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