Hydrofracturing or Overpressurisation Boreholes

Just the word ‘Hydrofracturing’ can cause hackles to rise but used in the development of water supply boreholes there is nothing but clean drinking water being pumped into the bedrock to open and clean out blocked fissures and allow groundwater to flow into a borehole.

When a borehole has been drilled through massive bedrock formations and a little groundwater seepage is present but not enough to be useful as a water supply overpressurisation is an option to develop the yield of groundwater. The fact that water is seeping into the borehole indicates that groundwater is present in the strata but it cannot move freely due to fractures and fissures being very narrow and tight with some natural sediment slowing the flow of groundwater.

When all other development techniques have failed

When all other development techniques have failed, hydrofracturing or overpressurisation can produce results. A special high-pressure packer is installed into the borehole and expanded. Water is then pumped through a control manifold down a rising main and out of the bottom of the packer. Pressure is built up in the borehole beneath the packer to say 1000psi and then locked off with a valve. If there are small fractures present, the pressure will drop off as water is forced through clearing any sediment away from the borehole proximity. As the pressure drops more and more water is injected clearing the fractures.

This technique can transform a borehole into a useful water supply.

Drilcorp has also used this technique when drilling into mine workings to break through a coal pillar into the target workings.

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