What could this be? It's been bubbling for a couple of hours. Alabama. My driveway. Lots of rain lately.

Clay soil. The bubbles aren’t flammable, I held a long lighter over them and they actually blew it out. I got close and smelled the bubbles, they didn’t smell distinctive, maybe slightly sewery. There are no utilities that I know of under there, but the area has been occupied for a long time, and my house is 100 years old.