Abstract:

The results of surface porosity obtained by scanning electron microscopy image processing can effectively reflect the development degree of shale organic matter pore. On the premise that the statistical sample is large enough, the pore size of organic matter can be quantitatively characterized relatively accurately. Due to the limitation of absolute resolution of scanning electron microscopy, the organic pore content was underestimated in the pore size range of less than 2 nm. The results of pore size distribution obtained by adsorption method need to be corrected. Combined with TOC and effective porosity, the porosity of shale organic matter can be calculated, and the proportion of organic and inorganic pore can be obtained indirectly. The data of 4 shale gas wells in southeastern Chongqing show that organic pore is the main type in Wulong and Dongsheng area, and the proportion of organic pore in bottom layer（① to ②） is high, up to 85.89 %. Pengshui area is controlled by organic carbon, and the proportion of organic pore is not more than 20 %. The organic pore proportion in Pingqiao area ranges from 20 % to 30 %, and the bedding fissures and laminar structures are relatively developed, especially the possible fissures or grain margin fissures between clastic particles and muddy interbeds in laminar structures contribute greatly to the inorganic pore. The proportion of organic pore is mainly affected by the abundance of organic matter and the degree of pore development of organic matter. The ratio of organic pore is highly consistent with the variation of TOC content in the vertical direction.

Key words: shale, pore, organic pore, inorganic pore, quantify