Отправлено: 10.01.17 12:36. Заголовок: Pore Space Connectivity and the Transport Properties of Rocks

Pore Space Connectivity and the Transport Properties of Rocks
Yves Bernabé, Min Li, Yan-Bing Tang and Brian Evans

Abstract — Pore connectivity is likely one of the most important factors affecting the permeability of
reservoir rocks. Furthermore, connectivity effects are not restricted to materials approaching a
percolation transition but can continuously and gradually occur in rocks undergoing geological
processes such as mechanical and chemical diagenesis.

In this study, we compiled sets of published measurements of porosity, permeability and formation factor,
performed in samples of unconsolidated granular aggregates, in which connectivity does not change, and in two other
materials, sintered glass beads and Fontainebleau sandstone, in which connectivity does change.

We compared these data to the predictions of a Kozeny-Carman model of permeability, which does not
account for variations in connectivity, and to those of Bernabé et al. (2010, 2011) model, which does
[Bernabé Y., Li M., Maineult A. (2010) Permeability and pore connectivity: a new model based on
network simulations, J. Geophys. Res. 115, B10203; Bernabé Y., Zamora M., Li M., Maineult A.,
Tang Y.B. (2011) Pore connectivity, permeability and electrical formation factor: a new model and
comparison to experimental data, J. Geophys. Res. 116, B11204].

Both models agreed equally well with experimental data obtained in unconsolidated granular media.
But, in the other materials, especially in the low porosity samples that had undergone the greatest amount of sintering or
diagenesis, only Bernabé et al. model matched the experimental data satisfactorily. In comparison,
predictions of the Kozeny-Carman model differed by orders of magnitude.

The advantage of the Bernabé et al. model was its ability to account for a continuous, gradual reduction in pore
connectivity during sintering or diagenesis. Although we can only speculate at this juncture about
the mechanisms responsible for the connectivity reduction, we propose two possible mechanisms,
likely to be active at different stages of sintering and diagenesis, and thus allowing the gradual
evolution observed experimentally.