Sludging - Asian sludge

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Icon sludge.png
Cross section of an Asian sludge
Asian sludge
Asian sludge in action

Sludging is a manual drilling technique in which water is circulated to bring the cuttings to the surface. The drill pipes are moved up and down. On the down stroke, the impact of the drill bit loosens the soil and on the up stroke, the top of the pipe is closed by hand (or a valve), drawing up the water through the pipe and transporting the cuttings to the surface. On the next down stroke, the hand (or valve) opens the top of the pipe and the water squirts into a pit, in front of the well. In this pit, the cuttings separate from the water and settle out, while the water overflows from the pit back into the well.

The borehole stays open by water pressure. Thickeners such as clay, bentonite or even cow dung are usually added to the water in order to prevent hole collapse and reduce loss of working water (drill fluid).

Suitable conditions

Suitable for unconsolidated formations: Sand, silt and clay. If rotated (including a drill bit) it may be possible to penetrate softer-consolidated formations such as stiff clays, soft sandstone, and weathered laterite.

It is difficult to drill harder layers. To overcome this problem the Rota sludge was developed.

Coarse gravel and other highly permeable materials (cracks in the formation) cause loss of working water and cannot be drilled. If very fine sands (quick sands) are encountered in the first three meter of the borehole, a temporary casing and swell clay are needed on the outside of this casing to prevent collapse.

Sludging (with or without rotation) can be used up to depths of about 35 meters.

Advantages Disadvantages
- Easy to handle and a temporary casing is normally not needed. It is possible to construct the drilling equipment locally.

- Faster as augering or percussion, as the drilling pipe can be easily extended during the drilling process, and does not need to be removed from the borehole during the process.

- The borehole stays open by water pressure. To prevent collapsing, fluid-drilled boreholes must be kept full of water during the entire drilling and well installation process.

Construction, operations and maintenance

Equipment is very cheap and can be produced locally.

Field experiences

Mainly used in India, Bangladesh, Nepal and Chad.

Manuals, videos and links

  • Drilling & well construction reference manual, Lifewater Canada, update 2004. Internet manual on hydrogeology, well construction, all drilling techniques, hand pumps and more. Download manual. Other information can be found on the Website of Livewater.
  • CARTER, R. C. (2005) Human-Powered Drilling Technologies. an overview of human-powered drilling technologies for shallow small diameter well construction, for domestic and agricultural water supply , Silsoe College , Cranfield University , Bedfordshire, UK Download
  • Drilling Boreholes for Hand pumps, Peter Wurzel, Skat, Switzerland, 2001 - A book on hydrogeology, well construction, drilling techniques, well development - Download. Website of SKAT
  • Low-cost shallow tube well construction in West Africa, M. Sonau, FAO - An overview of shallow tube well drilling techniques - website. Website of FAO documents.
  • A Water Handbook, Technical Guidelines Series, UNICEF, 1999 - Programming and implementation. Download.
  • Technology notes, section 7; Tube wells and boreholes, WaterAid - An overview of human-powered drilling technologies. Download. Website of
  • Multi-service procedures for well-drilling operations, field manual chapter 9, US Military Chapter 9, alternative well construction, manual drilling techniques - Download.