Ithaca Energy, the North Sea focused oil and gas company, reported a big jump in profits in the first half of the year on increased oil sales.The firm said pre-tax profits came in at $35.5m, up from $10m in the first half of 2011.Revenue increased by $28.5m over the period to $76.3m, resulting in half yearly earnings per share of 20c, up from just 3c the previous year. Ithaca was boosted by a strong second quarter, which saw oil sales volumes increase primarily due to the start of production from its Athena field and the inclusion of Cook and Broom liftings, which it acquired in the second half of 2011."This movement mainly comprises an increase in oil sales volumes, partially offset by a reduction in gas sales and a decrease in average realized oil prices," the firm said.The decrease in gas sales in the period was due to a reduction in gas volumes at its Anglia and Topaz sites, partially offset by the addition of Cook gas sales, it added.