Hydrochemical Assessment of The Devonian Keg River Formation

Transcription

1 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

2 Background and Objectives Regional Hydrochemistry Overview Local Devonian Hydrochemistry Hydrochemical Conceptual and Numerical Model Conclusions 2 17-Apr-12

3 Background Devonian Keg River Formation: proposed as disposal zone for process wastewater originating from insitu 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

4 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

5 Elk Point Group Local Stratigraphic Sequence Quaternary Cretaceous S&G Channels Clearwater Fm McMurray Fm. Upper Devonian McMurray Basal Sands Waterways Fm. Middle and Lower Devonian Watt Mountain Fm. Slave Point Fort Vermillion Keg River Fm. Contact Rapids Fm. Target Zone Paleozoic Precambrian Granite Wash Fm. Granite

6 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

7 Regional Hydrochemistry Overview River Athabasca River `` River N GRAPH SCALE 1.0 TOWNSHIP Fort McMurray

8 Regional Hydrochemistry Overview 8 17-Apr-12 HYDROCHEMICAL SEPARATION

9 Local Hydrochemistry Overview Groundwater Chemistry Data Wastewater Pilot Injection RAMP Database

10 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

11 Devonian Intervals Sampled and Wastewater Disposal Wells Total Injection = 1.7 Mm 3 (1983 to 1992) Interpreted zones of injection influence Pilot injection well

12 Hydrochemical Groups of Local Devonian Water Pilot Devonian Wells Quaternary, McMurray Basal wells and RAMP Surface water HYDROCHEMICAL SEPARATION

13 Hydrochemical Groups of the Lease TDS<4000 Native Devonian Formation Water Pilot Mixing of waters HYDROCHEMICAL SEPARATION

14 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 Apr-12

15 Saturation Index Saturation Index Water Speciation Saturation Indices Calcite Aragonite Dolomite Strontianite Gypsum Anhydrite Aqueous Silica Halite Total Dissolved Solids (mg/l) Saturation Indices Calcite Aragonite Dolomite Strontianite Gypsum Anhydrite Aqueous Silica Halite Total Dissolved Solids (mg/l)

16 Hydrochemical Processes Pilot Mixing Calcite dissolution or precipitation: CaCO 3 + CO 2 + H 2 O Ca HCO 3 - Dolomite dissolution or precipitation: CaMg(CO 3 ) 2 Ca 2+ + Mg CO 3 2-

17 Hydrochemical Processes Gypsum dissolution: CaSO 4 (2H 2 O) + H 2 O Ca 2+ + SO H 2 O Sulphate reduction: 2CH 2 O + SO 4 2-2HCO H 2 S Pilot Mixing

18 Hydrochemical Processes Sulphate reduction: 2CH 2 O + SO 4 2-2HCO H 2 S Pilot

19 Hydrochemical Processes Strontianite dissolution: SrCO 3 Sr 2+ + CO 3 2- Pilot Mixing

20 Hydrochemical Processes Pilot Mixing Halite dissolution: NaCl Na + + Cl -

21 Hydrochemical Conceptual Model Calcite dissolution and precipitation: CaCO 3 + CO 2 + H 2 O Ca HCO 3 - Main Hydrochemical Processes Dolomite dissolution and precipitation: CaMg(CO 3 ) 2 Ca 2+ + Mg CO 2-3 Gypsum dissolution: CaSO 4 (2H 2 O) + H 2 O Ca 2+ + SO H 2 O Sulphate reduction: 2CH 2 O + SO 2-4 2HCO H 2 S Strontianite dissolution: SrCO 3 Sr 2+ + CO 2-3 Halite dissolution: NaCl Na + + Cl - Wastewater Injection well Sampling wells Ca-Mg-HCO 3 Type Quaternary Deposits Shallower System Clearwater Fm. Aquitard McMurray Fm. Aquitard Waterways Fm. Hydraulic Barrier Na-HCO 3 Type Mixing water Na-Cl Type Middle and Lower Devonian Formations (Mainly Keg River) Lower System

22 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 name TDS/pH Well Wastewater Model 1 Model 2 (NETPATH Database No.) DW (19) 3245-(81) Well (82) Well 13-4 (17) Water Initial water 1 Initial water 2 Final water 1 Final water 2 Temp ( o C) ph Ca Mg Na K Cl SO 4 as SO Alk/TDIC * 708* 479* Fe F 1.92 ND Sr 8.96 ND (0.18)** H 2S(aq) as S 0.0 ND ND 74 + : Field Alk as CaCO 3; * : Field Alk as HCO - 3 ; ** only considered in Model 2. Concentration as milligrams per litre.

23 NETPATH Hydrochemical Modelling Results Model 1 (Devonian Native Water + Wastewater = Well 16-21)

24 NETPATH Hydrochemical Modeling Results Model 2 (Devonian Native Water + Wastewater = Well 13-4)

25 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