Sedimentary facies of Shahejie Formation in Jinzhou 20-2 Gas Field in Liaodong Bay

The reservoir of the upper of the second member of Paleogene Shahejie Formation in Jinzhou 20-2 Gas Field in Liaoxi low uplift has the characteristics of complex lithologies, deep buried depth, thin thickness and great lateral variations. The reservoir distribution is an important restriction factor for the development adjustment of the gas field. Based on petrography, this paper studied sedimentary microfacies and environment from the data of core observation and thin section identification, together with the well logging curve morphological feature and lithofacies assemblage pattern, and recognized four kinds of microfacies including organic bank, carbonate restricted platform, clastic bank and deep lake. Sedimentation landform of target formation in the study area was restored by application of seismic horizon flattening technique. Based on the division result of single well facies, the plane microfacies distribution of the upper of the second member of Shahejie Formation was analyzed combined with analysis of sedimentary environment and understanding of ancient landform restoration. It is suggested that sedimentary microfacies of the upper of the second member of Paleogene Shahejie Formation in Jinzhou 20-2 Gas Field is lake-island type sedimentation, and it is obviously controlled by ancient terrain. The reservoir lithology consists of carbonate rock, sandstone and peperite. Thus, relatively speaking, bioclastic carbonate is with the best reservoir properties and thick layer. Reservoir development and distribution are controlled by sedimentary microfacies.