On the northwestern margin of Junggar Basin, the complex volcanic oil reservoirs in the Carboniferous basement are highly concealed, poor physical properties, and difficult to explore or characterize. With the purpose of understanding the distribution of favorable reservoirs, the geological features, distribution law, and control factors of the reservoirs are fully explored based on analysis of the data from coring, logging, seismic analysis, and thin section in this paper. And some conclusions can be drawn as follows: (1) the Carboniferous rocks in the study area mainly include tuff lava, tuff, sedimentary tuff, tuffaceous sandstone, and tuffaceous glutenite; (3) the reservoirs have low porosity and permeability, the secondary pores and fractures provide the main storage spaces, the reservoirs fall into fractured reservoir and pored-fractured reservoir; (3) the favorable weathered crust reservoirs mainly exist in strong and moderately weathered zones in the vertical direction, which are 20-130 m from the top of the Carboniferous basement; in the planar direction, the reservoirs mostly concentrate around J353-J354-J336-J399-J132-J126 wells and around J12-J329 wells; (4) the reservoirs are mainly controlled by weathering and leaching, and the storage capacity is greatly improved by tectonic movement. This paper discloses the main controlling factors and distribution features of high-quality volcanic reservoirs in the Carboniferous basement on the northwestern margin of Junggar Basin, laying a solid basis and guidance for the exploration and development of similar oil and gas reservoirs.
