Correct me if I’m wrong, but I thought when oil rigs extracted the underground oil that they needed to pump in water to replace it and thus keep the land above from sinking.
Prehaps several wells ago, some genius of a rapidly rising manager realized they could save some money.
Most do not. Also, most are very deep and the oil is in the pores of rock, like a hard sponge. Remove the oil and the source rock remains.
Not true!
It’s not like they leave an empty chamber or void. The oil seeps through porous formations. Once removed it’s readily replaced by salt water from the same zone.
Often if conditions are favorable, water produced with the oil will be reinjected down the hole to a formation that will absorb it.
It's less about preventing subsidence, and more about the economics of hauling away the produced water by truck. Most of this water is nasty salt water. You just can't let it flow on the surface without creating a salt flat, and people don't really like that.