鄂尔多斯盆地乌审旗东区马五_(1-4)亚段碳酸盐岩储层孔隙特征与成因

The characteristics and genetisises of porosity carbonate reservoir from Ma5_(1- 4) submember,eastern Wushenqi in Ordos Basin

鄂尔多斯盆地乌审旗东区奥陶系储层低孔低渗,储层发育受沉积和岩溶地貌等多种因素控制。为探讨该区储层的特征及其成因,在岩心观察和测井曲线分析基础上,划分了苏里格气田东区马五1-4亚段沉积微相;利用薄片观察、压汞分析、扫描电镜等分析技术,研究了储层储集空间类型、物性特征、孔隙结构等储层特征及储层成因。研究后认为,马五1-4亚段储层孔隙包括膏核溶孔、膏晶模溶孔、晶间孔、晶间溶孔、裂缝等;孔隙类型组合形式有溶孔裂缝型、孔隙型、微孔型、裂缝-孔隙-孔洞型4种;沉积微相以潮上、潮间、潮下云坪和含泥云坪为主,纵向上变化较快;膏质或含膏云坪相最有利于储层发育,潮间带云坪相稍差,含泥云坪相最差;表生期石膏、硬石膏结核的选择性溶蚀决定了孔隙规模;岩溶古地貌控制地表水的流向,使碳酸盐岩溶蚀向下延伸,影响储层分布,马五4亚段成为该区最有利的储层;鼻隆和鼻凹等微构造对物性影响较大,鼻隆和鼻凹处孔渗较高,鼻翼最差。

The Ordovician reservoir of the Eastern Wu Shenqi in Ordos Basin is with low porosity and permea- bility, controlled by sedimentary and karst landform. To research the reservoir and its causes, differentiate the detail facies in MaS1.4 submember based on core observation and well log analysis. Reservoir space types, physical property, pore structures, reservoir characteristics are defined by thin section observation, mercury porosimetry, SEM and other methods. Conclusions are as follows： Pore types in MaSl~ submember are gypsum concretion and corrosion pores, intererystalline pores, intererystalline corrosion pores, cracks etc. There are 4 kinds of pore combinations： corrosion pore-fissure, pore, micro pore and fissure-pore-pore hole. The detail fa- cies include supratidal, intertidal, subtidal dolomitic flat and mud dolomitic flat, with quick variation in verti- cal direction. Paste and gypseous dolomite facies are best reservoirs, then it＇s intertidal dolomitic flat, the mud dolomitie flat is worst. Selective dissolution of gypsmu and anhydrite in epigenesist period controlled pore scale. Karst landform controlled the flow of surface water, lead to a deep carbonate erosion and effected the reservoir separation.Ma54 submember was the most favorable reservoir. The nose uplift, nasal concave and other micro-structure effected reservoir porosity ： higher porosity in nose uplift-nasal concave and lower porosity in pinna nast.