Main Page Marcellus Shale Hydraulic Fracturing, Fracing Or Fracking Process
Trucks Preparing For a Frac Job In The Marcellus Shale
What Is A Frac Job As Used In The Marcellus Formation?
Possibly the most controversial element of drilling for natural gas in the Marcellus shale is the use of a frac job, also known as fracking or hydraulic fracturing. In this process large pumps are hooked up to the newly drilled well and thousands of gallons of water, sand and a small percentage of chemicals are pumped into the shale formation several thousand feet below the surface to break apart the hard rock, creating fissures from which the shale gas is released. The fact that thousands of gallons of fresh water must be obtained from somewhere is reason enough for controversy.
In addition to the need for large quantities of water a frack job, fracing or fracking a well, (however you choose to spell it) is still controversial. In rare cases, when proper cementing procedures are not followed, frac fluid, which is a mixture of water and chemicals such as acids, can migrate or be forced into groundwater. In most situations, the groundwater lies from zero to one thousand feet deep, while the natural gas bearing formation lies at several thousand feet. See the map showing the depth of the Marcellus shale below. There are many layers of solid rock between the two zones and no way that a properly cemented well that on which a frac job is applied, could endanger groundwater supplies. The map below shows the depth of the Marcellus Shale, up to 9000 feet in Pennsylvania.
Stories of contaminated groundwater are rarely attributable to a frac job as the cause. The subject has caused a lot of controversy lately, and environmentalists are seeking to stop much of the drilling in the Marcellus shale on the grounds that groundwater could be polluted. Legislation is in the process that could prevent hydraulic fracturing throughout much of the area where the Marcellus shale lies. This would ultimately have the effect of reducing the amount of domestic natural gas available, and forcing us to rely on imported oil to fuel homes and power plants in the region.
Sound Science And Level Heads Should Prevail
Sound science needs to be used to determine if there are any zones that need to be avoided due to potential groundwater contamination, however due to the great depth of the Marcellus formation it is evident that groundwater contamination will not occur if wells are properly cemented and tested prior to the process of hydraulic fracturing. Hydraulic fracturing has been in use in the United States now for many years, without a major incident. The process of fracing or fracking has been used safely in the Barnett shale near Dallas, (which is similar in depth to the Marcellus shale) for over a decade, with no groundwater contamination issues. In fact there has never been a verifiable case of groundwater contamination as a result of hydraulic fracturing in the sixty years that the process has been done.
What Concerns Environmentalists
One thing about fracing or hydraulic fracturing that concerns environmentalists are the type of chemicals used in a frac job. Chemicals reported by the EPA to have been used legally in the past include Benzene, Phenanthrenes, Naphthalene, 1-methylnapthalene, 2-methylnapthalene, Fluorenes, Aromatics, Ethylene glycol, Methanol and Diesel. Safer frac fluid additives are now used in Marcellus shale wells. It is important to note that that many of these chemicals already exist naturally in the oil and gas bearing rock. Additives make up less than one half of one percent of frac fluid. Many of these additives such as citric acid, are ingredients in household products, foods and cosmetics. You can find a list here of those additives that Chesapeake Energy uses in a Marcellus shale frac job: Frac Job Fluid Ingredients Used In Marcellus Shale Wells . As much as seventy percent of the fluid from a frac job stays in the ground. What is recovered on the surface, the flowback water, as it is called, must be de-contaminated before it is returned to lakes or rivers or is pumped into deep disposal wells.
While the safety of groundwater is a legitimate concern, it is important to realize that the Marcellus shale, which lies several thousand feet below groundwater in most areas, contains it's own soup of naturally occurring petrochemicals in addition to natural gas. These, for millions of years have posed no danger to groundwater. A frac job in the Marcellus shale is isolated by impenetrable layers of many different kinds of rock. Shale, sandstone, limestone, chert, etc, in hundreds of layers, that lie between groundwater zones and the zone where the frac job is applied.
What Oil Drilling Companies Must Currently Do Before A Frac Job Occurs
Before a frac job occurs, oil drilling companies must test the integrity of the casing, or pipe that lines the wellbore. This heavy gauge pipe is usually brand new heavy gauge steel as required by law, and capable of withstanding thousands of pounds of pressure. The casing is cemented into the well, to ensure that the frac fluid does not travel back up the outside of the pipe into the upper zones where groundwater lies. A pressure test is done on both the casing and the cement. A formation integrity test or "FIT test" is done to test the isolation between the zones where the frac job will occur. A pressure recording chart or device is hooked up to the well on the surface and the well is pressured up to a certain level to perform these tests.
The chart records any bleed-off or pressure loss, which could indicate a defect in either the casing, formation or cement job. The results of these tests are reported to the appropriate state agency. In some cases a state inspector will remain on site during the testing process. Given the public mistrust of oil companies, and companies like Halliburton (one of the largest hydraulic fracturing companies) in general, you can understand how people might think these tests are faked or handled improperly. States such as New York, Pennsylvania and West Virginia have laws and processes in place to regulate hydraulic fracturing or fracing. If these laws are enforced properly there will be no adverse effects from fracking in the Marcellus Shale.
Map From Geology.com Showing Depth Of Marcellus Shale
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For More Information On How Horizontal Gas Wells Are Drilled See How Wells Are Drilled Horizontally