利用多尺度CT成像表征致密砂岩微观孔喉结构  

Multi-scale method of Nano(Micro)-CT study on microscopic pore structure of tight sandstone of Yanchang Formation,Ordos Basin

作　　者：白斌[1,2] 朱如凯[1,2] 吴松涛[1,2] 杨文静[3] Jeff Gelb Allen Gu 张响响 苏玲[1,2] 

机构地区：[1]提高石油采收率国家重点实验室 [2]中国石油勘探开发研究院 [3]中国石油长庆油田公司勘探部 [4]Xradia Inc

出　　处：《石油勘探与开发》2013年第3期329-333,共5页Petroleum Exploration and Development

基　　金：国家科技重大专项(2011ZX05001-002);国家自然科学青年基金项目(41002034);中国博士后科学基金(20090460390);中国石油勘探开发研究院青年基金(2010-A-26-08)

摘　　要：为全面表征致密储集层微观孔喉分布及结构特征,对鄂尔多斯盆地上三叠统延长组致密砂岩储集层样品进行纳米—微米多尺度CT三维成像研究。首先利用低分辨率微米尺度X-CT扫描获取直径为2.54 cm岩心柱内部微米级别孔喉结构特征,然后根据微孔分布特征,制备多个直径为65μm的样品进行高分辨率纳米尺度扫描,重构纳米级微孔三维结构模型,最终计算出样品的孔隙度和渗透率。在微米尺度下,孔喉大小不一,直径为5.4～26.0μm,呈孤立状,局部呈条带状;在纳米尺度下,微孔直径主要为0.4～1.5μm,纳米级微孔数量增多,孔喉为管状、球状,分布于矿物颗粒(晶体)内部或表面。纳米级球状微孔连通性较差,三维空间呈孤立状,多仅作为储集空间,而纳米级短管状微孔具有一定的连通性,与微米级管状微孔和邻近孤立球状纳米微孔具有一定连通性,兼具喉道与孔隙的双重功能。数值计算样品渗透率为0.843×10 3μm2,孔隙度为10%。Multi-scale （nano-to-micro） three-dimensional CT imaging was used to characterize the distribution and texture of micro-scale pore throats in tight sandstone reservoirs of the Triassic Yanchang Formation, Ordos Basin. First, the low-resolution Micro-CT was used to reflect the micro-pore texture of the core column with a diameter of 2.54 cm. Then, some samples with a diameter of 65μm was derived from different areas according the different characteristics of micro-pore texture of the core scanned by low-resolution Micro-CT and scanned by high-resolution Nano-CT. Thus, a three-dimensional texture model of nano-scale micro-pores was reestablished and the permebility and porosity data of the sample could be obtained. On a micrometer scale, the size of the micro-pores varies, and their diameters range from 5.4 to 26.0 μm. The micro-pores are isolated, locally in the shape of a band. On a nanometer scale, the quantity of nanoscale micropores increases, the diameter of which ranges from 0.4 to 1.5 μm. The pore throats are arranged in the shape of tube and ball inside or on the surface of mineral particles（crystals）. The ball-shaped micropores in nanoscale, often isolated in the three-dimensional space, show the poor connectivity and consequently act as the reservoir space. By contrast, the tube-shaped micropores in nanoscale show certain connectivity with micro-scale tube-shaped micropores and adjacent isolated ball-shaped micropores in nanoscale. Therefore, these tube-shaped micropores in nanoscale serve as throats and pores. Based on the calcution, the permeability of the samples is 0.843 × 10-3 μm^2 and porosity is 10%.

关 键 词：X射线CT三维成像 致密砂岩储集层 微观孔喉 纳米—微米级别 

分 类 号：TE122.1[石油与天然气工程—油气勘探]