I'm having a water well drilled on my property. The drilling crew has been working since Wednesday. They are using an airlift rig with a 6in bore. They are at 300ft and only have 4gpm. I would really like to determine what formation this well is in before I make a decision Monday on whether they should continue drilling. I really need to get ~15gpm from this well, but 30+ would be ideal.
The well is in the fall line hills area of Alabama. Specifically, it is here: 32.9672430, -86.8522270. That roughly corresponds to this location on the physiographic map of Alabama. The bore went through a few feet of topsoil, then about 30ft of brown/white/yellow clay then 60ft of grey/black clay. At 90ft he hit consolidated rock, a grey/black shale that produces rock fragments and a clay-like substance when pulverized. The well is cased to 100ft. At 260ft we hit water and the well was producing 4gpm. At 300ft the rate remained unchanged. The well driller has told me that the material alternates between hard and soft layers and that he has hit a few pockets of limestone. The shale fragments are scratched by steel, copper, and aluminum. There is no distinct odor from the shale. There are sparse fragments of quartz. I haven't seen any pyrite. The shale does not burn, even under a propane torch. The location has an outcropping of what I believe is sandstone with a good bit of quartz.
Since the bedding is shale, I think this well is in the Valley and Ridge formations. I think it is in the Coosa River valley formation, although the land drains into the Cahaba. The well driller has told me that the rock is Chattanooga Shale, but I'm not sure that is correct because it doesn't have any smell, doesn't seem to contain any pyrite, doesn't combust, and would have to be 200ft thick. From what I understand the Chattanooga Shale formation isn't that thick.
If this well is in Chattanooga Shale I may be out of luck because it's an aquiclude. That is unless I could drill through it and get into another formation within 450ft or so.
