The Xujiaweizi Fault Depression is located in the northern Songliao Basin, Northeast China.
The exploration results show that the most favorable natural gas reservoirs are in the volcanic rocks of
the Yingcheng Formation (K1yc). Based on seismic interpretation, drill cores and the results of previous
research, we analyzed the distribution of faults and the thickness of volcanic rocks in different periods of
K1yc, and studied the relationship of volcanic activities and main faults. Volcanic rocks were formed in the
Yingcheng period when the magma erupted along pre-existing fault zones. The volcanic activities strongly
eroded the faults during the eruption process, which resulted in the structural traces in the seismic section
being diffuse and unclear. The tectonic activities weakened in the study area in the depression stage. The
analysis of seismic interpretation, thin section microscopy and drill cores revealed that a large number
of fractures generated in the volcanic rocks were affected by later continued weak tectonic activities,
which greatly improved the physical properties of volcanic reservoirs, and made the volcanic rocks of
K1yc be favorable natural gas reservoirs. The above conclusions provide the basis to better understand
the relationship of the volcanic rock distribution and faults, the mechanism of volcanic eruption and the
formation of natural gas reservoirs in volcanic rocks.