A friend called the other night to catch up and chew the fat about things in general. I asked him if he was busy, etc., and he told me that he had lost a well that day. Not good, but it happens for all sorts of reasons. He had set a 4-inch PVC well in a 7-inch hole. The contract called for bottom to top cement. He set his pipe on bottom and ran an outside tremie line to cement. When he came back the next morning, the casing had collapsed about 8 feet downhole, so he was going to move over and redrill. I told him to hold up. I suggested that he go do some installations or service calls for the rest of the day, and that I’d be there in the morning.
When I got there, sure enough the casing was collapsed, but not crushed. It looked like it had just melted in on itself. I asked him about the formation at that depth. He remembered drilling through about 3 feet of very fine, flowing sand that took forever to circulate out, even at that shallow depth. A clue! Obviously, he had a large washout in the hole. No telling how big it was, but it was big enough to cause the problem.