Current status of the EGS project for water
injection in the superheated region at
Yanaizu-Nishiyama geothermal power plant

June 2, 2016
Takashi Okabe (GERD)

1

Presentation
1.
2.
3.
4.
5.
6.

Outline of numerical simulation to determine a recharge location
Drilling and logging results
Recharge operation
Acquired data
Discussion
Summary2

1. Outline of numerical simulation to determine a recharge location
3D recharge model :Create a superheated reservoir
based on 2D superheated models(both Chinoikezawa models)

Existing 3D model :Future decrease predictionFail to create a superheated reservoir

対策しない場合の減衰予測
Production
生産ヒストリhistory Prediction
without injection

Steamdecrease after 15 years
現在から約15年後の減衰（蒸気量約300t/h=>約200t/h）(300t/h⇒200t/h)
蒸気+熱水
Steam+Water

蒸気

Steam

Chinoikezawa
footwall fault

Chinoikezawa
southeast fault

3Chinoikezawa Footwall fault model
ＮＷ

ＳＥ

3D recharge model

Production block
Elevation(m)Chinoikezawa footwall model(C.F.M.)
Production block
Recharge block
Est superheated ratio
Temperature distribution

Distance(m)4(Liquid mobile in two phase condition) (Liquid immobile in two phase condition)
History matching

Recharge simulation

Recharge
Block

Comparisonof the results
Recharge simulation

Permeability
Porosity
Matrixsubdivision
Volume ratio
Fracture
spacing
Slr
SgrHistory matching

Recharge simulation

2

Major simulation parameter
Fracture

Recharge simulation

3
History matching

Parameter

History matching

1.0～
3.0E-14m2
0.1

Matrix(Chinoike)
0.0～1.0E25m2
0.001

Matrix(Refined)
1.0E-18m2

1

1

4

0.15

0.85

0.85

30×30×30m--

History matching

Recharge simulation

History matching

Recharge simulation

History matching

Recharge simulation

0.001

1.5
History matching

0.6

0.3

0.05

0.05

Recharge simulation

１
Refined Chinoikezawa Footwall fault model

Chinoikezawa Footwall fault model5

Steam saturation after 16 year’s injection(Recharge block 1.5:Elevation-1500m）
Comparison of irreducible water(Slr)
Refined Chinoikezawa Footwall fault model(３D)[ Slr = 0.3 ](Liquid immobile in two phase condition)

Well-6

Well-3 Well-8

Well-6

Well-5Well-3 Well-8

Well-6

Well-3 Well-8

Well-3 Well-8

Calculation
stopped after 8
year’s injection

Well-5Well-5Well-6

Well-5Chinoikezawa Footwall fault model(3D)[ Slr = 0.6 ] (Liquid immobile in two phase condition)

Well-6

Well-3 Well-8

Well-5Injection15t/h

Well-6

Well-3 Well-8

Well-5Injection30t/h

Well-6

Well-3 Well-8

Well-5Injection50t/h

Well-6

Well-3 Well-8

Well-5Injection100t/h

6Tracer test(2013) and field injection test results300
Well-1014T

well-733P

Chinoikezawa
fault

200

Tracer test

Chinoikezawa
Hanging wall fauldt

B

Well-96T

100

Well-17
35P

Chinoikezawa
Footwall fault
0

Well-423P
Well-1238P

Well-115T

Well-221T-100

well-19
10T

South-North(m）Well-632P-200

Well-536P

Well-12Well-1630P
Well-14
27P

-300

-400

Well-1528P
Well-834P

Well-18
39P

Well-331P

Chinoikezawa
South-East fault

-500

A
-600

-700
-300

◆：Feed point and/or lost circulation point＊：30P feedfeed＊：Well-16
pointpoint←：Interference（Red：Steam increase,←：Interference（Red：Steamincrease,
Blue：Steam decrease,Purple：Both）
Blue：Steamdecrease,Purple：Both）

-200

-100

0

100

Well-13
37P

Planned recharge well
200

300
400
Ease-West（m）

Field injection tests
500

600

700

800

900

7

Confidential
North-East（B）（m）

South-West（A）
-300
500

0

300

600

◆：Feed point and/or lost circulation point＊：Well-16 feed point←：Interference（Red：Steam increase,
Blue：Steam decrease,Purple：Both）◆：Feed point and/or lost circulation point＊：Well16 feed point←：Interference（Red：Steam increase、Blue：Steam decrease、
Purple：Both）

Optimal case from the aspect of recharge
effect and the risk

0Well trajectory forrecharge block3

検討項目
Check item
血の池沢下盤断層モデル
Chinoikezawa
footwall model
Past field injection tests
本地域における注水試験等の経験-500

RefinedChinoikezawa footwall model
血の池沢下盤断層追加検討モデル

Well-5

Elevation（m）

Chinoikezawa
Footwall fault

Recharge
block涵養ブロック

1
▲
▲
◎
◎
△

1.5
○
△
◎
◎
△

2
○
○
▲
◎
▲

3
◎
◎
▲
◎
▲

C.F.M. R.C.F.M.

Well trajectory forrecharge block2
Well trajectory forrecharge block1.5

LegendRecharge block3-1,000

Index
指標

Large
< EffectSmall
大＜効果 > ＞小小＜< リスク＞大
Small
Risk > Large

Recharge
effect涵養効果
Steamreduction
risk
大量注水による蒸気量減衰リスク
Short
circuit risk
ショートサーキットリスク

◎
◎
◎

○
○
○

△
△
△

▲
▲
▲

Well-10Well-9Well-6

Recharge block2

No bad influence is observed
injection below -1500masl

Well-19

Well-3

Recharge block1.5

Well-4Well-1-1,500Well-15
Well-8Recharge block1

Well-14

Well-2Chinoikezawa
Fault

Well-17
Well-12Well-7Chinoikezawa
Hanging wall fault

Well-18

Planned recharge well

-2,000Block1.5(-1400～-1600msl） in the
Chinoikezawa footwall fault model was
selected as a target.

Well-13

Well-16

Determination of the locationof the recharge well8

2. Drilling and logging results
Actual 14JN-R1 well trajectory and recharge block1.5

L/C
Drilling break
Recharge
block1.5

9

Casing program
Plan

ActualLiner hanger

Slotted liner
Slotted liner

Wellhead at 14JN-R1

10

Injection PTS and Fall off test
0

0

-30

5

10

PRESSURE [MPaG]
15
20

25

30

50

TEMPERATURE [Deg.C]
100
150
200

250

300

-25

SPINNER [RPS]
-20
-15

-10

-5

0

Casing Program

0

Well Dogleg(Deg./30m)
2
4
6
8

0

Well Inclination(Deg.)
10
20
30
40

14JN-R1 フォールオフ

10

200

50

12.5

250

160

12.0

200

120

11.5

150

80

11.0

100

40

10.5

50

10.0

0

Pressure at 2035m
Temperature at 2035m
Flow rate↓Shut-in

1760

1780

Injection rate (t/h)

Drilling
break

1840

7"CSG(top)1840.48m

1860

1880
12-1/4"
1890.00m

9-5/8"CSG
1880.54m

Pressure (MPaG)

5-1/2"TBG(end)1814.00m

1820

Temperature (deg.C)

1800

DEPTH [m]

1900

1920

L/C ratio
based on the
PTS analysis

0

Total L/C

1930m, 8%

2015/03/24 18:00

2015/03/24 20:00

2015/03/25 00:00

Date Time

1940

Fall off data

1960

1980

2015/03/24 22:00

1980m, 9%

2000

WellTESTTM analysis

Drilling
break

2020

Well name2040m, 76%2040

Permeability(k)20602080m-, 7%

2080

2100

8-1/2"
2100.26m

7"CSG(slotted)
2100.26m

逸泥掘削
注水中(66t/h)温度検層(2014.11.18)
Green12-1/4"裸坑時: Nov.18,2014
66t/h injection (after 12-1/4” drilling)
注水中(90t/h)温度検層(2014.12.5)
Blue :8-1/2"裸坑時Dec. 5, 2014
90t/h injection (just after 8-1/2” MWD掘進
drilling)
ﾄﾞﾘﾘﾝｸﾞﾌﾞﾚｰｸ
注水中(50t/h)PTS検層(2015.3.24)
Orange: March 24, 2015 50t/h injection
全量逸泥
注水中(100t/h)PTS検層(2015.3.24)
Purple: March 24, 2015 100t/h injection
部分逸泥
注水時流出深度割合

14JN-R1
2.39 mDarcy(2.36E-15m2)

Permeabilitythickness(kh)502.43 mDarcy-m(4.96E-13 m3)

Skin factor(S)

-4.15

坑井傾斜
ﾄﾞｯｸﾞﾚｸﾞ

11

BHTV logging in 8-1/2” hole(2090-2098m)(1930-1940m)(1980-1990m)(2030-2040m)

BHTV data at L/C and drilling break while drilling

12

Chinoikezawa
hanging wall fault

300
Well-1014T
well-733P

200

Chinoikezawa fault

B

Well-96T

100

Well-17
35P

Chinoikezawa
footwall fault
Well-423P

0Well-1238P

Well-115T
Well-221T-100

well-19
10T

North-South(m）Well-632P
Well-536P-200

Well-1630P
Well-1427P-300

Well-1528P-400

Well-834P

1930.71m, N87.7E, 77.9

Well-18
39P

Well-331P-500

Well-11

1940.59m, N70.1W, 70.5

A
-600◆：Feed point and/or lost circulation point
14JN-R1＊：Well-16 feed point←：Interference（Red：increse、Blue：decrease、
2093.7m, N59.0W, 44.0
Purple：both）
Planned recharge well

-700
-300

-200

-100

0

Chinoikezawa
south-east fault

100

200

300
400
East-West（m）

500

Well-1337P

2036.06m, N52.3W, 87.5

600

700

800

900

13

Lost circulation and/or drilling break while drilling(★) and BHTV analysis(strike and dip) 13

3. Recharge operation

14

Recharge

Existing OAG monitoring andoperation flow for injection*1DCS … Distributed Control System. Continuous
monitoring and remote operation of the electric
valves*2LCV … Level Control Valve. Control valve forwater level of buffer tank; Water level control
valveof buffer tank(for flowrate control, Header
Tank:H/T) located in water line downstream of theseparator.
*3BDV … Blow Down Valve. A kind of safety valve
to release header tank water to a pit.
Conditions for shut
down productiona)WHP >=0.7MPa or<=0.58MPab)Two phase pressure
More than 0.68MPa or
lower than 0.59MPa

Frequent
monitoring
Check
Steam/WHP/EC/pH every day

Fluid chemistry
・Check CL・H2S concentration
・Regular Sampling(Well-3, 5, 8 and 11)・Sampling frequency(daily after
starting recharge，depending on thesituation)

Check thetrend

PT monitoring at the recharge well ・Check trend and remarkable events

Behavior of the
production well by
DCS*1 frequently

Recharge stop

Seismic monitoringFeltearthquake？

conditions forshut down
production

Individual
problem ofwell？

Shut down
the well

Discussion

15

Hot spring monitoring

Frequent check of
LCV*2 apertureand H/T level by
DCS

conditions forshut down
injection

Geophysical /Geochemicalmonitoring

Reduce recharge
rate or stop
recharge

Conditions for shut down
injection①Water LCV aperture：H
alarm(75%) activation②H/T level：H alarm(75%)or L alarm(35%)
activation③Water BDV*3：Open

Check epicenter by
JMA data and seismic
intensity by aseismometer

Reduce recharge
rate or stop recharge
depending on
epicenter and the
depth

Check thetrend

Flowrate
and/or WHT
decrease
Reduce recharge
rate or stop
recharge

Discussion

Recharge stop

Fukushima Pref.
Area1, area tostop recharge：
Stop recharge
when felt seismic
event whose
intensity is larger
than 4 is occurred.

Survey area

Seismic monitoring point
Area2, area to cut
back the recharge
rate: Cut back therecharge rate
when felt seismic
event whose
intensity is larger
than 3 inside thearea of the redcircle whose radius
is 500m centeringon the bottomholeof the recharge
well is occurred.

Felt seismic event(M4.9), Oct., 2009.

ground surface(JMA)
ground surface(OAG)
ground surface (AIST)
wellbore (AIST)
wellbore (GERD)
Monitoring networkon ground surface
Monitoring network
In wellbore
Area1
Area2
Felt seismic Mag.
0.5 5.00m

1500Modified 1:50000 Miyashita
topographic map (GSI)

Recharge operation to felt seismic events (Plan)

16

4. Acquired data

17

Takiyagawa fault

Sarukurazawa fault

Chinoikezawa
Hanging wall fault

Chinoikezawa fault
Chinoikezawa
Foot wall fault

Well-5

LegendHigh temperature region

Well-6

Production well

Well-8Chinoikezawa
southeast fault

Suspended well
Injection well

Estimated fault(-1000m)
Feed points
Superheated region

Okuaizu geothermal field (Plan View)

Acidification region18涵養井の状況および蒸気・熱水生産量（2015/5/31-2016/2/07）
PT monitoringin the recharge well

Shut In(8/31)

100t/hShut In(12/26)

Injection forkill well

90t/h

60

70t/h

70t/h

40

2015

7/14:power outage
7/22:power outage

7/24

80

Power plantpreventive maintenancecheckup

9/4

10/16

40

12/16: pump trouble

11/27

Injection rate and cumulative injection rate

Downhole Pressure

0
1/8

2016

2/19

Downhole Temperature

13.0
Setting depth 2035m Superheated amount: 7.7℃
12.5
12.0
Max. temp
11.5
5/2: 313.27℃
11.0
10.5
10.0
9.5
9.0
8.5
8.0
7.5
7.0
3/20
5/1
6/12
7/24
2015

120

50t/h

8/17: pump trouble

20
6/12

160

70t/h

50t/h

6/21: torrential rain

5/1

70t/h

50t/h

50t/h

200

Short term Step rate

Change rate(7/31)

80

240

1/29:Well-8 PTS logging
2/19:Well-8 PTS logging

Saturation Temperature
360
Setting depth 1895m Superheated amount: 6.9℃
330
Superheated amount: 5.3℃
300
Max. temp
Max. temp
270
10/12: 305.83℃
1/30: 300.03℃
240
210
1/1-9: BH temp fluctuation
180
150
Pressure falloff analysis
Pressure falloff analysis
120
90
60
30
1/1-12: BH press fluctuation
0
9/4
10/16
11/27
1/8
2/19

PT monitoring data

It is considered to be greatly
affected by fluctuations at Well-8

2016

Temperarute (deg.C)

Injection Rate (t/h)

Short term Step Rate

100

0
3/20

Pressure (MPaG)

Amount of Injected Water

6/5,8,10,11:PTS logging
7/7-10:Well-5 PTS Sampler logging
6/26: Gas, 2phase tracer injection 8/25-28:Well-5 PTS Sampler logging

Amount of Injected Water(x1,000 ton)

Injection Rate

120

19

Production situation（Well 8）・Dec 23～24：Superheated amount decreased（22.4℃→18.0℃）
・Dec 24～25：Steam decreased（19.6t/h→16.8t/h）※Injection rate was reduced from 70t/h to 50t/h.
・Dec 26：Superheated amount decreased to 0.8℃
※Recharge operation was stopped.
・Dec 28～Jan 14：Separate from the power plant because of the cyclic effect・Jan 14：Join the power plant20

Production situation（Well 5,6）21

Geochemical monitoring（Well 8）
Volicanic#1: Volcanic gas inNorth-east Japan(Kiyosu,1985)
Volcanic#2: Volcanic gas
estimated by the analysis of
Okuaizu geothermal field.
Volcanic#3: Volcanic gas
estimated from Well-13 in the
Okuaizu geothermal field.

Isotope(total)
Black : Sampling 1 (April) Blown:Sampling2(June) Purple:Sampling3(Aug)
Blue:Sampling4(Aug) Aqua: Sampling5 (Nov) Green:Sampling6 (Dec)
Orange:Sampling7(Jan,’16) Red;Sampling8(Feb, ‘16)

Jan 13,2016
WHP increased(0.95→1.13MPaG)
Jan 13,2016
WHP stable(1.15MPaG)
WHP Lower stable (0.94MPaG)
Jan 13,2016
WHP decreased(1.14→0.94MPaG)

Feb 16,2016
Day after steam rate pulsation

He-Ar-N2 steam chemistry

・Steam chemistry moves to that of the air after therecharge re-started on Nov 27,2015.
・Isotope ratio moves to meteoric water.
→It is supposed that the production fluid includes riverwater.

Jan 13,2016
WHP Lower stable (0.94MPaG)
Jan 13,2016
WHP stable(1.15MPaG)
WHP increased(0.95→1.13MPaG)
Dec 25,2015
Day before steam rate pulsation
Nishiyama hot spring22 PTS+ sampler logging result at Well-5
Well 5
0.2

0.4

0

50

INCL[deg]

Well 5
1.2
250

0
0

200

400

600

0.4

0

50

INCL[deg]

SPINNER [RPS]

30 60

0.2

800

1000

0

30 60

PRESSURE [MPaG]
0.6
0.8
1.0
TEMPERATURE [Deg.C]
100
150
200

1.2
250

SPINNER [RPS]09009-5/8" CSG

0

PRESSURE [MPaG]
0.6
0.8
1.0
TEMPERATURE [Deg.C]
100
150
200

200

400

600

800

1000

Sampling depth
サンプル取得深度
950BC9-5/8" CSG

200

1000

DEPTH [m]DEPTH [m]

400

1050

7" CSG(slit)

600

800

1100

7" CSG(slit)

BC

Sampling
depth
サンプル取得深度
1000

1150

1200

1200

INDEX
PTS
Sampler
PTS
Sampler
PTSサンプラー検層
PTSサンプラー検層
PTSサンプラー検層
坑内サンプル取得深度
Downhole
Sampling Depth
PTS
Sampler(2015.7.7-10)[検層条件(H27.8.25)](2014.)
Condition (2015.8.25)（H26）（H27.7.7-10）(2015.8.25-28)（H27.8.25-28） ①1,180m(101.0g)
坑口圧力：0.62MPaG
WHP:
圧力
圧力
圧力
②1,125m(95.0g)
Press
Press
Press
Steam:
蒸気流量：14.5t/h
Temp
Temp
Temp
温度
温度
温度
③1,050m(90.2g)
Water:
Spin
Spin
Spin
熱水流量：0t/h
スピンナー
スピンナー
スピンナー
④950m(81.2g)

Logging result（0m～1,189m）

坑内洗浄時のスケール片
Wellradius may be narrowed by
等による坑径狭小？
scale
scraped while well cleaning

INDEX
PTSサンプラー検層
PTSサンプラー検層
PTSサンプラー検層
坑内サンプル取得深度
PTS
Sampler
PTS
Sampler
Downhole
Sampling Depth
PTS
Sampler[検層条件(H27.8.25)]
Condition (2015.8.25)(2015.7.7-10)(2014.)（H26）（H27.7.7-10） (2015.8.25-28)（H27.8.25-28） ①1,180m(101.0g)
坑口圧力：0.62MPaG
WHP:
圧力
圧力
圧力
②1,125m(95.0g)
Press
Press
Press
Steam:
蒸気流量：14.5t/h
Temp
Temp
Temp
温度
温度
温度
③1,050m(90.2g)
Water:
Spin
Spin
Spin
熱水流量：0t/h
スピンナー
スピンナー
スピンナー
④950m(81.2g)

Logging result（900m～1,189m:magnified image）

 From the logging results, no significant change was observed for the feed point situation.
 Reduction of superheated amount was observed(It may be caused by the well injection for cleaning) other than recharge effect .

23

Sample(Borehole Tracer) analysis at Well-5★Surface sampling
0.6

TFEA

Concentration(mg/kg)
濃度（mg/kg）

0.5

Well 5

0.4

TFEA
0.519

Flowrate
100%【Surface～FP1170m】
Production contribution： 33%

0.3
0.2
0.1

Nov '14Jul '15
Aug '150

Surface
地上

1,010m

1,050m

1,125m

1,180mTracer concentration at the sampling depths★Sampling@1010m

Flowrate

Ratio

100%

9.7%

90.3%

1.3%

89%

16.9%

72.1%

72.1%

●FP1026m

 Tracer concentration reduced by about 1/20
in one month.
 67% of production steam comes fromdeeper reservoir (deeper than 1185m) andthe rest(33%) comes from shallower
reservoir (shallower than 1185m) based on
the tracer analysis.

TFEA
0.587

★Sampling@1050m

Dilution

0.471●FP1088m★Sampling@1125m

0.588●FP1170m★Sampling@1180m

0.483●Deeper than FP1185m【Deeper than FP1185m】
Production contribution：67%[Past logging result of FP(deeper than 1185m)]
・1350m, 24%
・1540m, 33%
・1660m, 19%24

Tracer test(2015)

Gas tracer(PDMCH) detected

Two phase tracer(TFEA) detected25

L/C point(Recharge well)
Feed point(production wells)（Year 2013）（Year 2015）

Peak concentration distribution for PDMCH

26

AE/Micro seismic array

Existing station 5（OMS# ：OAG）
F: 4.5Hz，Fs=100Hz＋
Surface station
Borehole station

5
4
Total 14

YAE-9

Recharge point

YAE-8

Nanometrics
F: 20s～108Hz
Velocity＠
YAE2,3,42km

シンカーバー（キー付き）

坑内地震計（センサー部）

アームロック機構

OYO
F: DC～
200Hz，
Accelerometer
＠YAE-1&5

アームロック用
油圧ライン
YAE-7

キー

アーム

265mm
1485mm
1950mmOYO（ESG）
F: 20～1kHz，Accelerometer

アームロック機構

キー

ケーシング側キー溝

IESE(NZ)
Passive F: 15Hz
Velocity

信号ケーブ

Nanometrics datalogger
Realtime observation by Fs=1000Hz

27

Back
ground
注水開始前

0Step rate
ステップレート注水期間

500 m

0

500 m

57

58

50 t/h
注水期間
50t/h

0

70 t/h
注水期間
70t/h

500 m

0
59

500 m
60

28

After injection＜Total event＞
May 1, 2015～February 29, 2016
AE/Micro seismicity：2535 events，（Location calculation：1201 events）
EQ（Far event）：4622 events＜Occurrence of the events＞(till Nov.13)
・BG ：2.8 events/day ave.
・Step rate ：1.8 events/day ave.
・50t/h ：4.0 events/day ave.
・70t/h ：7.5 events/day ave.
・After injection：4.5 events/day ・Entire period ：4.7 events/day ave＜Local magnitude＞(till Nov.13)
・BG ： -0.53 ave.
・Step rate ：-0.58 ave.
・50t/h ： -0.38 ave.
・70t/h ：-0.37 ave.
・After injection：-0.59 ave.
・Entire period ：-0.47 ave.
29

AE/Micro seismicity （frequency of occurrence）

30

5. Discussion

31Recharge effect(spatial distribution)

L/C(Drilling break)Feed point

L/C of the recharge well and feed points of the production wells(Plan view)

32

NW

SE

Relationship between the feed points of the
血の池沢下盤断層系生産井のフィードポイントと涵養
production
wells in Chinoikezawa footwall
井のドリリングブレークとの位置関係
断面図 fault andthe L/C point of the recharge well

貯留層温度（℃）
Reservoirtemperature (℃)

Superheated
過熱度（℃） amount (℃)

フィードポイント
Feed point
ドリリングブレーク（14JN-R1）
L/C(Drilling break)Well-5Well-3Well-6
Well-8Cross 断面線
sectionL/C of the recharge well and feed points of the production wells(Cross section)

33

Recharge effect(PT monitoring data)

50t/h

70t/h

70t/h

Temperature level of 70t/h of
before the power plantpreventive maintenancecheckup

PT monitoring history in the recharge well at 1895m deep
Injection pressure after the power plant preventive maintenance checkup decreased by about 1.5 MPa
despite of the same injection rate.
Temperature after the checkup increased by about 10 ℃.
The reason above is due to fracture permeability above 1,895m increased and injection temperature
increased due to reduction of the injection rate below 1,895m. The permeability could change due tomicro seismicity and/or fracture aperture increase due to cold water injection.
Injection water level estimated from the downhole pressure is around 850m. It can be possible for therecharge water to affect all of the feed points including the shallowest one at 1,534m of Well-8 if fractures
are well developed in the reservoir.
34

Recharge effect(Effective radius by the injection)
Recharge image

Total injection：Approx. 170k tons
Calculation condition：Porosity：0.1(used in the simulation)，Thickness：Parameter(10m，20m)
Porosity
0.1

Thickness(m)Effective radius(m)

10

232.6

20

164.5

The effective radius changes depending on assumption of the thickness. The tracer test and the fact that the west part of the recharge
well is aseismic suggest that the west part could be more permeable than east part. It is possible for the recharge water to reach Well-8
although the recharge water is boiled while it travels to the Well-8.
35

Feed point of well-8
Drilling depth(m)Elevation(m)

1534
1873
1897
1965
2041

-1066
-1386
-1409
-1471
-1540

Prodction ratio(%)★
★

1890m(drilling depth)-1382m(elevation)

65
11
8
5
11

Recharge fluid flow

36Recharge effect(Production rate at Well-8)4040■Steam rate in this計測値１time (78days
checkup)2015/11/14(71日）■Steam rate in 2011(112days
production stop*1)
計測値２ 2011/2/15(111日)－Extrapolated function1
関数１－１－Extrapolated function
関数２2

35

30

Steam rate (t/h)
蒸気生産量（t/h）

Steam rate (t/h)
蒸気生産量（t/h）

30
25
20
15

25
20
15

10

10

5

5

0
-150

-100

-50

0

50

100

150

時間(日)
Days

Comparison between 2011 drawdown andthat in 2015(this time)■Steam rate in計測値１
this time2015/11/14(71日）(78days checkup)－Extrapolated関数１－１function 1－Extrapolated関数１－２function 3

35

200

0
-150

-100

-50

0

50

100

150

200

時間(日)
Days

Different extrapolation*1:Production stopped for 112 days(Oct.26,2010-Feb.14,2011)
due to pipeline maintenance.

37

Recharge effect to production wells

38Comparison between the simulation and the recharge experimentLiquid immobile case in two phase condition(Chinoike model)
History matching

Recharge period : about 4 months

Recharge simulation
Drilling
break

0 t/h

Cumulative steam

Liquid mobile case in two phase condition(Refined model)
History matching

Recharge simulation
Drilling
break

0 t/h

Cumulative steam

39

6. Summary① Production behavior of Well-8 is thought to be caused by the recharge.
② Based on the PT monitoring at the recharge well, fracture permeability above the PT
monitoring depth(1,895m) increased with decreasing injection pressure and increased
injection temperature with decreasing water flow around the PT monitoring depth after the
power plant preventive maintenance checkup(Nov. 27,2015).
③Steam rate of Well-8 is stable at about 20t/h between Dec 5 and Dec 23. Also thesuperheated amount tends to be constant (about 22deg.C) in the duration. This is thought tobe one of the good effects of the recharge.

④ In order to evaluate the recharge effect of Well-8 quantitatively, the behavior of the well
was compared with that of 2011. As a result, approx. 5t/h steam increase was estimated.
Based on the analysis of steam decline curve after the power plant checkup(2015), approx.
3t/h stream increase was estimated.
⑤ The Well head pressure of the productions wells increased after the checkup. This could becaused by the reservoir pressure increase generated by boiling pressure of the injected water(300deg.C) as well as recovery of the natural reservoir pressure.
40

⑥ The superheated amount lowered after the checkup. This is thought to be diffusion effect of
the injection water in the reservoir. It is possible to think that the stable steam production ofboth Well-5 and Well-6 near the recharge well is based on the recharge.
⑦ The tracer result suggests a connection between production wells and the recharge well. It is
possible to increase the steam rate by the pressure propagation generated by boiling of therecharge water.
⑧ Although the duration of the recharge is about 4 months, the steam production at the field isconsistent with the simulation result for the moment.

⑨ Thermal break through at Well-8 was observed at the end of December 2015. From theobserved Well- 8 steam stable behavior between Dec 5 and Dec 23, the slow decline of thesteam at Well-6 and the decrease of the superheated amount together with the slow decline of
the steam at Well-5, it is possible to maintain and/or increase of steam production by proper
control of the recharge operation.
⑩ Accuracy for predicting the thermal break through of Well-8 could be enhanced bycomprehensive analysis of superheated amount, isotope analysis and so on.

41

Thank you for your attention.

42