古岩溶地貌与古岩溶储层岩溶效应分析——以鄂尔多斯盆地东部奥陶系风化壳为例

以鄂尔多斯盆地东部奥陶系风化壳为对象，以大量地质录井及实验分析资料为依据，密切结合古岩溶储层岩性和物性分析，综合探讨了古岩溶地貌与古岩溶储层的岩溶效应特征。研究结果表明，盆地东部奥陶系风化壳储层岩石类型可归纳为白云岩类、次生灰岩类、石灰岩类、云化灰岩类等四大成因组合。古岩溶地貌不同，则与储层的岩性效应不同，石灰岩及云化灰岩类是斜坡台地及残丘和盆地残台及残丘发育的标志性岩类；白云岩及次生灰岩类则是斜坡台缘、斜坡阶坪及盆地洼地发育的基础岩类。古岩溶地貌不同，则与储层的物性效应不同，斜坡台缘效应最好，斜坡阶坪中等，斜坡台地及残丘中下，盆地残台及残丘较差，盆地洼地最差。斜坡台缘与斜坡阶坪分界为盆地东部古岩溶效应的重要转折点，居其两侧的小层渗透率随古岩溶地貌的变迁而逆向增减，发育红色和蓝色2种不同的效应模式。小层物性效应则与白云岩类和次生灰岩类的含量密切相关，其效应模式呈现出此消彼长同时又互为补充的特点。如果储层岩类组成过于单一、或者某类组分含量过低或过高，都将对古岩溶地貌发育产生重要的影响；适度比率的岩类组合或者混合岩化对古岩溶储层的物性效应更为有利。

The karst effect on the palaeokarst geomorphology and palaeokarst reservoir: A case study of the Ordovician weathering crust,eastern Ordos Basin,China

Based on the Ordovician weathering crust of eastern Ordos Basin,with a large amount of geological logging and experimental analysis data,closely combined with the lithology and physical property analysis of the ancient karst reservoir,the karst effect characteristics of the palaeokarst geomorphology and palaeokarst reservoir were studied synthetically.The results show that the rock type of the Ordovician weathering crust palaeokarst reservoir can be divided into four types,dolostone,secondary limestone,limestone and dolomitic limestone.The lithologic effect of the palaeokarst reservoir changes with difference of the palaeokarst geomorphology,limestone and dolomitic limestone are typical rock types of the development of slope tableland,slope monadnock,basin residual-tableland and basin monadnock.Dolostone and secondary limestone are basic rock type of the development of the slope platform margin,slope terrace and basin depression.The physical property effect of the palaeokarst reservoir changes with difference of the palaeokarst geomorphology,with the best physical property for slope platform margin,moderate for the slope terrace,lower-middle for the slope tableland and slope monadnock,lower for the basin residual tableland and basin monadnock and the lowest for the basin depression.The boundary between the slope platform margin and the slope terrace is the critical changing point of the palaeokarst effect in the east of the basin,the permeability of the sub-reservoirs on both sides of the boundary of geomorphology increased or decreased reversely along with the change of the palaeokarst geomorphology,this palaeokarst effect had two different effects model of red and blue.The physical property effect of palaeokarst sub-reservoirs was closely correlated to the content of dolostone and secondary limestone,this effect model presented its own characteristics of mutual growth decline as well as complement of each other.If the reservoir rock composition is too single,or some rock content is too low or too high,it would produce an important influence on the development of ancient karst landform;moderate ratio of rock types or combinations of migmatization was more favourable to the physical property effects of paleokarst reservoir.