Study on Quantitative Analysis Technology of Shale Reservoir Space

Unconventional oil and gas reservoirs, represented by mud shale reservoirs, have received a lot of attention. The main methods for evaluating reservoir space include CO2 adsorption (effective pore diameter interval ≤2 nm), N2 adsorption (effective pore diameter interval 2 nm–200 nm), high-pressure mercury injection (effective pore diameter interval >8 nm), micro-nano CT (effective pore diameter interval >500 nm), and NMR (effective pore diameter interval >2 nm) et al., the above method can only give the pore distribution interval and the contribution of different pore size intervals to the reservoir space, but cannot give the contribution of different types of pores to the reservoir space, which restricts the study of the main controlling factors of shale reservoir space. Previously, JMicroVision image processing software was used to manually depict micro and nano pores of shale obtained by scanning electron microscopy. However, this method would produce huge time cost of manual depiction, which is only suitable for individual or small amount of pore depiction, and cannot realize pore statistics and analysis with large data volume. In this paper, Corel DRAW Image processing software and image analysis software are used for batch analysis, extraction and processing of micro-nano pore photos of mud shale which are splintered by field emission electron microscopy in large field, and the storage space is divided into organic pores (fractures) and inorganic pores (fractures). The inorganic pores (fractures) were further subdivided into six categories: intergranular pores, clay minerals intergranular pores, pyrite intergranular pores, calcite intergranular dissolved pores, intragranular dissolved pores and microfractures. Then, the surface porosity and relative proportion of different types of pores, and the distribution frequency and surface porosity of pores with different diameters were calculated, and finally the quantitative analysis technology of shale reservoir space was formed.