Abstract: The reservoir fractures of  volcanic rock of Kenli 16 structure on the southern slope of Laizhou Bay depression   in Bohai Bay Basin are developed, which has a significant effect on reservoir quality. However, its formation period and distribution law are not clear, which restricts the in-depth understanding of the reservoir. Based on core, imaging logging and outcrop data, this paper studies the fracture types, formation stages and distribution of Mesozoic volcanic rocks in Kenli 16 structure. The main  results are as follows:  Six kinds of cracks are identified, including explosion cracks, crypto-explosion cracks, condensation shrinkage cracks, weathering cracks, structural cracks, and corrosion cracks. The fractures are mainly of middle  to high  angle. The condensation contraction fractures are mainly of medium scale, and the structural fractures are mainly of large scale.  The fracture opening  degree descends from pyroclastic rock, pyroclastic lava,  and sedimentary pyroclastic rock  to lava. The fracture formation period can be divided into five  stages, and a large number of structural fractures are formed under the strike-slip stress system. The fracture surface densities of each lithology  descend from lava,  pyroclastic lava, and pyroclastic rock  to sedimentary pyroclastic rock.The fracture surface densities of each facies  descend from lava flow subfacies, hot clastic flow subfacies, and hot foundation wave subfacies,  to collapse retransported accumulation subfacies. In the outcrop area, the fracture zone width of lava can reach 2 m, the cracks are mostly open, and the fault of the pyroclastic rock develops scratches, forming a decimeter-dense zone, which reduces the permeability of the rock. 

Key words: fracture genesis,  , distribution law, volcanic reservoir, Mesozoic, Bohai Bay basin, Laizhou Bay depression