1. n. [Formation Evaluation]

That part of the pore space that has a characteristic dimension less than 1 micron. In general, this includes not only very small pores but also the porosity associated with surface roughness. The water in this pore space is part of the capillary-bound water and the small-pore water. Water in micropores is not expected to flow on production. The term is also defined as porosity that cannot be seen at magnifications less than 50x.

See related terms: effective porosity,  small-pore water,  total porosity