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TitleUnderstanding shallow and deep flow for assessing the risk of hydrocarbon development to groundwater quality
AuthorRaynauld, M; Peel, M; Lefebvre, R; Molson, J; Crow, H; Ahad, J M E; Ouellet, M; Aquilina, L A
SourceMarine and Petroleum Geology vol. 78, 2016 p. 728-737, https://doi.org/10.1016/j.marpetgeo.2016.09.026
Year2016
Alt SeriesEarth Sciences Sector, Contribution Series 20150490
PublisherElsevier
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceQuebec
NTS22A/09
AreaHaldimand sector; Gaspé
Lat/Long WENS -64.5000 -64.3500 48.8333 48.7667
Subjectsoil; groundwater; groundwater pollution; groundwater flow; aquifers; oil seeps; gas seeps; fluid migration; drilling activity; oil and gas exploitation
Illustrationslocation maps; schematic cross-sections; tables; graphs
ProgramShale Gas - groundwater, Environmental Geoscience
AbstractIn recent years, concerns have been raised about the potential environmental impacts of oil and gas (O&G) exploitation, especially regarding groundwater resources. However, there have been few studies carried out to assess the actual risk of O&G exploitation based on specific local conditions. This paper reports on a study aiming to assess the potential risk to groundwater quality related to the development of a tight sandstone petroleum reservoir underlying a shallow fractured rock aquifer system in the Haldimand sector of Gaspé, Québec, Canada. In this generally rural setting, the drilling of a provincially permitted horizontal O&G exploration well was halted by new municipal regulations. Draft provincial environmental regulations were subsequently issued to define environmental requirements for hydrocarbon exploration wells. Our study thus also aimed to provide an example of how to comply with the new hydrogeological characterization requirements. This paper reports on the process followed to qualitatively assess the risk of O&G operations and natural oil seeps to groundwater quality. The assessment focused on indicators of potential preferential fluid migration paths between the reservoir level and shallow aquifers. Field work and data analysis were used to define geological, hydrogeological and geochemical contexts on which a numerical model was developed to represent groundwater flow, mass transport and groundwater residence time. The risk for groundwater quality was qualitatively assessed from the implications of the study area context relative to 1) the new provincial regulatory requirements; 2) potential contaminant release mechanisms related to O&G exploration drilling operations; and 3) the expected effects that contaminant releases could have on groundwater.
Summary(Plain Language Summary, not published)
This study aimed to assess the potential risk to groundwater quality related to the development of an "unconventional" tight sandstone petroleum reservoir underlying a shallow fractured rock aquifer system in the Haldimand sector of Gaspé, Québec, Canada. Our study found no indications of active natural preferential migration pathways from depth, as indicated by an efficient caprock that isolates the oil reservoir, sparse fracturing in the deep subsurface (100s of meters), and no geochemical indications of deep-shallow preferential paths. Furthermore, numerical modeling explains that regional groundwater flow patterns bring evolved groundwater with long residence time at shallow depths under Haldimand without the presence of preferential flow paths connecting deep and shallow levels.
GEOSCAN ID297849