The Cenozoic structural evolution and its influences on gas accumulation in the Lishui Sag, East China Sea Shelf Basin

• The structural events of the Lishui Sag have been quantitative analyzed.
• The Lishui Sag has experienced a multi-period burial history.
• The structural evolution can be subdivided into four stages.
• The influences of structural evolution on gas generation and accumulation are very important.

Given the natural gas pools that have been discovered at the Lishui Sag, this region has great potential as a favorable prospecting area in the East China Sea Shelf Basin, which is a gas-rich basin in China. Well and seismic data, special geological techniques, including erosion history reconstruction, balanced cross-section restoration and basin modeling, were used to reconstruct the paleostructure. The major conclusions of the Cenozoic paleostructure reconstruction in Lishui Sag included the following: The Lishui Sag experienced a multi-period burial history, including rapid subsidence in the Paleocene, a transition during the Eocene and slow subsidence in the Neogene, and uplifting and erosion in the Paleogene Oujiang and Yuquan movements. The burial history can be summarized into four evolution stages, namely, rifting, post-rifting, uplift-inversion and regional subsidence. The rapid subsidence facilitated the hydrocarbon generation, and the uplift-inversion created a lot of traps in the central uplift area and facilitated the hydrocarbon migration, and regional subsidence facilitated the preservation of accumulated hydrocarbons.