Controlling factors of hydrocarbon migration in Bachu area of Tarim basin

The factors that affect hydrocarbon migration are fault, carrier bed and unconformity in Bachu area. Fault is the main pathway of oil-gas migration in the vertical direction, and unconformity and carrier bed are the main ones of oil-gas migration in the parallel direction. Faults formed in the Caledonian stage, the Late Hercynian Stage and the Himalayas Stage. The scale of the fault of the Late Hercynian Stage and the Himalayas one is more biggish, and the main combination is the thrust. The two latter play important roles in the vertical migration, and accumulation of the oil-gas. The three main unconformities are T74 boundary, T70 one and T60 one. The relation of unconformity with around beds is parallel one, truncation one and overlap one. The overlap one has the best migration ability. Carrier bed includes the sandstone in the bottom of Carbonifeous-siburian system and the karst in the top of the lower Ordovician system. Three times structure movements decided three times hydrocarbon accumulation in Bachu area, and the oil-gas formed in the Caledonian Stage was adjusted by the structure movements in the Late Hercynian Stage and the Himalayas Stage, then formed the distribution of the oil-gas nowadays.