Development of Swelling- Rate- Controllable Particle Gels to … · 2018. 12. 7. · Delayed...
Transcript of Development of Swelling- Rate- Controllable Particle Gels to … · 2018. 12. 7. · Delayed...
Development of Swelling-Rate-Controllable Particle Gels to
Enhance CO2 Flooding Sweep and Storage Efficiency
Project No. DE-FE0024558
Baojun BaiMissouri University of Science and Technology
U.S. Department of EnergyNational Energy Technology Laboratory
Mastering the Subsurface Through Technology Innovation, Partnerships and Collaboration:Carbon Storage and Oil and Natural Gas Technologies Review Meeting
August 13-16, 2018
(a) Before swelling (b) After swelling
Cross-linked polymer powder, Super Absorbent PolymerSize ranging from nano-meter to millimeter
Preformed Particle Gel (PPG)
2
3
Presentation Outline• Technical StatusMm-size Particle Gels for Super-K ChannelsMicro-/Nano-gels for Matrix Conformance Problems Nanogel transport, plugging and EOR mechanisms
• Lessons Learned• Accomplishments to Date• Synergy Opportunities• Project Summary• Acknowledgement• Appendix
(a) Before swelling (b) After swelling
4
Mm-size Particle Gels for Super-K ChannelsTarget Conformance Problems
Targets: Super-K Channels Our Solutions
Achievement: Synthesized mm-sized swelling delayed CO2 resistant PPGs (10 um- mm)
5
Product 1: Swelling Rate Controlled to Days
0 1 2 3 4
0
10
20
30
40
50
60
SR (v
/v)
Time (h)
Meet the requirement: development of swelling rate controllable PPG
0 5 10 15 20 25 300
10
20
30
40
SR (V
/V)
Time (Days)Fast swelling within one hour
Traditional PPGs
Delayed swelling to days
New monomer addition to traditional PPGs
The new product overcome some problems of traditional PPGs Fast swelling rate, leading to injectivity issue Unable to travel long distance, only for near well-bore treatment
1% NaCl1% NaCl
6
Product 2: Swelling Rate Controlled to Months
Product 2 is good for in-depth fluid diversion
2nd crosslinker addition to traditional PPGs
Meet the requirement: development of swelling rate controllable PPG
0 50 100 150 200 2500
10
20
30
40
50
60
70
SR (V
s/V0)
Time (Days)
45C
60C
Swelling kinetics and Temperature effect (1% NaCl)
7
Product 3:CO2 Triggered Swelling Delayed Particle Gel
particle size 1-2 mm; 45 ℃
0 5 10 15 20 25 300
20
40
Swel
ling
Ratio
(Vs/V
0) DI Water/sCO2
1% NaCl/sCO2
DI Water
Time (Days)
Product good for in-depth reservoir deployment
Delayed swelling to weeks
Meet the requirement: development of swelling rate controllable PPG
In absence of CO2, size of the gel would not increaseUpon CO2 flooding, the gel would increase to 4 times of its initial volume
0 50 100 150 200 2500
20
40
60
Swel
ling
Ratio
( Vs/
V 0)
Time (Days)
1% NaCl
DI Water
Delayed swelling to months particle size 1-2 mm; 45 ℃
Mm-sized CPPG (Product 1) Plugging Efficiency to CO2
8
0
20
40
60
0 5 10
Frrg
Injection flow rate, ml/min
40k Frr1 40k Frr2
CPPG Frr1 CPPG Frr2
Compare to 40K, CPPG has much better plugging efficiency to CO2.
K=~23 Darcy 1 wt% NaCl
9
Mm-sized CPPG (Product 3) Plugging Efficiency to CO2
CO2 flooding experiment setup.
Select cores (permeability 50md) and frac.
Place fully swollen gel particles into fracture until pressure increases to 1000 psi.
Inject sCO2 to test breakthrough pressure. Measure stable pressure at different flow rates.
Inject 2 PV brine. Shut in the core holder. Keep core holder temperature at 60 ℃.
Test sCO2 breakthrough pressure. Measure stable pressure at different flow rates.
Analyze data.
Procedures
Matrix Permeability Around 50 md
Stone Type Sandstone
Fracture Width 0.5 mm
Gel Particle Size 100-125 Micron
Brine Used 1wt.% NaCl
0
100
200
300
400
500
600
700
0 200 400 600 800 1000
Diffe
rent
ial P
ress
ure,
psi
Injection TIme, min
Before Shut-in
After Shut-in
10
Core Flooding Experiment: Supercritical CO2
“Self-healing” behavior: Supercritical CO2 reached breakthrough at 617 psi in first
CO2 flood. After shut-in, another breakthrough at 437 psi was detected.
CO2 residual resistance factors increased after shut-in.
Pressure difference throughout the core. SCO2 Frr at different injection rates, before and after shut-in.
Shut in for 3 days
sCO2 Breakthrough
1000
1500
2000
2500
0 0.5 1 1.5 2
Resid
ual R
esist
ance
Fac
tor
Injection Rate, mL/min
CO2 injection before shut-in
CO2 injection after shut-in
1.75 cc/min
1.25 cc/min
0.75 cc/min
0.5 cc/min
1.75 ml/min
1.25 ml/min0.75 ml/min 0.5 ml/min
CO2 Resistant Micro-/Nano-gels for Matrix Conformance Problems
11
Targets-Matrix Problem Solution
Achievement: Synthesized a series of swelling-delayed CO2 responsible nano-particle gels that can transport into the in-depth of a reservoir.
Swelling Rate Controllable Nano-gels
(a) (b)
Tunable sizes: in the range of nano to microns
Nano-gel in powder form SEM images
12
14
Swelling Rate Controllable Nano-gel
Fast swelling in minutes
Traditional HPAM nano-gels
Delayed swelling to weeks
Product 1: CO2 triggered Swelling
• Traditional HPAM nano-gels had fast swelling rate within minutes• Product 1 swelling delayed to weeks
0 20 40 60 80 100 120
200
400
600
Diam
eter
of n
anog
el (n
m)
Time (min)
swelling in minutes
0 20 40 600
100
200
300
400
500
Nano
-gel
Siz
e
Time (Days)
15
CO2 Responsive Nano-gel with Swelling Rate Control
Product 2: CO2 responsive monomer used for micro/nano-gels
Meet the requirement: development of swelling rate controllable nano-gels
0 60 120 180100
150
200
250
300
Diam
eter
of n
anog
el (n
m)
Time (h)
Controllable Delay
Water
CO2
0 60 120 180 240 300 360
10
20
30
Zeta
Pot
entia
l (m
V)
Time(h)
In the presence of CO2
Swelling could be delayed in a controllable fashion: water flooding for nano-geldelivery and CO2 flow induced the increase of nano-gel size.
CO2
Nano-gel Thermal Stability
CO2 resistant Nano-gels had better stability than HPAM-type of nanogelsat different temperatures.
1 10 100100
200
300
60 °C 40 °C
Aver
age D
iamete
r (nm
)
Time (Days)
25 °C
16
17
Transport and EOR Mechanisms of Nanogels
Nanogel physicochemical
properties
Rheology of nanogel
dispersionsNanogel at oil/water interface
Nanogel on rock surface
Transport behavior and
mechanisms in porous media
Interfacial tensionEmulsion stability
Adsorption kineticWettability alteration
18
Property Nonionic nanogel (NN) Anionic nanogel (AN) Cationic nanogel (CN)
Charge Neutral Negative Positive
Zeta potential (mV) -1.76 -35.90 34.75
Original diameter (nm) 59.00 88.12 65.83
Swollen diameter (nm) 220.14 241.62 151.14
Polydispersity index (PDI) 0.236 0.268 0.482
Swelling ratio 51.92 20.61 12.10
pH (1000 ppm in DI water) 7.8 7.0 4.9
10 100 1000 10000
0
5
10
15
20
25
30
35
NN
AN
Inte
nsity
(%)
Dh (nm)
CN
Physicochemical Properties of Nanogels
Nanogels with same size distribution and
different charges were synthesized and used
for following characterizations and
evaluations.
Nano-gel Plugging Efficiency to Matrix
The plugging efficiency of the nano-gel to CO2 is more than 90%.
0.0 0.5 1.0 1.5 2.0 2.50
5
10
15
20
25
30
35
Residual resistance factor Plugging efficiency
CO2 flow-rate (mL min-1)
Resi
dual
resi
stan
ce fa
ctor
90
92
94
96
98
100
Plug
ging
effi
cien
cy(%
)
19
20
Oil Recovery Improvement by Nanogel Injection
oil
0 2 4 6 8 10 120
20
40
60
80
100
Diffe
rent
ial p
ress
ure
(psi
)
Injection volume (PV)
0
5
10
15
20
Oil
reco
very
(%)
NN injection 2nd flooding1st flooding
0 2 4 6 8 10 12 14 16 180
20
40
60
80
100
Diffe
rent
ial p
ress
ure
(psi
)
CN injection 2nd flooding
Injection volume (PV)
1st flooding
0
5
10
15
20
25
Oil r
ecov
ery
(%)
Nanogel injection
2nd flooding
emulsion
Nanogel for emulsification
Nanogel for water diversion
Rock core: Berea sandstone (negative charged), Φ: 20.5%, K: 87 mD
21
10 100 1000 10000
0
5
10
15
20
25
30
35
40
Inte
rfac
ial t
ensi
on (m
N/m
)
Nanogel concentration (ppm)
AN
CN
NN
0 500 1000 1500 2000 2500 3000 3500
5
10
15
20
25
30
35
40
45
1000 NN 2000 NN 5000 NN 10000 NN
Inte
rfac
ial t
ensi
on (m
N/m
)
Time (s)
10 100 1000
10
20
30
40
0 200 400 600 800 10001200140016001800
5
10
15
20
25
30
35
1000 AN 2000 AN 5000 AN 10000 AN
Inte
rfac
ial t
ensi
on (m
N/m
)Time (s)
10 100 10005
1015202530
0 500 1000 1500 2000 250005
1015202530354045
1000 CN 2000 CN 5000 CN 10000 CN
Inte
rfac
ial t
ensi
on (m
N/m
)
Time (s)
10 100 10000
10
20
30
40
EOR Mechanism 1: Nanogels for Interfacial Tension Reduction
Nanogels can rapidly reduce the oil/water interfacial tension.
The equilibrium interfacial tension is related to the nanogel concentration.
The equilibrium interfacial tension becomes constant when nanogel concentration above 1000 ppm .
22
EOR Mechanism 2: Oil-in-Water Emulsion Stabilization
Nanogels can stabilize oil-in-water emulsion for more than 6 months.The diameter of emulsified oil drops is from several to tens of microns.
AN CN NN
O/w emulsions was prepared with decane and nanogel dispersion (1% NaCl) at 25 °C
23
Dynamic Adsorption and Desorption Tests
Nanogel concentration measurement
24
0 5 10 15 20
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Injection pressure Nanogel concentration
Injection volume (PV)
Inje
ctio
n pr
essu
re (p
si)
0
200
400
600
800
1000
1200
Efflu
ent n
anog
el c
once
ntra
tion
(ppm
)
NN adsorption
0 1 2 3 4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Post injection volume (PV)
Inje
ctio
n pr
essu
re (p
si)
0
200
400
600
800
1000
1200
1400
Injection pressure Nanogel concentration
Efflu
ent n
anog
el c
once
ntra
tion
(ppm
)
NN desorption
0.00 0.25 0.50 0.75 1.00 1.25 1.50
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Injection volume (PV)
Inje
ctio
n pr
essu
re (p
si)
0
200
400
600
800
1000AN adsorption
Injection pressure Nanogel concentration
Efflu
ent n
anog
el c
once
ntra
tion
(ppm
)
0.0 0.1 0.2 0.3 0.4
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Post injection volume (PV)
Inje
ctio
n pr
essu
re (p
si)
0
200
400
600
800
1000AN desorption
Injection pressure Nanogel concentration
Efflu
ent n
anog
el c
once
ntra
tion
(ppm
)
0 5 10 15 20 25
0
2
4
6
8
10
12
14
Injection volume (PV)
Inje
ctio
n pr
essu
re (p
si)
0
250
500
750
1000CN adsorption
Injection pressure Nanogel concentration
Efflu
ent n
anog
el c
once
ntra
tion
(ppm
)
0.00 0.25 0.50 0.75 1.00 1.25
0
2
4
6
8
10
12
14
Injection pressure Nanogel concentration
Post injection volume (PV)
Inje
ctio
n pr
essu
re (p
si)
0
250
500
750
1000
1250CN desorption
Efflu
ent n
anog
el c
once
ntra
tion
(ppm
)
Dynamic Adsorption/Desorption of Nanogel
Nanogels are able to increase the injection pressure in sandstone saturated with water. Desorption process is depending on the electro-attraction between nanogel and rock.
Rock core: Berea sandstone (negative charged), Φ: 20.5%, K: 266.7mD
Adsorption:4.8 mg/g Adsorption:
5.3 mg/g
Adsorption:0.25 mg/g
Desorption:0.19 mg/g
Desorption:0.20 mg/gDesorption:
0.076 mg/g
Delivery of Nano-gel in Sandstone
25
# Diameter (mm) Length (mm) PV (cc) Permeability (md)
1 37.9 284 61.67 98
Core information
0 1 2 3 4 50
1
2
3
4
5
6
7
Frr
Flow rate (mL/min)
Permeability Reduction in Different Segments
28
𝐹𝐹𝐹𝐹𝐹𝐹 =𝑘𝑘𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑘𝑘𝑎𝑎𝑏𝑏𝑎𝑎𝑏𝑏𝑏𝑏
=𝑃𝑃𝑎𝑎𝑏𝑏𝑎𝑎𝑏𝑏𝑏𝑏𝑃𝑃𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏𝑏 𝑞𝑞
Segment 2
Segment 1
• Nano-gel can be delivered into the far wellbore area• After CO2 stimulation, nano-gel provides a sufficient plugging to segment 2 and no penetration
to segments 3 and 4
Accomplishments to Date
29
• Published 11 journal papers, one conference paper, and two presentations.• Synthesized nano- to millimeter-sized swelling-rate controllable CPPGs for
different conformance problems.• Evaluated the effect of water salinity, pH and temperature on CPPG and
nanogel behavior.• The plugging efficiency of mm-sized CPPG to super-K channels is more than
90%.• Nanogel synthesized under scCO2 conditions have narrower distribution than
those synthesized by emulsion methods.• Nanogel can transport through Berea sandstone, improve oil recovery by
increasing both micro- and macro- displacement efficiency. • Nanogel can be placed in the far wellbore and provide efficient plugging under
scCO2 condition
Synergy Opportunities• Industry Interest for mm-sized CPPG product scale-up and field
pilot test. – Currently our industry collaborators Conoco-Phillips (CP), Occidental (OXY),
and Daqing Wantong are interested in the products for pilot tests. • CO2 Storage Partnership Projects
– The new products can be used to solve early breakthrough or excess CO2production problems for CO2 EOR storage projects.
• Swelling-rate controllable nano-particles for wellbore leakage control from minor cracks that cement can not penetrate.
31
Project Summary
32
Key findings:• The swelling-rate controllable CPPGs have been successfully
synthesized. Their sizes are adjustable from nano to millimeter.• The swelling rate of CPPG can be controlled from a few hours to up to
a few months. • The synthesized particle gels is thermo-stable in sCO2.• Mm-sized CPPG can effectively reduce CO2 permeability in super-K
channels and their plugging efficiency is over 90%.• The nanogel can transport through common porous media and form
efficient plugging in far wellbore zone under scCO2 condition.Next Steps:• Run coreflooding test to further understand nanogel transport and
blocking mechanisms.• Test whether swelling-rate-controllable nanogel can be used for leakage
control.• Write the final project report
Acknowledgement• US Department of Energy• Industry: Conoco-Philips, Occidental Petroleum
Corporation• Project Manager: Kylee Rice• Graduate students
33
Appendix– Benefit to the Program– Project Overview– Organization Chart– Gantt Chart– Bibliography
34
35
Benefit to the Program • Program goals being addressed
– Develop technologies to improve reservoir storage efficiency while ensuring containment effectiveness.
• Project benefits statement– The research project is to develop novel environmental friendly
swelling-rate-controllable particle gels to improve CO2 sweep and storage efficiency. The new materials will overcome some distinct drawbacks inherent in the in-situ gels that are traditionally used for conformance control. The technology, when successfully demonstrated, will provide a novel cost-effective technology to the Carbon Storage Program’s effort of improving reservoir storage efficiency while ensuring containment effectiveness.
36
Project Overview: Goals and Objectives (1)
• Overall Goal: to develop a novel particle-based gel technology that can be used to enhance CO2 sweep efficiency and thus improve CO2storage in mature oilfields.
• Project Objectives:– Synthesize swelling rate controllable CO2-based polymer network
nano-particles at supercritical CO2.– To understand the correlation of particle gels and CO2/water/oil
flow by core flooding tests.– To understand the plugging mechanisms of particle gels for
different types of reservoir problems.
Project Overview: Goals and Objectives (2)
• Relevance to Program Goals– Novel materials will improve CO2 storage efficiency while
ensuring containment effectiveness.
• Success criteria – Swelling rate controllable particle gels in nano-size– Resistance to supercritical CO2
– Plugging efficiency of CO2 resistant particle gels – Successful delivery of nano-gels into target locations– Understand the relationship of CO2/water/oil by core-flooding
tests in the presence of particle gels.
37
38
Organization Chart
PI: Baojun BaiCo-PI: Mingzhen Wei
Senior investigator: Dr Lizhu WangTechnician: Ninu MariaGraduate Students
Ms. Adriane MelnyczukMs. Xindi SunMr. Yifu LongMr. Jiaming Geng
39
Gantt ChartTechnical Tasks
2016 2017 2018
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
1.0 Project management and planning and reporting
2.0 Synthesis and characterization of particle gels
2.1 Synthesis and characterization of micro- to millimeter-sized particle gels
2.2 Synthesis and characterization of CO2-based polymer network nano-particle gels at supercritical CO2 fluids
3.0 transport behavior of millimeter-sized particle gel through fractures or fracture-like channels and their plugging efficiency to supercritical CO2 fluids
3.1 develop criteria for particles passing through pore throats and open fractures
3.2 conduct core-flooding tests to understand the effect of particle gels on CO2/water/oil flow
3.3 deliver nano-particle gels for in-depth placement
3.4 develop the mathematical models
Bibliography1. Wang, L.Z., Long, Y., Ding, H, Geng, B. Bai, B., 2017, Mechanically robust re-crosslinkable
polymeric hydrogels for water management of void space conduits containing reservoirs. ChemicalEngineering Journal, v. 317, p.952-960. available at: https://doi.org/10.1016/j.cej.2017.02.140
2. Imqam, A., Wang, Z. Bai, B., 2017, The plugging performance of preformed particle gel to waterflow through large opening void space conduits. Journal of Petroleum Science and Engineering. V.156,p.51-61. available at: https://doi.org/10.1016/j.petrol.2017.04.020
3. Imqam, A., Wang, Z. Bai, B., 2017, Preformed-particle-gel transport through heterogeneous void-space conduits. SPE Journal. V.22, issue 05, pp.1437-1447,available at: https://doi.org/10.2118/179705-PA
4. Sun, X.; Baojun Bai, B. Dehydration of Polyacrylamide-based Super-absorbent Polymer Swollen inDifferent Concentrations of Brine under CO2 Conditions. Fuel, 2017, 210, 32-40. available at:https://doi.org/10.1016/j.fuel.2017.08.047
5. Geng, J., Ding, H., Han, P., Wu, Y. and Bai, B., 2018. The transportation and potential enhancedoil recovery mechanisms of nanogels in sandstone. Energy & Fuels. available at:https://doi.org/10.1021/acs.energyfuels.8b01873
6. Sun, X., Suresh, S., Zhao, X. and Bai, B., 2018. Effect of supercritical CO2 on the dehydration ofpolyacrylamide-based super-absorbent polymer used for water management. Fuel, 224, pp.628-636.available at: https://doi.org/10.1016/j.fuel.2018.03.103
40
Bibliography7. Geng, J., Pu, J., Wang, L. and Bai, B., 2018. Surface charge effect of nanogel on emulsification of
oil in water for fossil energy recovery. Fuel, 223, pp.140-148. available at:https://doi.org/10.1016/j.fuel.2018.03.046
8. Sun, X., Alhuraishawy, A.K., Bai, B. and Wei, M., 2018. Combining preformed particle gel and lowsalinity waterflooding to improve conformance control in fractured reservoirs. Fuel, 221, pp.501-512. available at: https://doi.org/10.1016/j.fuel.2018.02.084
9. Alhuraishawy, A.K., Sun, X., Bai, B., Wei, M. and Imqam, A., 2018. Areal sweep efficiencyimprovement by integrating preformed particle gel and low salinity water flooding in fracturedreservoirs. Fuel, 221, pp.380-392. available at: https://doi.org/10.1016/j.fuel.2018.02.122
10. Wang, L., Geng, J. and Bai, B., 2018. Highly Deformable Nano-Cross-Linker-BridgedNanocomposite Hydrogels for Water Management of Oil Recovery. Energy & Fuels, 32(3), pp.3068-3076. available at: https://doi.org/10.1021/acs.energyfuels.7b03649
11. Pu, J., Zhou, J., Chen, Y. and Bai, B., 2017. Development of Thermotransformable ControlledHydrogel for Enhancing Oil Recovery. Energy & Fuels, 31(12), pp.13600-13609. available at:https://doi.org/10.1021/acs.energyfuels.7b03202
41
Filtration Test of Nanogel (Product 1)
42
Measure core absolute permeability
Put into coreholder and add confining pressure
(500 psi)
Inject brine at 1 cc/min until water produced
from the outlet
Inject 1000 ppm nanogelat constant pressure (10,
15, 20, 30 psi)
Collect effluent every 30 sec until the production
rate research stable
Experimental apparatus design
Experimental procedures
Core # Length (cm)
Diameter (cm)
Pore volume (mL)
Porosity (%)
Permeability (md)
D6 1.079 2.51 1.02 19.15 36B1 1.073 2.50 1.05 19.84 84
Core information
Filtration Test Results
43
36 md
84 md
0 50 100 150 200 250 3000.0
0.5
1.0
1.5
2.0
2.5
Q (m
L/m
in)
cumulative time (min)
0 20 40 60 80 100 1200
2
4
6
8
10
12
Q (m
L/m
in)
cumulative time (min)
10 psi
15 psi
20 psi
30 psi
10 psi15 psi 20 psi 30 psi
The rapid production rate reduction and low production rate indicate that the nanogel cannot flow through the rock with permeability lower than 36 md
0 1 2 3 4 5 6 7 8 9 10
10
15
20
25
30
Nano
gel i
njec
tion
pres
sure
(psi)
Q (mL/min)
84 md
0.00 0.02 0.04 0.06 0.08 0.10
10
15
20
25
30
Nano
gel i
njec
tion
pres
sure
(psi)
Q (mL/min)
36 md
Residual Resistant Factor
44
Filtration test
Inject brine to determine the
residual resistant factor
Take the core out and clean the
surface
0
50
100
150
200
250
0 0.2 0.4 0.6 0.8 1 1.2
Frr
Brine injection rate (cc/min)
Frr-before surface cleaningFrr-after surface cleaning
0
10
20
30
40
50
60
0 0.2 0.4 0.6 0.8 1 1.2
Frr
Brine injection rate (cc/min)
Frr-before surface cleaningFrr- after surface cleaning
36 md
84 md
• Nanogel forms external and internal cake near the inlet in the rock with permeability lower than 36 md
• Nanogel can penetrate through the sandstone rock with permeability higher than 80 md
45
Nanogel Injection
• No pressure buildup at P1 and P2 during the nanogel injection• Nanogel can penetrate into the in-depth without forming surface plugging
46
0 2000 4000 6000 8000 10000
1
2
3
4
5
6
K-D model
NN
CN
Rel
ativ
e vi
scos
ity
Nanogel Concentration (mg/L)
AN
Rheology of Nanogel Dispersions
Krieger-Dougherty model:
The nanogel dispersions have a concentration-related rheology.
The interparticle reactions increase the viscosity of dispersions with high nanogel concentrations.
solvent viscosity
viscosity
Rigid nanoparticles
25 °C, 6 s-1
1% NaCl
Initial Study of Nano-gel Plugging Efficiency to Matrix
The plugging efficiency of the nano-gel to CO2 is more than 90%.
0.0 0.5 1.0 1.5 2.0 2.50
5
10
15
20
25
30
35
Residual resistance factor Plugging efficiency
CO2 flow-rate (mL min-1)
Resi
dual
resi
stan
ce fa
ctor
90
92
94
96
98
100
Plug
ging
effi
cien
cy(%
)
47
48
0 5000 10000 15000 200000
1
2
3
4
5
6
7
Pseudo-second order
Pseudo-first orderCN
AN
Ads
orpt
ion
(mg/
g)
Time (min)
NNPseudo-second order
Control Sample NN AN CN05
101520253035404550
Cont
act a
ngle
(°)
Nanogel for Rock Surface Wettability Alteration
The adsorption of nanogel on rock surface is controlled by electrostatic interactions.
Nanogels with proper hydrophilicities can alter rock surface to more water-wet.
Immerse core in nanogel dispersion
Φ=20.50%K=87.21mD
Nano-gel Synthesis and Evaluation
CO2 delivery pump
Synthesis under supercritical CO2
Reactor system
CO2 reactor
12
Nano-gel Plugging Efficiency after CO2 stimulation
50
Measure core absolute
permeability
Inject 5 PV nano-gel into
the cores
Put one core in the vessel and pressurize the
vessel using CO2to 1100 psi
Put the vessel into the 65 ℃ oven
and take the core out after 7 days
Inject brine to determine the
residual resistant factor
Inject brine into one core to determine the residual
resistant factor
• The plugging efficiency improved after CO2 stimulation in 40 md cores • There exists matching ratio between particle size and rock permeability for efficient plugging
0.00 0.25 0.50 0.75 1.000
10
20
30
40
50
60
After CO2 treatment
Resid
ual r
esist
ant f
acto
rFlow rate (mL/min)
Rock permeability: 40 md
51
Size Increase under CO2 Condition
Meet the requirement: development of CO2 resistant nano-gels
CO2
Acid labile crosslinker
stable crosslinker
Product 1
Product 2