Characteristics of Carboniferous Volcanic Reservoirs in Beisantai Oilfield, Junggar Basin

Table 3

Classification and characteristics of Carboniferous volcanic lithofacies in the Xiquan block.

Volcanic lithofacies	Subphase	Genesis mechanism and division mark	Rock type	Structure
Volcanic channel facies	—	The lava flow stagnates and fills the volcanic channel, the crater collapses, and fills	Mainly andesite	Glassy structure, fine-grained structure, spotted structure, etc.
Overflow phase	—	The magma containing crystal exudates and contemporaneous breccia flows along the surface under the combined action of the subsequent ejecta and its own gravity	Mainly andesite	Glassy structure, fine-grained structure, spotted structure, etc.
Outburst phase	Heat base and wave subphase	The gas-solid-liquid multiphase turbidity flow system under the action of a gas jet acts as a suspended mass transport near the surface under neutral action, and the debris-carrying vapor flows	Mainly crystalline tuff, etc.	Pyroclastic structure
	Empty subphase	Aerodynamic solid and plastic ejecta (under the influence of wind) in free fall	Mainly volcanic breccia, breccia-bearing tuff, breccia crystalline tuff, crystalline tuff, etc.	(Mainly crystalline tuff structure)
Volcanic sedimentary facies	—	Pyroclastics are transformed by water flow	Carbonaceous mudstone, tuff, etc.	Agglomerated structure, breccia structure, tuff structure, etc.