Got a call from a driller I had met on Facebook, and we had discussed jobs for quite a while. He said he had an irrigation well that was pumping sand, and had been doing it for a while. They didn’t drill the well, but inherited the service work. He had redeveloped and surged the well several times. It would improve for a little while, and then go right back to pumping sand. A lot of sand. Enough to plug irrigation equipment, erode valves and severely shorten the life of the pump. The owner decided it was time for a new well. The area was known for plenty of water, but the producing aquifers are very fine sand. I got to thinking about my younger days on the Texas gulf coast. We had some sands that required a 10-slot screen, and some wells that would make sand unless you ran a 6 slot. That’s a pretty fine slot, and not a lot of open area so, while it might work for a house well, it isn’t enough for an irrigation well. Time to consider a gravel pack.
I have seen a lot of discussion about gravel packs, and most guys say the same thing: Run a 20 or 30 slot screen and pack with 20-40 gravel. I’ve never heard anyone mention anything about running a sieve test on the aquifer, and designing the well to fit the conditions. Worked out usually, but when it didn’t, uh-oh. My friend asked me what I would do. I said, send one of your small rigs out, drill a small test hole, set the screen of your choice, see if it produces, and send me the formation samples all the way down. After a while, I received a heavy FedEx box full of carefully labeled samples. He had drilled a 3⅞ hole, run 20 feet of 10-slot screen into the producing formation and developed 35 gallons per minute. Bingo! Good aquifer, just a matter of designing the well right.