(Sharecast News) - Investment firm Riverstone Energy reported a third quarter profit of $33.3m (£26m) after $12m in realisations.The company said it realised investments in Carrier Energy Partners, Three Rivers Natural Resources and Rock Oil.Net asset value for the quarter was $21.03 (£16.14) a share.Riverstone announced a £55m tender offer for £55m at between £12.00 and £13.75 a share.Chairman Richard Hayden said the company had performed well in the five years since listing against a background of oil price volatility and a prolonged downturn of natural gas prices."The tender offer gives all eligible shareholders an opportunity to exit part of their shareholding in the company. The board remains positive about the value in the current portfolio, which continues to benefit from positive market conditions," he added.