(559v) Using CO2-Responsive Nanogel to Improve CO2 Flooding Sweep Efficiency and CO2 Storage Efficiency
AIChE Annual Meeting
2019
2019 AIChE Annual Meeting
Topical Conference: Advances in Fossil Energy R&D
Poster Session: Advances in Fossil Energy R&D
Wednesday, November 13, 2019 - 3:30pm to 5:00pm
Sun, Xindi (S&T-Student) Normal Sun, Xindi (S&T-Student) 2 43 2019-02-05T20:36:00Z 2019-02-05T20:36:00Z 7 1264 7195 Missouri University of Science and Technology 138 64 8395 14.00
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12.0pt;line-height:150%;font-family:" times new roman>Using CO2-Responsive
Nano-gel to Improve CO2 Flooding Sweep Efficiency and CO2
Storage Efficiency
millimeter-sized particle gels can only penetrate in the fractures or channels,
which are mainly focused on the near wellbore problems. However, the in-depth
plugging cannot be achieved by conventional millimeter-sized particle gel
treatment. Therefore, the nano-particle gels are
developed based on the demand of the in-depth plugging. In this study, a novel nano-gel with CO2 responsive property is proposed for the
first time. The CO2-responsive nano-gel can be
stimulated by CO2 to increase particle size; therefore to provide additional
plugging to CO2 flooding sweep efficiency and CO2 storage efficiency.
The novel CO2-responsive
nano-particle gel was examined using sandstone cores
in order to study the transportation behavior and whether it can form an
in-depth plugging during CO2 flooding. Six cores were used in
this experiment and were divided into two groups: one is the group with CO2
and another is the group without CO2. The permeability of the core
is 40, 130, and 370 md, respectively. The
plugging efficiency of the group without CO2 was measured directly
after nano-gel injection, while the
plugging efficiency of the other group was measured after CO2
stimulation in the high-pressure vessels using brine. Transportation
test of nano-gel was conducted using homogeneous
sandstone cores. Five pressure sensors are installed along the core evenly in
order to monitor the nano-gel transportation. The nano
line-height:150%;mso-fareast-language:ZH-CN">-gel was injected into the core until
the third pressure sensor has reading, then the brine
is injected into the core until the fourth pressure sensor has reading. After
placing the nano-gel in the middle of the
core, supercritical CO2 was injected into the core until CO2
breakthrough from the outlet. The core was then soaked in supercritical CO2
for 7 days to allow the interaction between the nano-gel and supercritical CO2.
The plugging
line-height:150%;mso-fareast-language:ZH-CN">behavior
was tested by
the following water floodi
line-height:150%;mso-fareast-language:ZH-CN">ng
nano-gel has a novel function that it can increase
its swelling ratio under CO2 condition. Therefore, after placing the
nano-gel in the in-depth, the nano-gel
can swell more during the post CO2flooding,
hereby divert the CO2 to unswept area to
increase oil recovery. In this experiment, the concentration of CO2-responsive
nano-gel is 2,000 ppm and the nano-gel
solution is prepared with 1% NaCl brine. text-indent:-.25in;line-height:150%;mso-list:l2 level2 lfo1"> 12.0pt;line-height:150%;font-family:" times new roman>1.2 12.0pt;line-height:150%;font-family:" times new roman en-gb>Sandstone rock text-indent:.5in;line-height:150%"> line-height:150%;font-family:" times new roman>The
sandstone rock used in this study has a permeability
around 100 md. The diameter of the core is 1.5 inch
and the length is 1 ft. text-indent:-.25in;line-height:150%;mso-list:l2 level2 lfo1"> 12.0pt;line-height:150%;font-family:" times new roman>1.3 12.0pt;line-height:150%;font-family:" times new roman en-gb>Supercritical CO2 text-indent:.5in;line-height:150%"> line-height:150%;font-family:" times new roman>The
CO2 used in this experiment is in supercritical CO2
condition. The CO2 is pressurized in an accumulator which is wrapped
with a heating pad, therefore, the pressure and the temperature is higher than
the CO2 critical point to achieve supercritical condition. text-indent:-.25in;line-height:150%;mso-list:l1 level1 lfo2"> 12.0pt;line-height:150%;font-family:" times new roman>2. 12.0pt;line-height:150%;font-family:" times new roman en-gb>Experimental apparatus design text-indent:.5in;line-height:150%"> line-height:150%;font-family:" times new roman>The
Figure 1 is the experimental apparatus design. The sandstone core is put into a
coreholder and secured by adding confining pressure.
Three pressure sensors are installed along the coreholder
evenly and two pressure sensors at inlet and outlet, respectively. The pressure
data is transmitted to the computer. The whole system is heat to 45¡æ. The back pressure regulator (BPR) is used to
increase the whole system pressure above CO2 supercritical point.
Keeping both temperature and pressure above the supercritical point can ensure
that the CO2 flow through the system is in the supercritical
condition. The nitrogen gas source is used to provide back pressure. The nano-gel and supercritical CO2 are injected
using two accumulators.
Figure
1 Experimental apparatus design
Nano-gel preparation line-height:150%"> " times new roman>The nano-gel concentration
is 2,000 ppm and the solvent is 1% NaCl brine. After
dissolve the nano-gel in the brine, the solution is
put into 65 " cambria math>¡æ
oven for 24 hours to allow the nano-gel reach an
equilibrium swelling ratio. The nano-gel is filtered
using 10 µm filter paper before use to remove any impurities. text-indent:-.25in;line-height:150%;mso-list:l1 level2 lfo2"> line-height:150%;font-family:" times new roman>3.2
Core
flooding procedures auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">1) Measure
the dry weight of the core. Vacuum the core and saturate the core with 1% font-family:" times new roman>NaCl
brine; auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">2) Measure
core wet weight to determine the pore volume (PV); auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">3) Set
back pressure at 1100 psi; auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">4) Measure
sandstone core permeability with 1% NaCl brine using
flowrates of 1, 2, 3, 4 cc/min; auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">5) Inject
0.5 PV of 2000 ppm nano-gel at 0.05
cc/min (1ft/day) flowrate (or inject nano-gel
until the second pressure sensor has reading); auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">6) Inject
0.25 PV of 1% NaCl brine at 0.05 cc/min flowrate (or inject brine until the third
pressure sensor has a reading); auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">7) Inject
supercritical CO2 using 4 cc/min at 65 ¡æ 12.0pt;line-height:150%;font-family:" times new roman>until CO2
breakthrough from the outlet; auto;text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">8) Keep
the CO2 accumulator connected with the coreholder
and soak the core in supercritical CO2 for 7 days; text-indent:-.25in;line-height:150%;mso-list:l0 level1 lfo3">9) Inject
water using 1, 2, 3, 4 cc/min flowrates to test the plugging efficiency.
normal">4. Results
line-height:150%">4.1CO2-responsive nano-gel plugging
efficiency text-indent:.5in;line-height:150%"> 150%;font-family:" times new roman>As shown in Figure 2, nano-particle gel has the best plugging performance in low
permeability cores after CO2 stimulation. After CO2
stimulation, the residual resistant factors (Frr) of
most of the cores were improved, which represents that the novel CO2-responsive
nano-gel plugging efficiency can be
improved in supercritical CO2 condition. The plugging efficiency of nano-particle gel to brine is plotted in Figure 4.5. The
results show that the maximum plugging efficiency is achieved in 40 md and it decreases with the increase of rock
permeability. After CO2 stimulation, the plugging efficiency to
brine is more than 90% in the 40 md core. mso-add-space:auto;text-align:center"> mso-no-proof:yes">
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">
CO2-responsive nano-gel transportation in
sandstone rock line-height:150%">4.2.1
Absolute permeability measurement and homogeneity test text-indent:.5in;line-height:150%"> 150%;font-family:" times new roman>As shown in Figure 3, the
differential pressure for each segment is almost the same, which indicates that
this sandstone core is nearly homogenous. The water absolute permeability for
this sandstone core is 98 md.
Figure
3 Absolute permeability measurement results
normal"> " times new roman minor-bidi>4.2.2 Nano-gel injection process and post water flooding process
text-indent:.5in;line-height:150%"> 150%;font-family:" times new roman>0.43 pore volume (PV) of nano-gel was injected at a constant flowrate of 0.05 cc/min. As shown in the figure below, thedifferential pressure for each segment is almost the same throughout the nano-gel injection process, which indicates that the 0.43
PV of nano-gel injection did not result in an
efficient plugging before CO2 stimulation. Therefore, the nano-gel can transport into the in-depth without forming a
surface plug or near wellbore plug. text-indent:.5in;line-height:150%"> 150%;font-family:" times new roman>After placing the nano-gel in the core, a 0.25 PV
brine was injected into the core in order to displace the nano-gel
near the inlet and push the nano-gel moving towards
the in-depth. line-height:150%">4.2.3
CO2 injection and soaking process text-indent:.5in;line-height:150%"> 150%;font-family:" times new roman>The supercritical CO2
was pressurized and heated in an accumulator. The CO2 was injected
into the core at a constant flowrate of 4 cc/min until
the CO2 breakthrough the core. The injection was terminated once the
CO2 production was observed. Since the supercritical CO2
broken through the core, the contact area between the CO2 and the nano-gel increased, therefore, the nano-gel
stimulation under CO2 condition was more efficient. The core was
then soaked in the supercritical CO2 by keep connecting the coreholder with the CO2 accumulator for 7 days.
The post waterflooding will be conducted to test the
plugging efficiency of the nano-gel after CO2
stimulation. line-height:150%">4.2.4
Post waterflooding process text-indent:.5in;line-height:150%"> 150%;font-family:" times new roman>After soaking the core for 7 days,
1% NaCl brine was injected into the core at various
flowrates. The results indicate that the brine injection pressure increased
after nano-gel treatment, which revealed that the nano-gel can provide a sufficient plugging to brine after
soaking in supercritical CO2. The residual resistant factor for each
segment and the whole core was calculated and plotted in Figure 4. As shown in
the figure, the segment 2 has the highest resistance to water flow, while the Frr for segment 3 and 4 was close to 1, which indicated
that the nano-gel was not penetrate into segment 3
and 4 or did not form a sufficient plugging.
Figure
4 Water residual resistant factor for each segment
after nano-gel treatment
authors would like to express their gratitude for the financial support
provided by the DOE under contract DE-FE0024558. line-height:150%"> " times new roman>