摘要
为了精确、直观地表征鄂尔多斯盆地西南部长6—长8段致密砂岩储层的微观孔隙结构,应用铸体薄片、扫描电镜与高压压汞等方法分析了储集空间的类型与物性特征,通过微米—纳米CT三维成像技术定量表征了微观孔隙的结构并对其三维孔隙的空间形态、大小、连通情况及分布特征进行了深入的研究,在此基础上进一步探讨了微观孔隙结构对孔隙度的影响。结果表明:长6—长8段致密砂岩储层发育多种类型的微观孔隙,常见有粒间孔、粒内孔、晶间孔与微裂缝4类孔隙类型。依据长宽比值(l/d)划分三维微观孔隙的空间形态类型,其中粒间孔为不规则状,粒内孔与晶间孔为球状,微裂缝多为管束状。微米尺度下不规则状与管束状孔隙发育,孔隙连通性较好,孔隙体积多为20~100μm^3,平均孔隙半径多小于5μm;纳米尺度下球状孔隙发育,孔隙连通性较差,孔隙体积多为104~107nm^3,平均孔隙半径多小于0.1μm。致密砂岩孔隙度与平均孔隙半径的相关性较差,其中管束状孔隙的数量、管束状与不规则状孔隙的平均半径对样品孔隙度的影响较大。由此可知微米尺度下管束状与不规则状孔隙是长6—长8段致密砂岩储层储集空间的主要贡献者。
In order to characterize the pore structure of Chang 6-Chang 8 members tight sandstone reser- voirs in the southwestern part of Ordos Basin accurately and visually,thin-section,Scanning Electron Mi- croscope （SEM） and high pressure mercury injection techniques were used to analyze pore types and reser- voir characteristics. Micro-nano CT imaging technology is adopted to give three-dimensional （3D） repre- sentation of pore spatial morphology, size and connection, and effect of pore type on porosity is further ana- lyzed in this paper. The results indicate that Chang 6-Chang 8 members sandstones have four major types of pore textures, including inter-granular pores, intra-granular pores, inter-crystalline pores, and micro-frac- tures. Pore spatial morphology of 3D is divided into three types by the ratio of length to width（l/d）. Inter- granular pores are irregularly shaped with 3D imaging, whereas intra-granular and inter-crystalline pores, and microfractures have spherical and pipe shape,respectively. Irregular-shaped and pipe-shaped pores are predominated at micro-scale, the pore connectivity is better. The pore volume ranges mostly from 20 to 100~m3 ,and the average pore radius is commonly less than 5~m. The spherical pores are predominated at nano-scale,the pore volume ranges mainly from 104 to 107nm3 ,with the average pore radius of less than 0.1μm. The correlation between porosity and pore abundance is poor. Pipe-shaped pore quantity, average radius of pipe-shaped and irregular-shaped pores have significant effect on sample porosity. Pipe-shaped and irregular-shaped pores at micro-scale have significant effect on porosity of Chang 6-Chang 8 members tight sandstone reservoirs.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2017年第6期909-919,共11页
Natural Gas Geoscience
基金
国家自然科学基金重点项目"致密砂岩微米-纳米级孔喉网络系统石油充注
运移和聚集机理"(编号:1330139)资助
