The well will cone when pulled too hard where water is present. I am surprised you got it to come back around after that. When pennywise says that the well coned on them what he is saying is that the water sand formed a cone inside the oil sand and pulled its way to the perfs blocking out the oil from entering. This is a big problem and usually kills wells. I am glad that you were able to save your well. We have had the same trouble with one of our oil wells offshore. Because we kept it in test and our operators watched it like a hawk we were able to cut the choke back and prevent future damage. It still made more water than before but we extended the life for several more years.