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Chapter 3

Hydraulic Fracturing

Oil &  gas drilling began in the San Juan Basin in the early 1920s, and really took off in the 1950s after a newly built pipeline to California allowed for easy export

Fracking Then and Now

If you ask a veteran oil & gas worker in the San Juan Basin about fracking, they are likely to say something like “Fracking? We’ve been fracking here for 60 years!”.

And it’s true: practices that we typically associate with fracking, like directional drilling and the injection of fluids into a well, have been part of “conventional” oil & gas extraction processes in the San Juan Basin since as early as the 1930s.

So what’s the big deal about fracking today?

Innovations in drilling technology – especially horizontal drilling – have made accessible deposits of hydrocarbons that couldn’t previously be extracted. Let’s review some basic geology of hydrocarbon formations.

The marine sedimentary rocks where oil & gas come from are called “source rocks”. Over time, both oil & gas tend to migrate and accumulate in the “reservoir rock”, a more permeable and porous formation like sandstone or limestone. “Conventional” oil & gas extraction targets the reservoir rock, there is some space (pores) in the reservoir rock for oil & gas to travel through the formation and up the well.

This simplified diagram shows the difference between a source and reservoir rock. Note that while the oil & gas appear to sit in “pool” in this photo, in reality small hydrocarbon molecules are embedded within the rocks.

High-Volume Hydraulic Fracturing

What is popularly called “fracking” today is known in technical terms as “high-volume hydraulic fracturing”. One major difference between “conventional” oil & gas drilling and fracking, is that fracking can reach and unlock hydrocarbons that have remained trapped within the “source” rock, such as shale formations. This is the case in the San Juan Basin, where companies have recently begun fracking the Mancos shale.

How exactly does fracking work?

  • A drilling location is prepared in a similar way as it is for “conventional” oil & gas drilling.
  • The well is first drilled vertically thousands of feet deep into the shale formation (approximately 6,000, but this varies by formation). The pipe is cased and cemented.
  • The wellbore then makes a vertical turn and drills horizontally for several thousand more feet.
  • The pipe casing is perforated.
  • Then, a very large quantity of fluid (a mixture of of water, sand, and chemicals – averaging 5 million gallons per frack job) is sent down the well at high pressures. The fluid flows through the small perforations in the casing and cracks, or fractures, the shale formation.
  • The sand contained in the fluid helps to hold the cracks open.
  • The fluid then flows back up through the well to storage tanks, and is then taken for disposal (underground injection) or treatment.
  • Now that the fracking job has been completed, natural gas or oil can flow through the cracks and up the well.


The answer is more complicated than it should be.

In short, fracking fluid is a combination of water, sand, and chemicals. Industry reports that chemicals make up only 1% of fracking fluids. It’s important to keep the 1% additives number in perspective: if the average fracking job uses 5 million gallons of fluid, then that’s about 50,000 gallons of chemicals per well.

As explained in this report, fracking fluids are exempt from regulation under the Safe Drinking Water Act and several other federal environmental statutes. Though laws vary state by state, generally speaking companies are not required to disclose what chemicals they use in fracking – the specific chemical mixture is considered a trade secret.

FracFocus, a collaboration between the Interstate Oil and Gas Compact Commission and the Groundwater Protection Council, is an online voluntary chemical disclosure registry where companies can choose – or in some states may be required – to report the chemicals used in fracking operations.

Many of the chemicals known to be used in fracking processes can cause serious human health impacts. (See this article in High Country News to learn about a now infamous incident of severe health impacts caused by exposure to fracking chemicals right here in Durango).  For more information, see this fact sheet compiled by The Endrocrine Disruption Exchange on chemicals used in fracking operations.

“Evaluating the relative volumes of the components of a fracturing fluid reveals the relatively small volume of additives that are present. The additives depicted on the right side of the pie chart represent less than 0.8% of the total fluid volume. Overall the concentration of additives in most slickwater fracturing fluids is a relatively consistent 0.5% to 2% with water making up 98% to 99.2%.”


Additional Resources

To take a virtual tour of a fracking operation, check out the FrackTracker Alliance website.

Did you know that fracking is currently exempt from regulation under several important environmental policies? Read OGAP’s report on fracking loopholes.

Fracking by the Numbers: Key Impacts of Dirty Drilling at the State and National Level (Environment America)

Read the Next Chapter in the SJCA Guide to

Oil & Gas in the San Juan Basin

Up Next….

Split Estate

Can minerals underground by owned by someone different than the land above ground?

Chapter 5

Local History

Oil & gas in the San Juan Basin.

Chapter 6

Just Transition

Renewables in the San Juan Basin.

Chapter 1

Oil & Gas Extraction

Drilling for oil & gas is a complex process that requires lots of equipment, infrastructure, people, and expertise.

Chapter 2

Coal Bed Methane

Find out how coal bed methane extraction is different from oil and gas extraction.