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FINAL REPORT 5.0 EXISTING ENVIRONMENT 5.1 Geology The bedrock of Nova Scotia contains an abundance of salt formations. Salt is mined by underground methods and by solution mining methods. The thickness, depth of burial and amount of structural deformation of salt formations varies considerably throughout the province. Salt formations which are suitable for gas storage in caverns must meet several criteria. The formations must be thick enough to easily accommodate the space required for storage caverns within the upper and lower boundaries of the salt. Also, the salt must be buried at a sufficient depth to withstand high pressure natural gas; the deeper the depth of burial, the higher the maximum allowable pressure, which improves the economics of a gas storage project. Finally, the structural deformation of the salt, which takes place over geological time, cannot be too severe, otherwise caverns will not form in an anticipated shape, in accordance with the geotechnical design, which maximizes strength and stability of the cavern. Many of the salt formations in Nova Scotia, such as in Pugwash, Nepan and Cape Breton, are highly deformed and folded and are not suitable for natural gas storage. The Alton Project area is underlain by the Shubenacadie – Stewiacke basin, which contains a large, flat-lying bedded salt formation referred to as the Stewiacke formation, which is part of the Windsor Group. This basin has been described by R.C. Boehner (1986) as: “The deposit’s thickness, its relatively undisturbed nature, its great lateral extent and reasonable depth, and the virtual absence of salt springs, all favor use for the future development of mines and underground storage facilities.” This description indicates potential for underground storage of gas in the Shubenacadie – Stewiacke basin. In addition to being underlain by bedrock of the Windsor Group, the Nova Scotia bedrock geologic mapping also indicates that Project components (pipeline, holding pond and mixing pond) are underlain by bedrock of the Mabou Group, also composed of sedimentary units (Keppie 2000) (Figure 5.1). In early 2005, 8 km of seismic data was acquired from Hunt Oil Company. This survey tied into the EOG/Hunt Cloverdale #1 well and the Hunt Alton 99-1 well, which had encountered 420 m of salt. This program allowed Alton to regionally understand the salt formation in the area surrounding the permits held today. In 2005, a gravity survey was conducted in order to correlate the seismic data with gravity in an attempt to gain a better understanding of the formation and to outline potentially deeper and thicker portions of the salt formation. Later that year, Alton conducted a 28 km seismic survey within the present salt and potash licences and mineral exploration licences. The survey defined an area with the desired geological characteristics to allow for the storage of hydrocarbons. In the winter and spring of 2006, Alton drilled a core hole 650 m to the north of the Hunt Alton 99-1 well to confirm the seismic interpretation and candidacy of the salt formation for the use of underground hydrocarbon storage. The drilling program was conducted on the Special Licence No.1-05. The Alton Project drilled a 946 m deep core hole, named ALT 06-01, through the salt formation. The core hole intersected the top of the salt at 470 m depth, with the bottom of the salt at 946 m depth. Geological and geochemical analysis as well as geotechnical testing of the drill core confirms the suitability of the salt formation for natural gas storage. Only the bottom of the salt formation, from approximately 858 m to 946 m depth, will be used for cavern development. This allows for higher pressures than a shallower cavern, and provides additional upper rock to ensure a proper seal to the surface. As a result of the drilling and seismic programs, Alton was able to confirm the salt formation’s suitability for the storage of hydrocarbons. © 2007 PROJECT 1012229. June 14, 2007 46 FINAL REPORT 5.2 Water Resources A desktop evaluation to determine the presence of potential water wells within approximately 500 m of the proposed water pipelines was completed using the most recent aerial photography (i.e., 2004) and the most recent topographic mapping (i.e., 1997). During the assessment, water supplies were assumed to be located on properties with one or more structures present. It was determined that there are approximately 60 water supplies located within 500 m of the pipeline. Of these, most are suspected to be either drilled or dug wells. No ground truthing of the desktop study was completed and therefore the actual number of water wells may be more or less than 60. Interaction between groundwater wells and gas leaking due to failure of a cavern is unlikely because the proposed caverns are much deeper than the maximum depth of potable ground water, and the intervening strata contain 380 m of additional impermeable salt, the physical properties of these salt formations make it unlikely to fracture, and safety systems and standards will minimize potential risks to groundwater users. © 2007 PROJECT 1012229. June 14, 2007 47 470000 472000 474000 476000 478000 Proposed Proposed Subsurface Facilities 0 Surface 0 0 0 0 Facilities 0 5 5 0 0 0 0 5 5 ECWbSM ECWcSM Alton Gas Storage Project Figure 5.1 ECWcSM Geology of the ALTON Project Area Water Intake Pipes CWB Brine Discharge Pipe Bridge Major Highway Collector Highway Paved Road 0 0 0 0 Unpaved Road 0 0 3 3 0 0 Rail 0 0 5 5 Contour (5m) Watercourse Waterbody Proposed Pipeline Route (20m Row) k 2 Holding Ponds o o r Proposed Surface Facilities B d Proposed Subsurface Facilities r ECW u H Surficial Cover e l t Post Last Glaciation (Holocene) t B i ig L Organic Deposits M e Sphagnum moss, peat, gyttia, clay a 102 d o Alluvial Deposits w Gravel, sand, mud; bedded coarse at base, finer at top, B r stream channels generally gravelly sand, flood plains sand o o k Marine Deposits Gravel, sand, silt, clay; locally overlain by peat (saltmarsh) 0 0 0 Proposed Water Intake McKay Siding 0 0 0 Last Glaciation (Wisconsinian) 1 & Brine Discharge System Rock Pile Pool 1 0 0 Glaciolacustrine Deposits 0 0 5 5 Sand, silt, clay, laminated to massive, massive or crudely stratified diamictons (mixture of gravel, sand, and mud) Glaciofluvial Deposits - Kame fields and Esker Systems Gravel, sand and silt, diamicton layers, poorly to well bedded, horizontal to angular beds, faulting and collapse features common Ground Morraine and Streamlined Drift - Stony Till Plain Narrows Pool Silty, compact, material derived from both local and dist. sources River Bedrock Geology S h Watering Brook Formation, Mabou Group, Carboniferous u e b k c e CWB mudstone, shale, gypsum, anhydrite, halite a n i a w Undivided Windsor Group, Windsor Group, Early c e t Graveyard Pool a Carboniferous S d res siltstone, mudstone, sandstone, shale, conflomerate, i ECW e gypsum, anhydrite, halite R Wentworth Station, Miller Creek, and MacDonalds i v Fort Ellis e Road Formations (B subzone), Windsor Group, Early r Carboniferous ECWbSM siltstone, limestone, dolostone Murphy Road and Green Oaks Formations (C-E subzone), 0 0 Windsor Group, Early Carboniferous 0 0 0 0 ECWcSM sandstone, siltstone, limestone, dolostone, anhydrite, gypsum 9 9 9 Stewiacke East 9 Map Parameters 9 9 4 4 Projection: UTM, NAD83, Zone 20 Date: June 06th, 2007 Scale 1 : 30,000 Note: Bedrock Geology mapping obtained from "NSDNR - Mineral Resources Project No.: 1012229 Branch Digital Products" - DP ME D00-01, Version 1, 2000. Digital version of Nova Scotia Department of Natural Resources Map ME 2000-1, Geo- 0 250 500 1,000 STEWIACKE logical Map of the Province of Nova Scotia, scale 1:500 000, 2000. - http://www.gov.ns.ca/natr/meb/pubs/pubs3.htm Metres Surficial Geology mapping obtained from "NSDNR - Mineral Resources Branch Digital Products" - DP ME D92-03, Version 1, 1997. Digital version of Nova Scotia Department of Natural Resources Map ME 1992-3, Surficial Geo- logy Map of the Province of Nova Scotia, 1:500 000, 1992. - http://www.gov.ns.ca/natr/meb/pubs/pubs3.htm 470000 472000 474000 476000 478000 FINAL REPORT According to the Nova Scotia Well Log Database of logs for wells constructed between 1940 and 2004, drilled wells in the vicinity of the Project are generally installed in sedimentary bedrock. This is corroborated by Nova Scotia bedrock geologic mapping which indicates that the Project is underlain by bedrock of both the Mabou and Windsor Groups which are both composed of sedimentary units (Keppie 2000). A summary of the pertinent well properties included in these logs is presented in Table 5.1. TABLE 5.1 Summary of Water Well Records in the Vicinity of the Project Overburden Well Depth Casing Length Estimated Yield Water Level Thickness (m) (m) (L/min) (m) (m) Minimum 4.6 0.8 9.5 0.5 1.5 Maximum 74.7 60.7 757 33.5 10.7 Average 25.7 20.1 93.2 8.9 6.1 Median 7.2 6.7 22.7 2.9 6.1 Number 22 22 16 14 2 Source: Nova Scotia Environment and Labour (NSEL). 1940-2004. Well Driller Logs. Groundwater quality from Mabou Group bedrock can be expected to be of good chemical quality with a tendency toward hardness. Iron and manganese concentrations in excess of relative aesthetic guidelines are found in approximately half of all wells located in Mabou Group bedrock (Gibb and McMullin 1980). Within the Windsor Group bedrock, the most expected concerns are high hardness levels, sulphate, total dissolved solids (TDS) and iron (Chang 1970).