Shale gas exploration and production, while gaining ground in many countries, still has its share of obstacles in Europe, including the issue of water.
Key misconceptions continue to circulate, slowing public and political acceptance. We’ve found that success for our clients starts with being able to provide the full range of answers and scientific evidence regulators and other stakeholders seek — and providing those answers and evidence very clearly and early on in the process.
These answers come from a keen understanding and risk assessment of the surface and subsurface, fracture modeling, analysis of reservoir conditions and integrated water management planning and risk assessment.
Here’s a brief look at the concerns around water and the role that a comprehensive risk assessment and water management strategy can play in moving forward with responsible shale gas exploration and production.
Spelling Out Actual Water Quantity
Many people believe that hydraulic fracturing uses massive amounts of water. In reality, each hydraulic fracture stimulation will typically use somewhere between a half and two Olympic-sized swimming pools full of water.
Assuming an operator drills 20 wells a year and stimulates 20 stages in each well, that would be 2,000,000 m3 of water used a year. That sounds like a lot, but by comparison, this is less than 0.01% of the total amount of water abstracted for domestic, agricultural and industrial use in England and Wales each year. In addition, there are options to reuse the flowback water to stimulate other stages or wells.
Comprehensive Analysis of Water Sources
Dynamic simulation models are used to calculate current and future water demands.
Every potential water source has to be assessed thoroughly for each project and tailored to local conditions. If nearby surface and ground water resources are not sufficient, water will need to be supplied via pipelines or by road. Road transport typically is used with initial operations, but pipelines may become more suitable as extraction continues.
Best Practices in Water Storage
Flowback water produced from the well operation is stored, depending on local regulations, in bunded tanks with leak control systems. These can either be onsite or in a centralized location. In addition, management of rainfall runoff from the well pad requires the tanks to have adequate capacity and to be able to withstand storm events.
Detailed engineering controls are essential during the construction of the water facilities to verify structural integrity and quality assurance.
Integrity in Well Design and Reservoir Analysis
While there have been no independently verified examples of aquifer contamination from fracking fluid as a result of formation stimulation in the United States, there has been some evidence of change in methane content in some shallow aquifers. This can be attributed to poor well construction or legacy contamination.
The importance of proper well design and well engineering cannot be underestimated. Excellence in cementing and casing is essential to help prevent migration of natural gas into water-bearing formations, along with ensuring that the stimulation of the target formation is constrained.
Using discrete fracture network (DFN) modeling to analyze the reservoir also goes a long way in minimizing risks.
Golder’s FracMan 3D DFN simulation approach, based on the input of geomechanical data, seismic attributes and other local features, provides visualization of the hydraulic fracturing process, revealing the presence of any critically stressed faults and fractures and the simulation and design of induced hydraulic fractures.
This technology has been developed over the past 25 years with insight from both clients and Golder geoscientists and reservoir engineers during our work in the radioactive waste, mining and the oil and gas industries.
Options in Water Treatment, Reuse, Return and Disposal
One of the options for treating flowback is to bring a temporary, package treatment plant onsite. This may be particularly attractive when constructing direct pipelines to municipal treatment plants, or other facilities is not a viable option.
Another option is to truck the water away to a remote treatment facility.
Depending on the treatment operation, water may be returned to the environment, typically to surface water, or may be reused. Some disposal of water, however, will always be necessary.
Integrated Water Management Strategy
Operators need to shape their approach to water treatment, reuse and disposal — as well as quantity, sources and storage — in their overall water strategy from the very start. Meticulous planning of the supply chain can save money, minimize risk and secure sustainability.
By establishing plans for every stage early on, and understanding the complete water lifecycle, hydraulic fracturing is far more likely to satisfy social, environmental and regulatory demands.
Please feel free to contact me at [email protected] to discuss your shale exploration needs and water issues.
ABOUT THE AUTHOR
Gareth Digges La Touche, Principal Hydrogeologist and Associate at Golder, works with clients on groundwater and fluid flow studies in the unconventional oil and gas and mining sectors. He holds a degree in Geology & Geography from Keele University and masters’ degrees in Computing in Earth Science from Keele and in Hydrogeology from Birmingham University. He is qualified as a Charted Geologist and European Geologist and is a Fellow of the Geological Society of London and the Royal Geographical Society.