Hydrochemical Assessment of The Devonian Keg River Formation Francisco Castrillon-Munoz, MSc., P.Geol. Senior Hydrogeologist Worley Parsons Canada
“Thinks are not always what they seem…” MACBETH W. Shakespeare
12 April 2012 Background and Objectives
Regional Hydrochemistry Overview
Local Devonian Hydrochemistry
Hydrochemical Conceptual and Numerical Model
Conclusions
2 17-Apr-12 Background
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)
3 17-Apr-12 Objectives
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
4 17-Apr-12 Local Stratigraphic Sequence
Quaternary S&G Channels Clearwater Fm
Cretaceous McMurray Fm.
McMurray Basal Sands
Upper Devonian Waterways Fm.
Watt Mountain Fm. Slave Point Middle and Fort Vermillion Lower Devonian Keg River Fm. Target Zone
Contact Rapids Fm. Elk Point Group Point Elk
Paleozoic Granite Wash Fm. Precambrian Granite 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
6 17-Apr-12 Source: Client Geoscience Group Regional Hydrochemistry Overview
River
Athabasca River
``
River N
GRAPH SCALE 1.0 TOWNSHIP
Fort McMurray Regional Hydrochemistry Overview
HYDROCHEMICAL 8 17-Apr-12 SEPARATION Local Hydrochemistry Overview
Groundwater Chemistry Data
Wastewater Pilot Injection
RAMP Database Local Sampling Events
• 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 Devonian Intervals Sampled and Wastewater Disposal Wells
Total Injection = 1.7 Mm3 (1983 to 1992)
Interpreted zones of injection influence
Pilot injection well Hydrochemical Groups of Local Devonian Water
Pilot Devonian Wells
Quaternary, McMurray Basal wells HYDROCHEMICAL and RAMP SEPARATION Surface water Hydrochemical Groups of the Lease
TDS<4000
Native Devonian Formation Water
Pilot
HYDROCHEMICAL SEPARATION Mixing of waters Mineralogy of Devonian Formations* 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
*Source: Client Geoscience Group
14 17-Apr-12 Water Speciation Saturation Indices Calcite 2 Aragonite 1 Dolomite
0 Strontianite
-1 Gypsum
-2 Anhydrite
-3 Aqueous Silica Halite
Saturation Index Saturation -4
-5
-6 0 1000 2000 3000 4000 5000 Saturation Indices Total Dissolved Solids (mg/L) Calcite 2 Aragonite 1 Dolomite
0 Strontianite
-1 Gypsum
-2 Anhydrite Aqueous -3 Silica Saturation Index Saturation Halite -4
-5 4000 5000 6000 7000 8000 Total Dissolved Solids (mg/L) Hydrochemical Processes
Pilot
Mixing
Calcite dissolution or precipitation: 2+ - CaCO3 + CO2 + H2O ↔ Ca + 2HCO3
Dolomite dissolution or precipitation: 2 2+ 2+ 2- CaMg(CO3) ↔ Ca + Mg + 2CO3 Hydrochemical Processes Gypsum dissolution: 2+ 2- CaSO4(2H2O) + H2O↔ Ca + SO4 + 3H2O
Sulphate reduction: 2- - 2CH2O + SO4 → 2HCO3 + H2S
Pilot
Mixing Hydrochemical Processes
Sulphate reduction: 2- - 2CH2O + SO4 → 2HCO3 + H2S
Pilot Hydrochemical Processes
Strontianite dissolution: 2+ 2- SrCO3 → Sr + CO3
Pilot
Mixing Hydrochemical Processes
Pilot
Mixing Halite dissolution: NaCl → Na+ + Cl- Hydrochemical Conceptual Model
2+ - Calcite dissolution and precipitation: CaCO3 + CO2 + H2O ↔ Ca + 2HCO3
2 2+ 2+ 2- Dolomite dissolution and precipitation: CaMg(CO3) ↔ Ca + Mg + 2CO3
2- Main Hydrochemical Gypsum dissolution: CaSO4(2H2O) + H2O↔ Ca2+ + SO4 + 3H2O
Sulphate reduction: 2CH O + SO 2- → 2HCO - + H S Processes 2 4 3 2
2+ 2- Strontianite dissolution: SrCO3 → Sr + CO3
Halite dissolution: NaCl → Na+ + Cl-
Wastewater Injection well Sampling wells
Quaternary Deposits Ca-Mg-HCO3 Type Shallower System Clearwater Fm. Aquitard
McMurray Fm. Aquitard
Waterways Fm. Hydraulic Barrier
Mixing Na-HCO 3 water Middle and Lower Devonian Type Na-Cl Formations (Mainly Lower System Keg River) Type Hydrochemical Numerical Model
Initial water (2 samples) + “Reactant Phases” Final water (target well) + “Product Phases” NETPATH Hydrochemical Modelling (Plummer et al 1994)
Table A Chemical Input for NETPATH Model 1 and 2
Well Wastewater Model 1 Model 2 Well name –TDS/pH (NETPATH Database No.) DW 1-16- (19) 3245-(81) Well 16-21- (82) Well 13-4 (17)
Initial water Water Initial water 1 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. NETPATH Hydrochemical Modelling Results
Model 1 (Devonian Native Water + Wastewater = Well 16-21)
NETPATH Hydrochemical Modeling Results
Model 2 (Devonian Native Water + Wastewater = Well 13-4)
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