Microscopic pore structure in shale reservoir in the argillaceous dolomite from the Jianghan Basin

摘要

We proposed the areal porosity method (APM) to quantitatively characterize the inorganic porosity. The principle is that the areal porosity of the images in rock thin section is almost equal to the porosity of the rocks. So inorganic porosity of shale oil reservoir can be calculated approximately by the ratio between inorganic pore area and viewed area in its SEM images. Different components in SEM images have different gray-levels. Compared with other parts in the rock, the pore has greater gray-level, so porous part and non-porous part can be distinguished from each other in SEM images. Based on the theories above, the ratio between inorganic pore area and viewed area in any one of the sections is nearly the same, assuming inorganic minerals and pores are distributed evenly in the shale oil reservoir. This article focuses on approximate calculation of inorganic porosity in a certain depth under different magnifications in the SEM images. Inorganic porous part in the SEM images can be identified and marked by means of image analyzing software. So inorganic porosity can be obtained by accounting the ratio of pore area and viewed area.