鄂尔多斯盆地延长组烃源岩17α(H)-重排藿烷的组成及分布研究

摘要

以鄂尔多斯盆地陕北地区延长组下油层组烃源岩及储层抽提物为研究对象,探讨了17α(H)-重排藿烷和18α(H)-新藿烷系列化合物的分布规律、影响因素及在石油地质中的应用.鄂尔多斯盆地延长组湖相烃源岩普遍分布170t(H)-C30重排藿烷(C30DiaH),但研究区各层烃源岩之间C30DiaH的相对丰度存在明显差异,深湖相缺氧环境的长7烃源岩相对丰度较低,而浅湖-半深湖相偏氧化环境的长7-长9黑色泥岩具有高-异常高的C30DiaH.Ts、C29Ts、早洗脱重排藿烷与C30DiaH之间表现出良好的正相关关系,说明在研究区重排藿烷类化合物可能与新藿烷系列具有相同的演化路径与形成机制.环境的氧化还原性和陆源的有机物来源等可能是制约17α(H)-重排藿烷相对丰度的主要因素,因此,不同油层组原油的17α(H)-重排藿烷相对丰度受到烃源岩的影响,用17α(H)-重排藿烷参数能很好地把研究区原油区分开来,为延长组不同油层的油源精细对比、油气富集规律和油气勘探提供可靠依据.%Based on the analysis of source rock and reservoir extracts in the lower part of the Yanchang Formation in the Ordos Basin,North Shaanxi,this paper describes the distribution rules,influencing factors and applications in petroleum geology of 17α(H)-diahopane and 17α(H)-neohopane.Relatively high abundances of 17α(H)-C30diahopane(C30DiaH) were detected in black mudstone,while various types of 17α(H)-diahopane were observed in different hydrocarbon source rocks of the Yanchang Formation in the Ordos Basin.The results showed that the black mudstone was deposited under anoxic condition of semi-deep or deep lacustrine facies has a low abundance of C30DiaH in the Chang-7 member.By comparison,the black mudstones with moderate-high abundances of C30DiaH in Chang-7 member to Chang-9 member were deposited under suboxic condition of shallow to semi-deep lacustrine facies.The extracts of black mudstones have moderate to high contents of C30DiaH with the high abundances of Ts,C29Ts and early-elution rearranged hopane,so the novel series of rearranged hopanes possibly has the same path and formation mechanism.The high concentrations of 17α(H)-diahopane may have relationship with the sedimentary environment and organic matter type.Therefore,according to the relative abundances of 17α(H)-diahopanes,the correlation between oil and source rocks was carried out in terms of 17α(H)-diahopane parameters.The geochemical significance of 17α(H)-diahopane lies in the fact that the oil-source correlation of the study area can be effectively solved,thus contributing to a better understanding of hydrocarbon generation and accumulation mechanisms and providing a better model for further petroleum exploration.