Hydraulic fracturing – fracking – is a technique used with directional drilling that lets us tap deeply buried oil and gas formations.
While it’s more expensive than conventional well drilling, today’s high energy prices make it profitable. Fracking has made the United States a net oil exporter for the first time in over 60 years and is being considered in other parts of the world. However, the long-term impacts and risks of this new technology have been studied yet.
When the remains of plants and animals get trapped in sediments and buried over long spans of time, they can form petroleum – a mineral made of hydrogen and carbon that exists as a liquid, solid or gas.
Bitumen, also known as tar or natural asphalt, is the semi-solid form. As liquid oil or natural gas, petroleum collects in reservoirs as a conventional oil and/or gas field or as an unconventional regional accumulation.
Here’s how a conventional field forms. Note the clear line between the oil or gas (green or red) and water (blue).
Shale gas is what the United States Geological Survey calls (PDF) a continuous or unconventional gas accumulation. It, as well as oil, is sometimes found in shale, a sedimentary rock. There is no obvious cap rock with this regional accumulation, and no clear-cut border with water.
The wells in the above diagram show how oil and gas drilling has been done – through a vertical well bore – ever since the days of Edwin Drake and others back in the 19th century.
No one in the US thought much about reaching all that unconventional gas until the country’s natural gas production began to decline in the 1970s. Today everybody has to think about it – those vertical wells produce on average about a third of what they did 40 years ago.
Basically, computers, GPS and other technological advances have allowed well bore drilling at angles, even horizontally.
Once the well is drilled, a liquid – generally water – is mixed with chemicals and sand and then injected under high pressure (see the two videos below for more details).
This makes tiny fractures in the rock along which gas, petroleum and the leftover liquid migrate through rock pores into the well. Pressure is then removed so the hydrocarbons will flow to the surface, and small grains of sand or aluminum oxide are injected to keep the fractures open.
Pros and cons of fracking
Hydraulic fracturing is most widespread in the United States, which has sizable shale deposits. However, the procedure is new. Long-term studies of its social and environmental impacts don’t exist yet, and the regulatory environment is also developing.
In such a high-tech, high-stakes matter, I think pictures speak better than words to convey the pros and cons of fracking.
The following two YouTube videos are by no means representative of all the issues raised by fracking, but they both impress this amateur as nice presentations of the two major sides of the ongoing fracking discussion in the US.
These include the industrial point of view:
and the environmental viewpoint:
An International Debate
Fracking is here to stay in the US, but other nations still have bountiful but untapped oil and gas shale deposits.
Political considerations may make Europe less willing to depend on energy imports from Russia, though there are technological and political hurdles to overcome there. China is believed to have even more unconventional gas reserves than the United States, but the geology is more difficult to work in and water resources in some regions are limited.
Hydraulic fracturing is expensive, but high oil and gas prices have made it a realistic option for a hydrocarbon-hungry world. Is it dangerous? The jury is still out on that.
The United States, at any rate, has moved far beyond its 1970s energy crunch. Every day more US wells are drilled and more information is collected that ultimately will tell the world whether fracking is overall beneficial, harmful or (most likely) somewhere in between.
- Natural Gas Production in the United States. (PDF) United States Geological Survey
- What is shale gas and why is it important? US Energy Information Administration
- US oil production hits 15-year high. Zack Colman, The Hill, December 4, 2012