HYDRAULIC FRACTURING AS AN ENVIRONMENTAL REMEDIATION TOOL

Fracturing was developed in the 1940’s-50’s as a method for stimulating production of oil and gas wells. In the 1980’s fracturing was first used for environmental applications and it has since become an integral component of the industry. The basic materials and methods used to create remedial fractures are similar to those used to stimulate hydrocarbon production, however, the scope, setting, and additives used are quite different. These differences are important because they affect the potential negative impacts of fracturing for gas production that have recently been highlighted in the popular media.

The creation of fractures for hydrocarbon well stimulation typically involves injection 10⁵ to 10⁶ gallons of solid/liquid slurry at depths of thousands of feet. The scale of environmental fracturing is small by comparison, with typical fractures created using a few 100 gals of slurry injected at depths of 100 ft or less. Environmental fractures are typically too small to impact offsite areas and require smaller injection pressures (typically < 200 psi), which limits the likelihood of creating leaks in well casings. Potentially hazardous additives may be required to maintain appropriate fracturing fluid rheology under the extreme conditions of hydrocarbon reservoirs. By contrast, fluids used during aquifer remediation are benign.

Remedial fractures have been created under a wide variety of site and geologic conditions, using a multitude of different proppant materials, and to treat a broad spectrum of contaminant species. The versatility of the injection method has allowed application in geologic formations ranging from glacial till to massive granite at depths from 1 to 100 ft bgs, and has been used for scopes ranging from source zones to dilute plumes under saturated and unsaturated conditions. Creation of sand-filled fractures in low permeability formations typically increases specific capacities of remedial wells by 10 to 50 times. This aspect of fracture application is used to enhance remedial systems that require injection or pumping of fluids from wells. Fracturing has also been used to enhance passive systems by emplacing chemical oxidants, reducing agents, and bioremediation amendments. In general, remedial fracturing does not cause environmental problems, it cures them.