African explorer Tullow Oil unveiled higher revenue but profits fell in the face of a 200m dollar increase in exploration write-offs.Tullow, which has interests in more than 150 exploration and production licences across 25 countries in Africa, Europe, Asia and South America, said revenue in the year to December 31st rose 13% to $2.65bn.Production rose 6% to 84,200 barrels of oil equivalent per day, although the price per barrel fell 2% to $105.7.However, Tullow said a fall in profit on disposals of $670m and a $200m increase in exploration write-offs reduced pre-tax profit by 72% to $313m and post-tax profit by 68% to $216m.In September, the group and partners OMV and Statoil made a breakthrough find in the Arctic off the coast of Norway.But the company has also faced disappointment after a well came up dry in Ethiopia last December, following other downbeat drilling updates in French Guiana and elsewhere.The lacklustre news led to speculation that Tullow could become a bid target for suitors including Norway's Statoil and Chinese oil companies at a possible 1,400p per share.Chief Executive Aidan Heavey said Tullow did well in 2013 and highlighted progress at projects in Ghana, Kenya and Uganda, which would significantly increase cash flow in up to five years' time.He said: "An ambitious exploration and appraisal programme is planned for 2014 which is targeting opportunities in our core plays in Africa and the Atlantic margins. We are well placed for an exciting year of growth."PW