During the drilling of a new water supply borehole, drill cuttings, fines and debris are often forced under hydrostatic head into the water bearing fractures blocking the free flow of groundwater through the bedrock and into the borehole. The borehole will underperform unless development work is carried out to maximise the yield.
An established water supply borehole may, over time, become less productive due to a slow build-up of minerals and fines deposited by groundwater passing through the fractures. These essential pathways narrow restricting flow of groundwater to the borehole.
Acidisation is one of a range of techniques used to develop a newly drilled borehole or to refurbish an older borehole that has gradually become less productive due to clogging or build-up of encrustation of the fractures and fissures feeding groundwater into the borehole.
The technique is mainly used in carbonate rocks such as Chalk or Limestone and involves the injection of a measured volume of Hydrochloric Acid into the borehole (usually several tonnes depending on the volume of the borehole to be treated).
The borehole is sealed as the acid is injected and when the acid comes into contact with the carbonate material a violent chemical reaction occurs resulting in large quantities of carbon dioxide gas. The expansion of the gas forces acid deep into the blocked fractures dissolving encrustation material and drilling debris. Pressure build up is controlled with a series of valves on the headworks of the borehole.
Obviously, this procedure can only be carried out by fully trained borehole engineers wearing specialist PPE.
Drilcorp’s Borehole Engineering division has acidized numerous Chalk and Limestone boreholes greatly improving their yield.
Drilcorp work with a number of prestigious clients from Local Authorities, Food and Drink Manufacturers, Consultants and Contractors and Water Utility Companies.