AIM-listed oil explorer Global Petroleum has had a positive result on the fifth well of its part-owned Leighton project.Texan Petroleum, the majority owner of the prospect, said Tyler Ranch #4 had encountered oil and gas shows in the Olmos reservoir at a depth of 2,701 metres.The oil and gas shows were over an interval similar to the first four production wells on the Leighton project.The well is currently drilling ahead at a depth of 2,835 metres, to a planned total depth of 3,444 metres, which should be reached in the next few days.Global Petroleum has a 15% working interest (11.25% net revenue interest) in the project.