Study on sedimentary characteristics of bioherm in Changxing formation in eastern Sichuan

In recent years,the prospecting research of bioherm is expeditious but the systematic study on bioherm in the platform is less in the eastern Sichuan basin.The sedimentary characteristics of the bioherm in the platform have been studied based on the outcrop,drilling core and logging data.The result shows that point reef and hill reef are well developed inside the platform.The point reefs such as Jianshuigou and Laolongdong is the unique feature.The reef building organism combined characteristic is consistent and its sedimentary facies distribution are symmetric.There are two cycles of sedimentation made up of the vertical rock-bafflestone-skeleton rock on the vertical.The mainly rock is micritic sponge reef limestone.Reefs proper are made up of bafflestone.The main reef-building organism is saccate spongia and moniliform spongia and their visceral foramen were filled by lime mud and a little biogenicdebris.The reef sedimentary facies can be divided into three subfacies-the reef base subfacies,reef core subfacies and reef flat subfacies.The reef mainy developed in the Changxing medium-term and its size is small.Through the study of sedimentary characteristics of eastern Sichuan reefs,and it can provide more reliable geological basis for the reef gas exploration and development.