A Study of Groundwater Quality from Domestic Wells in the Sussex and Elgin Regions, New Brunswick

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1 A Study of Groundwater Quality from Domestic Wells in the Sussex and Elgin Regions, New Brunswick Tom A. Al, Jessica Leblanc and Stephanie Phillips Department of Earth Sciences University of New Brunswick

2 Natural Resources Canada (Program of Energy Research and Development)

3 Objectives Focussed on the McCully Field because it is the only producing gas field in New Brunswick at the present time. McCully Field: Determine the geochemical characteristics of the gas, particularly the methane/ethane/propane contents, 13 C methane and 2 H methane and the 3 He/ 4 He isotope ratios. Measure the geochemical properties of the formation water, including water isotopes ( 18 O and 2 H) and the major and trace element composition. Domestic Wells: Determine the range of geochemical and isotopic compositions of shallow groundwater and any hydrocarbon gases that may be detectable.

4 Sample Locations: Domestic Wells N McCully Gas Field Elgin Sussex

5 Sample Locations: McCully Gas Field

6 Methods Groundwater samples collected upstream of any water-treatment system. The pump and water-lines were purged for approximately five minutes prior to sample collection. Field Measurements included ph, redox potential and alkalinity. Groundwater samples for major cations/anions and trace elements were filtered to <0.45 mm and acidified (cations and trace elements) to ph < 1 with ultrapure HNO 3. Analyses conducted at UNB by ICP-MS and IC. 18 O and 2 H analyses were conducted at the University of Ottawa G.G. Hatch Isotope Lab. Data for produced brine and gas composition are from Corridor Resources

7 Methods Water samples for dissolved hydrocarbon analysis were collected in 500 ml glass Wheaton bottles. Analyses (methane, ethane, propane) were conducted by GC/FID (method AQS90) at the Research and Productivity Council (RPC) labs in Fredericton. The method detection limit for methane is 0.01 mg/l. Water samples for determination of methane isotopic composition (δ 13 C and δ 2 H) were collected in 500 ml glass Wheaton bottles. Methane isotope analyses were conducted at the University of Ottawa G.G. Hatch Isotope Lab. Gas samples collected at the wellhead for isotope analyses (δ 13 C and δ 2 H) using pressure cylinders (SGS Canada Inc.).

8 Results

9 Produced Brine mg/l Seawater Na K Ca Mg Alk Cl Br SO 4

10 Gas Composition

11 Shallow Groundwater Minimum Maximum Mean Guideline Units Na a mg/l Mg mg/l K mg/l Ca mg/l Al μg/l Mn a μg/l Fe a μg/l Sr μg/l As b μg/l Pb b μg/l Ba b μg/l U b μg/l Cl a mg/l NO b mg/l SO a mg/l Br mg/l ph a E H mv a Alkalinity aesthetic c guideline: 22 recommended that concentrations be less than this threshold mg/l b maximum acceptable concentration c alkalinity reported as HCO 3

12 Comparison: Brine vs Shallow Groundwater Element Mean Deep Brine (mg/l) Mean Shallow Groundwater (mg/l) Na 10, K Ca Mg Alkalinity Cl 16, Br SO

13 Comparison: Brine vs Shallow Groundwater

14 Shallow Groundwater: Isotopes 0 2 H VSMOW GMWL SMOW Shallow GW MWL Truro Fritz et al. (1987) MWL Charlottetown Francis (1989) O VSMOW

15 Shallow Groundwater: Methane N 1.17 Penobsquis Elgin Sussex Methane (mg/l) > 1.0 > 1.0 mg/l

16 Methane Isotopes

17 Summary/Conclusions 26 domestic water well samples and samples of the gas and brine recovered from producing wells in the McCully field. Inorganic chemical properties of the shallow groundwater samples are similar to New Brunswick groundwater in general. There are a few minor exceedances of the aesthetic water-quality guidelines for sodium, iron, manganese, sulphate and ph, and there are several samples that exceed the maximum acceptable concentrations (MAC) defined by the New Brunswick government for arsenic, lead and nitrate. The water isotopes of the shallow groundwater samples are typical of recently recharged meteoric water. Only three of the shallow groundwater samples (two near Elgin and one northeast of the McCully Gas Field) contained detectable methane, at very low concentrations. None of the shallow groundwater samples contained detectable ethane or propane.

18 Summary/Conclusions. Methane in two shallow groundwater samples from the Elgin area is of thermogenic origin. The detection of thermogenic gas in shallow wells in an area without commercial gas production demonstrates the importance of conducting comprehensive baseline sampling prior to gas exploration and development. Produced brine from the McCully Gas Field is similar to seawater that has been modified by diagenetic processes (dolomitization, ion exchange, sulphate reduction). The analysis of isotopes from the McCully Gas Field demonstrate that the gas is thermogenic. Gas from the Frederick Brook shale is distinctly different ( 13 C- enrichment) from gas in the Hiram Brook. Small dataset, but there is no indication that development and production at the McCully Gas Field has affected the water wells.

19 Acknowledgments. Natural Resources Canada, P.E.R.D. Corridor Resources Homeowners NB Environment and Local Government