Study of the Application of Mercury Porosimetry Method to a Single Fracture

摘要

In recent years, there is increasing evidence both in the field and in the laboratory that the fluid flow in low permeability fractured media is unevenly distributed and predominantly occurs in selected preferred paths. In view of the experimental observation of flow channeling, conceptual models have been developed to interpret fluid flow and transport in fractured media as through a system of statistically equivalent channels, and to relate permeability and tracer transport measurements to fracture aperture parameters. Mercury porosimetry has long been used to study the void space of porous materials. In this paper, we apply the concept of mercury porosimetry for porous rock to a rock fracture by simulations of mercury intrusion and withdrawal in a single fracture with variable apertures. Our theoretical studies show that the total capillary pressure curve in a pressure-controlled test gives information on the distribution of all the apertures which control the tracer transport through the fracture. On the other hand, the second intrusion curve in a pressure-controlled experiment resembles the rison part of a rate-controlled experiment, and gives information on the small aperture distribution which control the flow permeability of the fracture. The ratio of the limiting mercury volumes of the second intrusion and the first intrusion capillary curves can confirm estimates of equivalent apertures derived from permeability and tracer transport measurements. Lastly, the fraction of trapped mercury may be related to the spatial correlation of the aperture variation in the fracture. 12 refs., 9 figs. (ERA citation 13:047421)