Abstract:

During the period of Late Permian, transgression from east to west occurred in Sichuan and its adjacent areas. The Upper Permian Changxing Formation reefs in East Sichuan were pinnacle and patch reefs which climbed on carbonate ramp with tragression. The Changxing reefs underwent five diagenetic environments, i. e. the sea floor,reef ialand tidal flat, subaerial, shallow to moderate burial and deep burial diagenetic environments. However, interreefs and non-reefS had never exposed and undergone meteoric diagenesis. They underwent from sea floor to shallow-moderate burial and deep burial diagenetjc environments. A lot of primary pores of reef rocks (shelter and growth framework voids, intrabiotic pores, interbreccia cavities, etc.) were almost filled by multi-phase cements of sea floor and burial diagenesis. Interreef biogenic debris and lime mud deposits had many micropores that were progressively vanished during burial compression process.Most of the dolomites of a reef body were formed by the replacement of compaction fluids which converged towards and through reefs in burial diagenetic environmemt and have good porosity and permeability. The main reservoir spaces are late solution pores and intercrystalline pores.