Top oil rig companies include Schlumberger, Halliburton, Saipem, Transocean and Baker Hughes. Most of the top companies, including Schlumberger, Transocean and Baker Hughes, specialize in offshore drilling. As of 2012, the top oil rig companies earn a revenue of $19 billion on average.
Schlumberger, a France-based company, is rated as the top oil rig company by GN Solid Control. The company reported a revenue of $27.16 billion in 2012. Most of the top oil rig companies conduct drilling operations in the Middle East, Africa, Asia and the Americas. Other companies, such as Transocean, rent out mobile drill rigs, personnel and equipment to oil and gas companies.