By Dr. Stephen Holditch
Texas A&M University
As recently as 2001, the production of gas naturally occurring deep inside shale rock provided less than two percent of total U.S. natural gas production. Today, it is approaching 30 percent. As late as 2007, it was commonly assumed that the United States would be importing large amounts of liquefied natural gas from the Middle East and other areas.
Today, almost overnight in natural-resource years, we are not only self-sufficient in natural gas, we have enough natural gas for the rest of this century on the basis of current demand. This same horizontal drilling and hydraulic fracturing technology is now being used in liquids-rich shales to increase oil production. These resource plays are in their infancy and can clearly improve the energy security of the United States.
Nonetheless, the hydraulic fracturing, or fracking, of shale rock to release gas trapped deep beneath the earth’s surface has inspired public fear-mongering, mostly around presumed threats to air quality and water quality. Most of that fear is unfounded.
The issues involving water quality are less serious and less real. No matter what you may read, hydraulic fracturing does not involve pumping toxic chemicals under high pressure near public aquifers. There has been some use of diesel fuel as an additive to hydraulic fracturing fluid in the past – but the use of diesel is quickly being eliminated in the field.
Some 99.5% of what is commonly used in fracking is a composition of pure water and quartz sand. Other agents are included, making up about 0.5% of the fluid. Three typical additives are guar gum (which is also used to thicken food products), detergents (just like the soaps you use at home to wash dishes and clothes), and bactericide (like the chlorine used to kill bacteria as it does effectively in most local drinkable water supplies).
No one recommends drinking soap or chlorine, but we have safely managed and effectively used these chemicals in our homes and local water systems for generations.
The impact of hydraulic fracturing on air quality can be more challenging. The full cycle of shale gas production – from initial exploration through the capture and transport of the natural gas and final site remediation – can result in the emission of ozone precursors such as nitrogen oxides, particulates from diesel exhaust, toxic air pollutants, and greenhouse gases such as carbon dioxide and methane.
Methane is the pollutant that requires the most attention. Some persons would rather see the methane flared than simply released to the atmosphere. However, most operators would rather not flare methane – as they wish to sell the product instead.
I served on a Secretary of Energy Advisory Board subcommittee, and we have recommended that industry accelerate cooperative efforts to establish best practices – and even encouraged the formation of a shale gas industry production organization dedicated to continuous improvement of best practices.
It will take time to determine if and what kind of organization should be formed. In the interim, there are already identified and accepted best practices that enlightened energy companies should engage in immediately – both to assuage public concerns about the impact of fracking on communities, wildlife and ecologies and to capture additional process efficiencies. In fact, most oil and gas operators already follow these best practices or they are developing plans to apply these ideas in the areas where they are operating with hydraulic fracking.
Below are just a few of the major practice recommendations in the report. (The full subcommittee report can be found at www.shalegas.energy.gov )
- Improve casing and cementing procedures to isolate the gas-producing zone from overlaying formations and potable aquifers. Loss of well integrity is simply the result of poor well completion – or poor production-pressure management.
- Control the entire lifecycle of the water used from acquisition to disposal. All water flows should be tracked and reported quantitatively throughout the process.
- Limit water use by controlling vertical fracture growth. Periodic direct measurement of earth stresses and the micro-seismic monitoring of water and additive needs will eliminate rogue methane migration – and save production money.
- Use multi-well drilling pads to monitor processes and minimize truck traffic and surplus road construction. The use of mats, catchments, groundwater monitors, and surface water buffers – all standard in the oil industry – should be industry standard in shale gas production as well.
- Declare unique and/or sensitive areas off-limits to drilling. There is such an abundance of natural gas reserves that have come from the fracking revolution that there is no need to be provocatively drilling beneath protected urban or wilderness spaces. This recommendation is also one of the most difficult to apply as the owners of the minerals in such areas have the right to produce those minerals. Fortunately, with long-reach horizontal drilling, many urban areas can be developed from remote pad sites with appropriate controls.
- Mitigate noise, air and visual pollution. Conversion from diesel to natural gas or electrical power for equipment fuel is an important first step … and can be substantially accelerated.
As the nation adjusts to the implications of this unexpected bonanza, industry would do well to quickly establish the kind of practices that encourage public confidence and insure that this marvelous resource is not wasted thorough inefficient, dangerous and provocative procedures.
Stephen Holditch is Head of the Department of Petroleum Engineering at Texas A&M University. He has been on the faculty since 1976 and is a member of the National Academy of Engineering. Dr. Holditch is a past President of the Society of Petroleum Engineers and was President of The Academy of Medicine, Engineering & Science of Texas which will present a special review of the history and future of hydraulic fracking at its annual conference in Houston January 12-13. Dr. Holditch was the author of one of the first scientific papers ever published on hydraulic fracturing in tight gas reservoirs, and for the past 35 years he has taught industry-leading courses on the analysis of unconventional gas reservoirs and the methodology of hydraulic fracturing.