鄂尔多斯盆地伊陕斜坡长9烃源岩特征与生烃潜力

Characteristics and Hydrocarbon Generation Potential of Chang 9 Source Rocks on Yishaan Slope,Ordos Basin

鄂尔多斯盆地伊陕斜坡发现多个长9烃源岩邻近的下组合含油有利区,为推进该区下组合石油勘探,亟需深化长9烃源岩特征及生烃潜力研究。利用测井、录井和岩心资料,分析研究区长9烃源岩分布特征。应用岩石热解、总有机碳、干酪根显微组分分析及饱和烃色谱-质谱生物标志化合物分析等方法,研究长9烃源岩地球化学特征与生烃潜力。结果表明,长9_(1)烃源岩在吴起、靖边、志丹、安塞等地区均有分布,厚度最大超20 m。长9_(2)烃源岩主要发育在甘泉—洛川地区,厚度最大超12 m。长9烃源岩有机质丰度较高,有机质来源于低等水生生物和陆源高等植物。有机质类型以Ⅰ型和Ⅱ_(1)型为主,处于成熟阶段,烃源岩生烃转化率高、生烃能力较强的区域主要为志丹—安塞地区。长9烃源岩多数为较好—好烃源岩,少数为优质烃源岩,具备较强的生烃能力和排烃能力,为伊陕斜坡延长组下组合石油聚集成藏提供了物质基础。

A number of favorable oilbearing areas have been discovered in the lower assemblage adjacent to the Chang 9 source rocks on Yishaan slope,Ordos basin.In order to promote the petroleum exploration of the lower assemblage in this area,it is urgent to deepen the research on the characteristics and hydrocarbon generation potential of the Chang 9 source rocks.The distribution of the Chang 9 source rocks were analyzed using well logging,mud logging and core data.The geochemical characteristics and hydrocarbon generation potential of the Chang 9 source rocks were studied by various methods such as rock pyrolysis analysis,total organic carbon analysis,kerogen maceral analysis,and biomarker analysis by saturated hydrocarbon gas chromatographymass spectrometry.The results show that the Chang 9_(1) source rocks are distributed in Wuqi,Jingbian,Zhidan,Ansai and other areas,with the maximum thickness of over 20 m,and the Chang 9_(2) source rocks are mainly developed in Ganquan-Luochuan area,with the maximum thickness of over 12 m.The Chang 9 source rocks hold a high abundance of organic matters that were originated from lower aquatic organisms and terrestrial higher plants.With TypeⅠandⅡ_(1) organic matters in dominance,which are in the mature stage,the Chang 9 source rocks exhibit high hydrocarbon conversion rate and especially strong hydrocarbon generation capability in Zhidan-Ansai area.The Chang 9 source rocks are mostly good and locally highquality rocks with strong hydrocarbon generation and expulsion capacities,which provides a material basis for hydrocarbon accumulation in the lower assemblage of Yanchang formation on Yishaan slope.