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Hydraulic Fracturing as a Soil Remediation Tool -Vs.- Fracturing to Produce Oil and Gas

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Recent news articles and government investigations have reported the contamination of water supply wells and intrusion of noxious materials into houses, allegedly resulting from the aggressive pursuit of natural gas and other hydrocarbons. In particular, these reports highlight contamination by chemicals that are injected to create hydraulic fractures in oil and gas reservoirs, as well as the hazards from uncontrolled oil and gas migration. These problems are a regrettable consequence of our country’s need to produce oil and gas, but they are by no means a necessary result of the hydraulic fracturing process itself.

Indeed, hydraulic fractures can be valuable tools in efforts to repair, clean-up, and restore soil and groundwater that have been contaminated by toxic chemicals – much of which results from the ignorance prevalent before the dawn of environmental consciousness several decades ago. Hydraulic fractures can optimally place treatment materials in situ, or can promote the removal of these contaminants through extraction wells.

FRx has been making hydraulic fractures to improve soil and groundwater remediation since 1994, utilizing practices that were developed at the US EPA Center Hill Laboratory in Cincinnati, OH. The Principals of FRx worked in those early development projects and have been implementing the soil remediation technologies for over 20 years. Our experience has identified four key factors that distinguish hydraulic fractures used for soil and groundwater remediation from those created to improve production of oil and gas:

Volume: Hydraulic fractures created to stimulate oil and gas production use massive volumes of fluid compared to fractures used for remediation. For example, hydraulic fractures created by FRx typically use 100 to 300 gallons, while fractures used in oil and gas often are 1,000 to 10,000 times larger. This is important because the volume of injected fluid controls the distance that the fracture will spread. The relatively small injected volume means that fractures used for remediation are simply too small to affect unexpected areas.

Depth: Hydraulic fractures in oil and gas reservoirs are created at depths of greater than 1000 ft, whereas fractures created for remediation are typically shallower than 100 ft. Hydraulic fractures tend to grow either laterally or upward. Upward growth introduces the possibility of unintentionally impacting shallower formations. In the case of deep oil and gas fracturing projects, these shallower formations may represent water supply aquifers or surficial deposits near residences. However, remedial fractures created at shallow depth for purposes of environmental remediation are intended to target the already contaminated, uppermost formation materials.

Pressure: The creation of hydraulic fractures in hydrocarbon-containing bedrock reservoirs requires pressures of thousands of pounds per square inch. In contrast, hydraulic fractures are created in soil with a small pump that generates about as much pressure as contained in a bicycle tire. This is important because high pressures can potentially stress well casings and annular seals, which can result in leaks. Leaky well casings represent direct pathways for introduction of contaminant materials (oil and gas) into potable water supplies. Also, the contents of new oil and gas reservoirs usually are under great pressure – enough pressure to push those fluids to the surface once a channel is opened. In contrast, soil and groundwater at contaminated sites usually are under no expansive pressure.

Chemicals additives: Hydraulic fractures, whether in the oil field or at a contaminated site, achieve their purpose because of the compounds they contain. FRx relies upon a set of compounds designed to effectively remediate contamination while being intrinsically safe. The slurry injected by FRx during creation of hydraulic fractures contains:

  • The remediation materials – often quartz sand or granular iron
  • Water – usually from a potable source
  • Suspending agent composed of:
    • Guar (a flour derived from a bean that grows in arid semi-tropical climates. Guar is used as a texturizer in foods and many consumer products such as cosmetics.)
    • Borax (20-Mule Team brand, straight from the grocery store.)
    • Cellulase enzyme (the same agent used by brewers to clarify beer)

In contrast, hydraulic fractures used in the petroleum industry are designed to effectively increase hydrocarbon production from reservoirs that typically are far below aquifers, so little regard is given to the hazards of their additives. In addition, the chemical conditions may be too severe for use of the innocuous materials utilized for remediation fractures. The significance of this is that the hydraulic fractures created in oil and gas reservoirs may contain exotic, hazardous additives that can contaminate aquifers, whereas the fractures created by FRx contain safe, commonly used compounds.

In summary, hydraulic fractures created by FRx are specifically designed to improve environmental problems at contaminated sites. Their only purpose is to reduce environmental risk and improve the quality of the site. Hydraulic fractures created by the petroleum industry have traditionally been designed to improve recovery of oil and gas from deep reservoirs, where water quality has typically not been a primary consideration. The end result is that hydraulic fractures created in the oil and gas industry may cause environmental problems, while those created by FRx will cure them.