Structural Features And Depositional Systems In Southeastern Junggar Basin

The tectonic evolution and sedimentary characteristics of the southeast of Junggar Basin is an important problem that constrains the oil and gas exploration, especially the formation of the Beisantai raised and its controlling of the sedimentary facies belt. Addressing these issues, this paper has studied the features of tectonic evolution of the southeast of Junggar Basin and the sedimentary system such as Jurassic and Cretaceous.On the fault throw and fault activity rate show that the main fault system of Permian is north-west. As to the Triassic– Jurassic period, development of the north east is the main fault system. While to the Neogene period, the development of the east-west is the main fault system. Adopting transit time method to recover the thickness of eroded strata, we find that the Beisantai raised of the Permian and the Cretaceous has the biggest erosion thickness, while the Fukang fault of the Triassic has the biggest erosion thickness. For Jurassic period, Beisantai area and Fukang fault have the biggest erosion thickness. To sum up, east-west structure is mainly affected by Hercynian and Himalayan tectonic activities, and the north-south trending tectonic is mainly affected by Indosinian and Yanshan tectonic Activities. Among these activities, the Indo-China movement of late Triassic activity is the formation of the checkerboard pattern, while the stage of Yanshan is the final stereo period.Through the core, drilling, well logging and seismic, geochemical data analysis, the J2t in southeast of Junggar basin developmental delta depositional system, Northern Shaqi uplift in the provenance primarily, and water expands gradually semi-deep-lake to deepen Beisantai's bulging sunk in underwater.J3q is the delta depositional system, give priority to with resources in the sounth of Tianshan, the influence of Yanshan I curtain, Beishantai's bulging scale increases, research area whole rise, water becomes shallow, dry climate, lakes smaller range. Qingshuihe period, eastern Junggar basin continued to rise, Semi-deep-lake to shrink dramatically, depth becomes shallow and partition becomes shallow water atrophy, sharply, Beisantai's bulging exposed the surface of the water and providing material sources. Then the transition from bottom of fan delta for delta depositional system.Through comprehensive analyzing the tectonic evolution and sedimentary characteristics, the larger fault throw region and intensive active faults development zone are the delta's main position into the lake. Breaking direction control the delta lobes body extension into the lake square, gravel rock concentrated development near the active fracture, gravel rock exhibition cloth long axis direction is consistent with the fault strike. Steep bank folding belt due to limited the provenance and the dispersive water, easy to form small fan delta. Gentle slope belt enhanced the provenance effects, it can form flower shape delta. The distribution of gully restricts sand body position, big ditch to big fan, small groove on small fan. Toutunhe period the North Slope of the basin is in a combined mode of heave - valley - gentle slope– depression. This place can develop large-scale Delta system and is the best reservoir development area. The main part of the front branch of delta has good physical properties, while gradually deteriorated to the end of the direction. The large-scale of the north delta has better physical properties than the small part of the south delta, while the front of the branch delta is better than the end of the branch .