BP plc announced that it started up the Thunder Horse South Expansion project in the Gulf of Mexico more than 15% or $150 million under budget and 11 months ahead of schedule. BP said the project - developed together with partner ExxonMobil (XOM) - is slated to boost production at Thunder Horse by 50,000 gross barrels of oil equivalent per day. The expansion project "marks the first of several major upstream start-ups expected before the end of this year and a major step toward goal of adding 800,000 barrels of new production by 2020.