Hydraulic Fracturing Explained
Proppant: Usually sand or ceramics
Hydraulic fracturing is a safe, proven and government-regulated technology that has been used in Canada for more than 60 years. In hydraulic fracturing, fluids are injected at pressures that exceed the natural stresses on the rock and cause it to crack, or fracture. Creating these fractures in hydrocarbon-bearing rock layers deep underground is not enough to allow oil and gas to flow into the wellbore.
Once the fractured reservoir rock is held open with fluid pressure, proppant, usually sand or ceramics, is introduced into the fluid to prop open the fractures. After the hydraulic fracturing process, the fracturing fluids are recovered and the fractures remain held open by proppant. The hydrocarbons trapped inside the rocks can now flow more easily through the cracks to the wellbore.
Watch these videos to see how hydraulic fracturing works:
- Video #1: Hydraulic Fracturing: How It Works (Imperial Oil)
- Video #2: Digging Deeper (CAPP)
- Video #3: Understanding Hydraulic Fracturing Operations (Canadian Society for Unconventional Resources)
- Video #4: Interactive video (Halliburton)
Areas of Activity
Hydraulic fracturing is most often used where oil and gas are trapped in “unconventional” source rocks, such as shale. This map shows shale gas basins in Canada and the US.
Need for Hydraulic Fracturing
The oil and gas industry in Canada was founded upon production of oil and natural gas from ‘conventional’ reservoirs, because they are the easiest to get out of the ground. However, as this graphic shows, conventional reservoirs are the smallest portion of Canada’s total oil and gas resources. Ironically, what are referred to as ‘unconventional’ reservoirs contain a far greater proportion of Canada’s hydrocarbon resources. The terms ‘conventional’ and ‘unconventional’ actually refer to the reservoir rock quality because oil and gas cannot be distinguished.
(md or milliDarcy is the measure of how freely hydrocarbons flow through rock.)
Industry needs to develop unconventional resources, such as tight oil, tight gas and shale gas, in order to have a continued supply of oil and gas now and into the future. Unconventional gas already accounts for more than 25% of the Canadian natural gas supply. Most of the activity directed at new production in Canada is unconventional so it is fair to say that unconventional has become conventional.
Oil and gas reservoirs aren’t really just conventional or unconventional. It’s more of a sliding scale between the two types. The illustration shows a rough categorization of various rock types. Where they fit on the sliding scale is all about permeability.
The Canadian Society for Unconventional Resources (CSUR) explains the link between permeability and hydraulic fracturing:
Permeability: the pathways between the pores in rock
“Most sedimentary rocks have the ability to store natural gas or oil in the small pores or spaces within the rock. However, the ability for these hydrocarbons to flow out of these reservoir rocks is controlled by the connectivity, or pathways, that link the pore spaces. In reservoirs with low permeability [such as shale or tight gas reservoirs], the connectivity of the existing pore spaces within the rock is not sufficient enough for the gas or oil to flow through the rock to the wellbore.
As a result, some type of reservoir stimulation is required. The purpose of hydraulic fracturing is to connect existing pathways within the reservoir to enable the oil or gas to flow more easily from the formation to the wellbore.”
How Hydraulic Fracturing Works
Hydraulic fracturing is only one of several steps in the development of a productive oil or gas well. Any oil or gas well represents a significant investment and therefore requires considerable technical design, planning and regulatory approvals before any visible work commences.
The first major activity at a well site is drilling. The term ‘drilling’ is often used as a catch-all word for all the activities that end up as ‘well construction’. This includes drilling, geophysical measurements (‘logging’), casing and cementing.
In simple terms, first, a wellbore is drilled to allow steel pipe to be sunk deep into the ground below the deepest potable groundwater. This pipe, known as the surface casing, is surrounded with cement in the bore hole to ensure that anything inside the pipe cannot contact any of the geological formations outside the pipe.
Graphic: Trican Well Service
Once the surface casing is set and tested, the remainder of the well can be drilled. Again, once the well reaches total depth, geophysical measurements are made (logging), and a casing pipe is lowered into the well and it too is cemented. The figure above shows an example where an intermediate casing has also been included. Geological conditions may make this necessary.
Well construction is now complete: the wellbore is drilled, cased and cemented. This seals and isolates all fresh water zones from the oil and gas zones, and isolates the oil and gas zones from each other.
Next, near the total depth of the well, known as the ‘toe’, often two to three kilometres below the surface, the production casing is perforated to allow access to the formation. Then hydraulic fracturing fluid is pumped into isolated sections or stages in the wellbore to create enough pressure to crack, or fracture the rock layer. The well will be fractured in many segments (stages) working back toward the vertical portion of the well (known as the ‘heel’). All this activity is monitored from the surface by monitoring pumping pressures, pumping rates and fluid properties and comparing these to expected values. Micro seismic monitoring may be used as an indirect measurement of what is occurring.
60 Years of Hydraulic Fracturing
Hydraulic fracturing is not a new process. In fact, hydraulic fracturing was first done in the US in 1949 and brought to Canada in the 1950s. Hydraulic fracturing was a key technology in the successful development of the Pembina Cardium field near Drayton Valley, where Canada’s first fracture treatment was performed several months before television arrived in Alberta.
Like television, the science and technology of hydraulic fracturing has evolved over the past six decades, and hydraulic fracturing has become ever more sophisticated and safe. For example, hydraulic fracturing is now often combined with horizontal drilling to access larger sections of the reservoir, making them commercially viable to produce.
Today, between Alberta and BC over 175,000 wells have been stimulated using hydraulic fracturing.
Hydraulic Fracturing Companies
Hydraulic fracturing is a highly complex and technological process, conducted only by people and companies with the expertise to do it right. In Canada, the main companies involved in hydraulic fracturing are also the Founding Members of the Working Energy Commitment.
For more information on hydraulic fracturing in Canada, visit:
- Chemical Disclosure Registry (FracFocus)
- Hydraulic Fracturing (CSUR)
- Hydraulic Fracturing (Canadian Association of Petroleum Producers – CAPP)
- Shale Gas Key Facts (Natural Resources Canada)
- Unconventional Resource Development and Hydraulic Fracturing (CSUR)
- Understanding Canadian Shale Gas (National Energy Board)
- What is hydraulic fracturing? (Alberta Energy Regulators)