Estimation of Porosity and Pore size distribution from Scanning Electron Microscope image data of Shale samples: A case study on Jhuran formation of Kachchh Basin, India.

Summary

The work is aimed at estimating the porosity of shale from the Jhuran formation (Kachchh Basin) through non-destructive technique. Shale is a sedimentary rock formed by compaction of fine grained silt and clay sized mineral particles. In recent times, free gas is present in clay-mud shale complexes also within laminae that are enriched in bioturbation. However, a significant amount of natural gas is present in organic pores located within insoluble organic matter which is called kerogen. And also, there is still a lack of knowledge on the effect of bioturbation on porosity and pore size distribution in unconventional reservoir, especially in Indian context. The shales of Jhuran formation are characterized by low permeability on account of bioturbation. The purpose of the paper is to demonstrate use of non-destructive technique for defining effect of bioturbation on pore volume of shale sample. The Scanning Electron Microscope (SEM) images were examined for a porosity and pore size distribution analysis using an open source image processing software (ImageJ). The methodology developed allows estimation of porosity and pore size distribution from the image processing technique which validated with routine core analysis (Helium porosimeter). SEM image analysis is essential as shale properties can be directly observed and key details regarding unconventional reservoir conditions better understood.

• SEM (Scanning Electron Microscope)
• Porosity
• Permeability
• Kerogen
• Bioturbation
• Software (ImageJ)