Characteristics and quantitative evaluation of volcanic effective reservoir in Jiamuhe Formation of Permian, northwestern margin of Junggar Basin

Key words:  Junggar Basin  Jinlong2 area  volcanic  effective reservoir  classification and evaluation

Abstract:

Based on a comprehensive analysis of geological, well-logging and production data, this paper summarized the characteristics of volcanic effective reservoir of Permian Jiamuhe Formation in Jinlong2 area, the northwestern margin of Junggar Basin. The lithology of volcanic effective reservoir mainly includes andesitic (welded) breccia, andesitic/basaltic brecciated lava and andesite. The reservoir spaces are mainly composed of stomata and dissolution pore, followed by intercrystalline pore and intergranular pore. The volcanic reservoir is totally characterized by low-medium porosity and low-extra low permeability. Using capillary pressure curves which represent different types of volcanic rock, it can be shown that the characteristics of the microscopic pore throat in effective reservoirs mainly express in fine pore type with unimodal coarse state, partial coarse state and bimodal partial coarse state. Based on the analysis and evaluation of macroscopic physical characteristics as well as microscopic pore structure, this paper further optimizes K-means clustering analysis method and typical Fisher discriminant method to set up quantitative classification and evaluation criteria and discriminant functions, which divide the volcanic effective reservoir into three types accordingly. This quantitative evaluation classification method was applied to the development test area, and yielded remarkable results. The method may provide strong technical supports for the efficient development of volcanic reservoir.