须家河组是川西坳陷的区域气层,由于埋深大,储层普遍经历了复杂的成岩作用,造成了现今储层的致密-超致密化,但在致密-超致密背景下仍发育部分储集性能相对较好的孔隙性储层.通过对研究区30余口井、7000余块岩石薄片、1000余块铸体薄片的观察与鉴定及其相关储层研究表明,火山碎屑溶蚀孔是须家河组二段、须家河组四段砂岩主要储集空间,是形成该区优质储层的主要控制因素,母岩风化搬运沉积下来的长石溶蚀不是形成中、高孔隙性砂岩的主要原因.因为同沉积期火山喷发作用形成的火山碎屑物含有较多的“易溶组分”,在成岩过程中易溶蚀脱玻化形成孔隙,从而控制了次生溶孔发育的较高渗透性砂岩储层的分布.因此,同沉积期火山作用的成分及其溶蚀作用强度是控制须家河组砂岩优质储层的发育、分布和形成本区中、高孔隙性砂岩的主要原因.甘孜-理塘陆间裂谷带上,晚三叠世火山活动强烈,是研究区火山物质的主要来源.%The Xujiahe Formation is a regional gas reservoir in western Sichuan Depression. Due to the great burial depth,the reservoir generally experienced complicated diagenesis,resulting in tight to supertight reservoirs. Even so,porous reservoirs with relatively good storage capacity were also developed. From observation of more than 30 wells, over 7 000 ordinary thin sections and over 1 000 cast thin sections in the study area as well as the research of related reservoirs, it is demonstrated that volcanic debris dissolved pores are the major storage space of sandstones of of the 2nd and 4th member of Xujiahe Formation, and are the major controlling factor of high quality reservoirs in the area. Dissolution of feldspar deposited through weathering and transportation of parent rock is not the major reason for the forming of sandstone with medium-high porosity. Volcanic debris from synde-positional volcanic eruption contain many "soluble compositions" ,which tend to be dissolved and devitrified to form pores during diagenesis, thus controlling the distribution of high-permeability sandstone reservoirs with well-developed secondary dissolved pores. Therefore, the compositions of debries from the syndepositional volcanism and their dissolution intensity are the major factors controlling the development and distribution of high quality reservoirs of the Xujiahe Formation and the formation of sandstone with medium-high porosity. Ganzi-Litang inter-continental rift area where volcanisms were strong during the Late Triassic was the major source for volcanic debris in the study area.
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