武隆黄草中上寒武统古岩溶储层特征

The characteristic of Huangcao Middle-Upper Cambrian reservoir

中扬子地台的渝东武隆黄草剖面在中上寒武统地层发育大量的孔洞层,主要集中在中寒武统的平井组和上寒武统的后坝组以及毛田组,为典型的古岩溶储层。表生岩溶带和潜流岩溶带的大部分孔洞是顺层分布,沿层面附近发育溶孔的基础上经过进一步溶蚀作用而形成,渗流岩溶带的孔洞则是呈窜洞分布,为淡水沿垂直或斜交层面的缝隙淋滤窜通沿层面发育的溶孔及溶洞进一步溶蚀而形成。经物性数据的统计分析,毛田组可评价为较好的裂缝—孔隙型储岩,平井组和后坝组可评价为中等的裂缝—孔隙型储岩。古岩溶储层的发育和分布的内在因素为可溶蚀的岩性,外因则是构造背景和后期的成岩作用。

A large number of vugular stratums develops in HuangCao Middle-Upper Cambrian of the eastern Chongqing Province in Middle Yangtze Platform.They assemble in Houba Formation of Upper Cambrian and Maotian Formation of Middle Cambrian.It can be defined to palaeokarst reservoir. Most vugular stratums distribute beddingly in epigenetic karst belt and submerged flow belt, which form from further denudation of dissolved pores acorss beding.Vugular stratums in vadose karst delt distribute communicating holes, which develop from further denudation of dissolved pores that water leacheate vertically or diagonally bedding surface. It is evaluated that Maotian Formation is preferable crack and hole reservoir, and Pingjin Formation and Houba Formation are mediocre crack and hole reservoir, from the statistics. Lithologic character affects the growth and distribution ofpalaeokarst inherently, and structural setting and deuteric diagenism affects outwards.