Fast and effective observations of the pore structure of tight sandstones at the same location by utilizing AFM and CF-SEM

Abstract

Atomic force microscopy (AFM), which allows 3D construction, nondestructive, and has a high resolution has been used to describe the pore structure of unconventional reservoirs. Due to its scalability, convenience, and flexibility, scanning electron microscopy (SEM) is widely conducted to describe the surface morphology of unconventional reservoirs. However, the two technologies are rarely combined to achieve fast and effective observations of the pore structure of unconventional reservoirs at the same location of the same sample (SLSS). In this study, nanoindentation technology is introduced to create a marked district (MD). Afterward, fast and effective observations of the pore structure of tight sandstones at the SLSS can be realized by searching this identifiable district with AFM and cold-field scanning electron microscopy (CF-SEM). The results demonstrate that AFM and CF-SEM rapidly capture observations of the surface morphology of tight sandstones at the SLSS. The method used in this study accomplishes the goal of fast and effective scanning at the SLSS (only a few minutes), while exhibiting the high potential of combining AFM and CF-SEM for comprehensively investigating the pore structure of reservoirs ranging from nanoscale to microscale. The most unique component of the presented method is that it is especially for the in situ observation of variations in the surface properties (morphology, electric, mechanical, surface force, and roughness) and pore size of all heterogeneous materials subjected to various external stimuli because the applied experimental technologies (nanoindentation, AFM, and CF-SEM) are all exhibit nondestructive properties. • AFM and CF-SEM can be applied to observe the surface morphology at the same location. • Nanoindentation technology can be applied to create an identifiable district. • Fast and effective observations at the SLSS can be achieved. • In situ observations of heterogeneous materials treated by various external stimuli can be realized.