Deformation mechanism and hydrocarbon significance of Eocene organic-rich fine-grained soft sediments in the Leijia Region, Liaohe Depression

The deformation structure of soft sediments has always been a research hotspot, which is of great significance for analyzing the tectonic and sedimentary evolution background of a basin, as well as the physical properties of reservoirs. Previous studies have reported that a large number of soft sediment deformation structures are developed in the western part of Liaohe depression. In this study, through core observation and thin section identification, various types of deformation structures are identified in the core samples which are collected from the upper Es4 in the Leijia region, western sag of Liaohe depression, such as liquefied dikes, liquefied breccia, convoluted laminae, annular bedding, synsedimentary faults, vein structures, etc. Based on the characteristics of core structure, single well profile and continuous well profile, combined with the regional background, this study clarifies that the deformation structure of soft sediments in the study area is mainly caused by seismic action. It is found that the permeability and porosity of deformation layers in the study area are higher than those of the undeformation layers, which proves that the deformation structure of soft sediments has a good effect on improving the physical properties of reservoirs.

Automated summary

Various deformation structures, such as liquefied dikes, liquefied breccia, convoluted laminae, annular bedding, synsedimentary faults, and vein structures, have been identified in the upper Es4 of the Leijia region in the western sag of Liaohe depression. These deformation structures are mainly caused by seismic activity and have a positive effect on improving the physical properties of reservoirs, as indicated by higher permeability and porosity compared to undeformed layers.