Main controlling factors and depositional model of source rock of Paleogene Shahejie Formation in Liaodong Bay Depression

Abstract

In the Paleogene Shahejie Formation of Liaodong Bay Depression, two sets of main source rocks are developed, namely the Es1 and the Es3 Formation. In order to determine the characteristics, main controlling factors and patterns of source rock development, firstly, we comprehensively use source rock geochemical and logging data to establish TOC logging prediction models for source rocks in two formations; secondly, we predict the TOC plane distribution of the two layers separately according to the prediction model; then, we use the tectonic subsidence history and sedimentary background data of the study area to analyze its relationship with the source rock development and determine the main controlling factors for the source rock development; finally, the source rock deposition models are established according to the main controlling factors of source rock development. The results show the source rock of the Es1 has high abundance of organic matter, the average TOC of the sample is as high as 2.41%, but the thickness of the source rock does not exceed 130 m; the abundance of source rocks in the Es3 is slightly worse than that of the Es1, the average TOC of the samples is 1.75%, the thickness of source rocks is generally larger, mainly 200-350 m; the rate of tectonic subsidence controls the thickness of the source rock, the amount of fracture extension controls the distribution shape of the source rock, and the degree of water stratification controls the degree of source rock enrichment; in the Es1 Formation, the source rock deposition model is the deposition model of the salinity layered water body in the saline lake basin; in the Es3 Formation, the source rock deposition model is the deposition model of deep water temperature stratification in the separated lake basin. To determine the main controlling factors and depositional patterns of source rock development provides a direction for subsequent exploration of favorable areas.