geothermal technologies office 2015 peer...
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1 | US DOE Geothermal Office eere.energy.gov
Public Service of Colorado Ponnequin Wind Farm
Geothermal Technologies Office 2015 Peer Review
EGS Reservoir Simulations & Long-term Performance
Modeling
Project Officer: Lauren Boyd
Total Project Funding,: $208,041
May 31, 2015
Principal Investigator: Rob
Podogorney
Presenter: Mitchell Plummer
Idaho National Laboratory
EGS
This presentation does not contain any proprietary
confidential, or otherwise restricted information.
2 | US DOE Geothermal Office eere.energy.gov
Relevance/Impact of Research
• Project objectives
– Interpret RRG-9 pressure/flow response to improve understanding of
reservoir response to stimulation
– Use numerical simulation to test hypotheses about reservoir response to
high-pressure / low-temperature well stimulation
• Challenge: Reservoir creation via well stimulation is the key to EGS
development, but limited data exist regarding geothermal reservoir response to
thermal and high-pressure injections. Analysis of those data is required to
understand impact.
• Impact on EGS development: Demonstrated success of stimulation tests will
provide risk reduction necessary to motivate industry to attempt EGS.
• Innovation: Many existing codes use sequential coupling to solve THMC
problems. Code development in INL’s MOOSE framework attempts to use fully
implicit, fully coupled approach.
• Impact to GTO goals: Reducing risks of EGS development is the first step
toward industry deployment of a targeted 100+ GW of EGS.
• Integration: Analyses support the larger “EGS – Concept Testing and
Development at Raft River” under direction of Joe Moore
3 | US DOE Geothermal Office eere.energy.gov
Scientific / Technical Approach
0 500 1 103
500
1 103
1.5 103
0.01
1
100
1 104
1 106
1 108
1 1010
1 1012
1 1014
Observ ations
Theis superposition f it
Flow rate
Transmissiv ity
Storativ ity
Time (min)
Pre
ssu
re (
ps
i) &
Flo
w (
gpm
)
T (
mD
*m)
& S
/
0 500 1 103
200
400
600
800
1 103
10
100
1 103
1 104
1 105
1 106
Observ ations
Theis superposition f it
Flow rate
Transmissiv ity
Storativ ity
Time (min)
Pre
ssu
re (
ps
i) &
Flo
w (
gpm
)
T (
mD
*m)
& S
/
0 500 1 103
0
200
400
600
800
100
1 103
1 104
1 105
1 106
1 107
1 108
1 109
1 1010
1 1011
1 1012
Observ ations
Theis superposition f it
Flow rate
Transmissiv ity
Storativ ity
Time (min)
Pre
ssu
re (
ps
i) &
Flo
w (
gpm
)
T (
mD
*m)
& S
/
0 500 1 103
1.5 103
0
500
1 103
100
1 103
1 104
1 105
1 106
1 107
Observ ations
Theis superposition f it
Flow rate
Transmissiv ity
Storativ ity
Time (min)
Pre
ssu
re (
ps
i) &
Flo
w (
gpm
)
T (
mD
*m)
& S
/
1. Apply multiple methods of analysis
to provide explanations for
observed response to stimulation
– Standard well hydraulics
diagnostics
– Numerical simulation, using thermo-
hydraulic-mechanics simulations
2. Modify FALCON code to extend
implicitly coupled fracture
mechanics, fluid flow & heat
transfer capabilities
3. Develop simulations to test
hypotheses about reservoir
– What models are consistent or
inconsistent with hydraulic data?
• narrows zone permeability,
• primary fracture extent,
• response at other wells, …
4 | US DOE Geothermal Office eere.energy.gov
Inference from pumping test anlaysis
• Response to lowest pressure injection provides best estimate of
initial permeability and compressibility.
– Transmissivity (permeability x thickness) ~ 2e-14 m3 (9.7e-7 m2/s)
• Slow pressure rise suggests unrealistic compressibility,
– Suggests presence of large fracture that effectively extends wellbore to
several meters radius.
– Consistent with borehole televiewer data and temperature profiles
– Note that dilation-induced changes in permeability would act to steepen
pressure response, apparent lower storativity
0.1 1 10 1000.01
0.1
1
10
100
1 103
1 104
Radius (m)
Fra
ctu
re a
pe
rtur
e (
mm
)
rwell
m
1 10 100 1 103
0.01
0.1
1
10
Radius (m)
Fra
ctu
re a
pe
rtur
e (
mm
)rwell
m
5 | US DOE Geothermal Office eere.energy.gov
2.4e-8 m Pa-1
4.8e-8 m Pa-1
1.2e-7 m Pa-1
2.4e-7 m Pa-1
Diffusivity impact, uncertain S
1-psi response contours, 100 gpm, 2 yr
Diffusivity impact, uncertain S
S0 x2 x5 x10
6 | US DOE Geothermal Office eere.energy.gov
FALCON improvements
– Developed solution method for use of lower-
dimension domains in higher dimension
models (eg. 2D fracture in 3D domain)
– Added reconstructed discontinuous
Galerkin method for high Peclet-number
problems
– Replaced mechanics with tensor mechanics
approach
– Developed well model
– Developing cohesive zone
model for fracturing
approach in finite elements
7 | US DOE Geothermal Office eere.energy.gov
Temperature anomaly analysis
• Small-scale, high-resolution heat
transport simulations to explain
DTS temperature anomalies in
cased portion of RRG-9
• Helped resolved concern that T
anomaly suggested casing leak
4/03 3/15
3/06
3/24
4/11
Bottom of casing
Bottom of casing
8 | US DOE Geothermal Office eere.energy.gov
Injection test analysis on the edge of precision, 2014 SULI student project
Wellhead pressure
Injection rate
Pre
ssu
re [
psi
]
• Plant, wellhead and
calculated bottomhole
pressure out of phase
with flow rate variation
• Hypothesize
uncompensated
temperature effect in
pressure sensor
• New BHP sensor
4/8/15
Time [days]
Flo
w [
gp
m]
• Used DTS data to calculate precise bottom-hole pressure (BHP) (sensor failed)
• Corrected for T-dependent density & hydrostatic head, pressure loss via flow, …
• Wellhead flow and pressure data suggest diurnal fluctuation that could be used
for transient pumping test analysis, but
Reduce residual between observed pressure and modeled pressure and
calculate hydraulic parameters
9 | US DOE Geothermal Office eere.energy.gov
Permeability response to thermal effects
• Numerical simulations of discrete
fracture response to thermal
stimulation demonstrate krel
dependence on unsupported
fracture length & T
• 2D simulations demonstrate how
thermal effects can reproduce
observed long-term evolution of
injectivity
10 | US DOE Geothermal Office eere.energy.gov
Fluid pressure Horizontal displacement field
(& fracture network colored by permeability)
DEM simulations of stress and permeability response
Short
ly a
fter
inje
ction s
tart
S
tea
dy s
tate
T
ime
11 | US DOE Geothermal Office eere.energy.gov
Shear slipping vs. opening?
Displacement vector fields
X
Y
DEM simulations of stress and permeability response
12 | US DOE Geothermal Office eere.energy.gov
Accomplishments, Results and Progress
• Applied pumping test analysis methods to interpret injection test pressure / flow response
• Used numerical simulation of heat transport in a well to test hypotheses about temperature
anomalies in well
• Made numerous improvements to FALCON for geothermal reservoir simulations
• Worked with EGI Ph.D. student to: – Develop FALCON modules that automate importing of FRACMAN-generated fracture networks
– Develop reservoir scale models that can reproduce observed pressure/flow response
• Worked with SULI student to develop a well injection model to simplify point sources in FALCON
• Worked with SULI student to use DTS data to calculate precise bottomhole pressure and
examine diurnal pressure/flow fluctuation
• Used discrete element fracture models, coupled to flow network model, to test hypotheses about
shearing response to thermal and high-pressure stimulation
• Developed discrete fracture THM models, using procedure developed by Rutqvist (1998) to
simulate elastic response of fractures to hydraulic jacking tests
Original Planned Milestone/ Technical
Accomplishment
Actual Milestone/Technical Accomplishment
Date Completed
Quarterly reports
Reports describing model modifications, analyses,
and simulation progress
Quarterly
Peer-reviewed manuscript on well hydraulics and
measurements
Conference proceedings papers February, 2015
13 | US DOE Geothermal Office eere.energy.gov
Accomplishments, Results and Progress
Technical challenges
• Lack of measured response at other wells (pressure, flow, tracer
return)
– Pumping test analysis without observation wells
• Non-uniqueness in fitted models
– eg. Constant flow at constant pressure after ~1.5 days
• Nearby connection to higher permeability zone
• Alteration to spherical flow regime, reflecting pressure diffusion into
adjacent hydrogeologic units
• Fracture opening; proximal drawdown decreases with pressure diffusion
14 | US DOE Geothermal Office eere.energy.gov
Future Directions
• Analyses, for hypothetical EGS and Raft River
case study, provide improved understanding of
reservoir response to well stimulation
• Continuing work focuses on 3D THM models and
large-scale reservoir properties that could
reproduce principle features of the observed
hydraulic response
– Use results of previous analyses to determine
appropriate scale and features of 3D THM model
– Summer, 2015: Work with EGI Ph.D. student, Jacob
Bradford to develop alternative 3-D THM models,
including single fracture zone response to thermal
and high-pressure injection effects
Milestone Status & Expected Completion Date
Peer-reviewed manuscript on well hydraulics
and measurements
May 1, 2015 (delayed from 2/28/15)
Peer-reviewed manuscript on reservoir
modeling
July 31, 2015
• Continue FALCON simulations examining relationship between flow and thermal strain
• Continue DEM simulations exploring fracture distribution effect on stress/strain & flow
15 | US DOE Geothermal Office eere.energy.gov
• Simulations and analyses have supported Raft River stimulation effort
– Design of stepped rate, hydraulic jacking, tests
– Implications of temperature anomalies in cased well section
• Work to date focused on implications of well flow/pressure response
– Calculated hydraulic properties and apparent response to stimulation
– Apparent radial flow regime at <1-day timescale
– Steady-state flow after ~1.5 days suggests fracture opening at 280 psi (~2
Mpa), or nearby high-k zone
– No evidence of proximal impermeable boundary (Narrows zone)
– Exploration of likely temperature-dependent injectivity response is consistent
with range observed in thermal stimulation efforts
• Current work
– Use discrete fracture THM model to simulate near-well fracture response
– Apply THM with mechanics to simulate permeability response to effective
fracture behavior
– Reproduce long-term pressure/flow response with THM models
Summary
Summarize the
key points you
wish the
reviewers and
the audience to
take away from
your
presentation.