Accumulation Regularity Of Lithology Reservoirs In Jurassic Baijiahai Area, Jungar Basin

Junggar basin is one of petroliferous basins with large-scale folds in the western of China. And Baijiahai area is located in the east of its center uplift zone. Baijiahai high is a inherited palaeohigh, which is always on the favorable pathway of oil and gas migration. Because of its superior geologic condition, Baijiahai area is a oil and gas accumulated area in the whole basin.This paper focuses on Baijiahai upswell-Fubei slope area, although its oil and gas exploration is rather complex. By guidance of sedimen tology, high-resolution sequence stratigraphy and petroleum geology, h igh-resolution sequence framework is built up by use of geophysical te chnology. The structures, depositional features, lithology of studied area are interpretated and described clearly on3D seismic data. Also, Jurassic strata of Baijiahai area is analyzed systematically in many ways, including structure characters, fracture feature, sedimentary fa cies and distribution, favorable sand bodies distribution, reservoir p hysical properties, hydrocarbon reservoir formational conditions and p rocess, the controlling factors of reservoir and so on. In addition, t he strata's lithology petroleum entrapment mode can be concluded, in o rder to predict geologic characteristic of the formation lithology res ervoir and distribution enriching methods.The study shows that:(1) Jurassic strata can be divided into2super-long cycles by researching the superstition styles. And tectogenesis and climate are the main controlling factors. Such as the first super-long cycle(Shui Xigou formation) reflects humid climate and stable tectonic condition, while the second super cycle (Shi Shugou formation) represents arid climate and unstable structure.(2) Under the east high west low landform background, the sedimentary facies in the synchronal sequence stratigraphy shows that facies in different climates are different. During LSC1-LSC5, the climate was wet, and the river in gravel and sand loads, delta and lake were developed. While river in low sediments supply was widespreaded in the arid climate of LSC6and LSC7.(3) The research demonstrates that the development of reservoir sand depends closely on the characteristic of sedimentary facies, but not on the type of facies. For example, river and delta in humid condition have strong carrying capacity as LSC1-LSC5, because of enough water supply. However, LSC6and LSC7are quite on the contrary.(4) The Permian and Jurassic system are the main Mesozoic source rock. And the better oil-generating sag in Permian is Dongdaohaizi sag and Fukang sag. Pingdiquan formation in Dongdaohaizi sag has started to enter the threshold of hydrocarbon generation since early Jurassic, and generates large amount of hydrocarbon in early Cretaceous. The main source rock is shale with coal interbedded in middle-lower Jurassic. And the source rock in Dongdaohaizi sag reaches to the low mature stage in early Cretaceous, and becomes the hydrocarbon-generating peak until Tertiary. While in Fukang sag, it has entered the the threshold of hydrocarbon generation in early Jurassic, and generates large amount of oil and gas in late Cretaceous.(5)There are multi-level slope belts in middle-lower Jurassic, and the slope belts can be classified into fault slope break and flexure slope break. According to the sedimentary facies'distribution, flexure slope break has a strong control on the sand, and the fault slope break largely influences the reservoir. Of course, the boundary faults and induced faults can both be the migration pathway and the cap for oil and gas, according to the development history, openness and contacts between two walls. Moreover, because there are multi-level slope belts in study area, denudation in different degrees happens in different positions in middle-lower Jurassic. As a result, updip pinch-out sandstone reservoir forms.(6) A series of stratigraphic overlap traps were formed in middle-upper Jurassic, mainly located in Toutunhe formation of Fubei slope area. And updip pinch-out trap exits in some area.The division of the sequence stratigraphy, the distribution of sedimentary facies, the relationship between deposition and slope breaks, the feature of lithologic traps are studied further, with the lithologic reservoir of Bai jiahai area in Junggar basin as the focus. Through research the on reservoir-forming conditions, the lithologic reservoir mode is set up, and the stratigraphic lithology accumulation rule of study area is summarized.