Shares in newly-formed energy investment company Riverstone Energy made a lacklustre debut on their first day of trading on the London Stock Exchange.The company said it had sold more than 76m shares at an issue price of £10 each, raising £760.3m. Conditional dealings started at 8:00 Thursday and by 12:31 they were trading at 960p. Unconditional dealings are expected to start on October 29th.Riverstone plans to generate capital growth by investing in the global energy industry with a particular focus on the exploration, production and midstream energy sub-sectors.Its board is chaired by former BG Group Chairman Sir Robert Wilson and also includes former BP Chief Executive Lord Browne. TB