Abstract: Based on statistical analyses on numerous experimental measurements, sub-layers of the high-quality shales in Changning, Southern Sichuan, were found to be strongly heterogeneous, and the factors controlling the development of highquality shale reservoirs were analyzed. There are high brittle mineral contents but relatively low clay mineral contents (mean 24.5%) in the lower reservoir of the Wufeng-Longmaxi Formation. The reservoir has various types of reservoir spaces, although organic matter pores dominate. Relatively strong vertical heterogeneity is noted. Porosity primarily varies between 0.73% and 10.25%, with an average of about 4.19%. The total gas contents in the five sub-layers in the Wufeng Formation and Long 1₁ sub-member of the Longmaxi Formation are 1.27~4.19 m³/t, with an average of 2.74 m³/t. The Long 1₁¹ sub-layer has the highest gas content, followed by the Long 1₁² and Long 1₁³ sub-layers, whereas the Long 1₁⁴ sub-layer has the lowest gas content. Sedimentation conditions are the basis for high-quality shale development. High contents of quartz and organic matter facilitate the formation of high-quality shale reservoirs. Compaction and cementation are the major mechanisms for densification in shale reservoirs, while dissolution and organic matter thermal maturity can improve the shale reservoir quality to a certain degree.

Key words: shale gas, reservoir heterogeneity, diagenesis, mineral compositions, organic matter contents, Southern Sichuan Region