关键词: 塔里木, 二叠系, 火山岩储层, 风化作用

Abstract: Petrology, mineralogy and geochemistry method such as thin section, cast thin section, scanning electron microscope observation, cathodoluminescence, energy spectrum and major element experiment were used to analyze the genesis of Permian volcanic reservoir in Yuenan Region, Tarim Basin. It is found that Permian volcanic reservoir, dominated by secondary pore space can be regarded as favorable reservoir because the porosity of the primary pore space can reach 14% and 13.1×10^?3 μm² respectively. Genesis of the secondary pore and cracks is the weathering, whose intensity increases with the depth decreasing. The porosity and the permeability is positively correlated to weathering. The thickness of weathering effect can reach at least 220 m. The weathering dissolution and leaching process take priority of weak plane, such as large number of primary pores, cooling contracted crack, cryptoexplosion fracture which generate in the cooling of volcanic and cleavage crack, twin stitch of primary mineral. Weathering sequence of feldspar phenocryst and matrix is found in rhyolite, weathering products are mainly illite, with small amounts of montmorillonite, and the entire sequence of clay minerals growth process is preserved. Weathering can modify substantially pore structure on the basis of primary porosity, and improve the porosity and permeability greatly, which is the main controlling factor of Permian volcanic reservoir of Yuenan Region, Tarim Basin.

Key words: Tarim, Permian, volcanic reservoir, weathering