0Additional Potential of Microseismic Monitoringin Geothermal Development

Nov. 20, 2017
Keita Yoshimatsu*, M. Tsuzuki (JOGMEC)
H. Nakata, T. Okabe, H. Hase, (GERD)
H. Asanuma, Yamaya, K. Okamoto (AIST)
Y. Abe (Okuaizu)

Overview1

1.

MicroSeismic (MS) Monitoring in Japan

2.

JOGMEC Enhanced Geothermal Systems(EGS) Project3.

Contribution of Microseismic Data inGeothermal Development

4.

Conclusions

1. MS Monitoring in Japan- Introduction

2

In Japan, “MS Monitoring” has been conducted mainly foran environmental monitoring in geothermal development.

MS monitoring can:
1. notify the operator to stop pumping if:• the fractures are approaching environmentallysensitive areas.
• relatively large magnitude events occur.
2. prove that large magnitude events did not occur duringgeothermal development.

1. MS Monitoring in Japan- Examples

3

From JMA Website
Yanaizu-Nishiyama
Geothermal Plant (YNGP)
Fukushima
Power plant

Japan Meteorological Agency
Local government
National Research Institute for
Earth Science and Disaster Resilience••

MS observation points

Various organizations are monitoring the microseismicity all over Japan.
OKUAIZU geothermal Co. Ltd. has been monitoring around YNGP since
1987, and reporting the results to the interested party every year.

2. JOGMEC EGS Project- Introduction

4Some geothermal power plants are facing difficulty sustaining
production of steam and hot water.
Since 2013, JOGMEC has been performing R&D of EGS
around YNGP.
In 2015, a recharge injection test was conducted.

2. JOGMEC EGS Project- Overview of Recharge Injection Test

5YNGP Location Map

Power plant

EGS Target：
Southeastern part ofChinoikesawa footwall

1km

Estimated faults

Recharge Well (14JN-R1)• TD: 2,100.26mMD (8-1/2” Hole)• KOP:1,560mMD• Recharge: approx. 2,040 mMD

2. JOGMEC EGS Project- Details of Recharge Injection Test

【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【Amount of Recharged Water】
1st: approx.120,000 ton, 2nd : approx. 50,000 ton

6

2. JOGMEC EGS Project7- MS Observation for EGS Test
Total 14 points

YAE 1-536.5cmNanometrics
F: 0.05～100Hz，Velocity2~3 m depth

Recharge Area

Recharge Point

1.45m

We were monitoring the microseismicity
for operating EGS test safely.
We used MS data to solve a problem inthe geothermal development for YNGP.

⇐ YAE 6
OYO (ESG)
F: 0.05～1kHz，
3C Acceleration
420 m depth

YAE 7-9 ⇒IESE (NZ)
F: 15Hz，Velocity286~386 m depth

1.53m

2. JOGMEC EGS Project- MS Observation Systems

8Interested party

3. Contribution of MS Data in Geothermal Development

9- Problem in Geothermal Development for YNGP

An initial geothermal model was built based on the existingdata (well log, MT).
A’
14JN-R1

Cap rockA1km

3. Contribution of MS Data in Geothermal Development

10- Problem in Geothermal Development for YNGP

A temperature simulation was conducted using
the initial geothermal model.
However, the results didn’t match the actual
temperature profile well.

A’AA’A

Temperature profile

ActualModel

Calculated by TOUGH2 Supercritical Module3. Contribution of MS Data in Geothermal Development- MS Data Used for Updating the Model

Baseline

11Monitoring term for analysis

Baseline (1 mo.):
207 events
Monitoring term (13 mo.):
3,633 events

Note :Nearly half the data was used to determine the positions of MS events.

3. Contribution of MS Data in Geothermal Development- Integration of the MS Events

1214JN-R1

MS events were plotted onthe resistivity map.
The events were occurredat the specific area.

3. Contribution of MS Data in Geothermal Development- Grouping using the MS data

A’

13A’A
⑨⑥②④

⑦

①⑧⑤⑩

A
Heat flow

The model was grouped by MS data, well-log and resistivity.
 Zone ① : Low resistivity, Observed the Microseismicity
 Zone ② : Very low resistivity, Observed the Microseismicity
 Zone ④&⑤: High resistivity, Not observed the Microseismicity

3. Contribution of MS Data in Geothermal Development- Mechanism of Microseismicity

14

Microseismicity is tiny (ML≦2.5) seismic events caused by shear slip ofexisting fractures. (in most of the geothermal cases).
Recharge well

Stable state

P: Pore-pressure

Receivers

Trigger
Shear slip

Fracture network model3. Contribution of MS Data in Geothermal Development- Characteristics of Microseismicity

Triggers• Increase of pore pressure- Expansion or Evaporation of recharged water

15
Recharge well

• Reduction in coefficient of friction- Moving of steam and hot water• Change in stress state- Moving of cold water (recharged water)
Microseismicity is not common in the following area.
• Very high permeability area
• Very low permeability area
(Clay rock, Argillic alteration zones)• Areas without existing cracks of fractures

Water

4. Geothermal Structure Modelling Utilizing Microseismic Data
- Updating the Model

Initial Model

16

Updated Model⑨⑥②⑦⑧⑤④①

Initial geothermal model was updated considering MS events.
We re-interpreted:• Cap rock shape (② is not a cap rock)• Movement range and boundary of recharged water(④&⑤ are very low permeability zone)⑩

4. Geothermal Structure Modelling Utilizing Microseismic Data
「更新前の地熱構造モデル」に基づく貯留層モデルによる自然状態シミュレーション結果の例- Comparison of the Temperature Simulation Results

A

BeforeA’Depth (m)Temperature (deg.C)

After

A’

A’

A

Temperature profile
Temperature (deg.C)

Depth (m)A

17

The accuracy of the temperature simulation was improved.

ActualModel4. Conclusions

18• MS monitoring are usually used for an environmental
monitoring in Japan.
• JOGMEC conducted the recharged injection test aroundYNGP for R&D of EGS while monitoring the microseismicity
for safe operation.
• We re-interpreted the shape of the cap rock and themovement range and boundary of recharged water using
MS data.
• Accuracy of temperature simulation was improved by using
the model which was built by MS data.

Additional potential of MS monitoring in geothermal
development has been indicated.

19

Thank you for your attention