A Revelation about Carbonate Exploration from the Discovery of Channels in Tazhong Area

Key words: 
• Tazhong area /
• channel /
• epikarst /
• carbonate

Abstract: The reservoirs of the Yingshan Formation are epikarst related, of which the short-term exposure between the above Upper Ordovician Lianglitage Formation and the beneath Lower-Middle Ordovician Yingshan Formation resulted in weak dissolution of surface rocks and undeveloped channels along the unconformity above the Yingshan Formation. Two sets of paleo-carbonate channels were discovered in the Yingshan Formation in Tazhong area by using strata slice and 3D visualization. Based on paleogeomorphology and patterns of distribution, the channels could be divided into two types, the surface ones and the underground ones. The channels fillings were identified by logging and lithology information. Based on the research mentioned above, the reservoirs were comprehensive accessed. The reservoirs relate to surface channels were mostly filled by shale during the process of exposure and thus not favorable for good reservoirs development. The reservoirs relate to underground channels were mostly preserved well with completed assemblage of reservoir-cap rocks, which were also confirmed as favorable reservoirs combined with drilling results. The discovery of channels do not only give new explanation for the genesis of paleo-karst carbonate reservoirs but also provide potential direction for further exploration and development of carbonate reservoirs in the Tazhong area.