Any drop in vertical loop costs?

Discussion in 'Vertical and Horizontal Loops' started by BlueHawk, Nov 23, 2020.

  1. BlueHawk

    BlueHawk New Member

    Hi all – I've been reading this 2018 analysis (PDF) by Oak Ridge National Laboratory on ways to reduce the cost of digging vertical loops.

    Have you seen any drop in cost in recent years? The ORNL report models different tweaks like "thermally enhanced" (TE) pipe, working fluid, and grout. For the pipe, TE means better insulation, and for the fluid, TE means better heat transfer than glycol. Any improvement in these materials is supposed to reduce the necessary loop depth, and therefore reduce cost. Have these improved materials, well, materialized? I can't tell if they're out there in the marketplace at this point.

    They also go into improved drilling rig technology, like electrohydraulic drilling, thermal-assisted, and water jet-assisted, all of which have the potential to reduce costs by reducing the time it takes to drill to a given depth. Has there been any adoption of improved drilling technology lately?

  2. gsmith22

    gsmith22 Active Member Forum Leader

    the guys that showed up to drill my wells had equipment that looked like it had been to hell and back probably from the early 1990s using standard air rotary methods. Spraying down the equipment radiator with water to keep it cool; had big oil leaks on my yard after that I had to essentially dig up so as not to have a mini Exxon Valdez at several spots in my front yard - it was a total shit show. This was about a year ago. Supposedly, all they do is drill for geothermal so you would think if the latest and greatest tech exists and makes that much difference, they would be employing it. Generally speaking, people have sunk costs in equipment and will run it into the ground and only adopt new when they have to spend the money anyway. I suspect any drilling tech is only incremental improvements - tinkering around the edges and not like doubling production so adoption will be slow and only when purchasing something new anyway. If production doubled, you better believe adoption would be quick because the equipment would pay for itself fast.

    On the piping and grout, there is a natural limit to how much any of it will help - your ground. It doesn't matter how fast the pipe and grout can transfer heat, if the ground can't transmit it any faster. Geo-pro is a well know grout maker for geothermal borehole grouting and they can easily create grout mixes that match the highest conductivity of any rock or soil. The pipe is so thin relative to the grout thickness and ultimately the thickness of the surrounding soil/rock that the pipe probably doesn't matter - again tinkering around the edges. But ultimately if you run the numbers on a borehole design, your soil/rock is almost always the determining factor on length unless something stupid is done like putting in straight bentonite grout without thermal enhancement effectively insulating the pipe from the soil. Best design practice would be to match grout thermal conductivity to soil/rock thermal conductivity (as best as practical) so soil/rock becomes the limiting factor on length.

    Assuming no environmental restrictions, you should be using methanol as the antifreeze in your loop. Ethanol would be second choice if methanol is not allowed by state/local epa (I had that issue in NJ). Never use glycol. Its a pumping nightmare and wastes electricity for no reason when methanol or ethanol exist. I would question any study that is basing their opinion on the use of glycol as the preferred antifreeze as it clearly doesn't understand best practice.
  3. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Best practices and reduced costs.... First let me start by saying everything above ^^^^ is gospel when it comes to design. I will digress when it comes to " tinkering around the edges". The technology already exists to speed up the whole process, making it more affordable. The resistance to adopt it is a leadership problem. A good water well driller is horrible at looping, and a looper often is a bad choice for water well drilling. To make the transition from water well driller to a production hole maker is hard thing to accomplish. It goes against everything they were ever taught, and is ingrained in their DNA.

    The same is true of the machine used to make the holes. A good water well machine is horrible at looping. and a dedicated looping machine is not good at drilling a water well. The next thing to consider is the lithology we are drilling. Lithology is split into two camps. Air rotary for hard rock, and mud rotary for unconsolidated formations. a third may be the mixed bag glacial till, that is where sonic shines.

    Air rotary machines are big and heavy, because they need to be. Last time I checked the smallest diameter capable of being drilled was six inch, based on down hole tooling. Lithology demanding air rotary is where the cost per bore is high. The machines are big and they do not operate with any sense of urgency.

    When mud rotary can be used it is fully the drillers and or the machines fault for not being productive. Many company's have one or two machines that must loop, water well, and perform other tasks. Not having a dedicated machine and driller to loop is a problem. We have all heard the adage that a machine that is a jack of all drilling, is not great at any of them.

    Looking at this more, we must apply the principles of manufacturing to the looping process. No wasted steps, no wasted motion, a machine that was purpose built to perform the task at hand. A time study in what happens when, and how, and why?

    This holy grail concept of reduced costs, increased production, geo for all can be achieved with technology we have now. it is the lack of implementation that is holding " geothermal for the masses " back.

    For a mud rotary primer in speed and productivity in the coastal plain of Delaware. My you tube channel is " waterpirate" I have 1 video of a 200' geo loop being drilled and installed in 18 minutes. Grouting took another 20 minutes. Bottom line, we move to the next hole every 45 minutes.

    It is a willingness to do things that get it done. I am currently running version 3.0 of the machine in the video.

    BlueHawk likes this.
  4. gsmith22

    gsmith22 Active Member Forum Leader

    the video is impressive essentially pointing out that quick production in unconsolidated formations is very achievable and with speed comes reduced labor/cost. I suspect you should be able to achieve that anywhere in the Atlantic coastal plain - essentially southeast of the Atlantic coast fall line encompassing southern NJ, all of Delmarva, and eastern MD and VA (not sure you travel that far).

    Unfortunately for me, I am northwest of the Atlantic coast fall line about 520ft above sea level. My wells were 400' into consolidated rock (~4' of soil overburden) with the upper ~100ft argillite followed by 300' in diabase. Air rotary was employed here and although I suppose sonic would have been possible, I got the sense (I asked about it) that it was being employed in "softer" formations probably more like the glacial till you describe (which I don't have here as we are south of the terminal moraines of the glacial ice age sheets). I can confirm that the machine was big, it drilled a six inch hole, there was no urgency, and I paid handsomely for the holes :) For comparison, the average speed of drilling in this formation took about 45 minutes to advance a 20ft rod. Each hole had twenty, 20ft rods and there were three holes. With the air purging the holes of pulverized rock debris, it looked like a volcano had erupted covering my lawn and trees. They averaged 1 hole per day and they grouted all three on the morning of day 4 followed by some cleanup (so like half a day on day 4). My sense was the density of the diabase completely controlled the speed of drilling and there wasn't much they could do about it. They were even using a brand new bit (saw them pull it out of the unopened wooden box it was shipped in) after taking nearly all of the first day on just part of hole #1.
    waterpirate likes this.

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