陆相盆地油页岩成矿规律:以东北地区中、新生代典型盆地为例

油页岩作为常规油气的重要替代或补充能源,在全球资源战略中的地位日益彰显。为了更好地揭示我国陆相油页岩的特征与分布规律,在总结多年油页岩勘查成果的基础上,分析了东北地区松辽和桦甸典型含油页岩盆地矿床特征及成矿特点,揭示了陆相坳陷与断陷盆地油页岩成矿规律。油页岩主要发育于三级层序的高水位体系域和水进体系域;古气候和沉积环境对大型坳陷盆地油页岩的形成有重要的控制作用,温暖湿润的气候条件使湖泊自身生产力大大提高,为油页岩形成提供丰富的物质基础;油页岩的平面分布受控于沉积环境的变化,主要分布于深湖—半深湖相,盐度较高使水体处于盐度分层,有利于有机质保存。构造条件对小型断陷盆地油页岩成矿起着至关重要的控制作用,通过控制可容纳空间而影响了油页岩的厚度分布及品质特征,油页岩主要富集相带为靠近控盆同生断裂一侧的半深湖—深湖环境,且靠近控盆同生断裂一侧油页岩厚度明显加厚和含油率增大;同时,干湿交替的气候控制了油页岩的层数和保存条件。对比分析表明:坳陷含油页岩盆地规模多为大型,油页岩矿单独存在、分布面积大,以中薄层中低含油率为典型特点;断陷含油页岩盆地规模多为小型,油页岩矿单独存在或与煤相伴生,以薄层高含油率或巨厚层中等含油率为典型特点。在三级层序的水进和高水位体系域中,有机质丰度和湖泊生产力较高,层状藻和结构藻较为繁盛,外源输入较低、水体盐度较大、还原性较强,且呈碱性环境,是油页岩形成的有利时期。因此,古构造、古气候和沉积环境综合控制下的丰富有机质来源和良好的湖水盐度分层是油页岩有机质富集的有利因素。

Metallogenic Regularity of Oil Shale in Continental Basin:Case Study in the Meso-Cenozoic Basins of Northeast China

As an important replacement or supplement energy for traditional oil & gas,the position of oil shale in global strategy becomes more and more obvious.In order to reveal the characteristics and distribution regularity of oil shale in continental basins better,based on the summary of exploration results of oil shale for many years,the deposit and metallogenic characteristics of typical oil shale bearing basins such as Songliao and Huadian basin in Northeast China have been analyzed,and the metallogenic regularity of oil shale in continental depression and fault basins has been revealed.It is shown that oil shale mainly developed in HST and TST within the third order sequence.Paleoclimate and sedimentary environment play important control action on oil shale formation in large scale depression basin,warm and humid climate greatly improves the lake productivity,which provides abundant materials for oil shale formation.The distribution of oil shale changes regularly by the evolution of the lake,oil shale mainly deposit in semi-deep to deep lake,high salinity causes the salinity stratification of the lake water,which is benefit for organic preservation.Tectonic conditions play a vital control action on oil shale mineralization in small fault basins,which affect the thickness distribution and quality characteristics of oil shale by controlling the accommodation.The accumulation belts of oil shale locate in semi-deep to deep lake close to basin-controlling contemporaneous fault,and oil shale obviously thicken and the oil yield increase near by the side of fault.Meanwhile,the altering wet and dry climate controls the number of layers and the preservation conditions.Comparative analysis indicates that the scale of depression oil shale bearing basin is large,oil shale exists alone,the distribution area is large,and characterized by thin-middle layer and low-middle oil yield.The scale of fault oil shale bearing basin is small,oil shale exists alone or associated with coal,and characterized by thin layer and high oil yield or thick layer and middle oil yield.During the period of HST and TST within third-order sequence,the organic matter abundance and lake productivity are higher,the stratiform and texture algae are relatively prosperous,exogenous input is relatively low,the water salinity is higher,the reducibility is stronger and the environment is alkalinity,which are the favorable periods for oil shale formation.Therefore,the abundant organic matter and favorable lake salinity stratification that are comprehensively controlled by paleostructure,paleoclimate and sedimentary environment are restrictive factors for the organic matter enrichment of oil shale.