This project had several reasons for cost over runs including but not limited to the following: They purchased a Gas Treatment plant that can not handle mercaptans and the gas they will be treating has mercaptans in it. This plant was made of stainless steel and will just sit there waiting to rust. They had to build a new plant that could treat this gas. Lets assume $500 million lost right there. I am not sure how much they spent on condensate return pumps in the field that can only handle clean condensate and in reality that condensate is far from clean. They have already had to rebuild 2 pumps and these pumps are straight from France.
As for sizing that was mentioned earlier this plant has 3 trains in it. Most of the equipment has been designed for approx. 36 000 bbl/day production, most of the equipment is similarly sized as any other facility. Therefore a pump purchased here would be similar to the one they would have bought for S1. Why they are F*ck ups is simple, build 3 separate plants one after another and you could have easily had train 1 (rename it S2) producing way earlier than actual first oil. Then build Train 2 (rename it S3) and so on after each other.
Another reason why they had so many cost over runs is because they hired Bantrel to be their CSU team. It is never in the best interests of the company (COP) to hire the builder to come in and do your commissioning. Bantrel wasted so many hours and made Millions by having this in the contract.
Why so many cost over runs, because it was mismanaged. The mismanagement has cost COP billions. You don't necessarily blame Bantrel they were given the green light by COP to waste billions and they did. And lets face it Ryan Lance (CEO) still has to make his US$ 27 000 000 bonus too, not to mention his US$15 000 000 million base salary.