Abstract:

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.

Key words: continental oil shale, depression basin, fault basin, metallogenic regularity, metallogenic model, Northeast China, oil shale