河道发现对塔中地区碳酸盐岩勘探的启示

塔中地区鹰山组为大型岩溶风化壳型油气藏。上奥陶统良里塔格组与中下奥陶统鹰山组地层暴露时间短，导致表层岩溶作用弱，古岩溶河流欠发育。利用地震沉积学（地震切片技术）以及三维立体雕刻等技术，在鹰山组内发现了2套岩溶古河道系统，根据河道发育古地貌以及河道的形态将河道分为明河、暗河。通过岩性以及测井资料确定了不同类型河道的充填物，并对本区储层进行了综合评价:明河相关的储层，在暴露期大部分被泥岩充填，明河相关的储层发育区为不利区；暗河相关储层发育区，储集空间充填程度低、具有完整的储盖组合，结合已钻结果，证实为有利储层发育区。河道的发现为塔中地区碳酸盐岩储层成因提供了新的解释。

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

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.