In 2014 the Council of Canadian Academies, a highly respected scientific panel, released a report outlining knowledge gaps associated with unconventional gas development. At the time, it suggested little was known about the effects of natural gas leaks into freshwater aquifers.
Water quality, water quantity and fugitive emissions are three of the four key areas of focus of the provincial government’s 2019 Scientific Review of Hydraulic Fracturing in British Columbia. Recommendations in this report include additional research relating to understanding fugitive emissions, with a focus on field-scale research experiments.
This understanding is valued by industry, governments, communities and Indigenous groups alike as they look to make more informed decisions, improve practices and guide policy and regulation.
This project fits under Geoscience BC’s Strategic Objective of ‘Understanding Water’ and the goal to:
- Expand the collection of baseline groundwater data and research on groundwater in the Peace Region to guide informed management of natural gas resources.
Specifically, the Assessment of Fugitive Natural Gas on Near-Surface Groundwater Quality project was designed to answer the following questions:
- What are the principal hydrogeological controls on the physical movement of fugitive gas in near-surface freshwater aquifers in northeastern British Columbia?
- What are the physical and geochemical conditions that affect fugitive gas typical of undisturbed near-surface fresh groundwater aquifers in the Montney shale-gas play?
- What geochemical changes occur when natural gas migrates into shallow freshwater aquifers in northeastern BC?
This project provides research needed to support the responsible development of BC’s unconventional natural gas resources. It helps to better determine and mitigate the risks associated with this development, improve monitoring and guide future remediation work.
The project took place 20 kilometres north of Hudson’s Hope at the Hudson’s Hope Field Research Station (HHFRS) in BC’s Northeast Region. The HHFRS was established within the northern part of the Montney Field to address the knowledge gaps associated with gas migration in complex geological settings and perform a controlled, natural gas injection in the shallow subsurface.
How was the data collected?
The project simulated a leaking gas well by releasing natural gas into a controlled environment and studying how gases travel through different sediment types and what impacts, if any, this has on shallow groundwater. Initial test releases used an inert gas such as nitrogen and a ‘tracer’ to test sampling methods before natural gas was released into the subsurface at a specific depth in a confined aquifer.
Water and gas sampling was complemented by monitoring for approximately two years using multiple disciplines, including geophysics, hydrogeology, geochemistry, microbiology, and micrometeorology.
This project was a core component of the University of British Columbia Energy and Environment Research Initiative (EERI), a field-focused research program directed by Dr. Roger Beckie and Dr. Aaron Cahill (now at Heriot Watt University) at the Department of Earth, Ocean and Atmospheric Sciences. Additional funding was provided by Natural Resources Canada and the BC Oil and Gas Commission. The project team included scientists from University of Calgary and Simon Fraser University.
What Was Found?
The project conducted a controlled natural gas release experiment. A measured volume of natural gas was purposefully released at a controlled rate into the subsurface while various monitoring methods traced its movement, alteration and measured any environmental effects.
The active injection began on June 12, 2018 at a natural gas release point 26 metres below ground level and lasted 67 days, releasing a total of 97.5 cubic metres of a gas mixture mimicking Montney natural gas. The research teams monitored and collected data for a period prior to injection and throughout the active injection. Post-injection monitoring continued for approximately two years after injection ceased and was ongoing as of May 2021 following the completion of the Geoscience BC funded element of the research.
The project used and tested a variety of techniques to monitor and detect gas migration including geophysical, hydrogeological and surface-based approaches.
The current findings at the research site suggest that gas migration in the early time after release of natural gas did not lead to degradation of groundwater quality. Based on data from the first two years, the impact on groundwater geochemistry included elevated hydrocarbon concentrations, but no significant changes in major or trace elements.
Analysis of the collected data concluded that approximately 75% of injected gas remained in the subsurface after approximately two years of monitoring. In this experiment, approximately 25% of the injected gas migrated upward toward the surface through (more porous) sand and silt interbedded layers. Surface detection shows that injected gas reached the surface through pathways (routes of least resistance for fluid flow) that are either natural, or anthropogenic, such as the groundwater monitoring wells on site.
Fugitive gas can travel laterally below low permeability layers, specifically a confining diamict layer (a type of glacial sediment) typical of northeastern BC. Vertical gas migration will be hindered by these low permeability layers, increasing the spatial footprint of leaked gas, and giving trapped gas time to dissolve into flowing groundwater. Some oxidation of the injected hydrocarbons also occurred, converting the gases to carbon dioxide, however the study of this association was not within the scope of the project.
Surface emission volumes (and therefore their effects in the atmosphere or upon surface infrastructure) depend on both the volume of the subsurface leak and the presence of the surface diamict, as well as the presence or absence of preferential flow paths through the diamict or other low permeability layers.