Abstract:  Volcanic rock reservoir evaluation is a critical foundation for oil and gas reservoir development, requiring the selection of parameters based on reservoir characteristics and data features to develop targeted evaluation methods. The Mesozoic volcanic rocks in the southern slope zone of the Laizhouwan sag in the Bohai Bay basin have yielded abundant core samples, special logging data, and conventional logging data from existing wells, providing a data foundation for conducting multi-parameter quantitative reservoir evaluation. This study uses this example to investigate quantitative evaluation methods for the Mesozoic volcanic rock reservoirs. The results indicate that the volcanic rock reservoirs in the study area are primarily pore-fracture type reservoirs, with fractures being a key factor influencing reservoir quality. Based on this, parameters such as logging porosity, nuclear magnetic resonance (NMR) T2 spectra, fracture density, and fracture opening were selected for correlation analysis to identify optimal evaluation parameters. Principal component analysis was used to assign weights to each parameter, and K-means clustering was employed for reservoir evaluation. When the volcanic rock reservoirs in the study area were classified into three categories, the clustering quality was high. Reservoir types are closely related to lithology; Type I reservoirs primarily consist of volcanic breccia, characterized by high porosity and large fracture opening. 

Key words: cluster analysis, reservoir evaluation, volcanic rocks, Mesozoic, Laizhouwan sag