Research Of Tectonic Modeling And Petroleum Accumulation Elements For South Margin Of Junggar Basin

On the basis of adopting and analyzing comprehensively the available results, geology and seismic data as well as core data, this paper is focused on the analysis of strata and sedimentary facies character distribution of south margin of Junggar basin, and on the studies of structure frameworks and development of foreland overthrust belt. On the basis of summarizing research of tectonic patterns, it classifies and evaluates the tectonic patterns existed in south margin of Junggar basin. By using the theory of fault-related fold and kinematics characters, research of tectonic modeling about local structures of south margin of Junggar basin was made. According to petroleum geology theories, testing, drilling and logging data, as well as petroleum accumulation and petroleum system theory etc., this paper presents the analysis and evaluation of the petroleum accumulation elements and the potential oil and gas structures.The tectonic patters of south margin of Junggar basin are composed of the composition of faults and folds mostly. The prominent tectonic pattern is anticline structure which is one kind of fold tectonics. Its distribution feature is anticlines exist row by row from front mountain to basin: in the west part of south margin of Junggar basin, the structural axis mainly goes west-northwest and the action of fault thrusting and strata folding are relative weak; in the central part of south margin of Junggar basin, the structural axis mainly goes east and the action of fault thrusting and strata folding are relative strong; in the east part, the structural axis goes northeast, east and northwest, and the action of fault thrusting and strata folding are medium.Three known petroleum systems were identified in the south margin of Junggar basin after our research, which are Permian petroleum system, Jurassic petroleum system and Tertiary petroleum system. This paper points out that the petroleum accumulation elements depend on the following four aspects: First is paleo-tectonics that controls the rules of petroleum migration and accumulation, and faults as main channels of oil and gas migration. These two aspects are essential to forming secondary reservoirs. Second one is the effective reservoir located in Fm AnJihai andits buried stratum, which are the most faverable reservoir and target layer. Third one is lower pressure sealed-box in the lower part of mudstone that is faverable to pertoleum accumulation. Fourth one is the structures formed in YanShanian Movement and not changed relatively in Himalayanian Movement, which are faverable to petroleum accumlation too.It is considered that three petroleum accumulation combinations exist in the south margin of Junggar basin by our research. They are upper combination, middle combination and lower combination. This paper sums up four types of petroleum accumulation possibly exist in the area. They are primary reservoir, secondary reservoir, combined reservoir and potential over-pressure sealed-box.It evaluates and selects eleven structures to be drilled for oil and gas exploration. These structures are Kadong anticline, Xihu anticline, Tugulu anticline, Dongwan anticline, Gaoquan anticline, Huoerguosi anticline, Manasi anticline, Well Fu-3 Faulted Nose, Anjihai anticline, Gumudi subtle anticline and Gumudi anticline. It would bring opportunity and development of oil and gas exploration in south margin of Junggar basin to drill these structures.