Abstract: Volcanic gas reservoirs have become important exploration target and increasing factor of oil and gas reserves. the average content of SiO2 is 74.4%, and the average Littmann Index is 2.26 in the area of interest. Most volcanic rocks in this area belong to acidic and calcalkaline volcanic suite. Because of deep buring, more rock types and less component difference, the volcanic rocks are difficult to be named and identified. The naming rule of “component + texture+ origin” is used to classify volcanic rocks in this case. Based on core observation, thin section analysis and the whole rock analysis, elemental capture spectroscopy（ECS） logging data is used to measure the content of the main petrogenetic elements and minerals and determine lithologic composition of volcanic rocks；fullbore formation microImager（FMI） image is used to identify rock texture and structure of volcanic rocks；conventional logging data reflects many characteristics of rocks, including the radioactivity, physical property and conductivity etc. So, it is used to identify synthetically volcanics by the method of principal component analysis. The results of research show that it is the most efficient method to identify volcanic rocks synthetical applying ECS, FMI and conventional logging data.

Key words: volcanic rocks, lithologic identification, principal components