Characteristics of source rocks in Shahezi Formation and implications for hydrocarbon accumulation, Changling Fault Depression, southern Songliao Basin

Abstract

The paleo-tectonics and sedimentary environment during source rock deposition controlled the macro distribution of source rocks. The deposition environment of the Lower Cretaceous Shahezi Formation (K1sh) source rocks, which are the main source rocks in the Changling Fault Depression of the southern Songliao Basin, was restored based on the theory that "basin prototype controlled source rock development". The distribution of preserved source rocks in the K1sh was determined using tectonic restoration. The paleo-environment of the Changling Fault Depression during the K1sh period was characterized by deep water, humid to subhumid climate and anaerobic freshwater, which was favorable for the deposition of source rocks. The Changling Fault Depression was composed of two relatively unified fault subsags during the K1sh period, and the K1sh source rocks were widely developed. After multiple stages of reversal, the Shahezi Formation was uplifted and eroded to different degrees, and the residual source rocks were mainly found on the present slope. This study provided a new idea for the oil and gas accumulation on the slope belt and the basin margin super-stripping belt. The Longfengshan-Dongling slope, the Chaganhua east slope and the Fulongquan west slope are favorable exploration areas for oil and gas exploration, where excellent source rocks were developed. In addition, the super-stripping zone of the Shahezi Formation is also favorable for hydrocarbon accumulation, showing a certain exploration potential.

Keywords

• source rock
• basin prototype controlled source rock development
• paleo-environment
• multi-phases of tectonic movement
• super-stripping zone
• shahezi formation
• changling fault depression
• songliao basin