My information is that Thunder Horse had technical troubles with valves of its balast system, causing it to bend over out of balance. I can provide nice photo's of it.

Another concern was that it proved difficult to secure it to its anchors in the deepwater current.

Whats happening with Thunderhorse is an real time example of how EROI will impact the energy world going forward. Getting deep water oil has a higher energy cost to begin with - if companies start anticipating and including higher depreciation values on machinery, downtime, transportation, hurricanes, insurance etc - at what point to the majors say 'lets make oil from coal instead of gettind it from GOM deepwater'? EROI of 5-1, 3-1? Somewhere certainly...
(translation: a repeat of 2005 hurricane season in 2006 will cause large approvals of Fischer-Tropsh plants)