Abstract: To address the problem of poorly understood structural characteristics of weathered volcanic reservoirs and lack of effective delineation methods, the four phase patterns of weathered volcanic rocks are established and classified from top to bottom, namely, strongly weathered clay phase, weathered hydrolysis phase, weakly weathered leaching and disintegration phase and unweathered parent rock phase, by taking weathered volcanic rocks in Shixi High, Junggar Basin as a study object and combining petrophysical experiments, FMI imaging data and comprehensive well logging and mud logging data. The weathered volcanic reservoir composite index and weathering composite index were constructed by using well logging data to finely classify the phases of weathered volcanic rocks, and the weakly weathered leaching and disintegration phase was clearly defined as the dominant phase of weathered volcanic rocks. The application in Shixi High, Junggar Basin is remarkable and provides a reference for the study of phases of the same type of volcanic reservoirs.

Key words: Shixi High, weathered volcanic rocks, phase pattern, reservoir composite index, weathering composite index