Shares in oil and gas producer Tullow Oil surged after the firm announcing that its Twiga South-1 exploration well onshore Kenya Block 13T has successfully encountered oil.Following media speculation in Kenya the firm said released a press release on Wednesday morning confirming the find, spurring a 3.11% rise in the share price to 1,425p.Tullow, which owns half of the operated interest in the well, said that drilling at Twiga South-1 is still ongoing and the firm said that it still expects a drilling result in early- to mid-November after the target depth has been hit and necessary sampling and analysis has been completed.Tullow's partner Africa Oil owns the other 50% of the project.The Twiga South-1 structure is the second prospect to be tested as part of a multi-well drilling campaign in Kenya and Ethiopia. It is the first discovery in block 13T following the Ngamia-1 discovery earlier this year in Block 10BB.