Porky's Hole Thoughts: Geothermal Drilling
August 1, 2006
Sometime back, I was a geothermal site inspector for a college. My job was to oversee and document all the geothermal holes drilled, closed loops installed, grouting of the holes and the testing of the loops.
The driller contracted was a geotechnical contractor, not a geothermal contractor. After I observed the drilling for several days, the college asked me if the contractor was qualified. I said the only way these people could drill a hole and install a loop properly was by accident. The drill crew wasn't well trained, and the equipment was in much need of repair and maintenance. They had two drills and six to eight employees on the site. It would take them several days to install one loop. They would drill several holes before attempting to grout any holes. Many times, the drilling in one hole would blow out in another hole. The drill would break almost daily. There was no qualified supervisor on site. The contractor/owner seldom came to see how the drilling was going, even when the crew was having problems.
The contractor/owner advised me he had 20-plus drills and couldn't be at every one. He further advised that he trusted his employees. When the boss doesn't care, the employees seldom care. I wanted to tell the contractor that he had 19 rigs too many, but I was only the inspector and to advise was outside of my job description.
The drill crew always was uncomfortable when I was around. They were less than honest when I asked them how deep they were or how the work was going. Most of the time, I stayed at a distance, counting the remaining drill stem on the drills to know the depth.
Nearing completion of the drilling, the crew was operating only one drill. I asked them, “Why?” They said, “Porky, you don't want to know.” I said, “I must put something in my report. What's wrong?!”
They advised that they were breaking the downhole hammer from the last joint. The “J” wrench didn't fit the flats on the hammer, so they used a 36-inch pipe wrench instead. While they were unscrewing the drill stem, the pipe wrench came loose and dropped the hammer down the hole. My response was, “That's no problem - just go back in the hole, screw into it and pull it out again.” The crew advised, “The pipe wrench fell in the hole on top of the hammer.” OK, last hole, lost hammer, lost wrench and lost hole. Forget it!
They ran 300 feet of 11⁄4-inch PVC for grout pipe, holding it by hand while running and pulling it. Again, I was the inspector and not a consultant. I couldn't advise them that this wasn't a good practice. Yep, on the first hole, they dropped the grout pipe. They let it rain on their bags of grout, again not a good practice.
A few months later, a qualified geo-thermal drilling contractor from Montana was hired. This company's equipment was in excellent condition, and the two employees were well-qualified and trained. These two men drilled, installed and grouted one loop per day in rock.
There's a big difference in having excellent equipment, a reliable, well-trained crew and a good manager and owner.
When consulting, I advise the drilling contractor to train his crews in the proper methods of installing loops and grouting the holes safely, and always have a qualified supervisor on-site when work is going on.
I also advise the geothermal buyer (owner) to have his own inspector to oversee the project and document the progress in his behalf.
Geothermal closed loop systems are up and coming. They are reliable, dependable and economical - if installed properly. They are a waste of money if done improperly or by untrained and uncaring people.