1. College of Earth Sciences��Jilin University��Changchun 130061��China; 2. ��esearch Institute of Exploration and Development��Liaohe Oilfield Company��PetroChina��Panjin 124010��Liaoning��China; 3. Inner Mongolia Tenth Geological Mineral Exploration Institute��Chifeng 024005��Inner Mengolia��China

Based on drilling cores of volcanic rocks in 32 wells with a total length of 11 431 m and the cut- tings and well logging data��the volcano lithology��lithofacies��vertical sequence and eruption stage of Dongying Formation have been studied by volcano stratigraphical seismic- well correlation�� The isopach map of volcanic rocks is sketched out based on the information of volcanic rocks in 225 wells with a total length of 56 923 m�� More than 600 measured porosity and permeability data of 43 wells are compared in order to study the reservoirs physical prop- erty of Dongying Formation volcanic rocks��and its relationship with the sedimentary rocks and the volcanic rocks of underlying the third member of Shahejie Formation�� The results show that the volcanic rocks are mainly composed of basalt and trachyandensite��and divided into 5 eruptive stages with the eruption cycles of mafic- intermediate- mafic volcanic ones upwards�� The spatial distribution of volcanic rocks is controlled by the main boundary faults��and the thickest volcanic rocks are formed at the intersection of Jiadong fault and its associated faults�� The porosity and per- meability descend with the increasing of burial depth for both volcanic rocks and sedimentary rocks�� The regional burial depth is shallower than 2 500 m for the Dongying Formation��and the physical property of volcanic rocks are worse than interbedded sandstone but better than the volcanic rocks in 2 500 m for the third member of Shahejie Formation�� The relationship between Dongying Formation volcanic rocks and reservoirs are is that: ��The averaged porosity and permeability (φ =15%��K =0. 4 ×10 ^-3 μm ² ) for Dongying Formation volcanic rocks are worse than its interbedded sandstone (φ =21%��K =29 ×10 ^-3 μm ² )�� �� The reservoirs physical property of Dongying Forma- tion volcanic rocks are better than the volcanic rocks in the third member of Shahejie Formation (φ =10%��K = 0. 45 ×10 ^-3 μm ² )�� The volcanic rocks act as cap rocks in the Dongying Formation��and as reservoir rocks in the third member of Shahejie Formation�� The controlling factor in determining volcanic rock as reservoir or cap is the relative level of porosity and permeability compared to the interbedded sedimentary rocks��