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TSpace Research Repository tspace.library.utoronto.ca
Asphaltene Deposition during Bitumen Extraction with Natural Gas
Condensate and
Naphtha
ZhenBangQi, Ali Abedini, Atena Sharbatian, Yuanjie Pang, Adriana
Guerrero, David Sinton
Version Author’s Post-Print
Citation (published version)
Qi, ZhenBang, Ali Abedini, Atena Sharbatian, Yuanjie Pang,
Adriana Guerrero, and David Sinton. "Asphaltene Deposition during
Bitumen
Extraction with Natural Gas Condensate and Naphtha." Energy
& Fuels (2017).
Publisher’s Statement “This document is the Accepted Manuscript
version of a Published Work that appeared in final form in Energy
and Fuels, copyright ©
American Chemical Society after peer review and technical
editing by the publisher. To access the final edited and published
work see
10.1021/acs.energyfuels.7b03495.”
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1
Asphaltene Deposition during Bitumen Extraction with Natural
Gas
Condensate and Naphtha
ZhenBang Qi,† Ali Abedini,
† Atena Sharbatian,
† Yuanjie Pang,
† Adriana Guerrero
b,‡ David Sinton
*†
† Department of Mechanical and Industrial Engineering and
Institute for Sustainable Energy, University
of Toronto, 5 King’s College Road, Toronto, ON, M5S 3G8,
Canada
‡ Suncor Energy Inc., 150 – 6 Ave SW, Calgary, AB, T2P 3E5,
Canada
ABSTRACT
Solvent bitumen extraction processes are alternatives to thermal
processes with potential for
improved economic and environmental performance. However,
solvent interaction with bitumen
commonly results in in situ asphaltene precipitation and
deposition, which can hinder flow and
reduce the process efficiency. Successful implementation
requires selecting a solvent that
improves recovery with minimal flow assurance problems. The
majority of candidate industrial
solvents are in the form of mixtures containing a wide range of
hydrocarbon fractions, further
complicating the selection process. In this study, we quantify
the pore-scale asphaltene
deposition using two commonly available solvent mixtures,
natural gas condensate and naphtha,
using a microfluidic platform. The results are also compared
with those of two typical pure
solvents, n-pentane and n-heptane, with all cases evaluated with
both 50 and 100 µm pore-throat
spacing. The condensate produced more asphaltenes and pore-space
damage than the naphtha,
and exhibited deposition dynamics similar to that of pentane and
heptane. This similarity is due
to the presence of a large amount of light hydrocarbon fractions
in condensate (~85 wt% of C5s–
C7s) dictating the overall deposition dynamics. Naphtha which
contains heavier fractions (~70
wt% of C8s–C11s) and aromatic/naphthenic components generated
less asphaltenes and exhibited
a slower deposition rate, resulting in less pore damage and
overall better performance.
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1. INTRODUCTION
Thermal processes such as steam-assisted-gravity drainage (SAGD)
have been widely
employed for bitumen extraction.1–3
SAGD involves injecting the saturated steam into the
reservoir to lower the viscosity of the bitumen by the steam
latent heat generation, which in turn
results in bitumen flow toward the producer under gravity
drainage. The typical time frame for
field scale SAGD process is over 10 years, depending on the
formation size, reservoir
characteristics, and operational parameters.4 While thermal
processes are effective, they have
significant economic and environmental challenges.4
Solvent-based processes are proposed as an
alternative to thermal processes to improve the recovery
performance and reduce the greenhouse
gas emission associated with bitumen production.5–8
However, hydrocarbon solvents have been
reported to have caused pore-throat plugging and reservoir
damage due to asphaltene deposition,
particularly near the well-bore.9–11
Asphaltenes are the heaviest fraction of crude oil, mainly
composed of aromatic rings containing heteroatoms (e.g.,
nitrogen, oxygen, sulfur, and metals)
attached to alkane chains. Asphaltenes are generally defined as
crude oil fractions that are n-
alkanes-insoluble and toluene-soluble.12
During solvent injection, hydrocarbon solvents
containing n-alkanes (e.g., pentane or heptane) dilute the
bitumen, which results in precipitation
of asphaltenes.13
The precipitated asphaltenes aggregate and form large asphaltene
micelles that
deposit on the rock surfaces.14–18
The removal of asphaltenes from the produced fluid can be a
benefit as it reduces the fluid viscosity, provided that the
precipitated asphaltenes cause minimal
or acceptable levels of reservoir damage via clogging of pores,
reducing the permeability of the
reservoir rock.19–22
Permeability reduction results in low recovery of both oil and
injected
solvents. Precipitated asphaltenes can also be a challenge for
down-hole production units as well
as the surface facilities. Therefore, it is important to
understand how and to what extend
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3
asphaltenes precipitate and deposit due to solvent injection in
order to properly design and
implement solvent-based injection processes as viable
alternatives to steam.
Asphaltene precipitation and deposition is a complex phenomenon
due to the complex
solvent-oil phase behavior. Series of experiments have been
carried out to quantify the
asphaltene precipitation and resulting formation damage during
enhanced oil recovery processes.
A high-temperature high-pressure PVT cell was used to study the
effects hydrocarbon solvent
dilution ratio, temperature, and pressure on the asphaltene
onset and precipitation rate.23–25
Slim
tube apparatus was also employed to monitor the pressure
fluctuation and flow turbulence as a
result of asphaltene precipitation during solvent
injection.26
In addition, high-pressure
coreflooding has been applied to estimate permeability reduction
as a result of asphaltene
deposition during immiscible and miscible CO2 injection
processes.27–29
Asphaltene deposition
during vapor extraction process with propane and butane has been
measured using sand-packed
physical models.30,31
In addition, the roles of morphology and mineralogy of the rock
were
analyzed with regard to asphaltene deposition and associated
reservoir damage.32
However, these
previous methods provide macroscopic damage measurements (e.g.,
permeability reduction), and
cannot resolve the pore-scale dynamics inherent to reservoir
processes.
Microfluidics is an emerging technology within the energy sector
that allows direct
visualization and rapid quantification of phase properties and
fluid transport.33–47
There is
precedent for microfluidic pore-scale analysis of asphaltene
precipitation and deposition.37,48–53
Asphaltene precipitation and deposition have been investigated
using a uniformly patterned glass
micromodel with a synthesized crude oil and n-heptane.48
Pore-scale of asphaltene precipitation
during solvent-based recovery processes were visualized using
micromodels, indicating that
asphaltenes reduced the displacement efficiency mainly through
blocking the pore throats and
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4
changing the surface wettability.37,49–51
Another microfluidic device was used to analyze the
dynamics of the asphaltene deposition in the porous media using
different volumetric ratios of n-
heptane.52
Once a local deposition was initially formed on a post, further
asphaltene deposition
grows in low-shear zone, which is against the fluid flow
direction. A similar microfluidic
platform was also applied to evaluate the role of chemical
dispersants on asphaltene deposition
kinetics. The results showed that the deposition rate is a
function of the intermolecular
interactions of asphaltene–dispersant system.53
The majority of the previous microfluidics-based
studies employed a synthesized crude oil (e.g., dissolved
asphaltene in toluene) and a single
precipitant or pure solvent (e.g., pentane or heptane). While
the results provide insight into the
dynamics of asphaltene precipitation, relevant asphaltene
deposition data from industrial solvent
mixtures is required for selecting a solvent that improves the
recovery with minimum flow
assurance problems.
Diluents (i.e., industrial solvents containing wide range of
hydrocarbon fractions) are
diluting or thinning agents which are used for reducing the
viscosity of the processed bitumen,
allowing it to be pumped through pipelines. Typical diluents are
in the form of natural gas
condensate, refined naphtha or synthetic crude oil.54
Recently, diluent has been applied for
solvent-based bitumen extraction processes in the field.55
Depending on the composition of
different diluents, they exhibit distinct phase behavior once
mixed with bitumen, and to date, the
available data on asphaltene deposition dynamics due to diluent
injection is limited.
In this paper, we determine the pore-scale of asphaltene
deposition using two pure
solvents (i.e., n-pentane and n-heptane) and two industrial
diluent samples (i.e., condensate and
naphtha) currently employed for solvent process pilot-test
implementations in the Athabasca
formation. Microfluidic chips with 50 and 100 µm pore-throat
spacings were imaged with optical
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5
and fluorescence microscopy to quantify the formation damage and
deposition dynamics during
solvent injection into bitumen-filled porous media. Scanning
electron microscopy (SEM),
fluorescent emission spectrum analysis, and viscosity
measurements are also conducted to
characterize the precipitated asphaltenes and deasphalted oils
obtained by each solvent.
2. EXPERIMENTAL
2.1. Fluids. A bitumen sample was procured from the Athabasca
oil sands in Alberta, Canada.
The fluid properties of the bitumen are presented in Table 1.
The bitumen molecular weight and
density were 596.8 g/mol and 1.017 g/cm3, respectively. For
convenience of transport, the
bitumen sample was diluted with toluene with mass ratio of 1:1.
Two pure hydrocarbon solvents
including n-pentane (Sigma-Aldrich, ≥99%) and n-heptane
(Sigma-Aldrich, 99%) and two
diluent samples namely condensate and naphtha (provided by
Suncor Energy) - with the fluid
properties presented in the Table 1 - were used for asphaltene
experiments. Suncor Energy
provided the measured values for molecule weight of the bitumen,
natural gas condensate, and
naphtha and the measured density. The fluid properties and
composition of the two diluent
samples were markedly different. The condensate sample contained
~85 wt% of C5s–C7s with a
molecular weight of 82.5 g/mol, that was much lighter than the
diluent sample. The naphtha was
rich in heavier hydrocarbon solvents, ~70 wt% of C8s–C11s, with
a molecular weight of 116.0
g/mol. The compositional analysis of the condensate and naphtha
samples are presented in the
Supporting Information. The asphaltene content of the bitumen
for all solvents was measured
using ASTM D2007 titration method at room temperature and
reported in Table 1.56
The
deasphalted bitumen sample for each solvent was collected after
removing the solvents using a
vacuum oven heated to 100 ºC. QUANTA FEG 250 ESEM was used to
take SEM images of the
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6
asphaltene particles produced by each solvent. All deasphalted
bitumen samples were mixed
with toluene with mass ratio of 1:1. The viscosity of the
deasphalted samples and the original oil
were measured using AR2000 Rheometer. Thereafter, the
deasphalted samples were mixed with
the solvents with mass ratio of 1:4. The fluorescent emission
spectrum for original oil and oil-
solvent mixtures were measured using Nikon A1 confocal
microscope with 486 nm laser as the
excitation source.
Table 1. Fluid properties of the Athabasca bitumen and
hydrocarbon solvents used in microfluidic
asphaltene experiments (the properties are reported at
21ºC).
Fluid Molecular
weight
(g/mol)
Density
(g/cm3)
Viscosity
(mPa.s)
Asphaltene
yield
(wt%)
Comments
Athabasca
bitumen
596.8 1.017 > 106
Bitumen sample has over 90
wt% of C20+ and over 70% of
C30+. There are little light
components in the bitumen (C1–
C10 < 0.1 wt%).
n-pentane* 72.15 0.626 0.23 43 n-C5 was purchased from
Sigma-
Aldrich with 99.5 mol% purity.
n-heptane* 100.20 0.684 0.41 29 n-C7 was purchased from
Sigma-
Aldrich with 99.5 mol% purity.
Condensate 82.5 0.648 0.28 35 Condensate sample contains ~85
wt% of C5s–C7s.
Naphtha 116.0 0.757 0.43 2 Naphtha sample contains ~70
wt% of C8s–C11s.
* Data of pure solvents are taken from National Institute of
Standards and Technology (NIST)
2.2. Microfluidic apparatus. Figure 1a shows the schematic
diagram of asphaltene deposition in
the porous media. A silicon-glass microfluidic chip was designed
and fabricated using deep
reactive ion etching (DRIE) and a shadow mask process. Two
distinct porous patterns were
fabricated to model the pore network of a typical oil sand
formation. The pore and grain sizes of
unconsolidated oil sands typically found in Athabasca formation
are in a range of 40–180 µm
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7
and 45–250 µm, respectively.57–59
Both patterns have the same diamond-shape grains (dp = 150
µm) but with two separate pore throat sizes of 50 µm and 100 µm
as shown in Figure 1b. The red
arrows represent pore throat and yellow arrows are defined as
the paths for fluid to flow in this
paper. The length and depth of the porous media were 5.4 mm and
60 (±1) µm, respectively. The
width for the micromodel was five posts for both pore throat
sizes. The porosities for the 50 µm
and 100 µm micromodel are 67% and 78%, respectively. A syringe
pump (Harvard Apparatus)
and a Isco pump (Teledyne-Isco 260D) were used to inject oil and
solvent into the microfluidic
chip, respectively.
2.3. Experimental procedure. The microfluidic chip was mounted
in a custom stainless steel
manifold. The chip and manifold were placed under the microscope
with required fluid lines
connected. An Olympus BXFM microscope with X-CITE 120 LED light
source connected to the
Leica MC 170 HD camera was used to monitor the process. Oil was
initially injected into the
microchip for several pore volumes using syringe pump to
completely fill the porous media with
no trapped air. Afterward, the solvent was injected into the
chip under constant flow rate of
30 µL/min using the Isco pump. The total volume for the 50 µm
and 100 µm microfluidic chips
is 0.4 µL and 0.5 µL, respectively. 30 µL/min flow rate is
equivalent to 1.25 liquid volumes per
second for the 50 µm chip and 1 liquid volume per second for the
100 µm chip. The time-lapsed
solvent-oil interaction and asphaltene deposition were imaged by
fluorescence microscopy with
FTIR filter cube (λex=475 nm/50 nm; λem=540 nm/50 nm). These
images were used to quantify
the asphaltene deposition rate for each solvent. Deposition rate
is most relevant with respect to
formation damage, and is distinct from other measures, such as
the total precipitation rate. Oil
exhibits fluorescent properties with a green color under the
microscope, which can be easily
differentiated from the asphaltenes which do not emit any
fluorescent signal due to
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8
quenching.60,61
At the end of each test, an optical scan of the entire porous
media was conducted
using the bright-field microscopy.
3. RESULTS AND DISCUSSION
3.1. Asphaltene and deasphalted oil characterization. The
characteristics of both asphaltenes
and the produced deasphalted oil varies greatly with the solvent
type. Figure 2 shows the SEM
images of the asphaltenes produced from all solvents tested in
this study under the 2000-fold
magnification. While the n-pentane asphaltenes are porous,
n-heptane produced asphaltenes with
a smooth surfaces and sharp edges. Differences in the morphology
of asphaltenes are due to the
differences in removal of resins and other lighter oil fractions
as well as rate of asphaltene
precipitation and dissolution.62–64
In contrast with n-heptane, n-pentane produces asphaltene
aggregates with more resins attached to the asphaltene
micelles11
. On the other hand, the
precipitation of asphaltenes with n-heptane is relatively slower
than that of n-pentane, providing
a longer time for asphaltenes to form aggregates with rigid
structures. The morphology of
condensate asphaltenes is similar to that of n-heptane
asphaltenes mainly due to the presence of
light fractions (pentane, heptane) in the condensate
composition. For naphtha case, the
morphology of the asphaltenes is different with that of other
solvents considered here.
Specifically, the naphtha sample has a much higher solubility
parameter due to presence of
heavier alkanes and naphthenic/aromatic components. The combined
effect was significant,
producing less asphaltenes than the other solvents. Here, the
asphaltene aggregates are soft with
powder-like structure and rough surfaces (Figure 2).
Figure 3a compares the fluorescent emission spectrum measurement
of the original oil with those
of the oil-solvent mixtures with precipitated asphaltenes taken
out of solution. In contrast with
the original oil sample, the fluorescent emission of the
mixtures was blue-shifted (moved left)
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9
and narrowed, agreeing with the dilution effects of the solvents
as reported in previous studies.65
While the oil emission is spectrally distinct from that of the
solvent-exposed oil, the mixtures
were not distinguishable at this excitation wavelength. Figure
3b plots the viscosity of the
produced deasphalted oil for each solvent. Since n-pentane
yields the largest amount of insoluble
asphaltene content (~43 wt%), the produced deasphalted oil has
the lowest viscosity (36 mPa.s).
In contrast, the naphtha deasphalted oil has the largest
viscosity (130 mPa.s) due to the small
yield of insoluble asphaltene (~2 wt%).
3.2. Asphaltene deposition in porous media. A series of solvent
injection tests were conducted
using two micromodels with 50 and 100 µm pore spacing with the
results shown in Figure 4.
Figure 4a shows a typical original full-scale image with the
deposited asphaltene particles in the
pore network (left side) with the corresponding post-processed
image using ImageJ software
(right side) in which the black area shows the area occupied by
asphaltenes. It is noted that the
inlet channel leading into the porous medium was initially
filled with the oil, which is an extra
source for asphaltene deposition in the porous media. Figure 4b
compares the amount of the
deposited asphaltenes obtained from all solvent runs for both 50
and 100 µm cases. Comparing
the two pure solvents, pentane precipitated a larger amount of
asphaltenes in the porous medium
than heptane – in agreement with previous studies.25
The condensate sample, however,
precipitated less asphaltenes than pentane and more than pure
heptane. We attribute this
difference to the large quantity of n-alkanes in the condensate,
specifically C5s and C6s (i.e., ~70
wt%), that resulted in significant asphaltene deposition in the
porous media (in between that of
pentane and heptane). The naphtha generated the least
asphaltenes in the porous media due to the
presence of heavier fractions in general. While the results are
consistent for both 50 and 100 µm
cases, the amount of the deposited asphaltenes in the 50 µm is
larger in all cases.
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10
Figure 5a through 5c quantify the percentage of damaged area,
pore throat blockage, and path
blockage as a result of asphaltene deposition for all solvents
in 50 and 100 µm micromodels. In
agreement with the optical overall images, pentane produced the
most severe damage to the
reservoir in terms of formation damages while naphtha produced
the least amount of damage. In
all cases the degree of formation damage reduced with increasing
the pore geometry, however
naphtha showed the most significant reduction in percentage of
damaged area from 68.7% to
38.5% (~44.0% reduction). All other solvents showed only
moderate reduction - n-pentane
(11.7% reduction), n-heptane (19.2% reduction), and condensate
(14.4% reduction). The trends
in total area damage are similar to those of pore-throat
blockage (Figure 5b). In terms of pore-
path blockage, however, the heptane and naphtha showed very
significant reductions in blockage
(Figure 5c).
3.3. Asphaltene deposition dynamics. Figure 6a shows the pore
area occupied by deposited
asphaltenes on a single post over 10 min of process in 50 µm
micromodel for all solvents with
the deposition growth quantified in Figure 6b. The intensities
of the brown color refer to
deposition in different times. Dark brown, lighter brown and the
lightest brown colors here
represent the amount of asphaltenes deposited on the post after
2, 5, and 10 min. It was observed
that majority of the asphaltenes deposited on the left tip of
the grain, and grew opposite to the
flow direction. The tip of the grain was the earliest point of
contact and a stagnation point where
the velocity of flow approaches zero, allowing asphaltene
particles to deposit – in agreement
with previous studies.52
The velocity profiles for both 50 µm and 100 µm cases are
presented in
the Supporting Information, showing the minimum flow velocity at
the tip and near the boundary
of the grains. After the initial deposition, the asphaltenes
accumulated and grew in size at the tip,
eventually reaching the adjacent grain to form a blockage in the
path. N-pentane has the highest
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11
asphaltene deposition rate followed by condensate, n-heptane and
naphtha. The early time
deposition of asphaltenes for heptane and naphtha (t = 2 min)
was very minimal - nearly
invisible, while the pentane and condensate resulted in severe
deposition with half blockage after
2 min and full blockage after 5 min. The results obtained here
provides insight to field-scale
process as the amount of oil-in-place is fixed in the reservoir
and thus different solvents have
different asphaltene deposition rates and lead to varying
degrees of reservoir damage.
With the strong performance of naphtha at early times compared
to the other solvents tested, we
analyzed the asphaltene deposition of naphtha over a longer
duration – 60 min in both 50 µm and
100 µm micromodels. Naphtha showed a significant reduction in
damaged area, pore-throat
blockage, and path blockage when the pore size was increased
from 50 µm to 100 µm. The time-
lapsed images of the asphaltene deposition in the both porous
media for naphtha at 2, 30, and 60
min were shown in Figure 7a. Figure 7b shows the asphaltene
deposition growth for both 50 µm
and 100 µm pore sizes. While the initial deposition rate in both
patterns was the same, the total
growth of deposited asphaltenes was larger in 50 µm case. Since
the pore space of 50 µm
micromodel is smaller, the deposited asphaltene aggregates
reached the adjacent post sooner and
blocked the entire flow path. This path blockage further
contributed to additional asphaltene
deposition, generating larger areas occupied by asphaltenes. On
the other hand, the pore spacing
is much wider for the 100 µm micromodel and the asphaltene
aggregates on a post could hardly
reach the adjacent post to block the entire path. With much less
flow hindrance and blocked
paths, the asphaltene particles flowed readily with the
deasphalted oil through the porous
medium toward the outlet. Furthermore, the narrow arrow shape
deposition has higher shearing
rate near the boundary of the deposited asphaltenes, leading to
less additional accumulation after
20 minutes of injection.52
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12
4. CONCLUSION
In this study, the asphaltene deposition during solvent
injection was studied using both pure and
industrial hydrocarbon solvents. The produced asphaltenes and
deasphalted oil sample for each
solvent-bitumen system were characterized. In addition,
microfluidic tests combined with high-
resolution optical imaging quantified in situ pore-scale data of
asphaltene deposition in the
porous media. The results indicated that:
The morphology of asphaltene particles and viscosity of produced
deasphalted oil as well as
the amount and rate of asphaltene deposition vary with solvent
composition.
The condensate with larger concentration of n-alkanes,
specifically C5s and C6s, produced
more asphaltenes with faster deposition dynamics similar to the
pure solvents, n-pentane and
n-heptane.
The naphtha, which contained heavier hydrocarbon fractions and
aromatic/naphthenic
components resulted in less precipitation of asphaltenes with
slower deposition rate and pore
damage in the porous media with a potential of minimal flow
assurance problems for field-
scale implementations.
The formation damage due to asphaltene deposition decreased in
larger pore sizes. This
reduction is more pronounced for naphtha case since the
deposited asphaltenes did not reach
the adjacent posts to block the entire path.
ASSOCIATE CONTENT
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13
Supporting Information. Compositional analysis of condensate and
naphtha; Asphaltene
deposition growth in the 50 µm and 100 µm microfluidic chips vs.
number of volume
displacement; The velocity profile inside the 50 µm and 100 µm
microfluidic chips.
AUTHOR INFORMATION
Corresponding Author
* E-mail: [email protected]; Phone: +1 416 978 1623
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
The authors gratefully acknowledge funding from Suncor Energy
Inc. for financial
supporting an ongoing collaborative research project on the
solvent injection process. The
authors would also like to thank Natural Sciences and
Engineering Research Council of Canada
(NSERC) for their funding support through the Collaborative
Research and Development
Program, the Discovery Grant Program, the Discovery Accelerator
Program, an E.W.R. Steacie
Memorial Fellowship (DS), and a Postdoctoral Fellowship (AA).
Support through the Canada
Research Chair Program is also gratefully acknowledged, as is
infrastructure provided by the
Canada Foundation for Innovation. Authors also thank Dr. Yihe
Wang for her assistance in
fluorescence spectrum measurements.
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Figure 1. a) Schematic diagram of asphaltene deposition in
micromodel with solvent flow direction
shown with red arrows, and b) pore-scale bright-field optical
images of micromodels with 50 and
100 µm pore spacing (red and yellow arrows represent pore throat
and pore path, respectively).
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20
Figure 2. SEM analysis of asphaltenes produced from different
solvents: a) n-pentane, b) n-
heptane, c) condensate, and d) naphtha under the 2000x
magnifications.
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21
Figure 3. a) Fluorescent spectroscopy comparison of original oil
and oil-solvent mixtures after
removal of precipitated asphaltenes. b) the viscosity of the
produced deasphalted oil for each
solvent. Viscosity tests were conducted off-chip with AR2000
Rheometer, using deasphalted oil
samples obtained by ASTM D2007 (error bar represents one sample
standard deviation of analyses
in triplicate). The percent asphaltenes removed is indicated
where applicable.
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22
Figure 4. a) Typical original full-scale image of the chip (left
side) with the corresponding post-
processed image using ImageJ software (right side); (b) post-run
optical microscopy of the entire
porous media for all solvent runs and both 50 and 100 µm
cases.
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Figure 5. Porous media damage quantification: a) total damage
area, b) pore throat blockage, and
c) path blockage for all solvents in both 50 and 100 µm
micromodels after 90minutes of runtime
when no significant change was observed afterward (equivalent to
2700 µL of solvent injection).
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24
Figure 6. Asphaltene deposition dynamics: a) pore area occupied
by deposited asphaltenes on a
single post over 10 min of process in 50 µm micromodel, and b)
average asphaltene deposition
growth in the model for all solvents.
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25
Figure 7. Asphaltene deposition growth in 50 and 100 µm
micromodels: a) pore-scale deposition on
the posts, and b) time-lapsed asphaltene deposition growth.