Experimental investigation of the pore shape factor in fluid imbibition model----taking the Longmaxi shale in Sichuan Basin as examples

Abstract

The current fluid imbibition models used in shale usually assume a pore shape to be circular, whereas the pore shapes significantly deviate from that. One approach to correct this deviation is to introduce a pore shape factor into the models although it is challenging. This paper provides a way to calculate the specific shape factors of irregular inorganic and organic pores in shale based on SEM images analyses. Then, combining with the percentages of the organic and inorganic pores, a group of weighted-average pore shape factors of Longmaxi shale samples was calculated (0.587～0.667). Another group of pore shape factors (0.359～0.615) was also matched from the shale fluid imbibition curves, close to the previous values, which confirmed the validity of the proposed method. This work may provide an effective support in exploring the fluid imbibition or flow mechanisms in shale, especially considering the strong pore wall effects under nano-scale.