Repairing a Borehole in the North of England
The company in question have several large diameter boreholes to provide their water needs and, unfortunately, at some point in the past one of these was damaged when service works were being undertaken, which the contractor involved was unable to resolve. Also the string of 300mm uPVC casing and 300mm stainless steel screen was unsupported at surface and this has caused further damage through compression of the well screen.
WB+AD Morgan Ltd. have been commissioned to remove the existing uPVC casing & stainless steel wedge wire screen from the borehole, undertake a CCTV condition survey and re-line with a new string of stainless steel casing & screen.
The 64m of sand pack surrounding the casing & screen has created a sand lock, causing trapping of the casing & screen in the borehole. WB+AD Morgan have designed and fabricated a hydraulic tool that will be lowered approximately 115m into the borehole and placed against the stainless steel well screen. High pressure water will then be utilised to activate the hydraulic ram, which has a pointed end, to penetrate the screen and forcing open the 2mm wedge wire screen slots to some 25mm to allow the sand to flow from the annulus into the screen. This process will then be repeated along the length of the screen, allowing the sand to flow freely from the annulus into the screen.
Once completed an eductor airlift system will be lowered into the borehole and the sand “hoovered” clear of the borehole. The sand will be recovered and stored for re-use. Once clear of all sand from inside, the casing & screen will be lifted clear of the borehole.
The borehole will then be CCTV surveyed and a new string of 300mm stainless steel casing & wedge wire screen installed. The string will be supported at surface to prevent compression and the annulus packed with sand for filtration. New headworks will be fabricated to allow for attachment to the 150mm delivery pipework and a new pump installed on a stainless steel JSL riser system attached to a new stainless steel headworks.