Carbonate Reservoir Rock of Composite Genesis and Its Dynamic Developing Process:An Example from Tahe Carbonate Reservoir
复合成因碳酸盐岩储层及其动态发育过程——以塔河地区奥陶系碳酸盐岩为例

The lower Paleozoic carbonate in the Tarim basin experienced many kinds of secondary dissolution,such as surface dissolution by atmospheric eluviation,burial dissolution by organic fluid,surface karst by meteoric water,hydrothermal alteration by magma-associated hydrothermal fluid,and so on.Taking the Tahe oilfield as an example,the Ordovician carbonates experienced three periods of strong surface karst at the middle Caledonian period in the west and north of Tahe oilfield,early Hercynian in the main block,and later Hercynian in the northwest part,respectively.Under the action of hydrocarbon-filling at the periods of Caledonian,later Hercynian and Himalayan,several time of burial dissolution were taken to the carbonates by organic fluid.The burial dissolution mainly developed to the south of the O2yj distinction line,and the space of carbonate reservoir acted by burial dissolution was overlaid to the early-formed one.Since the extensive magmatic-volcanic activities at the later Hercynian period (Permian) made the deep hydrothermal active,the hydrothermal alteration dissolved the carbonates remarkably.The hydrothermal-dissolved pores stacked on the previously existing reservoir space in the west and southwest of the Tahe oilfield.Therefore,the high quality of carbonate reservoir was formed rather by one single fluid than the composition of multiple dissolutions in a long-time dynamic process.