Casing within casing?

Discussion in 'Vertical and Horizontal Loops' started by rlscott, Jun 7, 2013.

  1. rlscott

    rlscott New Member


    We've recently started the install of our geo system (3 ton Waterfurnace with 450ft vertical loop) but have run into some problems with the drilling. Specifically, our driller was not able to hit rock in the first 220 ft so he installed 140 ft of 6" casing (until he couldn't push any more down). When the hole continued collapse, the decision was made to put in 250 ft of 5" casing. Well, only 180 ft was able to be installed until no more could go in and he was not able to drill further. This left us with one, mostly double cased, hole, 180 ft deep. He is coming out next week to discuss drilling a second hole and "trying something different" with this new one.

    I'm looking for opinions on the effect of double casing, with likely and air gap between the two, on heat transfer into the soil. Is that gap likely to fill with water in time? Would the loop have to be lengthened to compensate for this?

    Also, does anyone have experience with drilling through large amounts of overburden? I would have hoped to just drill down, pull the bit up and then shove in the tube before it collapses, but that's probably not realistic.

    If it helps, I am located in central Maryland with a lot that was a little too small for a horizontal loop and therefore went with the vertical. The driller is well respected and has been putting in wells for a long time. I would like to try and just relax and let him "handle it", but casing adds up fast and is pushing the cost of the project up quickly.

    Any help you can give would be appreciated,

  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome.
    The question about the caseing is a slippery slope at best. The reason being we lack any real data to quantify our assumptions. I am asumeing that you are in rock territory and the driller was hopeing to just case maybe 100' tops and then start in with the rock hammmer?
    I have had simmilar fun in Cecil county and many drillers shy away from that county as a whole. You have to have faith in your drillers ability to get the job done, however I would be reluctant to pay for any materials used in a failed hole. Check your contract and verify what your responsability is and try and re-negotiate how the 2 of you can move forward with a successfull project that is fair too you both.
    There are 2 methods of drilling that would make short work of your project. Sonic is one and dual rotary is the other. Both are very expensive.
    hope this helps
  3. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    Hi Robert,

    Your are right, a casing with in a casing will pretty much kill your heat transfer.

    We drill with a Sonic Drill which cases the hole while the loop is installed and then the casing is removed and used on the next hole

    You can see a video here


    There are not very many sonic rigs around that do Geo Loops so this might not be much help to you.
  4. rlscott

    rlscott New Member

    Thank you both for the insight. The installer was here yesterday, with the idea that the well was already finished, but wisely decided not to rip out our oil furnace just yet until the well is completed. One of the owners of the drilling company is coming out on Monday and I will listen to what he has to say about moving forward. The contract simply says install 450 ft of vertical loops with the additional cost of casing at $15/ft.

    Waterpirate, since you are somewhat local to me, do you know of any geo installers using a sonic rig in the Maryland area?

  5. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    To the best of my knowledge there is not a sonic nor dual rotary rig operateing in MD. Give the drilling company time to sort this out. Contrary to popular beliefs, nothing under the ground is gauranteed, and those of us who are really lucky, seem to land on dificult dril sites with some frequency. lol

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