致密气储层孔喉分形特征及其与渗流的关系——以鄂尔多斯盆地下石盒子组盒8段为例

发布时间：2018-12-18 03:35

【摘要】：选取鄂尔多斯盆地盒8段16块致密砂岩样品进行恒速压汞测试,结合同位样品核磁共振实验,分析了致密气储层孔喉分布特征;在此基础上,运用分形几何原理和方法,开展了致密气储层孔喉分形研究,并表征了分形与储层渗流特征和孔隙结构参数的关系。结果表明:致密气储层有效孔隙被亚微米—微米级孔喉所控制,其中孔隙主要为大孔和中孔,喉道由微喉道、微细喉道和细喉道所组成;致密气储层孔隙分布不具分形特征,而孔喉整体和喉道则符合分形结构,且分别对应分形维数D1和D2;基于储层孔喉分形结构与其渗流特征,将盒8段致密气储层孔喉分形结构划分为2种类型:Ⅰ型表现为阶段式分形特征,以进汞压力1 MPa为界,大于1 MPa孔喉具有分形特征,且储层阶段进汞饱和度主要由喉道贡献,反之,孔喉不符合分形特征,其进汞饱和度增量由孔隙贡献;Ⅱ型为整体式分形,进汞饱和度几乎全由喉道贡献。储层孔喉分形维数与渗透率、平均喉道半径和主流喉道半径存在较好的负相关性,与微观非均质系数呈现较明显的正相关性,而与孔隙度、平均孔隙半径和平均孔喉半径比之间没有明显的相关性。
[Abstract]:Sixteen tight sandstone samples from Box 8 member of Ordos Basin were selected for constant velocity mercury injection test. The pore throat distribution characteristics of tight gas reservoir were analyzed with nuclear magnetic resonance (NMR) experiments of the same sample. On this basis, the fractal theory and method of fractal geometry are used to study the pore throat fractal of tight gas reservoir, and the relationship between fractal and percolation characteristics and pore structure parameters of tight gas reservoir is characterized. The results show that the effective pores of tight gas reservoirs are controlled by submicron-micron pore throats in which the pores are mainly macropore and mesopore and the throat is composed of microlarynx and fine throat. The pore distribution of tight gas reservoir has no fractal characteristics, while the pore throat and throat accord with fractal structure, and correspond to fractal dimension D1 and D _ 2, respectively. Based on the fractal structure of reservoir pore throat and its percolation characteristics, the pore throat fractal structure of tight gas reservoir in Bo8 member is divided into two types: type I shows a stage fractal feature, with mercury pressure of 1 MPa as the boundary, and pore throat larger than 1 MPa with fractal characteristics. The mercury saturation in reservoir stage is mainly contributed by throat, whereas pore throat does not accord with fractal characteristics, and the increase of mercury saturation is contributed by pore. Type II is a integral fractal, and mercury saturation is almost entirely contributed by the throat. The fractal dimension of reservoir pore throat has a good negative correlation with permeability, average throat radius and mainstream throat radius, and has a significant positive correlation with microscopic heterogeneity coefficient, but with porosity, the fractal dimension of reservoir pore throat has a good negative correlation with permeability, average throat radius and mainstream throat radius. There is no obvious correlation between the mean pore radius and the average pore throat radius ratio.
【作者单位】：中国石油大学(北京)地球科学学院;油气资源与探测国家重点实验室;中国石油勘探开发研究院廊坊分院;中国石油大学(北京)非常规天然气研究院;
【基金】：国家自然科学基金项目(41272157) 国家科技重大专项(2016ZX05007-003) 中国石油科技创新基金(2014D-5006-0101) 中国石油大学(北京)科研基金(2462013YJRC038,2462015YQ0108)~~
【分类号】：TE312

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