Structural Feature Of Foreland Thrust Belt And Petroleum Accumulation At The North-Eastern Margin Of Jungger Basin, China

The Junggar basin is a Mesozoic and Cenozoic sedimentary basin developing upon the dual basement of Precambrian crystalline basement and Palaeozoic folded basement.The Carboniferous-Permian,the northeastern margin of Junggar Basin is in the stage of marine-continental transition phase and basin evolution.The marine,interactive marine and terrestrial deposit,terrestrial source rocks and volcanic rocks are developed.The paper focused on structual and sedimentary characteristics of the northeastern foreland thrust belt in Junggar Basin.From the aspects of materials,time and space to discuss the development of petroleum systems in the Jungger Basin.The paper comes into several conclusions:1) The northeastern margin of Junggar Basin was in the transitional stage of post-collisional compression to extension,not the rifted setting;it developped peripheral foreland basin since early Carboniferous to early Permian and the scale was not so large.2) Combining with the analysis of unconformity and seismic interpretation,bulit the tectonic sequence framework of the northeast margine of Junggar Basin.3) The northeast margin of Junggar Basin can be devided into three segments:the western,the middle and the eastern.The western tectonic style was mainly characterized with "basement-involved and imbricated thrust";the middle was "basement-involved and fault-propagation fold",lack of large fault but full of tight anticlines and faulted anticlines;the estern tectonic style was "basement-involved",the faults and folds were weak developped than the former parts.4) The thrust belt in northeast margin of Junggar Basin showes that:the collision of the western was earlier,stronger and the direction of the collision was mainly south-north while the eastern showed the feature as later,weaker and the direction mainly west-east.5) The oil and gas of Carboniferous are mainly near to hydrocarbon parts and the late volcanic reservoir reconstruction is a necessary condition for hydrocarbon accumulation. Carboniferous hydrocarbon reservoirs have two probable migratory mode,"C₁—C₂b Oil vertical migration","C₂—C₂b Gas vertical migration" and three conceptual plays, "sandy-conglomerates of the Upper Carboniferous","the interior interval of the Upper Carboniferous volcanic rocks" and "sandy-conglomerates of the Lower Carboniferous".The results show that the prospect of oil and gas exploration is bright.Dajing and Wutongwozi depression,comparing with the Wucaiwan depression,have the same good source rock-reservoir-cap rock combination and are the key area for the further exploration breakthrough.