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Shale gas well drilling diagram
Natural gas and technology
Our industry has been aware for decades that natural gas has been locked in shale and tight gas formations. The key has been finding and developing the advanced technologies to unlock these resources so they can be commercially viable.
Hydraulic fracturing
Unconventional gas resources such as shale are now being accessed using a process called hydraulic fracturing. This technique involves injecting a mixture of water, sand and a small amount of other additives into the well. The pressurized hydraulic fluid does the hard work of creating hairline cracks in the shale. These cracks, held open by the sand particles, allow the gas to flow up through the wellbore to the surface.
Hydraulic fracturing is not new. It was first used in conventional oil and gas extraction in the late 1940s in North America. Since then, more than one million wells around the world have been drilled using hydraulic fracturing. In Alberta, it has been used for more than 60 years to safely and reliably fracture over 167,000 wells.
What is new, however, is the use of multiple technologies in conjunction with one another to make accessing unconventional gas more feasible. By combining hydraulic fracturing with horizontal drilling, operators can safely produce affordable, reliable quantities of natural gas from shale and other unconventional sources.
Hydraulic fracturing fluids
Fracturing fluids are used to help create the tiny cracks in the rock to allow the gas to flow. These fluids typically consist of about 90 percent water and 9.5 percent sand. Many of the ingredients in the remaining 0.5 percent of the mixture have common consumer applications in household products, detergents and cosmetics. These chemicals are used to reduce friction, prevent bacteria growth and protect the rock formation, making the hydraulic fracturing safer and more efficient.
Additive | Chemical Ingredient | Purpose | Common use of chemical ingredient |
|---|---|---|---|
Acid | Hydrochloric acid or muriatic Acid | Helps dissolve minerals and initiate cracks in rocks | Swimming pool chemical and cleaner |
Antibacterial agent | Glutaralhehyde | Eliminates bacteria in water that produces corrosive by-products | Disinfectant; sterilizer for medical and dental equipment |
Breaker | Ammonium persulfate | Allows a delayed breakdown of the gel | Used in hair colouring, as a disinfectant, and in the manufacturing of common household plastics |
Corrosion inhibitor | Formamide | Prevents corrosion of the well casing | Used in pharmaceuticals, acrylic fibres and plastics |
Crosslinker | Borate salts | Maintains fluid viscosity as temperatures increase | Used in laundry detergents, hand soaps and cosmetics |
Friction reducer | Petroleum distillate | “Slicks” the water to minimize friction | Used in cosmetics including hair, make-up, nail and skin products |
Gel | Guar gum or hydroxyethyl cellulose | Thickens the water in order to suspend the sand | Thickener used in cosmetics, baked goods, ice cream, toothpaste, sauces and salad dressings |
Iron Control | Citric acid | Prevents precipitation of metal oxides | Food additive; food and beverages; lemon juice ~ 7% citric acid |
Clay stabilizer | Potassium chloride | Creates a brine carrier fluid that prohibits fluid interaction with formation clays | Used in low-sodium table salt substitutes, medicines and IV fluids |
pH adjusting agent | Sodium or potassium carbonate | Maintains the effectiveness of other components, such as crosslinkers | Used in laundry detergents, soap, water softener and dishwasher detergents |
Proppant | Silica, quartz sand | Allows fractures to remain open so the gas can escape | Drinking water filtration, play sand, concrete and brick mortar |
Scale inhibitor | Ethylene glycol | Prevents scale deposits in pipe | Used in household cleansers, de-icer, paints and caulk |
Surfactant | Isopropanol | Used to reduce the surface tension of the fracturing fluids, to improve liquid recovery from the well after the frac | Used in glass cleaner, multi-surface cleansers, anti-perspirant, deodorants and hair colour |
Water | Water | Used to expand the fracture and deliver proppant (sand) | Landscaping, manufacturing |
From drilling to production – step by step
At Imperial, we use our experience and technologies to responsibly develop natural gas resources to meet the needs of consumers. Let's walk through how natural gas is found, drilled and produced.
1. Finding the resource, preparing to drill: Before a well can be drilled, we carry out exploration activities to locate a place to drill. We study seismic data and run computer simulations to assess underground formations and select the best location to drill. We gather information on all applicable laws, permits and regulations, and develop project plans to ensure safe and environmentally responsible operations. We also share information about our project plans with community groups to identify concerns. Once we have met these requirements, we are ready to drill.
2. Drilling the well: The first step is to set up the rig and to start drilling in stages, adding new sections of drill pipe as the hole gets deeper. As we drill the well, we install protective steel casing that maintains the integrity of the well and protects the surrounding formations, including any groundwater aquifers. Once the casing is installed and cemented, we drill down until the well reaches the gas formation.
In many unconventional wells, the drill bit is turned to drill horizontally through the gas-bearing rock. A layer of production casing is cemented into place to ensure integrity between the target rock formation and the wellbore.
3. Completing the well: Once the drilling has reached the reservoir, and we are confident there are sufficient quantities of natural gas, the next step is to complete the well for production. We install the proper equipment to ensure an efficient flow of natural gas out of the well and up to the surface. Production tubing is placed inside the casing and connected to the wellhead, a device containing valves to control production rates. Natural gas can then be produced through the tubing up the well.
In the case of conventional gas fields, the natural pressure of the reservoir is usually enough for the gas to flow through the wellbore to the surface. However, additional stimulation is required for unconventional gas reservoirs. To complete these wells, we pump hydraulic fracturing fluid into the reservoir at high pressure to create a series of tiny cracks in the rock formation and enable the gas to be recovered.
4. Producing the well: Once the well is completed and the natural gas is flowing, the gas is ready to be moved from the wellhead by pipeline to a treatment plant.
From the wellhead to consumer
At the treatment facility, the gas is processed to meet market specifications (liquids and gases are separated, impurities are removed). These facilities are typically located in industrial areas and are not found in residential or agricultural areas where the wellhead may be.
After treatment, the gas is ready to be transported from the producing areas. Pipelines are the safest and least expensive way to transport natural gas. About 95 percent of Canada's natural gas is transported by transmission pipelines that move the gas from one region to the other. To keep the gas flowing throughout the pipeline, the gas is periodically compressed at different stages along the pipeline until it reaches distribution pipeline systems, usually located in large urban centres. The pressure is then reduced and the gas is ready to be delivered to residential, commercial and industrial customers.