Characteristics and genesis of dissolution and its influence over pores in sandstone reservoirs of the Cretaceous Bashijiqike Formation in DB gas field of Kuqa Depression are studied based on observation of cores

and normal/cast thin sections

analyses through cathodoluminescence microscope

scan electricity microscope

and characterization of reservoir physical properties

and etc.The result shows that the sandstone reservoirs in the Formation have ultra-low porosity and permeability and contain various types of dissolved pores.The reservoirs had experienced successively atmospheric water supergene leaching (dissolving carbonate cementation)

organic acid dissolution (dissolving feldspar)

weak alkaline dissolution (dissolving unstable debris)

and less weak alternative acid/alkali dissolution(dissolving quartzose)

resulting in intergrannular dissolution pores

dissolution fractures

large dissolution pores surpassing grain size

intragranular dissolution pores

and etc.A combination of the study with previous analyses

including stratigraphic burial history

and evolutionary history of organic matter and tectonics of the Formation

indicates that right timing between multi-staged dissolution and hydrocarbon charge was critical for forming prolific DB field.