Characterization method of shale pore structure based on nano-CT: a case study of Well JY-1

An analysis on nanoporous structure of organic-rich shale is the basis for evaluating the reserving properties of shale reservoirs and the exploration and development potential of shale gas resources. In this study, the nano-CT and 3D reconstruction technique is used to evaluate the shale pore characteristics and connectivity of the Lower Silurian Longmaxi Formation in the Jiaoshiba area of Sichuan Basin. The experimental results show that:(1)nano-CT can display the three-dimensional spatial structure of shale pores, and will be more conducive to characterize the shale pore characteristics in combination with other experimental methods; (2)based on nano-CT, four components including matrix minerals, organic matter, pores, and high-density minerals (such as pyrite)can be distinguished in shale samples with the volume ratio of 89.20%, 6.22%, 2.71% and 1.87% respectively; (3)the pore sizes evaluated by nano-CT range from 79 nm to 4.7 μm, dominated by 100~500 nm, mainly including organic pores and inorganic pores; (4)strong heterogeneity exists in shale pore, generally with better connectivity, dominated by grade III connectivity domains.