City sources predict the FTSE 100 will open down 25 points from yesterday's close of 5,499, pushed lower by a sell-off in both US and Asian markets as well as reports that UK GDP data out later today will show a contraction of 0.2 per cent in the June quarter. Tullow Oil has hailed an 'excellent' first half, with revenues up by a tenth and profits up by a half, driven by increased production, sustained high oil prices and profit on a Uganda farm-down. Sales revenues increased by 10% from $1,062m to $1,167m in the six months to June 30th. During the half-year, production increased by 3% from 75,100 barrels of oil equivalents per day (bopped) to 77,400. Meanwhile, the realised price of oil was $110.7 per barrel, slightly lower than the $112.0 per barrel price seen during the first half of last year.Organic revenue growth at British American Tobacco was robust in the first half, although currency headwinds in key markets held back reported sales growth. Revenues were flat in the six months to June 30th at £7,452m, more or less unchanged from the £7,438m reported the year before. However, on an organic basis (at constant rates of exchange), turnover was 4.0% higher, helped by continued good pricing momentum. "Despite the global economic uncertainty and the adverse impact of exchange rates, British American Tobacco has delivered another good set of results. The underlying business continues to perform well and we are confident of another year of good earnings growth," said Chairman Richard Burrows. Power systems group Rolls-Royce has won orders from a variety of customers worth in excess of 70m pounds to supply large thrusters for offshore drilling vessels. The group said that the orders are driven by a greater demand in oil and gas exploration in deep water and harsh conditions, as customers expand their drillship fleets. "Numerous drillships with Rolls-Royce thrusters have been delivered in the past few years, making Rolls-Royce the clear market leader for this type of propulsion," said Helge Gjerde, the Senior Vice President of the firm's Offshore division.