Azra N. Tutuncu, Colorado School of Mines Harry D. Campbell Chair in Petroleum Engineering

Director, Unconventional Natural Gas and Oil Institute (UNGI) EPA SAB Advisory Panel Member on Hydraulic Fracturing Research

Induced Seismicity

Monitoring for Environmental Safety, Geohazards and Risk Evaluation in Unconventional Shale Reservoirs

UNGI

December 5, 2013 Rio de Janeiro, Brazil

Outline

• Induced Seismicity Monitoring Effort

• Case Studies of Injection Induced Seismicity

• Coupled geomechanics and fluid flow modeling for stress

alteration during hydraulic fracturing near vicinity of a

fault

• Conclusions

Shale Reservoir Field Development and Production Challenges

• Surface and ground water contamination and air pollution and geohazard risk evaluation are among the key environmental challenges attracts significant research for sustainable global development of shale reservoirs

• Microseismic data along with coupled geomechanics and fluid flow models and coupled experiments can provide significant understanding on the stress alterations and associated changes and identifying any induced seismicity potential

UNGI Geohazard Risk Evaluation Gutenberg- Richter Law

• Expresses the relationship between the magnitude and total number of earthquakes in any given region and time period of at least that magnitude

M is the event magnitude b ~ 1.0 in seismically active regions A indicates the total seismicity rate of the region.

• For every magnitude 4.0 event there will be 10 magnitude 3.0 quakes and 100 magnitude 2.0 quakes. There is some variation with b-values in the range 0.5 to 1.5 depending on the tectonic environment of the region.

• During earthquake swarms, b-value can become as high as 2.5

Injection and Production Induced Seismicity Rocky Mountain Arsenal, Colorado

Modified after Evans (1966)

b ~ 1

Injection and Production Induced Seismicity

b ~ 0.91

Rangely Field Experiments, Colorado

Modified after Rayleigh et al. (1976)

Induced Seismicity?

Seismicity Permitted gas wells Permitted oil wells

Modified after USGS, TRRC (2013)

Induced Seismicity?

b ~ 1.0

Frohlich and Brunt (2013)

UNGI Observed Mechanisms in Microseismic Data

• There are four mechanisms occur in microseismic data • Dip-slip failure occurs near the beginning of the treatment stage • Strike-slip occurs near the end of the treatment stage • The b value analysis not show distinct values for the different mechanism types

Marcellus Shale, West Virginia Microseismic Inc. (2013)

Eagle Ford Microseismicity Oil Window

Horizontal Well #1 Horizontal Well #2

b ~ 1.9 – 2.1 b ~ 1.9 – 2.1

• An array of 51 geophones with 15 m between each sensor

• Crosslinked gel with 20/40 proppant

Eagle Ford Microseismicity Gas Window

Stage 3

Stage 8

Stage 9

Stage 13

Stage 14

b ~ 2.0 – 2.8

Stress Alteration and Injection Fluid Effect on Critically Stressed Fracture Induced Microseismicity

Observation Well 1

Observation Well 2

Observation Well 1

Observation Well 2

Gel Fracturing Slickwater Fracturing 3000

2500

3000

2500

2000 2000

1500 1500

1000 1000

500

500

0 -500

-500

-500 0 500 1000 1500 2000 -1000

-1000 -500 0 500 1000 1500 2000 2500

West-East (ft)

Nor

thin

g (ft

)

Easting (ft) Warpinski et al. (2005)

3rd Generation Coupled-Geomechanics-Flow Characteristics Laboratories

UNGI

Stress and Velocity Alteration Caused by Hydraulic Fracturing

150 ft.

400 ft.

650 ft.

Study area

Hydraulic fractures

Along hydraulic fracture, ft

0100

200300

400500

600

Along horizontal well, ft

0100

200

Depth, ft.

0

5000

10000

X

Z

Y

Along hydraulic fracture, ft0 100 200 300 400 500 600

0

50

100

150

200Hydraulic fracture

Fracture network

Along hydraulic fracture, ft

0 100 200 300 400 500 600

0

100

200

Tutuncu (2012)

200 m

45 m 122 m

Tutuncu (2012)

Stress and Velocity Alteration Caused by Hydraulic Fracturing Fluid Injection

Hydraulic Fracture

Hydraulic Fracture

σxx (MPa)

Hydraulic Fracture

Hydraulic Fracture

Hydraulic Fracture

Hydraulic Fracture

0.3

-0.2

0.2

0 0.1

-0.1

σyy (MPa) 1.4 0.8

-0.8

-1.4

0.4 -0.4

σzz (MPa)

-0.4

0.4

0

0.2

-0.2

4300 4250 4200 4150 4100

Vpx (m/s)

4900

Vpy (m/s)

4600

4300

4000

Vpz (m/s)

4020

3860

3700

Stress Alteration as A Function of Fault Proximity to Injection Well

Tutuncu and Bui (2013)

Fault

Velocity Alteration as A Function of Fault Proximity to Injection Well

Tutuncu and Bui (2013)

Conclusions

• Injection and production induced stress alteration introduces variations in the formation geomechanical properties that may increase potential risk for induced seismicity in the area

• Further research is ongoing using coupled geomechanics, acoustic emission and fluid flow experiments and modeling with various fluids to capture these alterations and associated induced microseismic activity relation

• Operators, regulators and academia should work in full collaboration to verify the distinct differences between the waste disposal processes and hydraulic fracturing operations and a continuous monitoring methodology should be implemented for better evaluation of the time dependent geohazard risks.

Thank You