利用显微X光CT对围压和孔隙水压条件下岩石试样的细微成像及其分析(英文)

MICROSCOPIC VISUALIZATION OF ROCKS BY MICRO X-RAY CT UNDER CONFINING AND PORE WATER PRESSURES

为得到岩石试样在各种围压和孔隙水压条件下的成像并分析其变形,利用显微X光CT系统获得具有5μm高分辨率的三维图像。为此,设计和制造了一个可以对岩石试样同时加围压和孔隙水压的新型压力容器。用此容器,对高20mm、直径10mm的Berea砂岩及Noto硅藻泥岩试样施加静水压并使之变形。在各种围压和孔隙水压条件下,每隔15°测试其径向尺寸。试样的平均直径随着有效围压的增长而单调减小。在此,有效围压被定义为围压和孔隙水压之差。随着有效围压的增加,其直径的变化根据不同的方向而不同,即其变形的各向异性特征得到了证实。Noto硅藻泥岩试样的各向异性比最大,达8%。实验结果表明,此显微X光CT方法可用来测试在各种围压和孔隙水压条件下一般方法很难测得、小或不规整试样的变形。

To visualize in detail the manner of deformation in rocks under various confining and pore water pressures, a micro X-ray CT system is used to obtain three-dimensional images with a high resolution of 5 μm. A new pressure vessel is developed to simultaneously supply both confining pressure and pore water pressure to rock specimens. Berea sandstone and Noto diatomaceous mudstone specimens with diameter of 10 mm and length of 20 mm are deformed hydrostatically. The diameters at every 15 o are measured under various conditions of confining and pore water pressures. The average diameter decreases monotonically with increasing effective confining pressure, which is defined as the difference between confining pressure and pore water pressure. Sensitive orientation around the specimen diameter during pressurization is recognized, deformation anisotropy during pressurization then emerges and the anisotropic ratios reach a maximum value of 8% in the case of Noto diatomaceous mudstone. The method of micro X-ray CT is applicable for deformation measurements of small and irregular rock specimens under various confining and pore water pressures.