留烃中大分子化合物含量较高.各项分析测试与试验研究表明,油质组分与沥青质相容性差,两者赋存状态差异明显,沥青质组分主要被干酪根所吸附,油质组分主要以游离态赋存于孔裂隙中.长7段富有机质泥页岩中较高的沥青质含量不会明显影响页岩油的可流动性.同时建立的"洗页岩中分离提取游离烃的方法",可作为页岩含油性快速评价的实用技术,定量表征结果表明长7泥页岩中游离烃含量较高,平均在5 mg/g左右,页理型页岩油勘探潜力很大.

Chang 8 oil reservoir is one of the most important hydrocarbon accumulation horizons in Jiyuan region of Ordos Basin.However,the research on genesis of the oil is still known little.In this paper,sterane and terpane biomarkers of compounds in oil from the region and source rock from Ordos basin were systematically analyzed.The oil is typical lacustrine-derived oil,with d13CPDB value generally from-31.11 ～-31.57‰.Its terpane distribution was characterized by relatively abundant 17α(H),21β(H) – hopanes.The relative content of C29 hopane of Chang 8 oil in NE migration-accumulation zone was higher,C29Ts takes second.The relative content of C30 rearranged hopane in SW migration-accumulation zone is higher,C30* hopane / C29 norhopanes is greater than 1.The oil contains rich pentacyclic triterpanes,a certain amount of pregnane,homo-pregnane,rearranged sterane and enriches αβ and βα isomers,while ααα-20R sterane isomers display an asymmetric "V"type distribution pattern.The biomarker distributions of the oils show that they were formed under a weak reducing and fresh water environment.The results of oil-source rock correlation showed that the oil was mainly derived from Chang-7 source rock.

The analysis of natural gas composition and carbon isotopes of methane confirms the existence of biogenic gas around the Tertiary Pliocene series and the Quaternary Pleistocene series in the Hetao basin. Detailed organic geochemistrcal data shows that the biogenic gas source rock of the middle and upper Pleistocene series in this area contains a high content of organic matters and typesⅡ2 and Ⅲ kerogens. The organic matter in the biogenic gas source rock is in low-mature stage, which is benefit for the formation of biogas. In addition, this article establishes a generation-evolution model of biogas, taking into account the region geology feature and temperature affection on the biogas generation, and puts forward that the best vertical extent for biogenic gas formation in the Hetao basin is in the middle of the Quaternary Pleistocene series, between 685 meters and 926 meters.

The Upper Paleozoic natural gas in the napped belt of the western margin of the Ordos basin is coal measure gas with lower non-hydrocarbon and higher hydrocarbon component concentrations.Based on the horizontal and vertical distribution of the Ro values of organic materials in the Taiyuan Formation,together with the evolvement characteristics of the tectonics,it is considered that the formation and accumulation of the natural gas are later than the occurrence of the napped belt(Late Jurassic),and the hydrocarbon mainly migrates vertically.The vertical change of the natural gas geochemical characteristics indicates that the accumulation is characterized by contemporaneous formation and balanced migration. The strong capability of hydrocarbon expulsion causes carbon isotopes of methane in natural gas relatively heavy.