古岩溶演化过程及对油气储集空间的影响——以鄂尔多斯盆地奥陶系为例

EVOLUATION PROCESS OF PALAEOKARST AND INFLUENCE TO RESERVOIR--A CASE FOR ORDOVICIAN OF ORDOS BASIN

岩溶作用是水对可溶性岩石的化学溶蚀和机械侵蚀与物质的迁移和再沉积的综合地质作用以及由此所产生的地质现象的统称。鄂尔多斯盆地奥陶系碳酸盐岩自沉积作用开始以后,经历了沉积成岩→溶蚀破坏→溶蚀充填→溶蚀改造等漫长的多期岩溶地质作用,古岩溶形态多种多样、大小多变、组构复杂。按照古岩溶形成的条件及控制因素可以将其划分为表生期岩溶和埋藏期岩溶2大类;表生期岩溶分为同生期层间岩溶和裸露期风化壳岩溶,埋藏期岩溶分为压释水岩溶和热水岩溶。认为古岩溶的演化过程控制着孔、洞体系的发育,对油气的储集空间的形成既有建设性又有破坏性的影响。

Karst roles include chemical solution and mechanical erode and substantial movement and redeposition due to the reciprocity of water and rock, which are a synthetical geological role. The carbonate rocks of Ordovician in the Ordos basin suffered from sedimentary formation stage and solution destroy and solution fill and solution rebuilt since sedimentary matter started to deposit. Palaeokarst have all kinds of styles and the complicated fabric. The palaeokarst styles may divide into surface Palaeokarst and burial Palaeokarst according to the condition of formation and the factor of control. The surface palaeokarst includes interval karst in the course of sedimentary and weathering crust karst in the course of denudation, The burial Palaeokarst includes the compaction released water karst and the hot water karst. Evolution process of Palaeokarst control to development of pore-cave system, construction and devastation exist at the same time in the course of development. So role of karst act as a important role on the influence of reservoir space.