seismicity induced by petroleum and geothermal fluid ... · fluid-driven fracture systems d i s t a...
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INDUCED SEISMICITYIn-Situ Laboratories for Understanding
Fluid-Driven Fracture Systems
Dis
tanc
e N
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)
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Cluster 1
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Depth view at fracture face Depth view at fracture face
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Depth view along strike Depth view along strike
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Cluster 1
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47˚ 47˚
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SoultzSoultz
FRANCE
GERMANY
SWITZERLAND
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rabe
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Soultz, Shallow Cluster Soultz, Deep Cluster
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View Trend 355˚, Plunge 55 ˚
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Horizontal Distance (m)Horizontal Distance (m)
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ne 5
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Occurrence Order Percentile
10% 20% 30% 40% 50%0 100%
Discrete fracture plane orientations imaged from the Fenton Hill reservoir. The distinct fracture edges resolved correlate with significant fracture-plane intersections.
A sub-cluster of events from the Fenton Hill HDR reservoir. Original locations (left) and refined locations (right) after obtaining high-precision arrival-time data. In the face-on view (bottom right) sharp, straight edges bound the location pattern.
Two event sub-clusters each delineating the intersection of two planes. Looking along line of intersection (top) and face-on views (bottom). Linear trends can be seen along fracture faces (bottom). The event sequences indicate early fluid invasion along linear trends.
Location of the Soultz HDR site.
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View Trend -80 °
Microearthquakes induced by fluid injection provide a means to study fluid migration, fracture creation and faulting, with an optimal combination of resolution and subsurface coverage. Supplemental information often available with induced experiments includes borehole imagery, stress measurements and fluid pressure and flow data, information that greatly
aids in understanding similar earth phenomena where little independent information exists. Further, the nature of induced microseismicity enables exceedingly high-precision locations to be obtained, revealing discrete fracture networks and fine-scale rupture sequence patterns with remarkable clarity.
Poles to planes
Cluster edgeorientations
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th (
m)
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East (m)
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Array 121-09
Treatmentwell 21-10
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m)
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Array 121-09
Treatmentwell 21-10
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m)
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Distance Along Strike (m)Number of EventsSB Total
Dep
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m)
05001000150020002500 10 20 30 40
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Proppant tag Microearthquake countWell Perforations
P
Compression
Dilatation
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S
EW
Compression
Dilatation
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S
EW
Fracture
orientation
Fracture
orientation
-1
0
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2Lo
g S
h/P
60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60Azimuth from Source
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Log
Sh/
P
60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60Azimuth from Source
S n
od
al
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od
al
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od
al
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od
al
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Tim
e (h
our)
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Slurry Rate (m3/min)
36 39 42
BH Pressure (MPa)
0.0 0.2 0.4 0.6
Proppant (kg/liter) Perforation Interval C Perforation Interval E
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Distance Along Strike (m)
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Geophone
Geophone
Injection
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East (m)
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Matcek Ranch
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Cook's Point
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De
pth
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SL
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Austin Chalk
Eagleford Shale
Geophones
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ion
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Hypocentermapped
planeorientations
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vatio
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t)
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Distance (ft) from GDCF 63-29 at 030 Degrees
SW NE
S E R P E N T I N E
Monitor Well 63-29
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1862-15BGL-1 1862-13 LC2
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Steam entry
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t)
NESW
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ulat
ive
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ctio
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3 )
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Julian Day 1998
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ber
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eser
voir
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roea
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uake
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ber
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bove
-Res
ervo
ir M
icro
eart
hqua
kes
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Injection
Microearthquakesabove reservoir
Microearthquakesin reservoir
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t)
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Number of Microearthquakes
Microearthquakesabove reservoir
Microearthquakesin reservoir
Seismometerstation
Microearthquakelocation
G R E E N S T O N E
S E R P E N T I N E
M E L A N G E
HT1
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Dep
th (
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Inferredcurrentlydrainedfracture
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Geophone
Co-seismicproductioninterval
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Dep
th (
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246° view
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0GT1
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Cross sectionview
Map view
Composite fault plane solutions indicate thrust displace-ment along the mapped, low-angle fractures. Induced stress changes are very small (<0.1 MPa).
Seismically active fractures correlate with previously depleted zones; current productive zone is aseismic.
Event rate changes correlate with production rate changes. Seismic response lags production by 2–3 weeks.
Locations of microearthquakes induced during a hydraulic fracture stimulation treatment in a tight-gas sand reservoir. The dashed lines mark the perforated interval.
Re-picking the data in a spatial sequence revealed a remarkable similarity of adjacent-source waveforms and evolution of waveforms along the treatment length. Systematic polarity changes and phase amplitude ratios indicate uniformity of focal mechanisms along the entire fracture.
Two stimulation treatments were mapped in the Giddings Austin Chalk field. Event locations at Cook's Point show greater width development and less length than the Matcek Ranch stimulation.
The wider stimulation zone imaged at Cook's Point is correlated with a greater production response.
Reflected phase off the base of the Eagleford allowed location depths to be constrained.
The fracture growth is characterized by systematic space-time patterns of seismicity along the treatment length.
Refined images after obtaining higher-precision arrival time data via waveform correlation.
Horizontal bands of seismicity correlate closely with the treatment interval perforation schedule and proppant placement.
Above-reservoir casing deformations have been observed in several wells in the southeast Geysers field. Deformation is concentrated over short depth intervals at the upper and lower contacts of a serpentine unit.
Both the above-reservoir and the deeper reservoir seismicity show correlations with reservoir injection activity in the study area.
Small magnitude events were detected above the reservoir by placing a downhole receiver array within the upper 800 feet of an abandoned well. Event occurence terminates near the base of the serpentine unit.
Fracture planes are delineated by production-induced events occuring over a 6-month monitor period.
Cumulative production and microearthquake event counts Originallocations
LeftLateralStrikeSlip
RightLateralStrikeSlip
High-precision locations
-15 -10 -5 0 5 10 15 20 25 30
Month before/after Hydraulic Stimulation
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Oil
Rat
e (b
bl/d
ay)
Cook's Point
Matcek Ranch
HYDRAULIC FRACTURE IMAGINGCarthage Gas Field, East Texas
PRODUCTIVE FRACTURE IMAGINGClinton County, Kentucky
WELL-BORE DEFORMATIONThe Geysers, California
Austin Chalk, Texas
P
TT
P
T
P
Seismicity Induced byPetroleum and Geothermal
ActivitiesJim Rutledge and Scott Phillips
Los Alamos National Laboratory
0 0.1 0.2 0.3 0.4Time (sec)
V
H1
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H1
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Upper Geophone
Lower Geophone
InstrumentationTrailer
Micro-earthquakes
Seismometer
Oil-Bearing Formation
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Fenton HillExperiment 2032
log10 Event Density (m-2)
Distance East (m)
Dis
tanc
e N
orth
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)
Depth (m)
Dep
th (
m)
Introduction
Microseismic fracture mapping at Los Alamos started with the Hot Dry Rock geothermal project. The fractured reservoir volumes created and stimulated during massive hydraulic fracturing were imaged using the microearth-quakes induced by injection. Seismic receivers need to be placed downhole at or near reservoir depth to detect the small magnitude events. In the 1990s we began to apply these techniques to oil and gas problems. In addition to the now well-known application of hydraulic fracture imaging, other applications include mapping natural, conductive fractures affected by extraction and pressure recovery operations, as well as monitoring and characterizing reservoir and overburden deformation induced by production.
Applications
Hydraulic fracture imaging
Natural fracture imaging - production induced - water-flood or CO2-flood front mapping
Monitoring waste containment and flow paths - hydraulic fracture injection disposal - CO2 geologic sequestration - thermal induced stress changes
Monitoring and characterizing reservoir deformation and subsidence