The Structure Feature And Oil-gas Distribution In Southern Margin Of The Junggar Basin

The southern margin of the Junggar basin has good petroleum geological conditions, and has huge exploration potential. It has become the hot area in oil-gas exploration in the western of China. After about half century studing, there have been found a large number of oil and gas fied. However,it had been affected by Hercynian structure,Indosinides,Yanshan structure,and Himalayan structure, results the structure of the southern margin of the Junggar basin become very complexly, this condition causes difficulties seriously for oil-gas exploration. So we must study the structural feature, structural evolution and the relationship between the evolution and oil-gas, this will be favour of the study in western exploration and the research in hydrocarbon accumulation of foothill belt. In addition, clear the potential and direction of exploration furtherly can afford reference for seismic and the arrangement of wells, these will be speed up the oil-gas exploration for foothill belt of southern margin in Junggar basin.This article uses plate tectonic theory, structural geology, petroleum geology and analysing for petroliferous basin, based on the structural feature and structural evolution of foothill belt, discusses the tectonic active affection for layers, structural feature and style, the buildup of oil-gas reservoir.The structure is too compecated,because it had been affected by Hercynian, Indosinian, late Yanshan, late Himalayan tectonic movement, so the structure is multi period, diversity and complexity. Because of this, this article proposes that the main structure is abnormal fault, the partial is compresso shear strike-slip fault and little normal fault in the area. And according to the plane features of the faults, divides the faults into four styles : north-east faults, north-west faults, nearly latitudinal direction faults and arc-like faults which from Tianshan Mountain’s the orogenic zone and the basin margin foothill belt, the four styles faults are differences in surface distribution and formation period. In addition, on the basis of the bend degree and the fold shape, this article summarizes the structure style of the study area, and divides the structure style into two style: base involved and cover sliped, furtherly divides into eight subtypes.The southern margin of the Junggar basin had suffered three structural evolution(fringe faulted depression from Caeboniferous to Early Permian, intracontinental depression from Latel Permian to Jurassic, foreland basin from Cretaceous to late Quaternary), this phenomenon results in many cyclic depositions, and multi-bank oil source, reservoir bed and the cover rock, this article sums up four of these arays. According to the contributing factors, the traps can be classified three types which are structural traps, non-structural traps and multiple traps, furtherly, it can be classified nine subtypes.About the hydrocarbon accumulation and distribution of southern margin of the Junggar basin, the areal uncomformable surface and fault is the migration pathway, positive structure is accumulation location. In cross line, these accumulations distributes in the the foothill belt arch structure regularly. but along with the deposition of new formations and the change of preservation conditions, the accumulation of layers become more and more new from foothill belt to basin.