Texan oil exploration and production company Cobalt International Energy Inc. has commenced a public offering of 50,000,000 shares of common stock, all of which will be offered by selling stockholders affiliated with U.S. and Canadian private equity firms First Reserve Corp., Goldman, Sachs & Co., Riverstone Holdings, The Carlyle Group, and KERN Partners. Cobalt was acquired by these firms at the time of its establishment in 2005, and went public in 2009.

Osum Oil Sands Corp. announced Thursday that it would raise $500 million via a private placement of 21.2 million common shares and 18.8 million callable common share purchase warrants. The financing was led by a combination of new and existing shareholders, including KERN Partners, Government of Singapore Investment Corporation, Warburg Pincus and Blackstone Capital Partners. Osum is based in Alberta, Canada.

Ausra, a Palo Alto, Calif.-based developer of a utility-scale solar thermal power plant, has raised $60.6 million in Series C funding. Kern Partners led the round, and was joined by Generation Investment Management, Starfish Ventures and return backers Khosla Ventures and Kleiner Perkins Caufield & Byers.