Patrick Leslie, Heather Kalf, Emily Zevenhuizen, Oksana (Ogrodnik) Kielbasinski, Sean Speer, Jon Fennell, Integrated Sustainability Consultants Ltd.
August 8, 2014
Executive Summary
This study provides a high-level assessment of the environmental net effects (ENE) of saline water use in the full lifecycle context of hydraulic fracturing operations. The ENE of saline water is determined based on a comparison against non-saline water as the “base case”.
A comparison between non-saline and saline water was chosen, as these two sources represent the most common type of water used for hydraulic fracturing operations. In addition, government agencies and stakeholders are gradually encouraging industry to shift their use of water from non-saline (typically surface water) to saline water (typically deeper bedrock aquifers) sources.
This study is intended to be used for regional and high-level assessment purposes and to guide further work around this topic.
The following flow diagram (Figure A1) defines the stages of the hydraulic fracturing process that were examined. Although a specific environmental effect may occur at numerous points throughout the lifecycle of this activity, each environmental effect was only considered for one block in the flow diagram.
Figure A1. Water Use in Hydraulic Fracturing
Environmental Criteria
The following environmental criteria were used to assess the impact of saline and nonsaline source water use within each block depicted above (where applicable):
Ecosystem: Impacts on living organisms (biodiversity) and their habitats due to construction, operations, and reclamation activities.
Air Quality: Greenhouse gas (GHG) emissions resulting from production and consumption of energy (i.e., diesel fuel use, and electricity provided through the grid system) and the corresponding GHG emissions (gases emitted into the air from industrial processes).
Waste: Volume of liquid and solid wastes generated as a result of treatment of the water (source water and produced water), which may require additional land disturbance for the construction of treatment and disposal infrastructure (i.e., landfills, deep well disposal systems, brine ponds).
Industry Survey
A targeted survey was prepared and provided to 15 member companies of Canadian Association of Petroleum Producers (CAPP) to gather relevant industry experience regarding water use in hydraulic fracturing operations. The results were used to augment and support the findings of this study.
Environmental Net Effects of Sourcing Water
The ENE of both saline and non-saline water sources with respect to water source infrastructure is mainly determined by the facility and source well footprints, access roads and other supporting infrastructure. For example, a river or lake infiltration system can disturb the riverbed and the local aquatic habitat during construction, operation and decommissioning. Alternatively, based on industry experience, a greater number of groundwater wells would be required to match the output volume of one river or lake intake resulting in greater footprint disturbance intensity.
For this study, the saline water source was compared to the most common non-saline water source currently used by industry (river: infiltration gallery) in order to determine the major ENE differences between saline and non-saline water for source water. It should be noted that the quality of these two types of water sources could vary significantly, resulting in a large ENE gap. Alternatively, in a scenario where a higher quality saline water source is compared to a lower quality non-saline water source, this gap may be minimized.
Environmental Net Effects of Transportation
The ENE between saline water and non-saline water, with respect to transportation, is mainly dependent on the effects of spills or leaks. Any spill or leak can cause environmental damage resulting from soil erosion, siltation of streams, and the introduction of foreign substances, or dissolved constituents to an area (i.e., salts and resulting soil salinization issues).
The land disturbance footprint is greater when transporting water via pipeline versus trucking. Access roads are built for site access; therefore, no additional disturbance from the trucking of water is normally required. Alternatively, construction of a pipeline requires clearing of vegetation and excavation, which causes greater land disturbance. In addition, it may be difficult to identify an appropriate water source in close proximity to operations, potentially resulting in the installation of a pipeline over a significant distance.
As shown in the following figure, there is also a large difference in the amount of GHG emissions produced by trucking water compared to pipeline transport.
Figure A2. GHG Emission By Transportation Type for Water Transport
Environmental Effects of Water Treatment
The water treatment ENE is directly related to the specific source water chemistry and downstream quality requirements for each specific application. These two factors are the primary indicators of the required treatment process, and therefore the associated ENE. Saline water may have a greater net environmental impact compared to nonsaline water due to the additional energy requirements for treatment commonly needed to meet compatibility with fracking operations. This equally extends to the waste by-products that need to be managed as a result of the treatment process.
Environmental Net Effects of Disposal (Waste Generation from Source Water Treatment)
The major ENE difference for the disposal of waste generated from saline versus nonsaline source water treatment is typically the volume of chemicals used for the treatment process. With the exception of the removal of total suspended solids (TSS), which results in the production of large volumes of solid waste, the need for chemicals to render saline water to a useful quality presents the risk of spills and releases into the environment and the associated detrimental effects.
Environmental Net Effects of Water Storage
The major ENE difference between saline and non-saline water storage is the increased impact to the surrounding environment in the event of a spill or leak of, or exposure to, chemicals in the saline water. To prevent such an impact, saline water is typically stored in engineered ponds (lined and monitored), C-ring containment structures, or above ground tanks, with mitigative measures in place. However, the need to engineer in containment leads to higher impact due to the requirement of additional physical footprint, containment infrastructure, and the associated equipment and activities for leak prevention and monitoring.
Environmental Nets Effects of Well Pads
The selection of saline or non-saline source water does not have a significant impact on the hydraulic fracturing fluid or the system infrastructure, as both non-saline and saline water require some form of treatment to ensure compatibility with hydraulic fracturing additives prior to storage on pad.
Environmental Net Effects Downstream of Wells
Variations in produced water quality have been found to be more dependent on the contact time with the formation, the volume of produced water, and the geological formation characteristics than on the quality of the source water used in the fracturing operations (Blauch, 2011).
Conclusion
This study takes a high level approach to comparing saline water and non-saline water in the hydraulic fracturing process, but recognizes that there may be a notable quality difference between the two sources themselves that may influence the overall ENE when compared. As such, it cannot be strictly determined, on a broad scale, if saline or non-saline water has a lower ENE as a more comprehensive approach to source water selection that takes into account regional demands and system capacity is required.