Hydrogeology of a shallow coalbed methane play: A case study of Ardley coal in west- central, Alberta

Transcription

1 Hydrogeology of a shallow coalbed methane play: A case study of Ardley coal in west- central, Alberta S.M. Harrison, M.Sc., P.Geol., P.Geo. SH Consulting Services In association with NLR Associates Inc.

2 Outline PART I Overview and Well Data Location Stratigraphy / Hydrostratigraphy Well Drilling / Completion / Testing Data Pressure Transmissivity (permeability) Water Chemistry PART II Production / Development / Regulatory Testing implications for well spacing Local Water Well Use Quantity / Quality Produced Water PART III - Regional Considerations Regional Pressure Regional Chemistry Synthesis Other

3 Study Location

4 Stratigraphic / Hydrostratigraphic Chart

5 Schematic Cross-section section 2000 A Cadomin X Disturbed Belt Schematic Cross-section central Alberta B Edmonton A B C C Coalspur Brazeau Paskapoo Scollard Wapiti Horseshoe Canyon X Lea Park & Colorado Belly River Mannville Paleozoic Precambrian Horizontal Scale (km) A to B Vertical Exag. A to B = 25 B to C B to C x 75 Distribution of coal Plains Area (section view; modified AGS-EUB) EUB)

6 Data Coal Testholes (red) High number of testholes Data used for various mapping themes (e.g. structure contour map showing the distribution of Ardley coal

7 Data Hydrochemistry (DST) W5M Some DST s show a-typical water chemistry. e.g. Anomalous DIC (bicarbonate or HCO 3 ) western part of area Indicator of biogenic gas?? Associated sulphate (200 mg/l) Higher gas content in parts of study area

8 0 Gamma Ray API W5M KB = 859 m asl Target W5M KB = 859 m asl 0 Gamma Ray API Paskapoo Fm 150 Scollard Fm 200 Coal Zone Paskapoo Fm (lower) Coal Zone approx. 9 m thick Scollard Fm (Ardley Coal Zone) Gamma Ray 0 API Bulk Density kg/m Density Correction -50 kg/m Photoelectric Effect Caliper 275 Gamma Ray 0 API Bulk Density kg/m Density Correction -50 kg/m Photoelectric Effect

9 Well Data what we wanted to What: evaluate and why Pressure Permeability Water Chemistry / Water Quality Why: Wet or dry coal Biogenic gas present Producibility Regulatory

10 Well 103 Field Methods Drilling / Completion Testing / Data Collection

11 Field Methods: Drilling Surface casing set Air/mud-drilled drilled to target Intermediate casing cemented at the top of coal target isolating coal Coal air drilled and reamed Liner set No well stimulation Well purged of fluid and allowed to equilibrate for 80 hours

12 Field Methods: Well Set-up and Testing Well 103 and obs. well Downhole sondes Pump rate in 103 = 26 m 3 minutes pump gas locks (i.e. end of pump-off test) Build-up period

13 Well Data: Pressure Build-up up Data Build-up up period approx minutes Static pressure head 1470 kpa (150 m or 50 m btop) Gas 120 min (125 m of drawdown)

14 Well Data: Permeability gas/water? Cooper-Jacob Semi-log method or Theis recovery Late time data where water phase is assumed dominant Definitely permeability <5 md (likely <1 md)

15 Well Data Water Chemistry/Quality Routine: Na-HCO 3 type water, TDS = 1920 mg/l Na = 836 mg/l Cl = 250 mg/l SO 4 = <5 mg/l HCO 3 = 1650 mg/l Trace Metals (dissolved): Low dissolved and total dissolved metals (only Fe and Mn above CCME DWQ guidelines) Hydrocarbon (regulated): No hydrocarbon (e.g. BTEX) Sodium Adsorption Ratio (SAR) EC 58 (restricts use as irrigation water, for example, without upgrade) 3140 µs/cm

16 Isotopes: Isotope Geochemistry (water and dissolved gas) δ CDIC enriched +22 δ CCH4CH4 depleted -46 to -51 δ O/δ 2 H meteoric 3 H non-tritiated (test-well) δ 2 H CH4 /δ 2 H H2O suggest CO 2 reduction pathway

17 Part I: Summary and Conclusions Detailed compilation of well data pertaining specifically to the ACZ (part) hydraulic regime: Chemistry fresh water <2,000 mg/l TDS; relatively high sodium (Na); high HCO 3 (Na-HCO 3 type water) Isotope Geochem Meteoric; biogenic gas present Pressure near normal hydrostatic pressure (water) Permeability low; likely on the order of 1 md or less

18 Part II Production / Development and Regulatory Data are important to evaluate reservoir character/flow system as it pertains to, for example, development / production (e.g. quantity/quality of water, well spacing, etc.); CO 2 sequestration Relationship to water wells within the area?? Code of Practice vs. Water Act

19 Results Review: Recall permeability is relatively low (to water) must move water (i.e. depressurize) to attain gas flow 100 m Downhole sondes Pump rate in 103 = 26 m 3 minutes pump gas locks (i.e. end of test) No interference effect

20 Production / Development Well Array: Yellow circle = 800 m radius Blue = water wells Red = prodn well (vertical)

21 Water Act may be applicable CBM Working Group / Alberta Environment EUB: 1. Code of Practice 2. Div. Approval 3. No Reporting Required <5m 3 /day no reporting required

22 Water Well Distn. Blue = water wells Test-well Within a 600 m radius test Yellow circle 800 m radius

23 Pressure vs. Depth (Test-well 103) 0 50 Paskapoo/Drift Hydrostatic gradient Well 103 Linear (Hydrostatic gradient) Depth (m) Data Gap Pressure (kpa)

24 s Piper Plot (water wells and 103) S3 Paskapoo / Drift observation well C l Na + K Mg SO S CO Ca + M g sea water fresh-water HCO S O S Ca C l

25 Part III: Regional Considerations Regional Pressure Pressure vs. Depth Hydraulic Head vs. Elevation Hydraulic Head vs. Topo Cross-section section Regional Chemistry Piper δ 18 O vs. δ 2 H δ 2 H H2O vs. δ 2 H CH4 Synthesis Summary and interpretation of data Framework Flow Data Requirements

26 Pressure / Hydraulic Head lowermost Paskapoo - Ardley - Scollard Hydraulic Head distribution Cross- section line B-B

27 Topo vs. Hydraulic Head Topography (KB elevation) vs. Hydraulic Head Hydraulic Head (m y = 0.457x R 2 = Group 1 Group 2 Linear (Group 1) correlation with topography possibly reflecting gravity or topo driven flow Topography (m asl)

28 Hydrostratigraphic Section B-B B Section B-B' 1200 Elevation (m asl) Well 103 Topography Test Interval Group 1 Hydraulic Head Group 1 Test Interal Group 2 Hydraulic Head Group Distance (relative) Cross-section section illustrating relative head differences in lowermost Paskapoo Ardley Scollard (Groups 1 and 2); break in hydraulic regime shown as dashed line

29 Chemistry Piper Diagram lowermost Paskapoo - Ardley - Scollard Well 103 is Na- HCO 3 type water Obs well shown for comparison (reflects higher sulphate) Water wells are Ca-Mg HCO 3 type

30 18 O vs δ 2 H regional δ 18 Water-line (solid) for Edmonton Station with GMWL (dashed) Well 103 plots along line suggesting meteoric origin

31 δ 2 H vs. H2O δ 2 HCH4 δ 2 H CH4 ( ) VSMOW CO 2 Reduction CO2 reduction trend line δ 2 Η CΗ 4 = δ 2 Η H2O /- 10 Coleman et al Aravena et al Aravena et al Aravena et al This Study S3 Martini et al δ 2 Η H 2 O ( ) VSMOW CO 2 reduction appears to be the methanogenic pathway Contribution of biogenic gas

32 SYNTHESIS Cross-section section B-B B Hydraulic head distribution Cross- section line B-B

33 Synthesis O/ 2 H meteoric Section B-B' 1000 Well 103 Elevation (m asl) Underpressured? Gas Prone? CO 2 reduction Topography Test Interval Group 1 Hydraulic Head Group 1 Test Interal Group 2 Hydraulic Head Group Distance (relative) Recharging meteoric waters represented by Group 1 ( Paskapoo( Water System ) Regional flow system with local flow components normal or near-normal normal pressure Biogenic gas (methanogenesis( methanogenesis) ) generation within carbon-rich rich facies (coal) leading to high DIC (i.e. high HCO 3 concentrations enriched in 13 C) Gas-prone lower system?? - significantly underpressured

34 Flow SW Disturbed Belt 00/ O/ 2 H meteoric Impact?? 00/ O/ 2 H meteoric Subcrop NE local flow line 02/ / Impact?? regional flow line Paskapoo Paskapoo Scollard well m asl Gas Prone? ACZ Scollard Gas Prone? Flow details?? Local vs. intermediate vs. regional Additional data

35 Well Log (Detailed View) Detailed View of the Coal Zone Haynes Member (?) H = 805 m TDS = 1920mg/L Gas/Water Perm = 1mD Isotopes ( 2 H, 18 O, 13 C) 200 coal zone Scollard?

36 Summary and Conclusions Detailed compilation of well data pertaining specifically to the ACZ (part) hydraulic regime: Chemistry Na-HCO 3 type water Pressure near normal pressure Permeability low likely <1 md Synthesis and interpretation of data within regional context suggests at least parts of the Ardley lie within the Paskapoo Water System and have a component of biogenic gas Data are important to evaluate reservoir character/flow system as it pertains to, for example, production (quantity/quality of water, well spacing, potential for CO 2 sequestration) Flow system?????

37 Thank you