International Workshop
on Geological CO2 Sequestration
Simulation Study of Pilot CO2 Injection
in Iwanohara, Nagaoka City, Japan
February 21, 2006
Hiroshi Ohkuma and Yuko Kawata
RITE/ENAA/Japan Oil Engineering Co., Ltd. (JOE)

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Chronicles of Pilot Test and Simulation
Japanese
Fiscal Year

EventsAvailable Data

* Geological study* Structure map &isopach map

2000* IW-1 drilled
2001* OB-2 & 3 drilled

2002* Pumping test at IW-1
* Acidization at IW-1
* OB-4 drilled

2003

2004

Simulation Study* Preliminary sensitivity study* Determination of observation
well locations* Adjustment of well locations* IW-1 core data
& examination of technical* OB-2 & 3 well logs
feasibility of the test plan
* Pumping test results * Same as 2001
* Pumping test results* Same as 2001 & 2002
after acid
* OB-4 well logs
* Injection rate
* IW-1 & OB-4 BHP * History matching* Logs at OB-2,3, & 4* IW-1 well logs

* CO2 injection started* CO2 breakthrough at
OB-2* CO2 injection continued* History matching* Injection rate
* CO2 breakthrough at* IW-1 & OB-4 BHP * Long-term prediction of CO2
OB-4* Logs at OB-2,3, & 4 fate
* CO2 injection completed

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Determination of Observation Well Locations(3/3): Area Extent of CO2 as Function ofCumulative Injection
tons

OB-4
100 m

OB-3

◆
-◆
100 m
70 m

120 m

IW-1

◆
OB-240 m

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IW-1 Pumping Test Data

Pumping test at IW-1 showed only top 12m (Zone-2) has
sufficient injectivity with average k of only 6.7 md and the welldamage was severe (skin factor s=6.88).The simulation model
incorporating these data implied:¾¾¾

Well damage should be removed
For safe injection the injection rate should be half of the initial plan(i.e., 40 tons/day →20 tons/day)
Injection should be limited over Zone-2 to observe CO2
breakthrough at two observation wells at least during the test
period (approximately 500 days)

Acidization at IW-1 was successfully carried out prior to theinjection, resulting in s=-2.9. The model with this negative skinsuggested the injection at 40 tons/day would be possible but it
was decided to inject at 20 tons /day during JFY2004.

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International Workshop on CO２ Geological Storage , Japan ‘06

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History Matching Parameters
Parameters to be matched:
¾
¾
¾

¾



IW-1 BHP at -1,018.90 m (Jul. 7, 2003 – Jan. 11, 2005)
OB-4 BHP at -1,034.96 m (Jul. 7, 2003 – Jan. 11, 2005)
Breakthrough of gaseous CO2 at OB-2 between Feb. 12 andMar. 10, 2004; Cumulative injection = 4,000 tons)
Breakthrough of gaseous CO2 at OB-4 between May 12 andJun. 14, 2004; Cumulative injection = 5,300 tons)

Varied Parameters:¾¾¾¾¾

Relative permeability curves and end points (Swir, Sgc, krg @Swir)
Zone-2 permeability and its areal heterogeneity
Vertical permeability
Well damage at OB-2
Rock compressibility

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Evolution of Simulation Studies

Injection
Rate
t-CO2/day

2002 Study
2003 Study
Actual Injection
Behavior

Skin
FactorData Pertaining to Relative Permeabilities
krg @ Swir
SwirSgc
Curves(fraction)(fraction)(fraction)Injection
Well BHP
2(kgf/cm )2000.82-0.84

00.060-0.065

SCAL Data 169→175

Prior toInjection

20-2.90.82-0.84

00.061-0.065

SCAL Data137

2003

20-2.9----119→1232004

40-2.9----124→129

2005 History-2.90.43-0.67
0.20
1.0Matching* BHP is the bottom-hole pressure at the gauge depth (-1018.90 m).
22** Initial pressure at the gauge depth was 110 kgf/cm . Maximum injection BHP was set at 190 kgf/cm .

2006/2/21
International Workshop on CO２ Geological Storage , Japan ‘06* 1.75(Sg )GoodMatch6

Relative Permeability Data
1.0

1.0Average krg
Average krw
Ave Imbibition krg

0.80.6k rg & k rw

k rg & k rw

0.8

0.4

0.2krgkrw

0.6

0.4

0.2

0.0

0.00510152025

Gas Saturation S g (%)

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0102030405060

Gas Saturation Sg %7

Areal Permeability Change (Zone-2 Average k)

kh=6.7 md
kh=3.35 md

OB-4IW-1OB-3

kh=26.8 md

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International Workshop on CO２ Geological Storage , Japan ‘06

OB-28

Matching of Injector IW-1 BHP

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International Workshop on CO２ Geological Storage , Japan ‘06

9Matching of CO2 Breakthrough at OB-2 & OB-4
Sg at OB-2;

Sg at OB-4

Actual BTat OB-4

Actual BTat OB-2

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Relative Permeability Hysteresis
Drainaige & Imbibition krg Curves（ Zone-2: Sgr=0.33)
1.0krw
krg Drainage
krg Imbibition

k rg & krw (fraction)

0.8

krg when Imbibition
starts at S g<1-S wir .

0.6

0.4

0.2

0.0
1.0

0.90.80.70.6

0.50.4

Water Saturation Sw (fraction)

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Sg Distribution in Zone-2 Middle
after 1000 years
Case P-1: Sgrmax=Sgc=0.2

Gaseous CO2 = 56.7 %of total injectedCase P-2: Sgrmax=0.33

Gaseous CO2 = 63.1 %of total injected

OB-4

OB-3

IW-1

OB-4OB-2

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OB-3

IW-1

OB-2

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Distribution of Solution CO2 in Zone-2 Middle
after 1000 years
Case P-1: Sgrmax=Sgc=0.2

Case P-2: Sgrmax=0.33

OB-4

OB-3

IW-1

OB-4

OB-2

CO2 in Solution = 43.3 % of total injected

2006/2/21
International Workshop on CO２ Geological Storage , Japan ‘06

OB-3

IW-1

OB-2

CO2 in Solution = 36.9 % of total injected13

Conclusions from Simulation Studies
Reasonable history match was attained with thefollowing factors:¾¾¾¾

Areal heterogeneity of permeability
High critical gas saturation: Sgc=20 %Significantly higher krg at Swir than SCAL data
Large formation damage around OB-2

Due to small k, gaseous CO2 movement by buoyancy
is limited and remains for long time (1000 years)
essentially in the same area as that at the end ofinjection. Breakthrough to OB-3 is predicted not tooccur in 1000 years.
 Some CO2 is expected to move in the up-dip
direction after injection ended but dissolves into
formation water. Formation water containing
dissolved CO2 moves downward very slowly.
2006/2/21
International Workshop on CO２ Geological Storage , Japan ‘06

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