|dc.description.abstract||Small scale deformation structures that mostly occur in highly porous rocks are called
deformation bands. Petrophysical characteristics of deformation bands are different from
those of host rock and they can act as barriers or conduit to fluid flow. The effect on fluid
flow is the most important property of these structures which is essential in many geological
fields; for instance oil & gas, CO2 storage and ground water flow, when permeability and
capillary pressure are the two major characteristics of the reservoir under study.
In this study, fluid flow experiments have been conducted on deformed sandstone sample
from Moab member of Entrada Formation in Waterfall Canyon, Utah which contains
cataclastic deformation bands. We have visualized one- and two-phase fluid flow in the
deformed sandstone. According to Gamma-Ray scanning, the bands in this sample are denser
than host rock and porosity and permeability in these bands were expected to be lower than
the surrounding un-deformed rocks.
In miscible displacement experiment, five brine floods through sandstone with deformation
bands was monitored using real time X-Ray image scanning instrument. To visualize the flow
of fluids through the sample, injection water was saturated by Natrium Iodine (NaI) tracer.
Removal of NaI tracer was done by injecting water saturated with NaCl with the same density
of NaI. In two phase experiment, first a full saturation of sample with NaI as water phase was
performed and thereafter draining of that was done using n-Decane (C10H22 ) as oil phase.
Saturation in sample for water phase and oil phase has been estimated as 55% and 45%,
respectively. Five experiments were performed with different inlet and outlet settings. The
flow pattern showed a complex, but repeatable trace of fluids through the sample as fluids
crossed deformation bands at same place in all experiments. In the two phase experiment the
oil did not completely replace the brine which might be due to increased capillary pressure in
the deformation bands.
Thin section study was performed on the same sample after the experiments to estimate
porosity and permeability from Back scatter Electron Image analysis (BSE) of the
deformation bands as well as the host sandstone. Estimated permeability for deformation
bands are between 350mD and 900 mD and for host rock is between 1500mD and 2000 mD.
Flow experiments and porosity and permeability estimated from BSE are in agreement with
each other and the former works (e. g. Torabi et al, in press, Torabi & Fossen 2009 and
Antonellini & Aydin, 1994) showing lower porosity and permeability in deformation bands
comparing to host rock. Furthermore, this work gains insight into the actual flow of fluids
through deformed sandstones by visualizing the flow pattern.||eng