Abstract: In-depth analysis is made on lithology, storage space type, porosity evolution, pore-fissure combination of volcanic rocks and their influencing factors in northwestern margin of Junggar basin. For given six types of the lithologies and the storage spaces and their forming mechanisms, it is suggested that the volcanic rocks with poor connective primary porosity didn't become effective reservoir rocks until the post reconstruction that allowed it to greatly improve the volcanic reservoir quality such as dissolution and tectonic movement appeared. Also, the process and controlling factors for such main the volcanic reservoir porosity evolution as andesite, volcanic breccia and tuff are analyzed. Based on these analyses, the evolution process in this area could be divided into five stages as follows: formation stage, weathering-leaching stage, burying and structural process stage, solution-reconstruction stage and oil-gas accumulation stage.

Key words: Junggar basin, volcanic rock, storage space, forming mechanism, evolution stage