塔里木盆地下古生界岩溶型储层类型及特征

塔里木盆地下古生界岩溶型储层可划分为同生岩溶、风化壳岩溶和埋藏岩溶等三种类型。同生岩溶型储层主要为礁滩体受三级或四级相对海平面下降导致的短暂暴露和淡水淋溶的产物。风化壳岩溶型储层包括层间岩溶和潜山岩溶两个亚类:层间岩溶为碳酸盐岩中—短期抬升剥蚀和淡水淋溶的产物,地形起伏平缓,与上覆碳酸盐岩呈平行不整合接触;潜山岩溶为碳酸盐岩长期抬升剥蚀和淡水淋溶的产物,地形起伏强烈,与上覆石炭系、侏罗系—白垩系碎屑岩呈角度不整合接触,包括石灰岩潜山和白云岩潜山。埋藏岩溶型储层又可分为原源埋藏岩溶和异源埋藏岩溶两个亚类,前者为有机酸、盆地热卤水、TSR成因的硫化氢等成岩流体作用的产物,后者为深源热液作用的产物。认为塔里木盆地岩溶型储层是多期次岩溶作用叠加改造的结果。

Types and Characteristics of Lower Palaeozoic Karst Reservoirs in Tarim Basin

Based on the observations of thin sections and cores from 90 wells,Three types of karst reservoirs can be recognized from Lower Palaeozoic carbonate rocks in Tarim basin.The karst reservoir developed during eogenetic stage resulted from the short-term exposure of Cambrian and Ordovician reef complex to meteoric water,which can be a response to the third-grade or the fourth-grade relative see level fall.The karst reservoir developed during telogenetic stage can be subdivided into intercalated karst and buried palaeokarst hill.The former resulted from the middle-term exposure of Cambrian and Ordovician carbonate rock to meteoric water,covered by upper carbonate rock with a pseudoconformity.The later,which can be subdivided into buried limestone and dolostone hills,resulted from the long-term exposure of Cambrian and Ordovician carbonate rock to meteoric water,covered by Carboniferous/Jurassic-Cretaceous clastic rocks with an angle unconformity.Subsurface karst reservoir developed during mesogenetic stage can be subdivided into buried karst and hydrothermal karst.The former resulted from the exposure of Cambrian and Ordovician carbonate rock to burial diagenetic fluid that include organic acid,basinal brine and TSR.The later resulted from the exposure of Cambrian and Ordovician carbonate rock to hydrothermal fluid.It is indicated that most of karst reservoirs were modified by multi-karstification in origin.