Study on the formation mechanism of the subtle oil/gas reservoirs in Chepaizi uplift,Junggar Basin

As petroleum exploration goes into a more mature stage,the search for subtle oil/gas reservoirs gradually becomes a main direction of oil/gas resource stratagem and the frontier area of petroleum geology research in China.The petroleum generation,migration and accumulation mechanism of Chepaizi uplift in Junggar Basin are discussed.Based on the analysis of the evolution histories of the basin,conduit frame work and potent source-rock,not only are the evolution of the energy fields but also the chemical dynamics,the fluid dynamics and kinematics controlled by the evolution of the energy fields studied by integrating geological,geophysical and geochemical means with basin simulation techniques.Detailed oil-to-source correlation showed that the oil/gas mainly originated from Permian dark mudstones in Changji sag and Jurassic coal seam in Sikeshu sag in turn.The driving mechanisms of hydrocarbon migration took on two modes of early buoyancy and late strong overpressure.Unconformities/ connected sand-bodies,faults formed dominant migration pathways.The accumulation models of subtle oil/gas reservoirs were attributed to two-source generating,two-stage charging,"stair-shaped" conduit and stratigraphic/lithologic traps accumulation.