1. MONITORING AND INTERPRETATION OF MICROSEISMS INDUCED BY FLUID INJECTION
N. R. Warpinski
Sandia National Labs

2. MICROSEISMS INDUCED BY FLUID INJECTION
Outline
Microseismic Overview
Interpretation
Are Results Meaningful For Long-Term Fluid Injection
How Can The Results Be Interpreted
Examples
Simulated (Based On Actual Results)
Actual Field Tests

3. MICROSEISMS INDUCED BY HYDRAULIC FRACTURING
Microseisms are generally seismic energy emitted by shear slippage along weakness planes in the earth
Hydraulic Fracture
Increases Stress
Increases Pore Pressure
Natural Fractures
Are Destabilized & Slip
Slippage
Emits Seismic Energy
smax
smin P
Leakoff
Stress
Natural
Fracture

4. MICROSEISMS Slippage Emits Both P & S Waves (Compressional & Shear)
Velocities Are Different
P Wave > S Wave
Detected At Tri-Axial Receiver
SHEAR SLIPPAGE
P(t1)
S(t1)
P(t2)
S(t2)
RECEIVER X Y P X S Y

5. MICROSEISMIC MAPPING Surface (Too Far) Treatment Well (Too Noisy)
FRACTURE
MICROSEISM
RECEIVERS
FRACTURE
MICROSEISM
RECEIVERS

6. MICROSEISMIC MAPPING Two Approaches For Offset Wells
MULTI-WELL
SINGLE-WELL
FRACTURE
MICROSEISM
FRACTURE
MICROSEISM
RECEIVERS

7. SINGLE-WELL MAPPING Distance And Elevation From Arrival Times
Direction From P-wave Particle Motion
Also
Microseisms: Small Amplitude, High Frequency
Receiver Distance = Typical Interwell Spacing
Requires: High Quality Receivers
FRACTURE
RECEIVERS
RESERVOIR
MICROSEISM

8. EXAMPLE MICROSEISM TRACE
12.5
25 msec

9. MICROSEISMIC TECHNOLOGY
PROCESSING
Automatic Event Detection (Event Comb)
Automatic Event Processing
P-Wave Arrival
S-Wave Arrival
P-Wave Particle Motion
Location Processing
Homogeneous Model
Joint P-S Distance Regression
Layered Model
Vidale/Nelson Algorithm
Elevation, Distance
Azimuth

10. ADDITIONAL DATA REQUIRED
Formation Velocity
Advanced Sonic Log (P & S Waves)
Crosswell Survey
Receiver Orientation
Perforations
Air Gun Or Other Source
Full-interval Scan
Surveys
Surface Survey (Well-to-well)
Deviation Surveys

11. MICROSEISMIC TECHNOLOGY
Procedure
Prior Day
Mobilize and Set Up on Site
Orientation With Airgun or Perforations
Background Monitoring
Frac Day
Fracture Monitoring
Real-Time or Near-Real-Time Processing
Well-Site Result
Demobilize

12. MICROSEISMIC VIEWING DISTANCES
Fenton Hill Granite (LANL)
Camborne Granite (UKDOE)
Austin Chalk (LANL)
Frio Sandstone (ARCO)
North Slope Sandstone (ARCO)
Barnett Shale
Mesaverde Sandstone
Frontier Sandstone
Cotton Valley Sandstone (UPR)
5000 ft
4500 ft
2500 ft
1500 ft
3000 ft
800 ft
1000 ft
2000 ft

13. MICROSEISMIC LIMITATIONS
Need An Offset Well
Treatment Well: Difficult Environment
Offset-Well Limitations
Spacing Between Treatment and Monitor Well Cannot Be Excessive
Quiet Environment (No Bubbling Perforations)
Reservoir Difficulties
Attenuation, Layering, Cultural Noise
Receiver Orientation
Physical Receiver Limitations
Size, Temperature, Pressure, Etc

14. MICROSEISMIC INTERPRETATION
Microseisms Originate In An Envelope Surrounding The Fracture, Giving
Height
Length
Azimuth
Asymmetry
MICROSEISMS
INDUCED BY STRESS
CHANGES NEAR TIP
MICROSEISMS
INDUCED BY
LEAKOFF
ENVELOPE
NATURAL FRACTURES

15. MICROSEISMIC INTERPRETATION
Highly Compressible Formation Fluids (Gas Reservoir)
COMPRESSIVE
TENSILE
SHEAR
LEAKOFF
DISTANCE
NORMAL TO
FRACTURE
PRESSURE Pf sc Pi
LEAKOFF
STRESS

16. MICROSEISMIC INTERPRETATION
Incompressible Formation Fluids (Gas Reservoir)
COMPRESSIVE
TENSILE
SHEAR
LEAKOFF
DISTANCE
NORMAL TO
FRACTURE
PRESSURE Pf sc Pi
LEAKOFF
STRESS

17. FULL POROELASTIC EFFECTS
Displacement At 1000 ft Distance (Normal To Fracture)
5000
5500
6000
6500
7000
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
Displacement (inches)
Depth (ft)
0.01 hr
0.1 hr
1.0 hr
10 hr
DATA
2D Fracture
k=50 md
f=0.2
n=0.22
E=6.e6 psi
H=100 ft
Pf=4500 psi
Pi=2600 psi
sc=4000 psi
Based On M.B. Smith Analysis In SPEJ, 1985

18. PORE PRESSURE DESTABILIZATION
Historical Data:
Earthquake Hazard Associated With Deep Well Injection -
A Report To The U.S. Environmental Protection Agency
USGS Geological Survey Bulletin 1951
C. Nicholson & R.L. Wesson, 1990
Long-Term Injections
Waste Injection And Oil-Field Operations
Large Destabilized Area
Moderate Earthquakes Detected At The Surface

19. Las Alamos Hot Dry Rock Results

20. Camborne Hot Dry Rock Side View of Microseisms 3 Hours 11 Hours
Scale = 200 m
3 Hours
11 Hours
27 Hours

21. SAN ANDRES WATERFLOOD (LANL)
inj
prod
mon

22. MICROSEISMIC MONITORING OF LONG-TERM INJECTIONS
Methodology For Microseismic Monitoring
Monitor Initial Injection Behavior
Image The Fracture
Obtain Fracture Azimuth
Examine Attributes Of Late-Time Behavior
Clustering And Linear Trends
Source Parameters And Stress Relief
High Stress Relief Associated With Tip Microseisms
Low Stress Relief Associated With Leakoff Microseisms

23. VALIDATION
How Does the Seismically Disturbed Zone Relate to the Actual Fracture Geometry
M-Site Experiments
Height
DownholeTiltmeters Measured Deformation
Length
Fracture Intersected a Lateral Well 287 ft from Treatment Well
Azimuth (2 Fracture Intervals)
Lateral Wells Intersected Fracture 135 & 287 ft from Treatment Well

24. M-SITE Field Laboratory For Fracture Diagnostic Research N72°W
MWX-3
(5-LEVEL WIRELINE ARRAYS)
N72°W
MWX-2
(TREATMENT WELL)
2 INTERSECTION WELLS
Two Monitor Wells
Three Test Intervals
ft Depths
Two Intersection Wells
4550 ft
4350 ft
Fully Characterized Site
IW-1B
Piceance
Basin
IW-1C 30
Distance, m
MONITOR WELL
(CEMENTED IN ARRAYS)

25. M-SITE LENGTH VALIDATION
150
300
450
600
-450
-300
-150
West-East (ft)
North (ft)
MWX-3
MWX2
MONITOR
N74W
AT INTERSECTION
INTERSECTION
WELL

26. MICROSEISMIC SIMULATIONS
Simulations Are Based On Microseismic Monitoring Results Actually Measured In Field Tests

30. MICROSEISMIC IMAGING EXAMPLES

35. MICROSEISMIC TECHNOLOGY
Conclusions
Process Monitoring, Optimization of Injection Procedures, and Regulatory Issues Make Subsurface Imaging an Important Capability
Technology Is Now at the Level to Apply Microseismic Diagnostics
Advanced Receivers
Fiber-optic Telemetry
Computer Processing
Understanding of Reservoir Structural Behavior