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Hydraulic fracturing is a controlled operation that pumps a mixture of fluids, comprised primarily of water, sand and a small amount of chemical additives, into the wellbore to the target formation at a high pressure. As the mixture is forced through perforations in the wellbore into the surrounding rock, the pressure causes the rock to fracture, allowing the gas to flow through the wellbore to the surface.
Hydraulic fracturing operations are designed with computer modeling software. These designs ensure that the fractures caused by our operations are contained within the intended rock formation. The actual dimensions, extent, and geometry of the fractures are controlled by the pump rate, pressure, volume and thickness of the fracturing fluid. Planning our hydraulic fracturing operations in this way allows us to continuously improve our approach for future operations. A recently developed technology, known as microseismic monitoring, allows us to monitor microseismic events associated with hydraulic fracturing in three dimensions and in real time. Where used, microseismic monitoring provides a way to evaluate important elements of each hydraulic fracture treatment, such as vertical extent, lateral extent and fracture complexity.
Unconventional natural gas reservoirs have extremely poor natural permeability – even though these reservoirs may contain large amounts of gas, it is extremely difficult to recover. Without hydraulic fracturing, recovering the resources found in deep shale formations would be virtually impossible. By creating small cracks, or fractures, in the rock formation, we allow natural gas and oil trapped within the very dense rock to flow through the wellbore to the surface.
Methane, a non-toxic gas, occurs naturally in groundwater aquifers in most geological sedimentary basins worldwide. Naturally-occurring methane can often be safely managed through water well maintenance. Methane gas exists in a dissolved state in groundwater and will bubble out when the water is pumped to the surface. For those on private water well supplies, spurting taps is a common result of this phenomenon. Methane is non-toxic and non-poisonous. It can pose an explosion or asphyxiation hazard only if it is allowed to build up in a confined space, so well owners are strongly encouraged to vent their water supply systems when gas is present.
When methane is present in well water and that water and methane are confined to a closed space, it is possible to ignite this naturally-occurring methane and cause a flash flame. This is the scene that has become common in recent critical films and news reports alleging that natural gas drilling contaminates well water with methane. However, provincial and state laws and regulations across North America require natural gas developers to observe measures to ensure the natural gas they are producing from deeper geological zones, as well as the water and additives they pump into the well, do not come in contact with groundwater supplies at shallower depths. Natural gas developers design and construct their wells with extensive protection and conduct well integrity tests to ensure groundwater is protected.
Our protection of groundwater starts with effective wellbore design and the proper execution of wellbore construction procedures. These procedures are highly regulated. Every natural gas well has an engineered steel casing system that is cemented externally to prevent any fluids from moving from the wellbore to groundwater aquifers. The casing design and cementing program conform to a written, engineered design which is specific to each well. This design is prepared by Encana and installed by independent qualified specialist contractors. The integrity of the casing and cement system are evaluated through field inspection and wellbore logging throughout the life of the well.
The actual fracturing takes place at depths typically thousands of feet deeper than any groundwater aquifers. Advanced technology, such as micro-seismic analysis and electronic wellbore logging, is used to confirm the fracture treatment is executed as designed and does not migrate out of the targeted formation.
Fracturing fluids are comprised primarily of sand and water. For each stage of the fracturing process, a very small amount of additives is injected into the wellbore within the hydrocarbon bearing rock along with the water and sand to improve the process. The make-up of fracturing fluid varies from one geological basin or formation to another and the difference between the formulations can be as small as a change in concentration of one specific compound. The number of chemical additives used in a typical fracture treatment also varies, depending on the conditions of the well being fractured. Each component serves a specific, engineered purpose.
We are committed to and support the disclosure of hydraulic fracturing chemical information. Our U.S. subsidiary participates in the FracFocus Chemical Disclosure Registry in the U.S. and we look forward to participating in the newly announced Canadian version of FracFocus.
Our Responsible Products Program helps ensure that the hydraulic fracturing fluid products we use in our operations are as safe, effective and as environmentally responsible as possible. The program categorizes the products we use based on their potential health and environmental impacts. After we’ve carefully assessed a specific product, we determine whether we need to implement any operational practices and/or controls or if we should discontinue using the product altogether.
Encana prohibits the use of any hydraulic fracturing fluid products containing diesel, 2-Butoxyethanol (2-BE) or benzene and we have informed our suppliers that any product containing these additives cannot be used in our hydraulic fracturing operations.
The program is a risk-based product assessment and management program. All of the hydraulic fracturing fluid products we use are carefully assessed based on their potential risk to human health or the environment. The program’s components include:
Yes, we may conduct predevelopment or baseline groundwater sampling. In some jurisdictions, such as coalbed methane development in Alberta, groundwater testing is currently required by regulation. In other areas the scope and extent of predevelopment or baseline groundwater testing is determined by site-specific factors including the depth and quality of local groundwater resources, the current and expected use of the groundwater in the area and the proximity to groundwater users and potential users.
We reuse as much of the flowback water as is practicable and/or allowed by regulation. Un-usable or excess flowback water is transported and disposed of in licensed disposal wells, in compliance with strict regulations.
We consider reusing water and using non-potable water whenever it is practical to do so in our hydraulic fracturing operations. Operating practices specific to the location take into account regulations in the area and provide guidance on the use of non-potable water and water reuse, storage and handling.
We recycle or reuse as much of the flow-back water as is practicable or allowed by regulation. Unusable or excess flow-back water is transported and disposed of in licensed disposal wells, and in compliance with regulations. We may also dispose of water in industrial disposal facilities in compliance with applicable state and provincial regulations.
Coalbed methane (CBM) is natural gas which is produced from coal seams. The coal in which CBM is found is located in various areas of the Western Canadian Sedimentary Basin.
CBM wells utilize different completions methods than those that are used to complete shale and other unconventional natural gas reservoir wells. What might be called traditional hydraulic fracturing is not used in CBM production. That's because coal, unlike other rock formations, is naturally fractured. This natural fracturing is called a cleat system.
In CBM completions the wells are stimulated by pumping nitrogen into a coal zone, which causes the natural cleats in the coal to be further interconnected. This helps release methane from the microscopic spaces that naturally exist in coal and allows it to flow into the well. Nitrogen is inert and safe - in fact, 78 percent of the air we breathe is composed of nitrogen.