As with any resource extraction activity, concerns have been expressed regarding the procedures used and their actual or potential environmental impacts. In the case of shale gas production, a major concern is related to the hydraulic fracturing used to open cracks in the shale which allow the natural gas to be more efficiently collected. A central focus is on both the volume of water needed for the "fracing" process, the chemicals used, and the potential for groundwater contamination and spills of the waste water water to surface streams and rivers.
The hydraulic fracturing process injects water, sand, and other ingredients at very high pressure into the well. The high pressure creates small fractures in the rock that extend out as far as 1,000 feet away from the well. After the fractures are created, the pressure is reduced. Water from the well returns to the surface (known as flowback), but the sand grains remain in the rock fractures, effectively propping the fractures open and allowing the gas to move. Most frac fluid used in shale gas wells consists of water, a proppant (generally sand), a friction reducing agent (to help the flow-back water return from the well at the end of the frac job), and other chemicals used to protect the well and to optimize performance.
The US Department of Energy estimates that for a typical well in the Marcellus formation, 80,000 gallons of water are needed for well drilling, and 3.8 million gallons for fracturing. Water and sand comprise more than 98 percent of the franking fluid. 30-70 percent of the fracking fluid returns to the surface as flowback. Thus, there is a large volume of contaminated water from each natural gas well that must be treated.
Hydraulic fracturing fluid typically contains a biocide which helps delay the biological breakdown of the gel used in the fluid to thicken it so that it can suspend the sand. Biocide volumes are about 0.001 percent of that of the fracturing fluid. For a 3.8 million gallon injection, this is about 38 gallons or slightly more than an average curbside trash can.
Halliburton Energy Services, Inc. (Houston, TX) (NYSE: HAL) was recently awarded two patents for irradiating fluids with ultraviolet light, eliminating the need for biocides. Patent number 7,678,744, "Hydrocarbon industry servicing fluid and methods of performing service operations," was granted on March 16, 2010 to Laurence Abney and four co-inventors. This invention is classified as 507/200 for well treating in the USPC class covering earth boring, well treating, and oil field chemistry. A 2008 Halliburton patent, number 7,332,094, "Irradiation system and methods of treating fluids in hydrocarbon industry applications," was classified as 210/748.11 for liquid purification or separation that destroys living organisms.
In mid-September 2011, Halliburton patent application 20110220371, "System and method for fluid treatment," was published by USPTO. The proposed invention provides a system that treats fracturing fluid with ozone and ultraviolet light, and then allows the fluid to be re-used in the well-drilling process. The application is classified as 166/401, for injecting a gas or gas mixture into a well. A companion application, 20110272155, "System and method for fluid treatment," issued on November 10, 2011, also provides ultraviolet treatment of fracturing fluid. Halliburton's CleanStream Service relies on these patents.
General Electric Capital Corporation (NASDAQ: GEC) takes a different approach to fracturing water treatment in patent number 7,842,121 "System and method for providing aqueous stream purification services," issued November 30, 2010. Larry Sanderson and three co-inventors invented a water purification system that includes a mechanical vapor recompression separator, a steam stripper, and a secondary recovery heat exchanger. Their invention is classified in the US classification system as 95/1 for gas separation processes with control responsive to a sensed condition. According to the inventors, their system provides oil and gas producers a more efficient way to process waste water and can provide a source of clean water for use in further well operations, for human and agricultural needs, or for reinjection into the ground. It is intended to be mounted on a truck — GE is now marketing its Mobile Evaporator through GE Water & Process Technologies (Trevose, PA).
Inventor William Kerfoot takes yet another approach to treating shale gas well flowback. His patent, US 8,016,041, "Treatment for recycling fracture water gas and oil recovery in shale deposits," uses an ozonation process for adjusting the oxidation/reduction (ORP) potential of the flowback water to strip it of hydrocarbon impurities and reduce its salinity. ORP is a measure of the tendency of a chemical species to acquire electrons and thereby be reduced. The treated water can then be reused in the drilling operation, or stored to further reduce the ORP and then released. The patent, issued on September 13, 2011, is classified as 166/310, which places it with other inventions that provide for entraining or incorporating treating material in flowing earth fluid, within broader well technology. Kerfoot Technologies (Mashpee, MA) is offering this system for use as part of a frac water recycling system that includes U.S. Patents 6,913,251; 6,984,329; 7,264,747; 7,326,002, and other pending applications.
In addition to biocides, other chemicals and compounds are added to the water used for shale fracturing. On August 16, 2011, Paul Berger was granted US patent 7,998,911, "Environmental friendly fracturing and stimulation composition and method of using the same." Assigned to Oil Chem Technologies (Sugar Land, TX), Berger’s patent uses non-toxic, readily available, biodegradable substances as the frac fluid additive. The invention, classified as 507/267, is found with others that provide an organic component that contains carboxylic acid, ester, or a salt thereof, within earth boring, well treating and oil field chemistry technologies.
Shale gas drilling and hydraulic fracturing operations often use open pits to store the flowback prior to treatment or removal to an offsite treatment location. H2O TECH, Inc. (Castle Rock, CO) owns patent number 7,731,854, "Situ system and method for treating an oil and gas well drilling fluid," issued June 8, 2010. The inventor is Robert Herbst. The invention treats flowback water in a storage pit using a floating electrocoagulation unit with positive and negative charged electrodes received in the drilling fluid in the first side of the pit. A generator is connected to the electrodes for applying positive and negative direct current and destabilizing contaminants in the fluid. Heavy sludge, colloidal solids and dissolved metals form stable precipitates that settle to the bottom of the first side of the pit. The treated water can be re-used in the drilling operation or discharged. Herbst's invention is considered by the USPTO to be technology that removes specified material as part of a liquid purification or separation process.
Ecosphere Technologies, Inc. (Stuart, FL) (OTCBB:ESPH) owns four patents supporting its Ozonix water treatment process. The most recent of these is 7,943,087, "Enhanced water treatment for reclamation of waste fluids and increased efficiency treatment of potable waters," issued May 17, 2011. Dennis McGuire and Sanjeev Jakhete are the inventors. The earlier patents, of the same title, are 7,699,988, 7,699,994, 7,785,470. These patents provide a mobile system that combines ozonation, hydrodynamic and acoustic cavitation, acoustic cavitation, and electro-chemical decomposition. The process destroys bacteria and oxidizes contaminants in the frac water, allowing it to be re-used or released. The '087 patent is classified as 422/20 for using sonic or ultrasonic energy as part of chemical apparatus and process disinfecting, deodorizing, preserving, or sterilizing technology.
Innovation is being applied to the cleanup of hydraulic fracturing fluids, helping to remove an issue of concern to those opposed to the development and use of domestic energy supplies. These and many other clean technologies are found in the patentECO Water Index.