RE: Flaring5 Oct 2020 11:17
C/o Junkeymonkey ADFVN
While drilling you have an open hole. Then you case it with casing pipe and cement it in. Then you go in again and drill an open hole (where the mud weight is holding back the formation contents), and then you case it and cement, etc ..... This can happen many times for a deep well. The last part of the drill when you are in the reservoir, you do not case when you come out of the hole. You run wireline logging. Having the ability to contact the formation directly gives better data. After logging, you can case or not case depending on the outcome, but most production wells will be cased in the production zone. In order to get production you have to perforate the casing with directional explosive charges on long gun arrays. This penetrates the casing, cement, and formation. The charges have varying properties for bigger hole, or deeper hole. As was stated on LSE today, and is completely wrong, one would never perforate the drill pipe (WTF), doing so would make you unable to circulate properly while drilling, and no one would let you near the drill floor with explosives to ram down the drill string anyways. The drilling is only for drilling. Cascadura was a challenge, so they cased it first before logging because they were afraid they were going to lose the well. It is possible to log through casing - this is called cased hole logging (as opposed to open hole logging), it works, but the data isn't quite as good and more limited than you have with an open hole.