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| Titel |
Effects of flow history on residual saturation during two-phase flow in porous media |
| VerfasserIn |
Homa Khosravian, Vahid Joekar-Niasar, Nima Shokri |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096757
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| Publikation (Nr.) |
 EGU/EGU2014-12273.pdf |
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| Zusammenfassung |
| During the process of immiscible displacement of a receding fluid by an invading fluid in
porous media one or more pores may be bypassed by the invading fluid as it advances through
the medium. This process creates disconnected fluid clusters which are left behind, trapped in
the porous structure. Enhanced knowledge of the parameters affecting the morphology
and distribution of the trapped fluid in porous media is required for exploitation
in various applications such as soil remediation or the enhanced oil recovery. In
the present study, we investigated the effects of flooding history on the amount
of the trapped fluid at different capillary numbers (defined as the ratio of viscous
to capillary forces) ranging from 10-6 to 10-3. In total 43 rounds of imbibition
experiments through spherical and crushed glass beads with particle sizes ranging
from 0.5 to 1 mm packed in a quasi-two-dimensional transparent Hele-Shaw cell
(100mm x 100mm x 4mm) were conducted. The dynamics and patterns of fluid phase
distributions were visualized using a high resolution CCD camera connected to a
computer. Dyed water as wetting and displacing fluid was injected into the glass cell
initially saturated with the nonwetting phase which was either Soltrol 220 or PCE
with the dynamics viscosity of 4.12 and 0.89 cP respectively. The injection of the
displacing fluid was continued until steady state was reached and no change in the phase
distribution was observed. At that point, the flow rate of the invading fluid was
increased and flooding was continued until reaching a new steady-state condition. This
procedure was repeated till reaching the maximum designed capillary number.
Our findings have two major contributions: (a) in a fairly homogenous quasi-two
dimensional model, not only the size and shape of the trapped oil clusters depend on the
history of flooding but also the residual oil saturation strongly depends on the history
of flooding rather than the ultimate flow rate. For example, remarkably less oil
entrapment was observed when the injection rate started from a low capillary number
gradually increased to the ultimate (high) capillary number compared to the case
when the injection was performed with the ultimate (high) capillary number; (b) a
non-monotonic relation between the capillary number and residual saturation was observed
which has been rarely reported in the literature as in most cases monotonic capillary
desaturation curves are presented. This observation may be due to homogeneous
distribution of pore sizes over the model causing a fairly homogeneous distribution of
capillary forces at the invading front. Consequently, as flow rate increases, instability at
the interface due to inverse viscosity ratio may increase the chance of trapping.
However, after a certain capillary number, further increase of the injection rate will
create enough drag force to mobilize the trapped zones resulting in reduction of
the residual oil saturation. This non-monotonic observation is consistent over the
examined viscosity ratio of 4.12 and 0.88 in both spherical and crushed glass beads. |
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