Quantifying solute spreading and mixing in reservoir rocks using 3-D PET imaging
File(s)
Accepted version
Author(s)
Pini, R
Vandehey, NT
Druhan, J
O'Neil, JP
Benson, SM
Type
Journal Article
Abstract
We report results of an experimental investigation into the effects of small-scale (mmcm)
heterogeneities on solute spreading and mixing in a Berea Sandstone core. Pulsetracer
tests have been carried out in the regime Pe = 6 − 40 and are supplemented
by a unique combination of two imaging techniques. X-ray CT is used to quantify subcore
scale heterogeneities in terms of permeability contrasts at a spatial resolution of
about 10 mm3
, while [11C]PET is applied to image the spatial and temporal evolution
of the full tracer plume non-invasively. To account for both advective spreading and
local (Fickian) mixing as driving mechanisms for solute transport, a streamtube model is
applied that is based on the 1D Advection Dispersion Equation. We refer to our modelling
approach as semi-deterministic, because the spatial arrangement of the streamtubes and
the corresponding solute travel times are known from the measured rock’s permeability
map, which required only small adjustments to match the measured tracer breakthrough
curve. The model reproduces the 3D PET measurements accurately by capturing the
larger-scale tracer plume deformation as well as sub-core scale mixing, while confirming
negligible transverse dispersion over the scale of the experiment. We suggest that the
obtained longitudinal dispersivity (0.10 ± 0.02 cm) is rock- rather than sample-specific,
because of the ability of the model to decouple sub-core scale permeability heterogeneity
effects from those of local dispersion. As such, the approach presented here proves to be
very valuable, if not necessary, in the context of reservoir core analyses, because rock
samples can rarely be regarded as “uniformly heterogeneous”.
heterogeneities on solute spreading and mixing in a Berea Sandstone core. Pulsetracer
tests have been carried out in the regime Pe = 6 − 40 and are supplemented
by a unique combination of two imaging techniques. X-ray CT is used to quantify subcore
scale heterogeneities in terms of permeability contrasts at a spatial resolution of
about 10 mm3
, while [11C]PET is applied to image the spatial and temporal evolution
of the full tracer plume non-invasively. To account for both advective spreading and
local (Fickian) mixing as driving mechanisms for solute transport, a streamtube model is
applied that is based on the 1D Advection Dispersion Equation. We refer to our modelling
approach as semi-deterministic, because the spatial arrangement of the streamtubes and
the corresponding solute travel times are known from the measured rock’s permeability
map, which required only small adjustments to match the measured tracer breakthrough
curve. The model reproduces the 3D PET measurements accurately by capturing the
larger-scale tracer plume deformation as well as sub-core scale mixing, while confirming
negligible transverse dispersion over the scale of the experiment. We suggest that the
obtained longitudinal dispersivity (0.10 ± 0.02 cm) is rock- rather than sample-specific,
because of the ability of the model to decouple sub-core scale permeability heterogeneity
effects from those of local dispersion. As such, the approach presented here proves to be
very valuable, if not necessary, in the context of reservoir core analyses, because rock
samples can rarely be regarded as “uniformly heterogeneous”.
Date Issued
2016-06-10
Date Acceptance
2016-04-11
Citation
Journal of Fluid Mechanics, 2016, 796, pp.558-587
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
558
End Page
587
Journal / Book Title
Journal of Fluid Mechanics
Volume
796
Copyright Statement
© 2016 Cambridge University Press. This paper has been accepted for publication and will appear in a revised form, subsequent to peer-review and/or editorial input by Cambridge University Press.
Subjects
Science & Technology
Technology
Physical Sciences
Mechanics
Physics, Fluids & Plasmas
Physics
convection in porous media
mixing and dispersion
porous media
POSITRON-EMISSION-TOMOGRAPHY
STOCHASTIC-CONVECTIVE TRANSPORT
HETEROGENEOUS POROUS-MEDIA
END PORE VOLUME
REACTIVE TRANSPORT
HYDRODYNAMIC DISPERSION
COMPUTED-TOMOGRAPHY
NONLINEAR REACTION
TRACER DISPERSION
SEDIMENTARY-ROCKS
Fluids & Plasmas
01 Mathematical Sciences
09 Engineering
Publication Status
Published
Date Publish Online
2016-05-10