EGS field test for sustaining reservoir
at Yanaizu-Nishiyama geothermal power plant

2 Jun, 2016

Table of contents

１．Outline of EGS Project
２．Field History

３．Early Reservoir Model (1989)
４．Steam Production History

５．Example of Production Data
６．Summary1１．Outline of EGS Project

ProductionWell

2PowerPlant

Injection
Well

Recharge
Well

Geothermal
Reservoir

Magma Body

• Some of geothermal power plants in Japan are facing difficulty in producing steam needed
to operate stably, due to the depletion of the geothermal fluid.
• To address this challenge, JOGMEC tries to research and development to stabilize theproduction of subsurface geothermal steam and hot water by not only improving accuracy
in evaluation of behavior of the fluid, but also recharging water to the geothermal reservoir.

Demonstration Field

3Outline
Field

Operator

Remarks

Yanaizu-Nishiyama Geothermal
Power Plant

Location: Yanaizu Town, Fukushima

SteamSupplier

Okuaizu Geothermal
Co., Ltd.

Affiliated Company of:
Mitsui Mining & Smelting Co., Ltd.

PowerGenerator

Tohoku ElectricPower Co., Inc.

YanaizuNishiyama

Plant capacity

65,000kW (Single flash type)The largest geothermal unit in JapanStart of commercial
operationMay 25, 1995

20 years of operation (as of Sep, 2015)

Reference: Thermal and Nuclear Power Engineering Society (2014)

Project ScheduleItems

4Contents(1) Project Planning, DesignManagement- Management of project and data

(2) Survey and Modeling- MT method, AMT method, Gravity survey- Integrated analysis, Development of geological model, geothermal(supplemental survey as needed to update models)(3) Design and Construction
Test Facilities- Design and drilling/construction of a recharge well and recharge facilities
intake, piping)(4) Well Test and Logging- Before recharge test: Well test and logging for monitoring well/s and- After commencement of recharge test: PTS sampler logging for(5) Operation of Recharge- Recharge of surface water (increase recharge rate in stages so as tolevel)(6) Numerical Reservoir
Simulation- Before recharge test: Forecast calculation for several cases to optimize
conditions- After commencement of recharge test: Update numerical model withobtained, and forecast calculation(7) Monitoring-(8) Preparation of Technical
Operation Manual- systematize recharge technique and prepare technical operation manualDown-hole continuous PT monitoring on monitoring well
Multi phase tracer test
Micro-seismic monitoring
AMT method
Hot-spring sampling

FY2013FY2014FY2015FY2016FY2017

２．Field History

51956 : Prospecting for black ore deposits and perlite in the Aizu area by Mitsui Mining &Smelting (MMS).
1974 : Geothermal exploration launched in the Nishiyama area by MMS.
1977 : Two- year Basic Exploration for Geothermal Development ‘the Nishiyama area’ by
Japan Geothermal Development Center.
1981 : Exploration resumed by MMS on Yanaizu Town’s request.
1982 : Two-year Promotion Research for Geothermal Development ‘the Okuaizu area’ by
New Energy Development Organization (NEDO).
1983 : Establishment of Okuaizu Geothermal (OAG) financed by MMS, Mitsui
Construction and Toshiba.
1984 : First exploratory well drilled by OAG.
1986 : Joint research undertaken by OAG and Tohoku Electric Power.
Feb. 1990 : Bilateral agreement on promoting geothermal development between OAG andTohoku Electric Power.
Jan. 1991 : Bilateral basic agreement between OAG and Tohoku Electric Power.
Dec. 1992 : Green light to construct a geothermal power station by the 122nd ElectricDevelopment Coordination Council.
Jun. 1993 : Conclusion of environment conservation agreement between OAG, Yanaizu Town
and Tohoku Electric Power.
May 1995 : Commercial operation start.

CONFIDENTIAL

Well Location Map(Plan view)３．Early Reservoir Model (1989)• Production & Re-Injection Zone
Production - CHINOIKEZAWA Fault- SARUKURAZAWA Fault
Re-injection - OIZAWA Fault• Numerical Model

7

NISHIYAMA
Hot Spring
TAKIYAGAWA
Fault
CHINOIKEZAWA
Fault

OIZAWAFault
SARUKURAZA
WA Fault

TAKIZAWAGAWA
Layer- NW-SE = 3.2 km - NE-SW = 4.6 km- Vertical = Surface ～ ‐2,000m-asl- 375 blocks- CO2 gas treatment

ColdWaterFlow• Conclusion
55 MWe : Feasible
75 MWe : Possible withsouth-eastern area development

Basement
RockDifficulties ：Porous Media Simulation (No-MINC)
Young Computing Technology
History Matching・・・

HotGeothermal
Water Flow

Schematic Reservoir Model

４．Steam Production History
1995-1997 65MW Output with 14 Production wells
1998-2000 Large decline down to 40MW
2000-2006 Holding 45MW with make-up well every year
2007Slow down the well adding→ Large decline
Acid fluid problem→ Shortage of steam8

５．Example of Production Data(1) Reservoir Pressure Drawdown
Drawdown = 54.3%
・Large drawdown
3.4～4.8MPa(1998)⇒1.1～1.2MPa(2013)
・Due to large cumulative production(2) Excess Temperature
・Excess temperature of well-5 and well-6
went up to 40℃ from 2005.
・Well-5 is descending but still high.
・Possibilities of acidic problem.
→ Careful monitoring.

Injection will solve these problems,and maintain the reservoir performance.

9６．Summary

10• Reservoir simulation in 1989 concluded that 55MW development is feasible,and 75MW development is possible. However, it had some difficulties intechnical issues.
• YANAIZU-NISHIYAMA Geothermal Power Station started commercial
operation in 1995 with output of 65MWe.
• From several years later, large steam decline caused lower MW output due tolarge drawdown of reservoir pressure.
• The large pressure drawdown in the high temperature reservoir caused
superheated steam production, and subsequently caused acidic problem insome wells.
• EGS technique will be effective in this field.

Thank you for your attention.