Controlling Factors and Characteristic of Carboniferous Volcanic Reservoir Fractures of Zhongguai Uplift in Northwestern Margin of Junggar Basin

Carboniferous volcanic reservoir fractures are the main flowing channel and effective storage space for the reservoir in Zhongguai uplift.There are original fractures,secondary fractures and artificial induced fractures.High-angle unfilled or half-filled shear fractures develop best among them,which are the key types of factures.The main orientations of fractures are near N-E and E-W,which have good validity because of the consistent or sharp angle with the current maximum principal stress direction.The tectonic fractures are mainly formed in stage of Hercynian tectonic movement.The influence factors of the fractures development mainly include the tectonic position,rock types,rock stratum,and etc.The fractures in different lithology show different development degrees;there is a linear relationship between the develop degree of fractures and the tectonic position.Fracture-developed zone presents banded distribution along fault belt.Layer thickness plays less apparent effect on the fracture development because of poor stratification of volcanic reservoir.The tectonic position and rock type are the key controlling factors of fracture development.