Current status of
the recharge experiment at
the Okuaizu geothermal field
November 20, 2019
T. Okabe, M. Kato, H. Nakata(GERD),
Y. Abe(OAG), H. Asanuma(AIST),
M. Tsuzuki, K. Yoshimatsu(JOGMEC) and
H. Kamenosono(JOGMEC, now KEPCO)
1

Presentation
1. Project Overview
1.1 Purpose and the schedule
1.2 Project structure
1.3 Okuaizu geothermal field
2. Present achievements
2.1 Recharge Test in 2015 and its results
2.2 Workover and recharge test in 2018
3. Summary21. Project Overview
1.1 Purpose and the schedule• The purpose is to develop a guideline for an artificial water recharge technology and todevelop a technical manual through a verification test and numerical simulation
clarifying the impact of artificial water recharge on the geothermal reservoir and/or hot
spring aquifer.
Research & Development

FY2013

FY2014FY2015FY2016FY2017FY2018FY2019Project Planning, Design & Management
Geological/Geophysical Survey andModelingIf necessary

Design and Construction of Test
Facilities (including wells)

WorkoverWell Test and Logging
Injection was stopped due tointerference with the nearest
production well

Operation of water injection
Numerical Reservoir SimulationMonitoring
Preparation of Technical Operation
ManualModelling & Forecast

Field data analysis & model upgrade

BackgroundOperation

31.2 Project Structure
JOGMECContract
Project leader

GERD- Project Planning, Design &Management- Survey and Modeling (MT)- Well Test and Logging- Numerical Reservoir Simulation- Monitoring (Downhole PT, Tracer test,etc.)- Preparation of Technical Operation
ManualJOGMEC
GERD
OAG
AIST

GERD
OAG
- Design and Construction ofTest Facilities- Operation of Recharge Test
- Monitoring (Hot-springsampling )- Preparation of TechnicalManual- Local Coordination

Tohoku Electric Power Co., Inc.
(Yanaizu-Nishiyama Power Plant)
Cooperation

AIST- Project Planning, Design- Survey and Modeling (AMT ,Gravity)- Monitoring (Seismic, Resistivity)- Preparation of TechnicalOperation Manual: Japan Oil, Gas and Metals National Co.
: Geothermal Energy Research & Development Co., Ltd.
: Okuaizu Geothermal Co., Ltd.
: The National Institute of Advanced Industrial Science and Technology

41.3 Okuaizu geothermal fieldYanaizunishiyama
Geothermal Plant

Fukushima

Turbine size was changed to30MW on 28th August, 2017.

Aizuwakamatsu

24 years of operation in 2019Tokyo5Seki(1991)

Well-2

Acidification region
Superheated region

Okuaizu geothermal field (Plan view)
626"

155.00m

PlanActual

20" CSG
150.00m

20" CSG
154.39m

26"

155.00m

ECP743m
17-1/2"

1,005.00m

13-3/8"CSG
1,000.00m

13-3/8"CSG
997.32m

17-1/2"

1,005.00m

9-5/8"CSG
Liner hanger

Casing program and a picture of
the wellhead

5-1/2"TBG
1,814m12-1/4"

1,880.00m

8-1/2"

2,225.00m

12-1/4"

1,875.00m

9-5/8"CSG
1,880.54m

1,880.00m

7" Slotted liner

7" Slotted liner
1,840.48～2,100.26m

2,225.00m8-1/2"

2,225.00m

72. Present achievements
2.1 Recharge test in 2015 and its results【Term】
1st : Jun. 4, 2015 ~ Aug. 31, 2015 (88 days)
2nd : Nov. 27, 2015 ~ Dec. 26, 2015 (29 days)

Recharge Rate

【Recharge rate】
1st

2ndMS Monitoring

Removeinjection pipe

【Amount of recharge water】
1st: approx.120,000 ton, 2nd : approx. 50,000 ton
Steam increase, NCG decrease and easing of acidification were observed. Decrease of the steam
rate and cyclic effect of the steam with the brine production was observed in late December atWell-8. The recharge operation was stopped on Dec. 26. This is because of thermal
8breakthrough from shallow LC zones caused by cementing problem of 9-5/8” casing.

Recharge effectAlthough effect by reservoir pressure increase while themaintenance increases the steam rate, recharge operationis conducive very much to increase Well-8 steam based on
the tracer and NCG results.

Steam rate(t/h)

Well-8 production history

Recharge

19t/h

30% steam increase

14t/h

Well-8 NCG change

NCG(wt%)14131211Before the recharge : 8.9 wt% 109After the recharge : 5.0 wt% 8

Well-8
14JN-R1掘削
5/25

NCG decrease
6/24

7/24
11/30

78/21

65Dilution by steam increase

4/22
3/22
1/26

12/2

12/25

432(涵養)1001/4 02/4 03/4 04/4 05/4 06/4 07/4 08/4 09/4 10/4 11/4 12/4 13/4 14/4 15/4 16/4 17/4

9

AE/Micro seismic array

Existing station 5（OMS# ：OAG）

F: 4.5Hz，Fs=100Hz＋
Surface station
5
Borehole station 4Total 14
YAE-9

Recharge point

YAE-8

Nanometrics
F: 20s～108Hz
Velocity＠YAE1-5

2km

YAE-7OYO（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: 15HzVelocity

Nanometrics datalogger
Realtime observation by Fs=1000Hz

10Back ground0500 mRecharge point

70 t/hRecharge stage
0500 mNumber of events
per day
Local magnitude

Back ground(May)

Step rate
50t/h(Jun.) (Jun.-Jul.)

70t/h(Jul.)

After injection(Aug.-Nov.)

2.8

1.8

4.0

7.5

4.5

-0.53

-0.58

-0.38

-0.37

-0.59

AE/Micro seismicity monitoring result11Model improvement

A

Initial Model

A’

Updated Model⑨⑥②Cap rock⑦⑧⑤④⑩

①Heat Source

Initial geothermal model was updated considering MS events.
We reviewed:• Cap rock shape (② is not a cap rock)• Migration area and boundary of recharged water(④&⑤ are very low permeability zone)

12

New faults evaluated13

TOUGH2 simulation (Challenging)

Natural state⇒History matching⇒Injection for superheated areaA

BeforeA’Depth (m)Temperature (deg.C)

A

After

A’

Depth (m)A

Temperature profile
Temperature (deg.C)

The accuracy of the temperature simulation was improved.

A’ActualSimulation

142. 2 Workover and recharge test in 2018(1)Present26"坑159.00m

20"CSG
150.00m20"CSG
154.39m

26"坑
159.00m20"CSG
150.00m

ECP
743m
17-1/2"坑 13-3/8"CSG
1002.00m
1,000.00m

13-3/8"CSG
997.32m(3)Metal packer+casing cement(2)Side track20"CSG
154.39m

26"坑
159.00m20"CSG
150.00m

ECP
743m

ECP
743m
17-1/2"坑 13-3/8"CSG
1002.00m
1,000.00m

13-3/8"CSG
997.32m20"CSG
154.39m

17-1/2"坑 13-3/8"CSG
1002.00m
1,000.00m

13-3/8"CSG
997.32m

Side track
12-1/4"坑1560.00m～1,610m12-1/4"坑1890.00m

9-5/8"CSG
1880.54m

12-1/4"坑1890.00m

7"孔明管
Slotted liner
2100.26m

12-1/4"坑1560.00m～1,610m

9-5/8"CSG
1880.54m

L/C behind the casing

12-1/4"坑1890.00m

9-5/8"CSG
1880.54m
7"孔明管
Slotted liner
2100.26m

7"孔明管
Slotted liner
2100.26m
8-1/2"坑2100.26m

8-1/2"坑2100.26m

8-1/2"坑2100.26m

Injection water

Metal packer

12-1/4"坑1560.00m～1,610m

Plug back15

Metal Packer deployment during cement curing

Metal Packer【Bonding】

Enlarged view

Metal Packer

A bit goodGoodA bit good 16

Result of the recharge test

During the workover, recharge test to checkthe present recharge situation for long term
recharge operation in future was conducted
for a month. Injection rate was 5t/h.

Existing Fault
Well06

Steam increase(1.4t/h)Production was suspended in advanceto prevent interference caused bywater injection : H30/11/22~12/18

Estimated Fault

Steam increase(1.7t/h)TargetRecharge Well17

3. Summary①In 2015 recharge tests, 170,000t water was successfully injected and a response to recharge(increase in steam flow) at Well-8 is observed and is estimated by approx. 30%.
Although further study is required about the recharge effect, production rate at wells close tothe recharge well increased. In addition, non condensable gas(NCG) decreased at those wells as
another benefit of the recharge operation.
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.
②In 2018 recharge tests, a response to recharge (increase in steam flow) at Well-3 and Well-6 isobserved and is estimated by 1.7t/h and 1.4t/h respectively.
③New geothermal model was created with new information from the latest technologies such
as MT 3 dimensional analysis, PTS + sampler logging, high temperature PT monitoring, etc.
④The accuracy of the simulation was improved based on the geothermal model, and detailssuch as (1)permeability of the formation , the range and boundary of fluid migration, (2) newfaults, and (3) the relationship between the fracture and the fault were revealed.
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3. Summary(Cont.)⑤A metal packer and cementing procedure was used to shut off the leakage at 7 ” casing shoecompletely and it was deployed successfully . The metal packer was used for the first time inJapan.
⑥In 5-7/8 “ drilling, the main injection zone at about 2030m in the original well was captured
at 2023m of the side track well as expected.
⑦Recharge test was started from July 2019 and is currently ongoing. An artificial recharge
technology manual applicable to geothermal areas in Japan will be created with analyzing longterm recharge test data and establishing appropriate recharge injection design andmanagement technology considering economic aspects.

Introduced cutting edge technology

a. 3D MT analysis
b. Recharge simulation for superheated reservoir (add supercritical option)c. New technology(combination of the focal mechanism analysis, scattering analysis,
migration method and accurate hypocenter determination) for flow path identificationof injected water based on microseismic monitoring data
d. High temperature borehole PTS+fluid sampler
e. High temperature (300deg.C) downhole pressure/temperature measurement
f. Installed high temperature downhole seismic tools
g. Installed a metal packer for the first time in Japan19

Thank you for your attention.

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