Abstract: The fault has dual functions in migration and accumulation of oil and gas,the one is to destruct hydrocarbon reservoir,another is to seal oil and gas.So,evaluation of fault role is very important in the exploration and development.Taking Hongche fault belt in northwest Junggar basin as example,based on the oil-gas composition difference of the reservoirs located on the north and south side of the belt,the fault role in oil-gas destruction and preservation in different geologic times.It is showed that the difference of fault intensity between the south and north fault area of the Hongche fault belt and heterogeneity in Yanshanian movement led to the different control on oil-gas reservoirs.Because the movement in the north area was stronger than the south of the Hongche fault belt did in the late Yanshanian movement,the south area is beneficial to gas accumulation and the light oil reservoirs form in north because of the loss of gas.

Key words: reservoir, heterogeneity, pore structure, Toutunhe Formation, Luliang Oilfield, Junggar Basin