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

摘要： 通过普通薄片及铸体薄片观察、扫描电子显微镜、阴极发光、能谱分析及主量元素分析等岩石学、矿物学、地球化学手段, 对塔里木盆地跃南地区二叠系火山岩储层成因机理进行系统研究。研究发现, 二叠系火山岩储层中以次生储集空间为主, 孔隙度可高达14%, 渗透率最高可达13.1×10^?3 μm², 可以作为有利的储层。风化作用是次生孔隙和裂缝的主要成因, 风化作用强度由深到浅逐渐增大, 储层物理性能与之呈正相关关系, 风化作用在跃南1井中影响范围达220 m左右。风化过程中, 火山岩在冷却阶段产生的大量原生孔隙、冷凝收缩缝、隐爆裂缝及矿物本身具有的解理缝、双晶缝等薄弱面是优先发生溶蚀、淋滤的部位。在流纹岩中发现长石斑晶及基质的风化序列, 确定风化产物以伊利石为主, 含少量蒙脱石, 并且保存了黏土矿物整个序列的生长过程。风化作用能在原生孔隙和裂缝的基础上改善火山岩的孔隙结构, 使储集空间类型复杂多样, 大大提高了储层物理性能, 是塔里木盆地跃南地区二叠系火山岩储层的主控因素。

关键词: 塔里木, 二叠系, 火山岩储层, 风化作用