There has been much clamor over the use of hydraulic fracturing, or "fracing," to unlock vast resources of not only natural gas but also oil in Ohio. Several myths have been circulating about this process which is absolutely essential to making the horizontal wells being drilled in the Utica and Marcellus shale formations productive.
Some groups and individuals have been quick to predict apocalypse from fracing, claiming that the practice poses an extreme danger to underground water systems. But such hysteria has been fueled by much misinformation. This article is being written to dispel some of the misconceptions about fracing.
This article is being written to dispel some of the misconceptions about fracing. One such misconception is that fracing is dangerous when, in fact, it is not when done responsibly. Energy companies planning to drill for oil and gas in the Utica shale that underlies parts of Ohio have placed the highest priority on safeguarding underground water sources. In fact, there will be a minimum of five layers of protection through the shallow zones from which people obtain their drinking water.
The Ohio Revised Code 1509 which spells out all requirements for oil and gas drilling states: "a well shall be constructed using sufficient steel or conductor casing in a manner that supports unconsolidated sediments, that protects and isolates all underground sources of drinking water as defined by the Safe Drinking Water Act, and that provides a base for a blowout preventer or other well control equipment that is necessary to control formation pressures and fluids used during the drilling of the well and other operations to complete the well." The myth that drilling and fracing operations aren't subject to the Safe Drinking Water Act is indeed just that - a myth.
Companies that will be drilling Utica shale wells in Ohio will generally start out by pile driving a very large diameter piece of pipe or casing, usually about 26 inches in diameter and 40 feet long, into the earth. As an alternative to pile driving this casing, a borehole 30 inches in diameter may be drilled and the same casing is run in the hole and cemented in place. This is called conductor casing and serves as the foundation for the well.
Next, a company will typically drill a large diameter borehole about 17 1/2 inches in diameter, using air or fresh water through the deepest fresh water zone and continuing a minimum of 50 feet below it. A second string of pipe usually about 13 3/8 inches in diameter called surface casing is run in the hole and cemented over its entire length back to the surface. During this process, an inspector from the Ohio Department of Natural Resources (ODNR) is required to be on location to monitor the casing and cementing operation to ensure that clean cement is circulated back to the surface. This process instantly provides two layers of protection across the fresh water zones.
Next a vertical borehole approximately 12 1/4 inches in diameter is drilled down to a depth of approximately 1,000 feet above the targeted producing zone, i.e. the Utica shale which is expected to vary in depth from about 6,000 feet to 9,000 feet in Ohio. Another string of pipe called an intermediate casing string is run in the hole and cemented back to the surface. Again, an inspector from the ODNR must be notified and given the option of coming on location to ensure once again that clean cement is circulated back to the surface. This ensures a third and fourth layer of protection across the fresh water zones. The bottom of the intermediate casing string represents the approximate kickoff point from which the process of drilling the horizontal borehole begins.
A special drilling assembly is then used to build a curve over approximately the next 500 to 1,000 feet of depth to the point where the drill bit enters the shale formation horizontally. The horizontal section of the borehole having a diameter of approximately 8 3/4 inches is then drilled approximately 5,000 to 7,000 feet into the shale. At that point, another string of pipe usually 5 1/2 inches in diameter called production casing (one more layer of protection) is run in the hole and cemented in place from the end of the horizontal section clear up into the vertical section of the intermediate casing.
The fluids including spent frac fluid, oil, salt water native to the shale, natural gas liquids, and natural gas from a well extracted from the formation will generally be produced through yet another string of metal pipe called production tubing that is run inside the production casing. This can provide yet a sixth layer of protection through the shallow fresh water aquifer. A diagram of a typical horizontal well completion is shown in attached figure.
With the well properly cased and cemented, the process of fracing can now be addressed. The fracing process has been in use since the 1940's to extract natural gas and oil from rocks. It was not until 2003, however, that a Texas oil and gas company began using multiple stage frac treatments coupled with the technique of horizontal drilling to recover vast amounts of shale gas in north Texas. Horizontal wells and multi-stage fracing have since been used to unlock natural gas reserves in the Marcellus Shale in Pennsylvania, New York, Ohio and West Virginia, and in other shale formations in North Dakota, Montana, Louisiana, and Arkansas.
Fracing is a process in which a mixture of water, sand and chemicals is injected under high pressure through perforations or holes created in the production casing that has been cemented in place in the shale.
It is done in the shale far below the water table at depths of 7,000 to 9,000 feet. The frac fluid injected into a well does not mix with the groundwater due to the fact that the aquifer has been protected with four to six layers of steel casing and cement.
The fracing process creates a vertical crack or fracture in the rock that is generally about a 1/8 to 1/4 of an inch in width, less than a few hundred feet in height, and extends less than 500 to 800 feet in length away from the horizontal well bore to access oil and gas in the rock that would otherwise be inaccessible. Some people worry that the fracture created will extend all the way back up to the fresh water aquifer or even to the surface of the earth. This is another myth. The fact of the matter is that all of the service companies working in Ohio that perform frac treatments couldn't pump enough water, sand, and chemicals under a high enough pressure to create such a fracture.
If it is impossible to create a fracture that extends back to the surface, how then might frac fluid get into the fresh water aquifer?
For the water and chemicals used in the fracturing treatment to contaminate the fresh water aquifer, the fluid would somehow have to penetrate several layers of steel casing (production tubing, production casing, intermediate casing, surface casing) and cement. In a few vertical wells across the country where only one string of surface casing was cemented to surface and no intermediate string was run (only two layers of protection) a few incidents have been reported. In almost every incidence, however, the cause of the contamination was traced to an inadequate casing cement job. This concern is alleviated by having companies run special survey tools on the casing and cement after it is given a chance to harden to ensure that there is a competent cement bond around the outside of the pipe.
In the case of the Utica shale wells, an ODNR inspector is notified and has the option to be on location when any casing is run and cemented to make sure that the cement job is properly executed and clean cement is circulated back to the surface. Results of the cement bond surveys are also supplied to the ODNR.
The disposal of waste water from the fracing process is, of course, a concern. Spent frac water may not be produced back to the surface and pumped into creeks, lakes, sewage treatment plants, etc. in Ohio. That practice is absolutely forbidden under Ohio oil and gas law. Spent frac water must be flowed back into plastic-lined pits approved by the ODNR and the Ohio EPA or into containment trailers located on the well site. It must then be hauled off location and properly disposed of in a manner that satisfies ODNR and EPA regulations. No exceptions!
Though there have been no documented cases of ground water contamination in Ohio due to fracing and only a small number of other surface water contamination episodes, companies are taking extra precautions to make sure the disposal of wastewater from the fracing process is done safely. The energy industry has developed methods to recycle injection fluids, thereby cutting back on the amount of wastewater requiring treatment and disposal.
Companies are also publicly documenting the chemicals they use in their frac fluids. Though some of the chemicals in their pure form are toxic, they generally account for less than one half of one percent of the injected frac fluids. The chemicals are diluted even further because they are mixed with salt water or brine that is native to the shale formation when produced back after the frac job. Research is under way by several companies to come up with even more benign chemicals for use in fracing. In Ohio, companies are required to submit a copy of the ticket from their frac jobs that details chemicals used along with volumes of fluids and treatment pressures to the ODNR. A website called www.fracfocus.org is also available to the public to examine what companies are using in their frac treatments.
Barring an increase in taxes on oil companies, investment in fracing (along with horizontal drilling) will surely grow while generating huge economic and fiscal benefits for companies, landowners, and states alike. Oil companies plan to use the same drilling technique to produce oil elsewhere in the country. Among the areas that possess great potential for additional oil recovery are Alaska, North Dakota, Montana, California, Michigan, Pennsylvania, New York, and Louisiana.
In a recently-published study, the National Petroleum Council cited the importance of fracing. It said fracing is partly responsible for the dramatic turnaround in U.S. oil and gas production in recent years, and concluded that "under the most optimistic assumptions the U.S. and Canada combined could produce up to 22.5 million barrels per day, with oil shale formations producing 3.3 million barrels of oil per day."
Today 95% of wells drilled in the U.S. require fracing to make them productive. The practice has already been used about a million times in the U.S. over the course of 60 years. It is closely monitored and regulated. Even EPA Administrator Lisa Jackson has said that fracing can be done responsibly to develop the energy resources we need.
If America wants to reduce its dependence on foreign oil and develop its own sources of reliable and affordable oil and natural gas, we must ramp up domestic shale production utilizing horizontal drilling and hydraulic fracturing methods and do it in a responsible manner. There will always be a modest amount of risk, but the benefits to Ohio's economy and our nation far outweigh them.
Dr. Robert W. Chase is chair and professor of Marietta College's Department of Petroleum Engineering and Geology.