Volcanic rocks in the Jiamuhe Formation are favorable reservoirs in Jinlong oilfield.It is a key step for exploration and development of volcanic reservoirs to analyze the characteristics of volcanic reservoir and define the distribution of favorable reservoir facies belts.Based on core

thin section

high pressure mercury injection and reservoir property data

this paper defined the characteristics of lithology and property of the volcanic rocks

and predicted the distribution of favorable volcanic reservoirs.The results show that the volcanic reservoirs consist of volcanic lavas

volcaniclastic lavas

volcaniclastic rocks and depositional volcaniclastic rocks.The volcanic reservoirs in Jinlong Oilfield are characterized by medium to low porosity and low to extra low permeability.The reservoir spaces are divided into pore vs. fracture classes according to their shapes in the rock

and primary vs. secondary categories on the basis of genesis

of which the contraction pores and fractures are the main reservoir spaces of the volcanic reservoirs in Jiamuhe Formation.Volcanic rocks with different lithologies and petrofacies have different types of mercury-injection curves.There are 3 curve types featuring respectively in fine pore throat with bimodal positive skew distribution

fine-micro pore throat with unimodal positive skew distribution

and micro pore throat with unimodal negative skew distribution.Overall

the micro-fine pore throats are predominant and the sorting is poor to moderate.Lithologically

the volcanic breccias

basalt and andesite are the most favorable reservoirs in the study area

while as to petrofacies

the best reservoirs occur in the explosive facies and the upper part of the effusive eruption facies.The best favorable reservoir facies belt is located at the middle part of the study area and is in NW-SE-trending banded distribution.