18/07: Pnuematic Fracturing
Pneumatic Fracturing can best be described as a process whereby a gas is injected into the subsurface at pressures exceeding the natural insitu pressures present in the soil / rock interface (i.e. overburden pressure, cohesive stresses, etc.) and at flow volumes exceeding the natural permeability of the subsurface.
Visit ARS Technologies website on Pneumatic Fracturing for more information.
In the last ten years Pneumatic Fracturing has emerged as one of the most cost effective methods for enhanced remediation of contaminated soils and groundwater. The general approach of the technology is to create a network of artificial fractures in a geologic formation that serves two principal functions. First, the fractures can facilitate removal of contaminants from the geologic formation. Second, the fractures may be used to introduce beneficial substrates into the formation. The overall objective of fracturing is to overcome the transport limitations that are inherent at many remediation sites. Fracturing is a well established concept that has been applied in various forms within the petroleum and water well industries for more than 50 years.
The result of this action is the propagation of fractures outward at rates of 2+/- m/sec. Fracture propagation distances of 30 to 60 feet are common in rock formations. Unconsolidated materials such as silts and clays typically exhibit fracture propagation distances of 20 - 40 feet. In most geologic formations the propagation is relatively uniform around the injection well. Examination of a Pressure vs Time History curve provides evidence that the cohesive bonds within the geologic matrix are broken and the creation of a fracture network occurs within the subsurface.
The type of geologic formation that can be fractured has a dominant influence on the results of the fracturing technology. Fine-grained soils such as silt and clay normally respond well to permeability enhancement by pneumatic fracturing. The permeability of tight bedrock formations can also be increased by fracturing. The initial pre-fracture permeability of the formation appears to play a significant role in the amount of permeability enhancement that can be expected. The lower the initial permeability of the formation, the greater the expected increase in formation permeability. Conversely, if the initial permeability is higher, the observed improvement will be less. In this respect, there appears to be an upper limiting permeability that cannot be exceeded by fracturing. When using fracturing to deliver liquid or solid supplemental media a wider variety of formation types are treatable including sands, gravels, and highly fractured bedrock, and the upper limit concept does not apply.
Visit ARS Technologies website on Pneumatic Fracturing for more information.
In the last ten years Pneumatic Fracturing has emerged as one of the most cost effective methods for enhanced remediation of contaminated soils and groundwater. The general approach of the technology is to create a network of artificial fractures in a geologic formation that serves two principal functions. First, the fractures can facilitate removal of contaminants from the geologic formation. Second, the fractures may be used to introduce beneficial substrates into the formation. The overall objective of fracturing is to overcome the transport limitations that are inherent at many remediation sites. Fracturing is a well established concept that has been applied in various forms within the petroleum and water well industries for more than 50 years.
The result of this action is the propagation of fractures outward at rates of 2+/- m/sec. Fracture propagation distances of 30 to 60 feet are common in rock formations. Unconsolidated materials such as silts and clays typically exhibit fracture propagation distances of 20 - 40 feet. In most geologic formations the propagation is relatively uniform around the injection well. Examination of a Pressure vs Time History curve provides evidence that the cohesive bonds within the geologic matrix are broken and the creation of a fracture network occurs within the subsurface.
The type of geologic formation that can be fractured has a dominant influence on the results of the fracturing technology. Fine-grained soils such as silt and clay normally respond well to permeability enhancement by pneumatic fracturing. The permeability of tight bedrock formations can also be increased by fracturing. The initial pre-fracture permeability of the formation appears to play a significant role in the amount of permeability enhancement that can be expected. The lower the initial permeability of the formation, the greater the expected increase in formation permeability. Conversely, if the initial permeability is higher, the observed improvement will be less. In this respect, there appears to be an upper limiting permeability that cannot be exceeded by fracturing. When using fracturing to deliver liquid or solid supplemental media a wider variety of formation types are treatable including sands, gravels, and highly fractured bedrock, and the upper limit concept does not apply.
