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A Risk-based Groundwater Modelling
Study for Predicting Thermal Plume
Migration from SAGD Well-pads
Rudy Maji, Ph.D., Golder Associates
Solaleh Khezri, M.Sc., AB Scientific Intern (Golder Associates)
Don Haley, M.Sc., Golder Associates
Michael De Luca, M.Sc., P.Geol., Brion Energy
Outline
Motivation
Problem Statement
Numerical Model Construction
Numerical Model Results
Summary and Conclusions
April 30, 2015 2
Motivation –
Why Thermal Plume Migration Matters
Elevated temperatures increase the mobilization of chemical
constituents that are naturally present in sediments.
Since the start of thermal in-situ oil sand production, increased levels of
Arsenic was observed in groundwater downgradient of several steam
injection wells at the Cold Lake site.
April 30, 2015 3
Problem Statement –
Steam Assisted Gravity Drainage (SAGD)
April 30, 2015 4
Area of Interest
Problem Statement –
Conceptual Model of Heat Plumes Near Wellbores
April 30, 2015 5
Groundwater Flow
Aquitard
Aquifer
Aquifer
Aquitard
Aquitard
Problem Statement –
Modelling as a Screening Tool
Generic modeling can be used as a screening tool as one input into a
risk based assessment of solute migration from multiple SAGD well
pads.
If the risk at a particular well pad is considered potentially significant, site
specific models (deterministic or stochastic) can be developed to help
evaluate and quantify the risk of thermally enhanced solute migration.
Site specific model could also be used to aid in the design of the
Groundwater Monitoring Plan (GWMP), as directed in the DRAFT
Guidance for Groundwater Management Plans for In Situ Operations:
Assessing Thermally-Mobilized Constituents
April 30, 2015 6
Numerical Modelling – SAGD Well-Pads in MacKay
River Commercial Project Area
April 30, 2015 7
Well-Pad AJ
Well-Pad AB
Well-Pad AA
Streams (SW Receptors)
Numerical Modelling –
Borehole Lithology Around Well-Pad AJ
April 30, 2015 8
Model
LayerFormation
Horizontal
Hydraulic
Conductivity
(m/s)
Thickness
(m)
Layer 1 Undifferentiated overburden (Clay Silt Till) 1E-7 10
Layer 2 Undifferentiated overburden (Clay Silt Till) 1E-7 10
Layer 3 Undifferentiated overburden (Sand Till) 5E-5 5
Layer 4 Undifferentiated overburden (Clay Silt Till) 1E-7 10
Layer 5 Joli Fou Formation (Shale) 5E-8 10
Layer 6 Grand Rapids 4 Formation (Sandstone) 3E-4* 10
Layer 7 Grand Rapids Formation (Shale) 5E-8 5
Layer 8 Grand Rapids 5 Formation (Sandstone) 1.6E-5* 5
Layer 9 Grand Rapids Formation (Shale) 5E-8 5
Layer
10Grand Rapids 5 Formation (Sandstone) 1.6E-5* 10
Layer
11Grand Rapids 5 Formation (Sandstone) 1.6E-5* 10
* Hydraulic conductivity values derived from pumping tests.
Numerical Modelling –
Sources and Receptors
Sources Receptors
Pad AJ, Pad AA and Pad AB Surface water streams, Aquifers
(Overburden Aquifer, Grand Rapids 4
and 5)
April 30, 2015 9
Numerical Model Construction –
Model Domain
April 30, 2015 10
Wells with Geology Logs
SAGD Steam Injection Wells
Model Domain
Well-Pad AJ
Well-Pad AB
Well-Pad AA
Numerical Model Construction –
Numerical Mesh
April 30, 2015 11
Well-Pad AJ
Well-Pad AB
Well-Pad AA
Element Size Around SAGD
Wells: <1 m to 9 m
April 30, 2015 12
Streams
• 11 Numerical Layers
• Each Layer 5 m to 10 m thick
• 9 Different Hydrostratigraphic Units
Numerical Model Construction –
3-Dimensional Numerical Block Model
Numerical Model Construction –
Boundary Conditions
April 30, 2015 13
Average Hydraulic
Gradient: 0.25%
Constant Temperature of 5 ˚C
at Surface and Inflow Nodes
X
Y
Numerical Model Construction –
Heat Loss in the Steam Injection Well Versus Depth
April 30, 2015 14
Steam Temp= 230 ˚C
at surface
Steam Temp= 220˚C
at top of McMurray
Steam Temp= 226˚C
at bottom of Grand
Rapids 5
Numerical Model Construction –
Representative Steam Injector Design
April 30, 2015 15
Numerical Model Construction –
Representation of a SAGD Well Using the BHE Boundary
April 30, 2015 16
Borehole Heat Exchanger
InjectionRecovery
InjectionRecovery
Numerical Model Results –
Calibration to Temperature Change Along the Wellbore
April 30, 2015 17
Recovery Injection
Numerical Model Results –
Modelling Cases
Case 1: Steaming of well-pad AJ for 38 years
Case 2: Steaming of all three well-pads for 38 years simultaneously and
movement of thermal plume after cession of steaming
April 30, 2015 18
Numerical Model Results – Case 1 (Single Well Pad):
Thermal Plumes at Well-Pad AJ
April 30, 2015 19
Quaternary Aquifer
Depth: 20 m
Max Temp: 145.7 ˚C
KH= 5E-5 m/s
Grand Rapids 4
Depth: 45 m
Max Temp: 104 ˚C
KH = 3E-4 m/s
Grand Rapids 5
Depth: 80 m
Max Temp: 153 ˚C
KH = 1.6E-5 m/s
363
m
380
m
418
m
Note: After 38 years of steaming
Numerical Model Results – Case 2 (Cumulative Effects):
Thermal Plumes in Quaternary Aquifer - All 3 Well-Pads
April 30, 2015 20
363 m
367 m
366 m
KH = 5E-5 m/s
Depth: 20 m
Note: After 38 years of steaming
Numerical Model Results – Case 2 (Cumulative Effects):
Thermal Plumes in Grand Rapids 4 Aquifer
April 30, 2015 21
418 m
420 m
422 m
KH = 3E-4 m/s
Depth: 45 m
Note: After 38 years of steaming
Numerical Model Results – Case 2 (Cumulative Effects):
Thermal Plumes in Grand Rapids 5 Aquifer
April 30, 2015 22
380 m
382 m
386 m
KH = 1.6E-5 m/s
Depth: 80 m
Note: After 38 years of steaming
Numerical Model Results – Case 2 (Cumulative Effects):
Vertical Profiles Through Each Well Pad
April 30, 2015 23
K=1E-7 m/sK=5E-5 m/sK=1E-7 m/sK=5E-8 m/sK=3E-4 m/s
K=1.6E-5 m/s
K=5E-8 m/s
Well Pad AJ
Well Pad AB
Well Pad AA
A
A
A
A’
A’
A’
K=1E-7 m/sK=5E-5 m/sK=1E-7 m/sK=5E-8 m/sK=3E-4 m/s
K=1.6E-5 m/sK=5E-8 m/s
Well Pad AJ
A A’
Well Pad AB
B B’
Well Pad AA
C C’380 mNote: After 38 years of steaming
A’
A
Numerical Model Results – Case 2 (Cumulative Effects):
Length of 50 ˚C Isotherm From Steam Injector
Depth (m) Length of 50 ˚C
Isotherm (m)
Hydraulic
Conductivity (m/s)
1 1.3 1E-7
10 4.6 m 1E-7
20 8.3 5E-5
25 8.6 1E-7
35 6.9 5E-8
45 5.2 3E-4
55 5.9 5E-8
60 7.5 1.6E-5
65 9.9 5E-8
70 13.4 1.6E-5
80 20 1.6E-5
90 22 1.6 E-5
April 30, 2015 24
Highest Aquifer K
Intermediate Aquifer K
Lowest Aquifer K
Note: After 38 years of steaming
Numerical Model Results – Case 2 (Cumulative Effects):
Temperature Increase in Underlying Aquifers
April 30, 2015 25
Well-Pad AB
Well-Pad AA
Well-Pad AA
Well-Pad AB
Grand Rapids 4
Grand Rapids 5
Quaternary
Grand Rapids 4
Grand Rapids 5
Quaternary
Note: Location is immediately downstream of the injector and below the streams
210 m
605 m
Numerical Model Results – Case 2 (Cumulative Effects):
Thermal Plume Migration after Cessation of Steaming
April 30, 2015 26
Time= 0
Max T= 152.5 ˚C
Time= 50 years
Max T= 13.7 ˚C
Time= 10 years
Max T= 34.5 ˚C
Time= 25 years
Max T= 22 ˚C
380 m 520 m450 m
600 m
Time= 100 years
Max T= 10 ˚C
NOTE: Results are for Well Pad AJ
Summary and Conclusions
The distance from Pad AJ to the nearby stream is larger compared to that of
Pads AA and AB; hence, the simulated thermal plume from Pad AJ doesn’t
reach to the nearby streams.
The simulation results suggest that thermal plumes originating from the Pads AA
and AB would intersect the nearby streams, hence pose a greater risk compared
to the Pad AJ if solute migration is thermally enhanced.
The 50 0C temperature plume travels only a few tens of metres; hence, the
potential zone of Arsenic mobilization is simulated to be within a few tens of
metres, provided the enhanced mobilization effect decreases as temperature
drops.
April 30, 2015 27
Summary and Conclusions
The temperature of the porous medium in the immediate vicinity of the steam
injection well is significantly less (approximately 150 0C) than that of the steam
inside the well bore (approximately 230 0C).
The change in temperature in the porous medium around a steam injection well
is affected by:
The insulating properties of the well bore casing and grout system
Formation hydraulic conductivity and thereby groundwater velocity
(efficiency of the groundwater to “flush” heat away from the well bore)
April 30, 2015 28
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