Transocean Ltd. is one of the worlds largest offshore drilling contractors and is based in Vernier, Switzerland. The company has offices in 20 countries, including Switzerland, Canada, United States, Norway, Scotland, Brazil, Singapore, Indonesia and Malaysia. In 2010, Transocean was implicated in the Deepwater Horizon oil spill resulting from the explosion of one of its oil rigs in the Gulf of Mexico. On 23 November 2015 Transocean announced that it intent to delist its shares from the SIX Swiss Exchange due to financial reasons. The delisting will be effective on March 30, 2016. After the delisting the shares will be removed from the Swiss blue-chip index Swiss Market Index.