Difference between revisions of "Jetting - general"

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- The use of large quantities of water, the use of drilling fluids to greater depths and a motor pump make the equipment cost relatively high.  
 
- The use of large quantities of water, the use of drilling fluids to greater depths and a motor pump make the equipment cost relatively high.  
 
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[[Image: Drilling Method Selection.jpg|thumb|center|600px|Drilling Method Selection. Chart: WEDC Loughborough University Leicestershire.]]
 
  
 
==Construction, operations and maintenance==
 
==Construction, operations and maintenance==

Revision as of 01:49, 1 June 2012

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Jetting icon.png
Manually rotated jetting
Typical drill bit

Jetting is also based on water circulation and water pressure. As opposed to sludging, water is pumped down the drill pipe and the ‘slurry’ (water and cuttings) is transported up the borehole between the drill pipe and the borehole wall. A motor pump is used to achieve an adequate water flow. The drill pipe may simply have an open end, or a drill bit can be added. Partial or full rotation of the drill pipe can be used. Thickeners (additives) can be added to the water in order to prevent hole collapse and reduce loss of working water (drill fluid).

Jetting is practiced in a wide range of varieties. The most simple consists of driving a plastic pipe down with water pressure from a motor pump (no drill bit and no rotation, with the water flow jetting the sand up). The depth is limited (no drill bit and extendable pipes). Other systems make use of extendable plastic or galvanized pipes and a drill bit and are rotated during drilling. With these systems greater depth can be reached.

Suitable conditions

Suitable for weakly cohesive sands and silts. Manual jetting is generally used up to depths of 35 meters.

Advantages Disadvantages/limitations
- Very quick in fine and medium sand formations.
 - Generally limited to sandy soils. Soft clay will be penetrated only very slowly and coarse gravel and other highly permeable materials (cracks in the formation) cause loss of working water and cannot be drilled. 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.

- A large amount of working water needs to be available on the drilling location (several 200 liter drums/hour). The drilling and well installation needs to be done on the same day. Leaving the borehole open during the night has a high risk of collapsing.
- The use of large quantities of water, the use of drilling fluids to greater depths and a motor pump make the equipment cost relatively high.


Construction, operations and maintenance

Jetting

All drilling equipment, except the motor pump and some valves, is locally produced.

Costs

Field experiences

Jetting is mainly used in Niger, Chad, Madagascar, Nigeria, Senegal, Burkina Faso, Uganda, Kenya, Soudan, Benin, Sri Lanka and western countries.

Reference 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. - Website & download of technical notes: http://www.lifewater.ca/manuals.htm
  • Drilling Wells by Hand, Cliff Missen, Wellspring Africa, draft 4 - Manual on Percussion drilling, well construction, manufacturing tools - Website: http://www.wellspringafrica.org
  • Drilling water wells by hand, GWAM, Ghana - Manual on hydrogeology, well construction, Percussion, manufacturing tools, implementation - Website & download: http://www.ghanamission.org
  • Drilling & well construction reference manual, Lifewater Canada, update 2004 - Internet manual on hydrogeology, well construction, all drilling techniques, hand pumps and more. - Website & download of technical notes: http://www.lifewater.ca/manuals.htm
  • Wells Construction: Hand dug and Hand drilled, Richard Brush, Peace Corps 1980 - Manual on hydrogeology, well construction, all drilling techniques, manufacturing tools - Website: http://www.peacecorps.gov
  • Shallow Wells, DHV Consulting Engineers, 1978 - Manual on hydrogeology, well construction, auger drilling, machine drilling - Website: http://www.dhv.nl
  • Low-cost shallow tube well construction in West Africa, M. Sonau, FAO - An overview of shallow tube well drilling techniques - Website & download of technical notes: http://www.fao.org/docrep/W7314E0v.htm
  • A Water Handbook, Technical Guidelines Series, UNICEF, 1999 - Programming and implementation - Website & download: http://www.unicef.org
  • Technology notes, section 7; Tube wells and boreholes, WaterAid - An overview of human-powered drilling technologies - Website & download of technical notes: http://www.wateraid.org/uk
  • Borehole and hand pump implementation, operation and maintenance, Connect International, 2004 - A manual for field staff of NGO’s - Website: http://www.connectinternational.nl
  • Multi-service procedures for well-drilling operations, field manual chapter 9, US Military - Chapter 9, alternative well construction, manual drilling techniques - Website: http://www.globalsecurity.org
  • Understanding low-cost Well Drilling, Stephen Greenwood, Technical paper 61, VITA - Technical paper on low-cost well drilling techniques - Website: http://www.enterpriseworks.org
  • Rural Water Supply Network - Useful network and website for information and downloads related to Rural Water Technologies - http://www.rwsn.ch

Acknowledgements

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