秦岭—大别造山带南侧兴山地区中上寒武统白云岩储层特征

CHARACTERISTICS OF MIDDLE-UPPER CAMBRIAN DOLOMITE RESERVOIR IN THE XINGSHAN AREA OF THE SOUTHERN MARGIN OF QINLING AND DABIE OROGENIC BELT

秦岭—大别造山带南侧兴山地区中上寒武统白云岩储层较为发育。在野外露头剖面测量的基础上,结合常规薄片鉴定、扫描电镜、图像分析、物性分析等测试手段,认为该区中上寒武统白云岩有效储层主要为泥粉晶云岩、颗粒云岩和细晶—中晶云岩等。泥粉晶云岩的有效储集空间以晶间孔为主;颗粒云岩主要包括鲕粒云岩、砂屑云岩和砾屑云岩等,有效储集空间主要包括粒间孔和粒内溶孔;细晶—中晶云岩非选择性溶孔和晶间孔较为发育。储层的形成与演化主要受到沉积作用和成岩作用的共同影响。其中沉积作用是储层形成的基础,决定了储层的空间展布特征。尽管平坦的沉积底形以及频繁的相对海平面变化导致储层多呈薄层状,但储层厚度较大,而且白云石化和埋藏阶段的选择性溶蚀使得颗粒云岩以及细晶—中晶云岩孔隙度变高,连通性变好,成为中上寒武统较好储层。

The Middle--Upper Cambrian dolomite reservoirs are well--developed in Xingshan area of the southern margin of Qinling and Dabie orogenic belt. Based on geologic survey on field outcrop profiles, as well as tests on conventional thin sections, SEM, image, petrophysical property, etc. , it has been found out that effective Middle--Upper Cambrian dolomite reservoirs are composed of micritic--crystalline powder dolostones, granular dolostones and kryptomere--mesocrystalline dolostones and so on. Effective reservoir spaces in micriticcrystalline powder dolostones are dominated by intercrystalline pores. Granular dolomites include oolitic dolostones, dolarenites and dolorudites with effective reservoir spaces consisting of intergranular pores and intragranular corrosion pores. Moreover, non--selective corrosion pores and intercrystalline pores develop in kryptomere--mesoerystalline dolomites. Formation and evolution of above--mentioned reservoirs are mainly controlled by effects of sedimentation and diagenesis. Sedimentation is the basis and determines spatial distribution characteristics of reservoir. Flat sedimentary landform and frequent changes of relative sea--level lead to the formation of lithologic interbed. Dolomitization and selective dissolution after burial make granular dolostones and kryptomere--mesocrystalline dolostones with good porosity and permeability come into being. They work as good reservoirs in the Middle-Upper Cambrian.