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Canadian Natural Gas Unconventional Gas and Reservoir Stimulation Technologies

Unconventional Gas and Reservoir Stimulation Technologies nn






Natural gas from unconventional sources is an important engine of growth and employment for Canada’s natural gas production industry. New technologies – enhancing the capabilities of time-tested gas production methods – have unlocked the vast potential of natural gas from unconventional sources that were previously not economically viable for development. According to a 2010 estimate by the Canadian Society for Unconventional Gas, Canada has a marketable natural gas resource base between 700 -1300 Trillion cubic feet (Tcf), enough to support current production levels for over 100 years. Stringent and long-standing regulations govern natural gas development in Canada. The gas industry complies with these regulations to ensure development of the resource is conducted in a sustainable manner respecting human health and environmental integrity. Canadian jurisdictions also regulate the interface between water and the natural gas industry, and the application of evolving hydraulic fracturing techniques for unconventional gas development is no exception. These regulations are set and administered by a number of ministries, including environment, natural resources, sustainable development, energy, and others. In addition, major producing jurisdictions have oil and gas regulatory entities. Industry continues to work with regulators and policymakers to ensure development is conducted in a responsible manner.


What is Unconventional Gas? The term “unconventional gas� refers to the types of reservoirs where the gas is found, and in some cases the mechanism of storage in an underground reservoir. The three most common types of unconventional natural gas are:


Shale Gas, found in extremely fine-grained, essentially impermeable sedimentary rocks requiring complex reservoir stimulation to help the natural gas flow.

Tight Gas, found in the pore space of sedimentary rocks that have very low permeability. Reservoir stimulation is required to recover tight gas resources.

Coal Bed Methane (CBM) is formed during the process of coalification. In this process, methane is generated and trapped as peat turns into lignite and later, into coal. In coal seams, methane is primarily stored by adsorption to solid hydrocarbon molecules. A range of

reservoir stimulation methods are used to recover the resource.

The traditional way to produce conventional natural gas is by drilling a well that taps into rocks in the subsurface, where gas is stored under compression in the pores of permeable rock. This gas is easily produced. However, natural gas also occurs in abundance in less permeable geological formations, where the gas is trapped much more tightly within the rock. These widespread gas fields are found in several regions in Canada and form the basis for the country’s unconventional gas industry.

A Wellspring of Innovation Releasing the gas from these formations is the goal of unconventional gas production. Central to the matter is the fact that natural gas resources are not limited to a single type of rock formation. Geological characteristics and rock types vary, resulting in unique 3

characteristics at different locations. Each location requires site-specific techniques to extract the resource, and each gas well requires careful analysis to match the well’s parameters with the methods used.

With the underground target in mind, each surface location must be surveyed and assessed with care at every stage of exploration and development. Through full evaluation, engineers and scientists are able to determine the most suitable well drilling techniques. The terrain, environment, water resource, and built structures 3

of the surrounding area are evaluated. Then, moving deep underground, the rock types and distribution, and subsurface structures are studied. With so many factors at play, there are dozens of combinations of inherent conditions and operator choices to design a well. It is often necessary to employ reservoir stimulation techniques, often referred to as fracturing or “fracing,� where the rock holding the natural gas is cracked, much like safety glass being shattered. By using a combination of techniques customized for each well that may include horizontal drilling and multistage reservoir stimulations, natural gas producers can access natural gas found in a variety of challenging geological formations.

Drilling Advances in horizontal drilling capability in recent years (including specialized rigs, drilling bits, and bit steering technology) have extended the lateral reach of horizontal wells and broadened the scope of application of horizontal drilling. The turning radius from the vertical wellbore to the horizontal leg continues to be a constraint at shallow depths, 4

generally limiting use of this drilling technique to deeper reservoirs. Horizontal wells also have environmental benefits. For unconventional gas reservoirs which require many closely spaced wells, the use of horizontal drilling reduces surface disturbance since

many wells can be drilled from a single surface location (a multi-well pad). Multi-well pads offer a significantly smaller footprint than multiple vertical well pads, roads, pipelines, and surface facilities, and a corresponding reduction in habitat fragmentation.


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monitoring is employed to detect extremely small ground movements deep in the subsurface, identifying the orientation and complexity of fracturing generated by the operation. Importantly, the technique also identifies both the lateral and vertical extent of the induced fracturing. When applied during hydraulic fracturing operations, microseismic monitoring allows modelling to optimize the orientation and spacing of future wells, and the optimal number and spacing of hydraulic fracturing stages in the horizontal well. Detailed production testing enables identification of areas where the rock was successfully fractured and areas where fracturing was inadequate or where hydraulic fracturing fluid did not flow back to the well, remaining in the reservoir and inhibiting production. In some places and for some resources unconventional gas development can require


large quantities of water. In all situations Canadian regulators and the natural gas industry are focused on the protection of surface and groundwater and the mitigation of risk. All Canadian jurisdictions regulate the interface between water and the natural gas industry, and the application of evolving hydraulic fracturing techniques for unconventional gas development is no exception. These regulations are set and administered by a number of government ministries, including environment, natural resources, sustainable development, energy, and others. In addition, major producing jurisdictions have oil and gas regulatory entities – either provincial boards or the federal National Energy Board. In some reservoirs fracturing is the most water-intense activity associated with natural gas production. There is a very wide range in the volume of water used for hydraulic fracturing operations, a function

of the geology and reservoir characteristics. In many regions a typical fracturing operation in a deep horizontal shale gas well might use between 3500 m3 to 15000 m3 of water to enhance the recovery of the gas. In other areas fracturing operations may use several times this water volume, and elsewhere fracturing operations may use gases or other liquids, and no water at all. The hydraulic fracturing operation typically takes place only once per fractured well, at the beginning of the well operation. Most wells then produce for 20 to 30 years without requiring any further fracturing and related water use. In recognition of the intensity of water use in some regions, natural gas producers are considering (and in some cases implementing) methods such as water recycling techniques, or fracturing with non-potable brackish water to offset increased demand for water and to reduce impacts on surface water and aquifers.

Photo courtesy of Calfrac Well Services Ltd.

Multistage Hydraulic Fracturing Operation Underway In some shale development areas the length of horizontal laterals and the number of fracturing stages is increasing. This has the effect of increasing the amount of water used 100% to fracture each well, but is offset by 3% 3% 4% 4% capturing a greater volume of the resource with each well and ultimately90%reducing the number of wells and 14% 13% 16% 18% well pads that would otherwise be required. 80% Canadian Electricity Generation Portfolio - 1990 to 2007




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Production Operations at a Multi-Well Padt

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16% 2%

15% 4%

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Natural Gas

Photo Courtesy of Trident Exploration Corp. 7

Common Fracturing Techniques Name


Pros and Cons

Frac-Through-Coil (FTC)

Steel coiled tubing is fed into the wellhead from a specialized unit. At the bottom of the coiled tubing, a set of tools isolates the targeted zone from the rest of the well and allows the slurry to be placed into the targeted zone. The operator on surface raises and lowers the coiled tubing as needed, usually working from the bottom of the well and moving upwards.

• Coiled tubing units can stimulate multiple isolated zones • There is a decrease of time on location, and a smaller footprint in comparison to larger fracs that require more equipment • Requires fewer employees to operate • Pumping rate is limited due to friction, total reach (length) of coil is highly variable reflecting local conditions • Increased equipment costs

Abrasive Jet Multi Stage Fracturing

A unique coiled tubing approach that combines isolation and perforating into one tool.

• Combines many technologies to speed up completion of the well and to reduce costs • It also reduces the amount of services needed for the well which decreases the environmental impact around the wellhead • Patent limitations and licensing costs • Limited pumping rates due to coiled tubing and pipe configurations • High utilization of coiled tubing and associated costs

This coiled tubing-deployed bottom hole assembly (BHA) incorporates an abrasive jet perforating nozzle and an isolation technique - multi-setting bridge plugs or sand plugs.

Multi-Stage Packers

Isolates specific zones for treatment. After the first zone is treated, a ball/dart is launched into the well, pushed by the frac fluid. This object seats on a frac port to both isolate the first zone and open the second zone, this process is repeated on each zone. Once all zones have been fraced, the balls are milled out to open the ports for production.

• The use of this treatment allows for multiple zones to be treated, with specialized programs for each zone • Initial cost for isolation packers is high, if issues occur while placing tools some, or all, of the well may be lost • Post treatment milling of balls and packers is costly and time consuming • Balls and darts can get caught and zones may be lost, unable to properly complete the well • Delay from stimulation to milling can locally damage the reservoir making production difficult

Plug and Perf

The deepest set of perforations in a well are stimulated, then a bridge plug is set to isolate the zone. A second set of perforations can then be introduced and fractured. The bridge plugs are removed when all fracturing is complete.

• The process can repeat itself for as many times as needed to cover the zone of interest • This process is slow and multiple services are needed sequentially to ensure smooth operation • Long standing history of process • Workable distance from wellhead is limited • Increased delay from stimulation to production may reduce well productivity

Acidizing (typically with a diluted solution of hydrochloric acid) is used as a fracture treatment, pre-treatment prior to a fracture and/or as general maintenance measure to clean a wellbore.

• In many fracturing operations a relatively small volume of acid is pumped ahead of the frac slurry as a ‘spearhead’ to improve communication with the formation prior to the fracture • Longstanding common practice • Reduces pressure required to fracture the formation, and increases production by removing scale deposits

Chemical Treatments

Acid treatments


Gas Treatments

High Rate Nitrogen

Nitrogen gas is pumped into a formation at high rates and pressures. Used for shallow application, typically coalbed methane (CBM). Occasionally a small amount of sand proppant is added to the nitrogen, in essence creating a high-powered sand blast. Nitrogen is commonly used as an energy source additive for fracturing fluids.

• Opens cleats, or natural fractures, in the coal and removes damaged areas in order for natural gas to flow more easily into the well • No fluids are added to this system; therefore no added chemicals are introduced into the formation • High Rate Nitrogen is limited in its ability to stimulate • Energy is unable to transfer very far from the near wellbore area

Liquid CO2

Pure liquid Carbon Dioxide (CO2) is pumped into the wellbore.

• No added chemicals are required • Most Liquid CO2 fracture treatments are done for research and development because CO2 is considered to be a low-damaging fluid in terms of its impact on the rock • Liquid CO2 is limited in its ability to suspend a proppant and has limited potential for commercial natural gas production

Commonly used as an energy source additive for fracturing fluids (shake a pop can).

Liquids & Proppants The slurries (fluids) used in unconventional natural gas extraction are mixes of liquids and proppants. For hydraulic fracturing operations the objective is to have a liquid suspension of proppant that can be pumped at high pressure into the well bore. The liquid is usually then thinned so that it can be recovered from the well, while leaving behind the proppant to increase the permeability of the rock. Once the treatment is complete and the well is pumped out, all fluid is collected and taken to a processing plant. No fluid is left behind on location; it is all carried away and processed, recycled or properly disposed of.

Fluids Water is the basis for most hydraulic fracturing. Water sources may include recycled fracturing fluids, produced water from other oilfield operations, or brackish (salty) water that is drawn from below the water table, but the most common source today is surface fresh water. Water may be pumped as a mixture with methanol for water-sensitive rocks. Recently there has been a huge increase in the use of recycled fracturing fluids in North America, with many “slickwater fracs” re-using the flowback water from a previous treatment many times over. Fracturing oil is another fracturing fluid that is being re-used. Frac oils are either recycled for re-use or sold as production oil. In the past diesel has been used but it is very uncommon, and is prohibited in some jurisdictions. New technology has introduced the safe and regulated use of liquid propane as a fluid medium instead of water or frac oil.

Additives To enhance the performance of the fracturing operation various additives can be blended with the fracturing fluid. 9




Gellants or gelling agents: increase viscosity, proppant suspension and provide lubrication. Guar Gum (most common gellant in use)


Guar bean, grown in India and Pakistan. Used as a food Creates a natural polymer chain. Can be refined muladditive. tiple times to improve its qualities such as methanol tolerance, decreased hydration time, and increased viscosity.

Chemically produced long-chain molecule, known as a polymer. Commonly used in water treatment as a flocculent, or for products such as soft contact lenses.

Used to make water slippery for slickwater fracturing.

Naturally occurring elements, mined at various locations.

Increases the viscosity of the liquid by linking the polymers.

Potash, used in the preparation of many types of fertilizer. Potassium chloride is used occasionally as a table salt substitute.

Reduces damage to reservoirs by inhibiting the reaction of certain clay minerals with water.

Crosslinkers : used in small quantities to join polymers in a three-dimensional shape. Boron, zirconium, titanium, or iron Clay Control: used in water sensitive formations to prevent clays from swelling. Potassium Chloride

Breakers: Breaks the polymer chain created by the gelling agent. Oxidizers

Manufactured substances that release oxygen

Reduces viscosity of polymers and allows the fluid to flow back to surface


A naturally occurring agricultural by-product

Consumes Guar Gum polymers.

Surfactants: lower the surface tension on the fracturing fluid. Flow back additives

Akin to soap, these additives enhance the ability of water to flow back to surface following treatment.

Allows easier flow back of the fluid after the treatment is complete.

Can be derived from bacteria or plants, or prepared from chemicals. Biocides are used in pesticides, antibacterial cleaners. Many companies are evaluating alternatives including ultraviolet light.

Prevents introduction of bacteria that can produce highly toxic hydrogen sulphide (H2S), corrosive acids, or fouling chemicals or precipitates in the reservoir.

Biocides: Prevent the introduction of sulphate reducing and other bacteria into wells Natural and manufactured biocides

Used in small quantities. Energizers: gases used to energize (or foam) fluids for fracturing treatments.


Carbon Dioxide (CO2)

Common element found in the atmosphere. Carbon Dioxide can exist as a liquid, gas or solid, (known as ‘dry ice’).

Odourless and non-toxic. Improves the recovery of fluid, while reducing the potential of formation damage. Carbon Dioxide is moderately soluble in water and highly soluble in oil, particularly under pressure.

Nitrogen (N2)

A naturally occurring element, nitrogen is stored, transported and pumped as a cryogenic liquid, then heated and injected into the wellbore as a gas.

Improves recovery of stimulation or well fluids.

Guar Beans – source of the most common additive.

Proppants Commonly-used proppants include sand, ceramic, or resincoated sands. Many different proppants have been used in the past, including walnut shells and glass beads.

A wide variety of proppants are available for modern hydraulic fracturing operations Sand is the most common proppant used in fracture treatments. Sand must meet industry specification (API) and is sourced both locally and imported from the United States. Ceramic proppants are a manufactured alternative to 11

sand. This type of proppant tends to be stronger and more crush resistant to stress than natural sand. Generally, these are manufactured from fired clay. Resin-coated sands are tacky, which reduces proppant flowback when the fluids are withdrawn from the wellbore. Resin coated proppants are usually pumped in small quantities at the end of jobs. A chemical activator is sometimes pumped with a resin-coated

proppant in order to activate the sticky qualities of the resin. Other resin-coated proppants do not require the use of an activator because they are temperature-sensitive and activated by the hotter temperature in the reservoir.

under pressure through the steel plumbing or production casing to push against the rock formations hundreds to thousands of meters below the surface of the ground. The pressure in both cases must be below the pressure rating of all of the plumbing it encounters and the fluid must withstand the rigors of the process it goes through.

through pipe. Why? Water likes to grab onto the plumbing and push back against the pumps. This friction causes the pump to work harder meaning the working pressures in the plumbing are higher and the amount of energy, horsepower, and fuel needed to do the work also goes up. In order to work at the long distances away from the surface the characteristics of water must be changed to allow safe and efficient work, and this is done with additives.

Hydraulic fluid in the tractor is commonly a type of oil that is a very good lubricant, being slippery and thick, and can hold these properties as it is cycled many times as the equipment is used. Hydraulic Fracture fluid is more commonly a water-based entity and water is not slippery or thick when compared to hydraulic oil. Slipperiness and thickness are the two features that are critical to the success of being able to push water

Water by itself cannot move sand or other proppants. It needs help from gravity and large volumes of water like in a flood to build up speed to be able to pick up rocks and material or particles and move them down a river. To make water a better transporter of particles at low flowing rates it is necessary to change its characteristics and make it thicker to better carry or hold up a particle.

How Fluids Work: A Closer Look When heavy equipment has actuating arms like the forks on a tractor for lifting bales of hay, these forks are moved by hydraulic fluid being pushed through hoses to cylinders to exert force and lift or lower the bales of hay. The fluid is placed under pressure by a pump and controlled by valves that allow the fluid to flow into or out of cylinders that extend or contract depending on the desired effect. The flow of the hydraulic fluid moves from an area of high pressure to an area of lower pressure as directed by the plumbing and the valves along the flow path. The pump must be able to exert more pressure into the fluid than the forces exerted by the metal frame and the bale of hay resisting the raising of the actuating arms. Hydraulic fracturing uses fluid in a similar way. Fluid is pushed 12

Guar flour, commonly used in many households for making gravy, has the attributes of making water both thick and slippery, and is added to water in hydraulic fracturing fluid. Only a few grams of the guar flour will thicken a litre of water and make it very slippery. The slipperiness allows the fluid to slide more easily through the rough steel pipe and the thicker fluid increases the water’s ability to carry particles, such as sand. Another important aspect is to maintain the stability and physical constitution of the rock and clay that holds the natural gas. To ensure that the clay materials do not react by pulling the water molecules onto themselves and swelling when the hydraulic fluid is pushed into the formation, geologists study the clay minerals that are present in the zone of interest. By using the additive potash or potassium salts in the water it is possible to inhibit clay-water reactions, allowing the water to move past the clay particle without any effect to the formation. The proppant or sand that is added to hydraulic fracturing fluid is designed to prevent the closure of the cracks created when the hydraulic fluid is 13

pushed into the rock. The spaces left are passages that are “propped” open and allow flow. So far three additives, guar flour, potassium salts, and proppant have been added to water to change its characteristics so it will easily carry sand or proppant through a steel plumbing system into a zone of interest without changing the formation’s chemistry. Now that there are cracks filled with proppant and fluid, the fluid must get out of the way to allow hydrocarbons to flow to the well otherwise it acts like glue and seals the propped space. Hundreds to thousands of meters below the surface the weight of the world is crushing down on the injected fluid and the fluid will just carry the proppant back out when the pumps release the pressure on the fluid. The hydraulic cylinder will reverse flow. The fluid needs to lose its ability to transport or carry proppant for the work, leaving the proppant in the cracks, to be successful. The increase in the carrying power of water was a result of the guar flour additive. Guar flour is simply a starch. Starches are sugars that many living organisms break down to produce energy. This breaking down of the sugar

chain changes the starch so that it loses many of its original characteristics including its ability to thicken water. Enzymes are naturally occurring and common, and break the sugar chains. Enzymes are found in most living organisms and are easily collected and used as an additive in hydraulic fracturing fluids. Once the enzyme breaker is added to the fracturing fluid it slowly breaks down the guar starch or guar gum. This reduces the thickness of the carrying fluid (breaks it) which results in a thinner fluid dropping and slipping away from the proppant. When this occurs only the water follows the steel production plumbing back to surface when the pump pressure is released. The breaker enzyme is fragile and it needs specific conditions to remain active. It needs food, the guar gum, and the environmental conditions to sustain it. Several hundred meters into the ground the conditions are very hostile and not suited to enzyme survival. As long as the enzyme can do its job and break down the thickness of the fluid prior to deteriorating its job is completed. To enhance fluid flow back to surface it is common practice to add soap or surfactant to the 14

fluid. Soap reduces the surface tension of water which lets the water slip out of the formation without forming water bridges or blocks across the propped openings. When a Fracturing Fluid contains additives to thicken, control clay swelling, breaking the fluid and a surfactant for better fluid recovery, it is very advantageous to add a gas. Using gas as an additive will reduce the amount or quantity of additives required by reducing the amount of water needed to transport proppant into the formation. Because the gas is under pressure it helps push the water back out of the formation treated. Much like a can of pop after being shaken up and opened, the gas expands as the pressure is released propelling the thinned water back to the surface to be collected. Adding gasses – or in the case of carbon dioxide a liquid – reduces the water-clay contact and further prevents the swelling of clays or formation damage to occur. Water comes in a variety of chemical compositions. Variations in water composition cause industry to work with different chemicals to counterbalance the issues caused by the water itself. The biggest concern is bacteria in

the water. In an environment that is warm and wet, sulphate reducing bacteria can multiply and quickly turn a “sweet” well, relatively pure for production purposes, into a sour gas well through the bacterial production of highly toxic hydrogen sulphide. Other types of bacteria can produce corrosive acids, slimes, and other undesirable compounds that plug up the reservoir. Bacteria must be controlled, and most municipalities in North America use chlorine in water treatment to kill bacteria. This is a highly regulated process and is constantly monitored by regulators. Using domestic water supplies from treatment plants for industrial purposes does occur, but where possible fracturing fluids will be generated from water sources close to where the work is being conducted. These sources are most often fresh water, but they also contain all the bacteria, algae, decaying organic matter, sediments and anything else that is present in the water body. To stay ahead of the biological growth that can quickly accumulate in a holding tank, it is prudent practice to add a biocide to the tank. These biocides are powerful but are limited in both quantity and effectiveness, and after 2-3 days many biocides are completely used up. Re-treatment can be

required if the water is not used in that time frame. As with any process, science and technology drive innovation quickly. In a few short years innovation results in new designs that result in better and easier tools to address human interests. Similarly the hydraulic fracturing industry has also pushed to advance technology and each service company works with scientists and chemical suppliers to develop leading-edge fluids to meet operator and public demands. Because of the intense competition between companies fluid systems are trade secrets. To summarize: Hydraulic Fracturing Fluids need to have unique characteristics so they can travel multiple kilometres from surface into the reservoir while retaining their core properties, and within a short time change back into water for the return multiple kilometre trip to surface. They commonly contain all or some combination of: Water, thickener and a friction reducer, clay swelling suppressant, breaker, water friction reducer/ bubble maker/ water reducing support entity, thickening and more clay control gas, bug and bacteria killer and commonly some sort of proppant, usually sand.

The Regulatory Environment Whatever the methods chosen for the production of natural gas, stringent and long standing regulations govern both conventional and unconventional natural gas development in Canada. The industry is committed to environmental responsibility, health and safety, and sustainability. Industry continues to work with regulators and policy makers to ensure that all development is conducted in an appropriate manner. In Canada when a company is transporting chemicals or goods from their base of operations to another location they are bound to follow regulations that govern these activities. The purpose 15

of the federal Transportation of Dangerous Goods (TDG) Act and related regulations is to promote and ensure public safety; and the Act and regulations apply to all persons who handle, offer for transport or transport dangerous goods by any means. These rules are enforced and monitored by inspectors

and have monetary and confinement penalties associated with them. These penalties are applicable to all persons responsible for the violation of these regulations. According to the regulations all persons who handle and or transport goods must be trained and certified, and that certification must be renewed every three years.

Each person who takes the training is issued a copy of the regulations and is expected to retain the documentation as they go on with their duties. The TDG regulations are complimented by the nationwide communication system, WHMIS (Workplace Hazardous Materials Information System) which supports the safe use, handling and storage of products in a workplace. All employers are required to develop and implement an education program for all workers who work with, produce or are near products. They must also support the program so employees can apply the information supplied from MSDS (Material Safety Data Sheets) and Supplier

and Workplace labels to ensure the safe use, handling, storage and disposal of these products. MSDS documents provide information on potential hazards, safe handling, transportation, storage, and emergency procedures related to the potential hazards of a substance. MSDS documents also identify what the appropriate response should be if a handling accident occurs, how to recognize symptoms of overexposure, and what to do if such an incident happens. All additives that are used in Hydraulic Fracturing fall under these regulations and are strictly adhered to at all times. All staff and management for all of the service companies are aware of the regulations and are mandated to follow the rules set out by the federal

government. In addition to these regulations the Government of Canada plays a key role in protecting human health and the environment from the risks of chemical substances under a number of laws. Under the Canadian Environmental Protection Act, 1999 (CEPA 1999), for instance, scientists at Health Canada and Environment Canada assess chemical substances to determine if they pose a risk to human health and/or the environment. The Government of Canada develops regulations and other risk management measures based on the findings of these assessments. Two key programs by which the Government of Canada manages substances are the

Chemicals Management Plan and the New Substances Program. Substances for use in the oil and gas industry (e.g., lubricants, drilling fluids, corrosion inhibitors, surfactants, fracturing fluid additives, desulfurization agents, and bacteria control agents) are subject to these two programs. The CEPA 1999 provides for the regulations that are an integral part of the federal government’s national pollution prevention strategy. These regulations become a complete management approach for toxic substances and were created to ensure that no new substances, including chemicals and polymers, are introduced before an assessment of whether they are potentially toxic has been completed, and any appropriate or required control measures have been taken. More details on the programs and information on the regulations, research and decisions that must be adhered to by all industries, including then oil and gas industry, can be found on various Government of Canada websites: Transportation of Dangerous Goods Workplace Hazardous Materials Information System Chemicals Management Plan: New Substances Program:


Appendix Endnotes 1.


Hexion Speciality Chemicals. “Fracturing Proppants”. aspx?id=629 (Accessed January 27, 2010).

Canadian Natural Gas is a made-in-Canada advocacy project sponsored by the following associations:

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Please recycle. © 2011 Canadian Natural Gas.

Unconventional Gas and Reservoir Stimulation Technologies