I was just reading an interesting article over on arstechnica “Why it took so long to dial back oil production, despite the glut“. Its mostly about why the oil companies would rather keep extracting oil at a loss than to stop it.
In a lot of cases it is just as simple as turning off the tap at the surface. The issue comes when oil is pumped out of the ground, water also comes with it. The water in this case is just separated and tossed aside as waste. The oil is all they are after.
When they do turn off a well to stop extracting oil, the water and oil build back up in the cracks in the rocks and settle back into a mix.
That mix when they open the well back up could be different than it currently is and have much more water. To the point that the well would never produce enough oil to make a profit again.
It makes sense why they would rather keep going at a loss, than take the chance on the well being useless.