Uganda has officially revised upwards its estimated oil reserves by 40 percent to 3.5 billion barrels after appraisal activity in two blocks revealed more crude deposits, a senior government official told Reuters on Monday.The east African country discovered commercial hydrocarbon deposits in its western region along the border with the Democratic Republic of Congo in 2006 and estimated reserves at 2.5 billion barrels. However, production has been repeatedly delayed by contractual disagreements, tax disputes and infrastructural setbacks."We have been doing a lot of appraisal work over the last several months on the wells in blocks 1 and 2 and the reserves have been increasing and now we’re able to confirm that we have about 3.5 billion barrels in place,” Ernst Rubondo, the commissioner for the Petroleum Exploration and Production Department, told Reuters.Block 1, found on the northern tip of Lake Albert is operated by a local unit of France’s Total SA while block 2 is operated by UK explorer, Tullow Oil.Total entered Uganda’s burgeoning petroleum industry early this year after it and China’s China’s CNOOC took up a third each of British explorer Tullow Oil’s exploration assets in the country for a total of $2.9 billion.East Africa has been a focus of hydrocarbon exploration after substantial deposits of crude oil were found in Kenya, although commercial viability has yet to be established, and new major gas reserves were discovered in Tanzania and Mozambique.