川西地区须家河组二段是该区天然气的主要产层，其主要储集空间为溶孔、溶洞和裂缝，储层为特低孔特低渗储层，平均孔隙度仅为4%。通过大量薄片观察和统计分析，认为储层发育的主控因素是沉积相和成岩作用，其中沉积相对储层的控制主要通过粒度、石英矿物含量等体现;对储层影响较大的成岩作用主要包括胶结作用、溶蚀作用和裂缝。通过显微镜下储层成岩作用特征观察和扫描电镜、阴极发光、电子探针微成分资料分析，确定出了成岩矿物形成顺序并统计出了各类胶结物、充填矿物的相对含量，定量研究了不同时期储层的剩余孔隙度，指出储层致密化时期在燕山运动早—中期（J₂x—J₃sn末）。

The second Member of Xujiahe Formation in western Sichuan is the chief pay of natural gas, the main reservoir spaces of which are solution pores, solution cavities and cracks. The reservoirs have extraordinary low porosity and permeability with an average porosity of only 4%. After observation and statistical analyses in lots of slices, the main controlling factors of reservoirs development are sedimentary facies and diagenesis. Sedimentary facies control the reservoir mainly by grain grade and the quartz content, while the diagenesis chiefly affects the reservoir through cementation, dissolution and fractures. Through diagenesis features observation and analyses under microscope, scanning electronic microscope, cathodoluminescence and electron spectrum, the forming sequences of diagenetic minerals are determined; and through statistics of all kinds of cementations, the relative contents of guest minerals, the different periods of residual porosities were quantitatively studied. The reservoir densification period is determined in the Early Middle Yanshan Movement (J₂x—J₃sn).