Abstract: The Changxing formation of Late Permian in northeastern Sichuan basin is in the carbonate platform-basin (trough) sedimentary environment where many boundary reefs and point reefs occur in the edge and local upland in the platform. These reefs can be divided into the type of transgressive remedy and the type of transgressive advance side by side in terms of the rising speed of sea level and the growth rate of the reefs. Their lithologic association, storage and distribution are studied. The latter belongs to lithologic association to be shallower upward with water and reconstructed intensely by dolomitization and dissolution, with developed dolomite and secondary porosity as well as preferable reservoir quality, mainly distributed in the Middle-Upper Changxing formation nearby the Kaijiang- Liangping area, being the most favorable exploration target. The former is darken upward and composed of lime, with low porosity and poor reservoir quality, mainly distributed in the Middle-Lower Changxing formation nearby Chengkou-Exi area, being as the probable exploration target in its fractured area.

Key words: Sichuan basin, Changxing formation, reef, lithologic association, reservoir quality, distribution