陕甘宁盆地中部奥陶系风化壳古岩溶发育特征

PALAEOKARST FEATURES OF ORDOVICIAN WEATHERING CRUST IN THE CENTRE OF SHANGANNING BASIN

陕甘宁盆地中部奥陶系风化壳天然气储集体，属于古岩溶长期发育的产物。本文依据古岩溶发育的形迹，将古岩溶类型划分为层间岩溶、风化壳岩溶、缝洞系岩溶三类。并以水岩相互作用的原理，讨论了三类不同成因的古岩溶形成的古水文条件及发育特征；提出了三类岩溶的识别标志，并阐述了古岩溶型储集层的地质特征及发育规律，开拓了储层地质学的研究思路。

The gas reservoir of Ordovician weathering crust in the centre of Shaanganning basincan be regarded as product of palaeokarst developed for a long time. Three types ofpalaeokarst,i.e., interbedded karst,weathering crust karst and fissure-vug system karst aredivided on the basis of its morphologic features.According to the principles of water-rock in-teraction, the palaeohydrologic conditions are analysed under which the three types ofpalaeokarst formed.Criteria are put forward for identification of the different palaeokarsttypes.The geologic characters and development regularities of palaeokarst reservoir are alsooutlined. A new train of thought for researching reservoir geology thus has been opened up.