By Amanda Solliday / Posted September 14, 2012/Indiana Public Media/Shared as educational materials
Photo: Gerry Dincher (Flickr)
Natural gas wells like this one in Pennsylvania have begun popping up around the U.S. as natural gas has become a more popular energy source.
Oil and gas well operators that use hydraulic fracturing or fracking in Indiana must now report, among other things, the materials and the volume of chemicals used in the fracturing fluid. The mandates results from new legislation that went into effect on July 1.
Fracking is a technique that pushes water, chemicals and sand into the ground under high pressure to crack rock formations. In addition to oil and gas, it is also used to extract coal-bed methane.
Between 2005 and 2010, as many as 23 percent of the new oil and gas wells drilled in Indiana used hydraulic fracturing.
Herschel McDivitt, Director of the Oil and Gas Division at the Indiana Department of Natural Resources, says the state requirements are in response to public concerns over potential effects of the fracking fluids on human health and water environmental safety.
“With the new legislation, what Indiana has done is positioned itself to be able to gather this information, make it available to the public and stay abreast of any changes in the technology,” McDivitt says.
The DNR posts the information about the chemicals in an online database.
Hoosier Environmental Council Senior Policy Director Tim Maloney says the requirements will increase transparency.
“The disclosure will provide greater attention to the potential risks and ultimately lead to the use of less toxic and risky substances,” he says.
This Indiana law is stricter than federal requirements. There is nothing on the books nationally that mandates the reporting of chemicals using in hydraulic fracturing.
Proppants and fracking fluids.
A proppant is a material that will keep a induced hydraulic fracture open, during or following a fracturing treatment, while the fracking fluid itself varies in composition depending on the type of fracturing used, and can be gel, foam or slickwater-based. In addition, there may be unconventional fracking fluids. Fluids make tradeoffs in such material properties as viscosity, where more viscous fluids can carry more concentrated proppant; the energy or pressure demands to maintain a certain flux pump rate (flow velocity) that will conduct the proppant appropriately; pH, various rheological factors, among others. In addition, fluids may be used in low-volume well stimulation of high-permeability sandstone wells (20k to 80k gallons per well) to the high-volume operations such as shale gas and tight gas that use millions of gallons of water per well.
Conventional wisdom has often vacillated about the relative superiority of gel, foam and slickwater fluids with respect to each other, which is in turn related to proppant choice. For example, Zuber, Kuskraa and Sawyer (1988) found that gel-based fluids seemed to achieve the best results for coalbed methane operations, , but as of 2012, slickwater treatments are more popular.
Ignoring proppant, slickwater fracturing fluids are mostly water, generally 99% or more by volume, but gel-based fluids can see polymers and surfactants comprising as much as 7 vol% of a gel-based fluid, ignoring other additives.  Other common additives include hydrochloric acid (low pH can etch certain rocks, dissolving limestone for instance), , biocides, emulsion breaker and emulsifiers.
Radioactive tracer isotopes are sometimes included in the hydrofracturing fluid to determine the injection profile and location of fractures created by hydraulic fracturing. Patents describe in detail how several tracers are typically used in the same well. Wells are hydraulically fractured in different stages. Tracers with different half-lives are used for each stage. Their half-lives range from 40.2 hours (Lanthanum-140) to 5.27 years (Cobalt-60). Amounts per injection of radionuclide are listed in the The US Nuclear Regulatory Commission (NRC) guidelines.The NRC guidelines also list a wide range or radioactive materials in solid, liquid and gaseous forms that are used as field flood or enhanced oil and gas recovery study applications tracers used in single and multiple wells.
Except for diesel-based additive fracturing fluids, noted by the American Environmental Protection Agency to have a higher proportion of volatile organic compounds and carcinogenic BTEX, use of fracturing fluids in hydraulic fracturing operations was explicitly excluded from regulation under the American Clean Water Act in 2005, a legislative move that has since attracted controversy for being the product of special interests lobbying.
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