Abstract:

Tazhong-Ⅰ slopebreak zone is located at the north margin of the large carbonate platform developed on the northern slope of Tazhong paleo-uplift.The northwest trending slope break is 220 km long and 8-18 km wide.It developed large reef-flat complexes in the Upper Ordovician and harbors giant condensate gas reservoirs with burial depth of 3 700-7 200 m.High-quality seismic profiles are hard to acquire here because of the undulate dunes at the surface and complex structures underground.And the accuracy of lateral reservoir prediction is low due to the deep burial depth of the Ordovician carbonate reservoirs,high heterogenity,and multiple controlling factors upon reservoir development.However,a set of methods have been developed and applied successfully to the prediction of the reef-flat carbonate reservoirs through analyzing geophysical responses to various types of Ordovician reef-shoal complex reservoirs based on geologic log,core,and test data.The application of these methods has accelerated the exploration of large condensate gas reservoirs in the slope break zone.

Key words: logging response, seismic response, reservoir prediction, well site optimization, slope break zone, reef-flat complexe, Tazhong area