hydrochemical assessment of the devonian keg river formation€¦ · regional hydrochemistry...
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Hydrochemical Assessment of The Devonian Keg River Formation “Thinks are not always what they seem…” MACBETH W. Shakespeare 12 April 2012
Francisco Castrillon-Munoz, MSc., P.Geol.
Senior Hydrogeologist
Worley Parsons Canada
2 17-Apr-12
Background and Objectives
Regional Hydrochemistry Overview
Local Devonian Hydrochemistry
Hydrochemical Conceptual and Numerical Model
Conclusions
3 17-Apr-12
Devonian Keg River Formation:
proposed as disposal zone for process wastewater originating from in-
situ project
historically used as a wastewater disposal zone
regional chemistry indicates water saline (>4000 mg/L)
local water samples (i.e., swabbed or pumped) returned TDS less than
4000mg/L TDS (DW13-04, 16-21, DW 09-03, DW 04-22)
Background
4 17-Apr-12
Review existing data & reliability (i.e., geology,
hydrogeology and hydrochemistry regional and local)
Determine natural salinity of Keg River Formation
beneath the Lease
Provide an explanation for the presence of water
in the Keg River Formation that does not appear to
be native
Objectives
Local Stratigraphic Sequence
Quaternary S&G Channels
Upper Devonian Waterways Fm.
Middle and
Lower Devonian
Cretaceous McMurray Fm.
Watt Mountain Fm.
Slave Point
Fort Vermillion
Keg River Fm.
Clearwater Fm
Contact Rapids Fm.
Paleozoic Granite Wash Fm.
Precambrian Granite
Elk
Po
int G
rou
p
McMurray Basal Sands
Target Zone
6 17-Apr-12 Source: Client Geoscience Group
Paleogeography of the Keg River Formation
• Interpretation based on Keg River isochore, well logs, cores, and seismic data
• Present day depositional thicknesses affected post-depositional dissolution/brecciation
• Laterally equivalent carbonate build up and progressive/intermittent evaporite basin/sub-basins
• Dissolution of laterally equivalent evaporites possibly encouraged late stage brecciation and
significant thickness reduction
``
Fort McMurray
Athabasca
River
River
River N
Regional Hydrochemistry Overview
GRAPH SCALE
1.0 TOWNSHIP
8 17-Apr-12
Regional Hydrochemistry Overview
HYDROCHEMICAL
SEPARATION
Local Hydrochemistry Overview
Groundwater Chemistry Data
Wastewater Pilot Injection
RAMP Database
• Three Quaternary
Wells
• Three McMurray Basal
Wells
• 13 Devonian Wells
standing
• Eight Devonian Wells
sampled
Note:
Some Devonian wells not
sampled due to reduced formation flows
Local Sampling Events
Devonian Intervals
Sampled
and Wastewater
Disposal Wells
Interpreted zones of
injection influence
Pilot injection well
Total Injection = 1.7 Mm3
(1983 to 1992)
Hydrochemical Groups of Local Devonian Water
Devonian
Wells
Quaternary,
McMurray Basal wells and RAMP
Surface water
HYDROCHEMICAL
SEPARATION
Pilot
Native Devonian Formation
Water
Mixing of waters
Hydrochemical Groups of the Lease
TDS<4000
HYDROCHEMICAL
SEPARATION
Pilot
14 17-Apr-12
Represented predominantly by:
•Calcite
•Dolomite
•Halite
Devonian formations deposited in meso-saline (calcite / dolomite) to
hypersaline (halite) environment
Gypsum (possibly anhydrite) were also precipitated
Presence of trace bitumen staining within vugs noted in some cores
Authigenic source of organics suspected
Mineralogy of Devonian Formations*
*Source: Client Geoscience Group
Saturation Indices
-6
-5
-4
-3
-2
-1
0
1
2
0 1000 2000 3000 4000 5000
Total Dissolved Solids (mg/L)
Sat
ura
tio
n In
dex
Calcite
Aragonite
Dolomite
Strontianite
Gypsum
Anhydrite
AqueousSilicaHalite
Water Speciation
Saturation Indices
-5
-4
-3
-2
-1
0
1
2
4000 5000 6000 7000 8000
Total Dissolved Solids (mg/L)
Sat
ura
tio
n In
dex
Calcite
Aragonite
Dolomite
Strontianite
Gypsum
Anhydrite
AqueousSilicaHalite
Calcite dissolution or precipitation:
CaCO3 + CO2 + H2O ↔ Ca2+ + 2HCO3-
Dolomite dissolution or precipitation:
CaMg(CO3)2 ↔ Ca2+ + Mg2+ + 2CO3
2-
Hydrochemical Processes
Mixing
Pilot
Gypsum dissolution:
CaSO4(2H2O) + H2O↔ Ca2+ + SO42- + 3H2O
Sulphate reduction:
2CH2O + SO42- → 2HCO3
- + H2S
Hydrochemical Processes
Mixing
Pilot
Hydrochemical Processes
Sulphate reduction:
2CH2O + SO42- → 2HCO3
- + H2S
Pilot
Strontianite dissolution:
SrCO3 → Sr2+ + CO32-
Hydrochemical Processes
Mixing
Pilot
Halite dissolution:
NaCl → Na+ + Cl-
Hydrochemical Processes
Mixing
Pilot
Wastewater Injection well Sampling wells
Ca-Mg-HCO3 Type
Na-HCO3
Type Na-Cl
Type
Mixing
water
Quaternary Deposits
Waterways Fm.
Middle and Lower Devonian
Formations (Mainly
Keg River)
Shallower System
Hydraulic Barrier
Lower System
Calcite dissolution and precipitation: CaCO3 + CO2 + H2O ↔ Ca2+ + 2HCO3-
Dolomite dissolution and precipitation: CaMg(CO3)2 ↔ Ca2+ + Mg2+ + 2CO3
2-
Gypsum dissolution: CaSO4(2H2O) + H2O↔ Ca2+ + SO42- + 3H2O
Sulphate reduction: 2CH2O + SO42- → 2HCO3
- + H2S
Strontianite dissolution: SrCO3 → Sr2+ + CO32-
Halite dissolution: NaCl → Na+ + Cl-
Main Hydrochemical
Processes
Hydrochemical Conceptual Model
McMurray Fm. Aquitard
Clearwater Fm. Aquitard
NETPATH Hydrochemical Modelling (Plummer et al 1994)
Initial water (2 samples) + “Reactant Phases” Final water (target well) + “Product Phases”
Table A Chemical Input for NETPATH Model 1 and 2
Well name –TDS/pH
(NETPATH Database No.)
Well
DW 1-16- (19)
Wastewater
3245-(81)
Model 1
Well 16-21- (82)
Model 2
Well 13-4 (17)
Water Initial water 1
Initial water
2 Final water 1 Final water 2
Temp (oC) 7 7 7 7
pH 7.72 8.1 7.54 8.05
Ca 407 10 333 102
Mg 196 1 144 45.5
Na 2320 80 694 488
K 16 6 14 13.9
Cl 4060 23 1520 759
SO4 as SO4 580 20 235 26.6
Alk/TDIC 342+ 181* 708* 479*
Fe 0.22 0.2 0.71 0.1
F 1.92 ND 1.78 2.35
Sr 8.96 ND (0.18)** 3.77 2.86
H2S(aq) as S 0.0 ND ND 74
+ : Field Alk as CaCO3; * : Field Alk as HCO3
- ; ** only considered in Model 2 . Concentration as milligrams per litre.
Hydrochemical Numerical Model
Model 1 (Devonian Native Water + Wastewater = Well 16-21)
NETPATH Hydrochemical Modelling Results
Model 2 (Devonian Native Water + Wastewater = Well 13-4)
NETPATH Hydrochemical Modeling Results
Conclusions
• Two distinctive hydrochemical groups observed in the Keg River
Formation
• Chemical equilibrium models and mixing models indicate:
• Higher TDS water observed beneath the Lease represents natural
Keg River Formation
• Lower TDS water observed beneath the Lease represents mixing
with previously injected wastewater