The structural evolution of the middle section of the West Sichuan Depression in the Sichuan Basin controlled the hydrocarbon accumulation in the Middle Triassic Leikoupo Formation

Abstract

The Middle Triassic Leikoupo Formation of Jinma-Yazihe structure in the middle section of Western Sichuan Depression has submitted over 100 billion cubic meters of proved natural gas reserves. An industrial gas flow has also been obtained in Xinchang and Majing area, and the controlled and predicted reserves have been submitted. However, the relationship between structural evolution process and hydrocarbon accumulation configuration is still unclear. Through the analysis of vitrinite reflectance, scanning electron microscopic observation, analysis of fluid inclusion of peripheral outcrop and drilling samples, and combined with structural interpretation, the following results have been indicated. It is clear that the local structure in the middle section of Western Sichuan Depression was formed in the early Indosinian, and the Early-Middle Jurassic was a critical tectonic evolution period for hydrocarbon accumulation in the Leikoupo Formation. Meanwhile, the faults connected to sources or "contact" fault migration system provided pathways for natural gas migration, which was conducive for hydrocarbon enrichment. The local paleo-structural high points with a good configuration of key accumulation factors such as reservoirs and transport systems and weak structural deformation are the most favorable exploration area.

Keywords

• tectonic evolution
• fault
• hydrocarbon migration
• hydrocarbon accumulation
• leikoupo formation
• middle triassic
• middle section of western sichuan depression
• sichuan basin