AIM-listed oil and gas group Roxi Petroleum has said that drilling and logging tests at the first well of its flagship BNG project in Kazakhstan have shown a bigger oil interval than previously thought.After three core samples of well A5, the thickness of the gross oil-bearing interval was estimated to extend to at least 51 metres between the depths of 4,365 and 4,383 metres, according to an update on 19 August.This was an improvement from the 33-metre interval found at the time of the second core sample on 11 August and the 12-metre interval seen from the first core sample on 5 August.Roxi, which owns a 58.41% stake in BNG, then decided to drill the well rather than take additional core samples to determine the full extent of the interval. This drilling and mud logging found that the thickness of the interval is now at least 105 metres between 4,322 and 4,437 metres. "The 105 meters gross interval is an excellent outcome. How far further the interval extends will be for another time to determine," said chairman Clive Carver.Roxi has decided to complete the well at 4,442 metres due to safety reasons related to different pressure and temperature conditions at lower depths. Flow testing will then commence."More than ever we look forward to the results of the flow test," Carver said.The stock was only 0.6% higher at 23p by 08:24 on Monday but has now risen 550% since the first oil discovery at well A5 on 9 July.BC