鄂尔多斯盆地中部延长组烃源岩生物标志化合物特征

1.陕西延长石油(集团)有限责任公司研究院,陕西 西安 710075; 2.西安石油大学 地球科学与工程学院,陕西 西安 710065

鄂尔多斯盆地; 延长组; 烃源岩; 生标参数; 母质来源

Biomarker characteristics of hydrocarbon source rocks of Yanchang Formation in central Ordos Basin
DONG Li-hong1,DU Yan-jun1,LI Jun2,HE Bin1

(1.Research Institute of Shananxi Yanchang Petroleum(Group)Co.,Ltd.,Xi'an 710075,China; 2.School of Earth Sciences and Engineering,Xi'an Shiyou University,Xi'an 710065,China)

Ordos basin; Yanchang Formation; source rock; biomarker parameter; organic matter origin

DOI: 10.13800/j.cnki.xakjdxxb.2018.0413

备注

鄂尔多斯盆地三叠系延长组原油和烃源岩的有机质组成、沉积环境和演化程度相近,以往采用正构烷烃、类异戊二烯烷烃、甾萜烷等生物标志化合物进行精细油源对比还存在着一定的困难。文中对鄂尔多斯盆地中部三叠系延长组长7~长9油层组三套烃源岩的生物标志化合物参数的系统精细研究,优选特征参数,对烃源岩的成熟度、沉积环境及母质来源进行分析。研究发现:C29甾烷ββ/(ββ+αα)、C29Ts(C29藿烷+ C29Ts)、C*30/(C*30+C30藿烷)、姥植比和甾烷ααα20RC29/C27在表征研究区三套烃源岩成熟度及母质来源方面具有较好的效果。C29甾烷ββ/(ββ+αα)和C29Ts(C29藿烷+ C29Ts)反映研究区不同层位成熟度差异不明显,但同层位不同地区存在差异,志丹县以东的靖边-安塞地区较低。C*30/(C*30+C30藿烷)、姥植比和ααα20RC29/C27甾烷显示不同层位烃源岩的沉积环境、母源输入有差异,长7和长8油层组烃源为弱还原-弱氧化条件下的半深湖-浅湖水生生物输入为主,长9油层组烃源岩以氧化-弱氧化条件下的湖沼高等植物输入为主。

The organic matter composition,sedimentary environment and evolution degree of the oil and source rocks in the Triassic system of ordos basin are similar.In the past,it is difficult to compare the fine oil source with nalkanes,isoprene alkanes,steroid and other biomarkers.We studied on biomarker characteristics data and optimize parameters of source rock from Chang 7,Chang 8 and Chang 9 oil bearing formation of Yanchang formation,Triassic in Odors basin.The article analysed maturity,depositional environments and organic matter origin and summarized biomarker characteristics of source rock from each formation in different block.The research indicates that the biomarker parameters including C29sterane ββ/(ββ+αα),C29Ts(C29hopanes+C29Ts),C*30/(C*30+C30hopanes),ratio of pristane to phytane and sterane ααα20RC29/C27 are of preferable applicability in characterizing maturity and organic matter origin of the three source rock formation.The maturity deviation from different source rock could not be apparently reflected by the parameter C29sterane ββ/(ββ+αα)and C29Ts(C29hopanes+C29Ts)in majority area.In the area of Jinbian-Ansai,next to the west of Zhidan county,the source rock's maturity stays relatively low degree.The parameter of C*30/(C*30+C30hopanes),ratio of pristane to phytane and sterane ααα20RC29/C27 indicates that source rock possess different depositional environment and the original composition of organic matter in each formation.Source rock from Chang 7 and Chang 8 deposit in semi-deep lacustrine environment to lake shore environment,is in weak-reduction and weak-oxidation condition.Original organic matter is mainly made up by aquatic life.Source rock from Chang 9 deposit is in lacustrine-swamp environment with weak-oxidation condition,its original organic matter is mainly made up by plant from lacustrine-swamp.