Characterization of the pore size distribution with SEM images processing for the tight rock

The unconventional resource is a research hotspot of the present oil and gas development. The tight rock of the unconventional reservoir has the characteristics of the complex pore structure and the nanometer scale pore system. Study of the pore structure would help us understand the fluid transport property within the tight rock. A quantitative method to describe pore size distribution for the tight rock with scanning electron microscope (SEM) image processing was proposed in the paper. The tight oil outcrop samples in the Jurassic System in Sichuan Basin were collected to make SEM experiment. The nanometer pore could be seen clearly in SEM images. The threshold value method was used to distinguish the pore and the matrix of the segmented image to obtain the binary SEM image. The pore size distribution of the tight rock was extracted from the binary image with the mathematical morphology method. Both the histogram and the porosity accumulation diagram of the pore size distribution quantitatively indicate the pore structure of the tight rock. The results also show that the pore structure quantitative characterization with SEM image processing is an effective and economical method for the tight rock.