Structural Features And Hydrocarbon Accumulation In The Piedmont Zone On The Northeastern Margin Of Junggar Basin

The relation among structural evolution and hydrocarbon accumulation in piedmont zone on the northeastern margin of Junggar basin and adjacent orogenic belts, is a hot issue on tectonic geology and petroleum exploration in piedmont zone of Western China in recent years.According to the structural geology,interpretation of seismic profile and subsidence history,structural features and structural deformation styles have been presented. Additionally, the source rock, hydrocarbon accumulation period, hydrocarbon accumulation assemblage and favorable exploration areas are discussed.(1)According to the field geological survey,well-log geology and zircon U-Pb dating, the periods of the pyroclastic rock in Dibei 1 well and of the coal-bearing series in Zhaheba outcrop section are clear, as well as their stratigraphic horizons belonging. Also, the regional stratigraphic correlation and tectonic sequence framework are built.(2)By the seismic profiles calibrated with the sequences of Dibei 1 well,the structure style of fold overthrust belt running from north to south in the Wulungu and Dibei high,which has experienced multi cyclical extrusion and strike slip since early-middle Hercynian deformations,should be attached the Altay and Almantai thrust nappe structure.(3)By the differential uplifting-subsidence history of the piedmont zone on the northeastern margin of Junggar basin and adjacent orogenic belts, after the ocean-continent transition of the late Carboniferous to early Permian,the basin-range differential uplift were proposed: the mountain uplift and the basin subsided slowly from late Permian to early Jurassic, the basin-range has be uplifted with different elevated degree since Cenozoic.(4)Based on the conditions of source rocks, reservoir rocks, and structural traps,Three potential reservoiring assemblages of the early and middle Carboniferous,the middle and late Triassic , the early and middle Jurassic are predicted to exist. Additionally,the Wulungu-Dibei high and the north slope of it is the important destination of oil and gas migratory concentration, Dibei-2 and Dibei-4 fault anticline are the favorable exploration targets.