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Keywords:

  • Neotectonism;
  • China;
  • rift basins;
  • Tertiary;
  • synrift;
  • lacustrine source rocks;
  • depocentre migration;
  • post-rift plays

Tectonic activity offshore China during the Late Miocene and Quaternary (“neotectonism”) generated unconformities, resulted in depocentre migration, created new faults and initiated earthquake activity. This episode of structural disturbance, which occurred during post-rift thermal subsidence, modified pre-existing hydrocarbon accumulations and formed new pools. Constructive effects of neotectonism occurred in the Bozhong Depression, Zhu #2 Depression and the Yinggehai Basin. These effects included the formation of new structural traps, migration routes and source kitchens. Destructive effects occurred in the Xihu Depression where oil/gas fields were partially breached by post-trap peneplanation and faulting. There are pools with active gas leakage through neotectonic faults and this seems to suggest a dynamic balance between outboard leakage of gas and inboard migration of hydrocarbons.

This paper summarizes understanding of the past 15 years of offshore exploration in China which has primarily focused on Neogene reservoirs. Data used for this report include extensive coverage of conventional P-wave and multi-component 2D and 3D seismic data, drilling results and extensive geochemical and geological analyses.