A breakthrough technology using an absorbent form of silica removed nearly all of the petrochemicals from water produced by hydraulic fracturing (hydrofracking) in natural gas shale wells and other geologic formations, Energy Department scientists reported late last week.
The water cleaning technology, which now is being tested in field demonstrations, could hold the key to significantly reducing potential environmental impacts from producing unconventional gas and oil, according to scientists with the Department of Energy's (DOE) National Energy Technology Laboratory (NETL).
According to the NETL scientists, ABSMaterial's "Osorb" technology uses swelling glass to remove impurities to clean flowback water and produced water from hydrofracked wells.
"Several existing treatment techniques separate dispersed oils from water, taking advantage of the density difference between oil and water," noted DOE's Jenny Hakun. "However, very few technologies effectively address dissolved hydrocarbons, slicking agents and polymers that prevent flowback water from being recycled or discharged."
Two pilot-scale Osorb-based water treatment systems have been built to date: a nonregenerating skid-mounted system that handles inputs of up to 4 gal/minute, and a 60-gal/minute trailer-mounted system, which included a mechanism for Osorb regeneration.
ABSMaterial, based in Edmiston, OH, has used these systems on several water samples, including flowback water from the Marcellus, Woodford and Haynesville shale formations, and produced water from the Clinton and Bakken formations, Hakun noted.
In independent testing, the skid-mounted system removed more than 99% of oil and grease, more than 90% of dissolved volatile compounds known as "BTEX" (benzene, toluene, ethylbenzene and xylenes), as well as "significant" amounts of production chemicals.
Concurrent testing also was performed on produced water streams using the trailer-mounted system.
"One major oil services company conducted a full pilot test in the field using produced water from the Clinton formation in Ohio in July 2010 and March 2011," Hakun said. "These tests showed that total petroleum hydrocarbon levels were slashed from 227 milligrams per liter to 0.1 milligrams per liter."
The project's results "have led to commercial interest from several global energy companies and future collaborative efforts." ABSMaterial also plans to deploy a trailer-mounted, 72,000-gal/day water purification system for field use in North America by mid-2011.
NETL, the Office of Fossil Energy's (FE) research laboratory, is funding "multiple projects" to develop environmental tools and technologies, like Osorb, to help exploration and production companies improve management of water resources, usage and treatment.
According to DOE, Osorb is a hybrid organic-inorganic nanoengineered structure that is considered a breakthrough in hydrocarbon removal technology because it rapidly swells up to eight times its dried volume when it's exposed to nonpolar liquids. The swelling process is completely reversible, with no loss in swelling behavior even after repeated use, when absorbed species are evaporated by heating the material, DOE noted.
"Produced waters are by far the largest-volume byproduct associated with oil and gas exploration and production," Hakun noted. "Approximately 21 billion bbl of produced water, containing a wide variety of hydrocarbons and other chemicals, are generated each year in the United States from nearly one million wells."
According to a white paper produced for DOE by the Argonne National Laboratory, the byproducts from gas drilling are more toxic than water produced by oil wells.
"Produced waters from gas production have higher contents of low molecular-weight aromatic hydrocarbons such as BTEX than those from oil operations; hence they are relatively more toxic than produced waters from oil production," the white paper stated. "Studies indicate that the produced waters discharged from gas/condensate platforms are about 10 times more toxic than the produced waters discharged from oil platforms."
The project was funded through the federal government's Small Business Innovation Research Program and is the second project under FE's Oil and Natural Gas Program to show significant success treating produced or flowback water, DOE noted.
Several other projects will be conducting demonstrations focusing on other water treatment technologies during the remainder of fiscal year 2011.