Punctured well screen, West Sussex
We were called out by a commecial water supplier to urgently diagose and repair a punctured well screen that was affecting public supply in West Sussex.
About the commercial borehole:
400mm diameter to 51m deep
Cased to 12m with steel casing- steel screen to base of borehole with 3mm slot
Sand pack behind well screen 5 to 10mm
Geology: soft sands and bands of sandstone
Public water supply problems
The borehole was pumping sand, there was infill at the base of the borehole.
Investigation using CCTV by our team showed that a hole in the flexible rising main, caused by torque twist, had punctured the well screen via the high velocity jetting action.
This allowed the sand pack and soft sand from the formation to flow into the borehole.
How we repaired the punctured well screen for the commercial water supply company
- Fabricate hydraulic (water only) casing “punch” to perforate the existing well screen allowing the remaining sand pack to flow into the screen.
- Remove remaining sand pack via an air lift eductor system and store for future use.
- Remove damaged well screen and install new stainless steel wedge wire screen and re-introduce the collected sand pack.
- Develop borehole to settle sand pack and re-install pump on a new rigid riser pipe.
As a result...
The public water supply borehole was returned to operational for the water supplier; the public was able to run their taps again!
Image: Well Screen
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