Analysis And Evaluation Of Mesozoic Intermountain Basins (Groups) In Western Liaoning And Its Peripheral Areas

Here in the western part of Liaoning Province at the eastern end of Yanshan Mountains,the NNE-trending linear rift basins are clustered on the E-W fault block uplift.They are Mesozoic basin groups formed in Middle and Late Jurassic,evolved to Early Cretaceous and terminated in Late Cretaceous——Mesozoic Basin Group in Western Liaoning.The driving force is the destruction of the North China Craton by the subduction of the Western Pacific Plate since the Mesozoic.Studies suggest that the North China Craton was destroyed in the Middle and Late Jurassic(108-155 Ma),Large-scale magmatic activity and partial lithospheric thinning may occur in the Early Cretaceous(130-120 Ma).Deep-seated destruction shows that the eastern craton block has changed from a thick craton low geothermal "stable continental lithosphere" to a thin high geothermal "active continental lithosphere".This causes the gradual loss of cratonic properties of the eastern continental block.The shallow tectonic response is marked by extensional processes,such as the formation of Songliao-Western LiaoningNorth China/Bohai Bay rift basins and the appearance of metamorphic core complexes.This reflects the transformation of tectonic system and basin-range pattern from compression to extension and from East-West to north-east.Songliao-Liaoxi-Bohai Bay/North China Basin is a large Mesozoic-Cenozoic rift basin which is rich in oil and gas resources in eastern China.They have a generative relationship with each other.According to the stratigraphic sequence of filling basins,the basins in Western Liaoning are in the lower position.It is a Mesozoic Intermountain residual basin occurring in the regional uplift zone.Geological survey and research show that source rocks,oil seedlings and oil and gas show on the surface or shallow surface.For example,oil sand grade oil Seedling were found in the outcrop of Siguanyingzi Basin,Kazuo Basin.In Niuyingzi Coal Mine of Lingyuan,small amount of crude oil seeps out from coal seam in many coal wells.Songliao Basin is in the middle,Bohai Bay Basin is in the upper,oil and gas pools are deep in the ground kilometers-kilometers below.According to tectonic and sedimentary evolution,the Mesozoic basin group in Western Liaoning is classified as early Mesozoic(T_J)basin group and early Late Mesozoic(K1)basin group,including T_K1 diachronic basin.The early Late Mesozoic basin group(K1)is a series of geese with uplifts and depressions along the NNE direction.Geological survey and research show that the Jurassic and Lower Cretaceous of the Mesozoic basin group in Western Liaoning have favorable conditions for oil generation,reservoir and cap formation.Moreover,Beipiao Formation,Jiufotang Formation and Shahai Formation are identified as the main targets for oil and gas exploration.That is to say,the existence of Beipiao Formation,Jiufotang Formation and Shahai Formation in the basin group in the study area is the material basis for comprehensive basin evaluation.Based on the comprehensive analysis of regional tectonic conditions,sedimentary facies conditions,source-reservoir-cap assemblage conditions and geochemical indicators of source rocks,It is confirmed that Kazuo-Jianchang Basin,Fuxin-Yixian Basin,Lingyuan Basin and Jinlingsi-Yangshan Basin are the dominant basins for comprehensive index conditions of hydrocarbon evaluation.