Influence of shale bedding on development of microscale pores and fractures

Abstract

The characteristics of bedding development have an important impact on the spatial distribution of shale pores and fractures. However, there is a lack of systematic study on the pore and fracture structure of bedding development characteristics. In this paper, the geological control mode of shale type on the development characteristics of pores and fractures is revealed; pore-throat models under different shale lithology conditions are constructed; the control mechanism of bedding development characteristics on the spatial distribution pattern of pores and fractures is clarified. Results show that: (a) The pore space size varies widely from nanoscale to micron-scale or even millimeter scale, and is mainly concentrated in the nanoscale range. (b) For shale samples No. 1-7-1 No. 21-7-1, although the proportion of organic matter and mineral area in different samples varies greatly, the difference between the proportion of organic pore area and the proportion of mineral pore area is not significant, and the proportion of organic pore area is much higher than that of mineral pore area. (c) The pore diameter of shale has strong heterogeneity; minerals have an important impact on throat diameter; maturity has an important impact on throat length; geological compaction and tectonism will have an impact on the tortuosity of shale reservoir pores; the controlling effect of pore connectivity on shale wettability is mainly reflected in the connectivity of hydrophilic and lipophilic pores.