Zhao Jianhua, Jin Zhijun, Hu Qinhong, Jin Zhenkui, Barber Troy J, Zhang Yuxiang, Bleuel Markus
School of Geosciences, China University of Petroleum (East China), Qingdao, 266580, China.
State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing, 100083, China.
Sci Rep. 2017 Nov 13;7(1):15413. doi: 10.1038/s41598-017-15362-0.
An integration of small-angle neutron scattering (SANS), low-pressure N physisorption (LPNP), and mercury injection capillary pressure (MICP) methods was employed to study the pore structure of four oil shale samples from leading Niobrara, Wolfcamp, Bakken, and Utica Formations in USA. Porosity values obtained from SANS are higher than those from two fluid-invasion methods, due to the ability of neutrons to probe pore spaces inaccessible to N and mercury. However, SANS and LPNP methods exhibit a similar pore-size distribution, and both methods (in measuring total pore volume) show different results of porosity and pore-size distribution obtained from the MICP method (quantifying pore throats). Multi-scale (five pore-diameter intervals) inaccessible porosity to N was determined using SANS and LPNP data. Overall, a large value of inaccessible porosity occurs at pore diameters <10 nm, which we attribute to low connectivity of organic matter-hosted and clay-associated pores in these shales. While each method probes a unique aspect of complex pore structure of shale, the discrepancy between pore structure results from different methods is explained with respect to their difference in measurable ranges of pore diameter, pore space, pore type, sample size and associated pore connectivity, as well as theoretical base and interpretation.
采用小角中子散射（SANS）、低压N物理吸附（LPNP）和压汞毛细管压力（MICP）方法相结合，研究了美国尼奥布拉拉、沃尔夫坎普、巴肯和尤蒂卡主要地层的四个油页岩样品的孔隙结构。由于中子能够探测N和汞无法进入的孔隙空间，SANS获得的孔隙率值高于两种流体侵入法获得的孔隙率值。然而，SANS和LPNP方法显示出相似的孔径分布，并且两种方法（在测量总孔隙体积方面）显示出与MICP方法（量化孔喉）获得的孔隙率和孔径分布不同的结果。利用SANS和LPNP数据确定了多尺度（五个孔径区间）N无法进入的孔隙率。总体而言，在孔径<10nm时出现了较大的无法进入的孔隙率值，我们将其归因于这些页岩中有机质为主和与粘土相关的孔隙的低连通性。虽然每种方法都探测了页岩复杂孔隙结构的一个独特方面，但不同方法所得孔隙结构结果之间的差异是根据它们在孔径、孔隙空间、孔隙类型、样品尺寸和相关孔隙连通性的可测量范围以及理论基础和解释方面的差异来解释的。
