for what they call “derrick flooring.”
This is also known as Rig Matting. Sweet gum is not a species that most sawmills want because typically they have a hard time selling it. It is not used in dimension lumber. It is also not treatable. Meaning pressure treaters do not want it. So, all the Southern Yellow Pine mills in Texas and LA, MS, AL, GA do not want it.
However, make a mat out of it that you can drive on and then throw away or sell for salvage value at the end of the drill and it is fine.
The guy I used to sell in ND eventually switched to buying 3x12 Ponderosa Pine. Made in the Black Hills of SD. He could buy that cheaper. Like I said they were just using it keep the drilling pipe out of the dirt. Same thing with the Sweet Gum. They are buying it because it is CHEAPER than other alternative species.
Bingo. They also put it on the pad so that they can walk the rig to drill multiple wells off of the same pad.