How to design and choose a proper casing pipe for bore wells?

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Dear friends,

We are drilling bore wells in our project area in Indonesia. The bore well will be drilled into a sand/gravel aquifer. Historical experience from a near by located wells is that we will get a water source at 400 ft - 450ft.

I need some inputs for designing and opting type of casing pipes. Some of near by wells have opted for steel pipe, but they are costly and will start corroding after some time. (That is what some available literature says).

Can you please guide me about what are the types of casing suitable to our site? Are there any rule of thumb to follow? We will be hiring agencies for drilling the wells, but I need to have good knowledge well in advance about my requirements. Thanks.

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19 Answers

  2. Suggest you find well drilling contractor who has the equipment and experience and "know-how" to do the job right the first time. Also well casing material suppliers are a good reference that you can use. I see you already received a lot of good advise. If you need water purification equipment after drilling your well....please let me know.....William Danshin, President, WaterCorp, Canada.

  3. Thank you everyone for the comments and replies. I am going through them and will revert back.

    Answered on by

  6. Casing Material Selection

    There are rare cases where materials are a problem.  For 99 percent of wells that require casing you can get by with 4inch PVC.  Hard rock wells only need a few meters of larger diameter surface casing.  Hard rock wells can be open holed below the surface casing and should not exceed a depth of more than 250 feet.   A well of this size casing can easily do 20 gallons per minute.  If cased , the pipe must be mill slotted and the annular space  backfilled with sand across the slotted pipe and clayey soil, enviroplug or siliceous Class A Portland cement in the annular space.  The siliceous Portland cement will not crack. 

     

    Bill Turner

    WaterBank 

     

  7. Many factor can come into play!

    My experience with our wells we have steel casing and PVC it depends on a number of factors, most especially soil types, water quality, etc.. We had galvanize down pipes that were eaten like Swiss cheese from Iron, and Manganese and Brackish water intrusion. Screen Slot size in your casing can be effected by other factors such as Iron and slime forming bacteria clogging screens and the pump, so you will need to take Water Quality testing for these things into account prior to drilling!

  9. Do it simple and easy : CPVC is OK for me as Satendra says. Polyethene could do it too

  10. The reference of GROUND WATER AND WELLS given above by Walter is the best since you are talking not only about the type but the designing also. For designing any water well, one needs to know many factors- type of aquifer, aquifer grain size, discharge required from the well etc etc. So do read the book. It has a chapter devoted to designing of wells.

  11. Well drilling :General &Technical specifications.

    Casing

    Design Details

    The basic well design is shown in the Figure (according to the Special Conditions Data Sheet).The Borehole will be drilled with bits of sufficient size to accommodate the specified casings. The estimated Borehole size and depth for each casing is according to the Special Conditions Data Sheet.

    The location of the well screen - perforated casing sections - ( if any ) will be determined according to the water bearing strata as the Engineer may direct.

    The Contractor may submit an alternative construction plan for the borehole, provided it permits the lowering of a diameter pump(1) to a depth of around (2) and the sealing of the layers as specified above. Such alternative shall be subject to the Engineer’s approval in writing and to be obtained prior the commencement of the work. The Contractor shall not make any changes in the borehole and the casing dimensions and specifications detailed above or in the quality or type of casing without the prior approval of the Engineer, this approval must be applied for at least one week prior the performance of the work concerned.

    The casing permanent diameter will:

    - be large enough to accommodate the pump, with enough clearance for

    installation and efficient operation,

    - be of sufficient size to ensure that the uphole velocity is not less than 1.5 m/sec

    - provide an annulus between well casing pipe (protection pipe) and the permanent

    pipe that is sufficient to accommodate centralizes and permit cementing with a trimie pipe if needed.

    The permanent pipe diameter will be (5) and will be installed (---) m below the water level . The permanent casing shall be Grade J-55 having steel pipe schedule 40.

    Three strings of casing will be provided for well production. Protection steel pipe sch. 40 to be large enough to accommodate the permanent steel pipe with enough clearance between protection pipe not less than 25 mm around for quartz installation and sufficient to accommodate centralizer.

    The protection steel pipe to be installed and to a depth of about 2 meters below ground

    Water level to prevent pollution and stabilize the top soil and upper soft formation.

    • Permanent steel pipe sch. 40 as a pump house casing will be installed to a depth of

    About ---- meters having out side diameter not less than ---- inch.

    • Lower slotted casing s / steel pipe to prevent sloughing of the borehole in the lower formations if required, the perforation slots shall be made by the contractor either by mechanical cutter or by flame cutter subject to engineers approval and shall be (5-7) mm wide and (70-100) mm between ends of adjacent slots. The casing will

    60

    be installed in the borehole to prevent caving and sloughing of loose rocks. Well screen opening to be selected to ratain about 90 percent of the filter pack after development or more. And the slot size of the filter should be accordingly to soil sieve analysis and screen diameter.

    • Filter pack shall be placed between around the slotted casing and protection pipe and should be (5-8) m up the ground water level. And should be chosen to retain most of the formation material. The screen diameter is selected to satisfy a basic principle enough open area must be provided so that entrance velocity of the water generally does not exceed the design standard of 0.1 ft/sec. (0.03 m/s)

    All casing shall be new, having couplings and buttress thread with a thread protection and of perfect roundness and uniform in wall thickness within detectable limits. Casing ends to be connected by welding shall be mill beveled. The welded casing joint shall develop strength equal to 100 percent of the pipe strength. Should a joint fail or break, the Contractor shall be responsible for the failure. All casings shall be butts welded by certified welders.

    The Contractor shall install each type of casing in one string and to the depth selected by the Engineer. Final casing depths will be selected from information obtained during the drilling and geophysical logging.

    The Contractor shall install each string of casing true and plumb to line. All casing shall be centralized in the borehole. Centralizers shall be installed as specified herein

               

  12. Consult a good reference manual

    Jasmin,

    In your role you need some fundamental knowledge about well construction criteria.  I suggest that you purchase a copy of Groundwater and Wells , 1986, Johnson Division.  Johnson is a famous maker of well screens here in the US.

    Another good reference, but harder to find, is Water-Well Design and Construction, by RL Harlan, KE Kolm, and ED Gutentag, Developments in Geotechnical Engineering, 60, Elsevier, 1989.

    There are two primary aspects of well design - hydraulic design and structural design.  Your current question relates to the latter condition, structural design.  The general objective is that the well must not collapse under its own weight, the screen not collapse either, and the material not loose strength over the design period of the well, nominally 50 years.  I have worked on wells that are functional after 100 years, but thats not usual.  

    It is not unusual to see PVC well casing to 500 feet.  The designer needs to pick a pipe-wall thickness that has enough strength to stand up under its own weight.  Screen selection has to have the same considerations of strength under compression.  PVC screens are not strong, so you may be looking at a hybrid - PVC casing and a stainless steel screen.  They are expensive.  Don't shy away from using good materials that are more costly, remember the design life aspect.  Don't rule out steel casing if the cost-life cycle analysis provest it out, but you have to consider loss of strength over time due to corrosion - as others have experienced in your area. On the flip side, the price of PVC is linked to oil - this may be the lowest pricing for PVC casing we will see for some time!

    Another are not to skimp on is the hydraulic design.  I don't have time to go into details here but the money spent on a high quality, high open area screen can be recouped in the first several years of operation due to decreased pumping (power) costs.  Again, consult and study Groundwater and Wells and you will be well informed.

    Best regards,

    Greg

     

    Answered on by

  13. How to design and choose a proper casing pipe for bore wells?

    Please refer to the attached link, http://www.indiawaterportal.org/questions/frequently-asked-questions-faq-borewells-covering-all-stages-selecting-site-maintenance#Casingpipes

  14. Excellent reference for well construction

    Choosing the correct material is difficult without good knowledge of the geology, water chemistry, and use of the well. An excellent reference to help design a well and choose the correct materials is "Groundwater and Wells." The editor of the second edition (1986) is Driscoll and that is the version many hydrogeologists and drillers have on the shelf. The more recent third edition was edited by Robert Sterrett.  The Johnson Well company puts the book together although it is available from Amazon and other sources.

    -----
    Walter Weinig, PG

  15. Thermoplastic Casing Pipes

    You might consider ASTM F480 "Standard Specification for Thermoplastic Well Casing Pipe and Couplings Made in Standard Dimension Ratios (SDR), SCH 40 and SCH 80" as a useful standard for all types of plastic casing pipes.  I am chairman of the ASTM Sub-committee with jurisdiction over this product standard which has been in continuous publication since 1976.  Bryan

  16. The material is depending on your chemical conditions in the boreholes and the required stability, often related to the diameter. Another dependency is the method of how the pipes will be put into the ground. Some exploration methods will require steel some not. I would recommend you to check the websites of some manufacturers. They often have some guidelines for usage fo their products.