• reef complex;
  • carbonate platform margin;
  • Changhsingian;
  • Yuanba Gas Field;
  • SW China

The Yuanba Gas Field is the second largest natural gas reservoir in the Sichuan Basin, SW China. The vast majority of natural gas reserve is embedded in the Changhsingian platform marginal reef complexes. Integration of facies analysis, well-seismic calibration, well logs, seismic profiles, and RMS attribute allows reconstruction of the reef complex structure, and five growth cycles of overlapping accretionary reefs are recognized. The carbonate platform margin reef complex comprises reef core, fore reef and back reef facies associations. The retrograding–prograding growth pattern and northwesterly migrating trends of overlapping accretionary reefs were likely controlled by short-term sea-level changes superimposed by local currents prevailing in the eastern Palaeotethyan Ocean. Copyright © 2012 John Wiley & Sons, Ltd.