Qatari Minister of Energy and Industry Mohammad Al-Sada announced here Sunday that a new gas field containing 2.5 trillion cubic feet was discovered in the \"North 4\" area within the country\'s territorial waters.  The Qatari minister told reporters that the lifespan of the new off-shore gas field would depend on management and production quantity, adding that production would begin in the next few years.  He regarded the reserves of the new gas field as being \"considerable\" in line with relevant international standards, noting that Qatar Petroleum was looking into the best technical and economic option to manage the field.  The minister pointed that the field would be developed jointly with Germany\'s Wintershall and Mitsui Gas Development Qatar.  The minister, who is also chairman and managing director of Qatar Petroleum, said he was very pleased with the discovery, which he said has crowned four years of intensive exploration.  He added that the discovery was part of an effort by the country to \"prudently explore for and develop our natural resources\" with a view to contributing to the country\'s economic prosperity.