Regularity Of Mineralization And Resources Potential Of Oil Shale Of Qingshankou Formation In Songliao Basin

The reserves of oil shale are very rich in our country. The proved reserves is the fourth in the whole world from2003to2006, the oil shale was the first time to be evaluated as unconventional oil and gas resources by national evaluation system in a national project named "a new round of oil and gas resources evaluation" organized by the Ministry of Land and Resources, National Development and Reform Commission and the Ministry of Finance. Songliao Basin is one of regions where have most abundant of oil shale resources. The shale oil reserves of Songliao Basin are15.4billion tons. Its reserves take about96%account of the whole reserves in the Songliao Basin and its peripheral Basins. The Oil shale of Songliao Basin is occurred in the first section of Cretaceous Qingshankou Formation and the first and second section of Nenjiang Formation. In this study, this main point is focused on establishing the sequence stratigraphic framework and analysising metallogenetic laws and resources potential of oil shale in Qingshankou Formation of Songliao Basin.In this study, based on theoretical methods, such as sequence stratigraphy, sedimentology, reservoir geology and an analysis of data through well logging, core etc, the sequence stratigraphic framework and sedimentary facies of Cretaceous Qingshankou formation in Songliao Basin were studied and analyzed. Sequence stratigraphic framework was established on the basis of previous research achievements for reference. Qingshankou formation was dividied into three three-level sequences, which are SQ1, SQ2and SQ3from top to bottom. Oil shale in the first section of Qingshankou formation was formed by anaerobic condition of semi-deep-deep lacustrine facies which provided preservation condition of material base and organic matter. Oil shale mainly grew in the middle-lower part of descending half-cycle in three-level sequences SQ1which usually formed nearby the biggest flooding surface. Oil shaleis usually considered as condensed section (CS) in stratigraphic sequence in the period of biggest flooding surface. It indicates under-compensating state of basin and represents slow process of sedimentation. Black oil shale in the first section of Qingshankou formation corresponds to the biggest lake transgression of variation curve of datum level in Songliao Basin. It shows that oil shale was the products of this basin in the period of biggest flooding surface.Ancient structure, climate and sedimentary environment are main controlling factors for mineralization of oil shale in Songliao Basin. Through this study, it is believed that ancient structure is a crucial factor of controlling development of stratigraphic sequence and it controls sedimentary features of a whole basin. Moreover, flourishing terrestrial plant in damp and warm climate provided plenty of terrestrial materials for lakes. These materails provided material base to produce oil shale and controlled its formation and preservation with anaerobic sedimentary environment of semi-deep-deep lacustrine facies. Besides, in this study, the crucial factors of mineralization of oil shale were analyzed, its mineralization regularity was summarized and mineralization mode of Songliao Basin was established.Based on the full extent of geological exploration, geological characteristics of oil shale and temporal and spatial distribution, which used for certainty and evaluation of optimum area, burial depth, thickness of oil shale and oil content were believed as main evaluation indices to establish optimum programs of favorable target area for oil shale in the first section of Qingshankou formation.