HR: 0800h
AN: H11E-0333    [Abstracts]
TI: Dedolomitization and Flow in Fractures
AU: Singurindy, O
EM: olga.singurindy@weizmann.ac.il
AF: Weizmann Institute of Science, Dept. of Environmental Sciences and Energy Research, Rehovot, 76100 Israel
AU: Emmanuel, S
EM: simon.emmanuel@weizmann.ac.il
AF: Weizmann Institute of Science, Dept. of Environmental Sciences and Energy Research, Rehovot, 76100 Israel
AU: * Berkowitz, B
EM: brian.berkowitz@weizmann.ac.il
AF: Weizmann Institute of Science, Dept. of Environmental Sciences and Energy Research, Rehovot, 76100 Israel
AB: The evolution of porosity and hydraulic conductivity resulting from the incongruent dissolution of fractured dolomite was studied experimentally. Two types of flow experiments were carried out: (1) reactive flow in quasi-2D rock fractures (geometries consisted of a through-flow fracture that connected the inlet and outlet, and an oblique fracture that did not connect them), and (2) 3D fractured/intact linear corefloods. Experimental results demonstrated a strong influence of flow conditions on aragonite/calcite formation processes in fractured dolomite. Mixing at fracture intersections induced aragonite precipitation that led to an irreversible reduction of sample hydraulic conductivity. Clogging of the samples was more rapid for oblique fractures than for through-flow fractures. Oblique fractures were always filled with precipitated material in both 2D and 3D fracture flow experiments. To further study the dynamics of porosity evolution during mixing induced precipitation of calcite at a fracture intersection, a 2D finite element numerical model was developed. The influence of two different expressions that relate specific surface area to porosity was also explored. During the simulations, porosity was reduced primarily in regions in which significant degrees of mixing occurred, effectively creating a barrier to further mass transport. The results demonstrate that mixing induced precipitation can account for systems in which only portions of high porosity regions are filled. Mixing induced precipitation thus represents a viable mechanism that can account for porosity infilling in both fractured and porous geological systems. The simulations also indicate that the choice of functional form for the specific surface area plays an important role in controlling porosity patterns. As specific surface area is currently one of the least constrained parameters in models of porosity evolution, this result highlights the need for future experimental studies.
DE: 5114 Permeability and porosity
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting