AIM-listed oil and gas group Roxi Petroleum has announced further positive results from drilling at its flagship BNG project in Kazakhstan.The third core sample of Well A5, the first deep well at BNG, showed the thickness of the gross oil-bearing interval extends to at least 51 metres between the depths of 4,365 and 4,383 metres.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, has said that to determine the full extent of the intervals it will now drill and log rather than take additional core samples. "Once this has been completed and after delivery of additional equipment Roxi intends to put Well A5 on flow test," the company said.Chairman Clive Carver said that the size of the gross oil-bearing interval at Well A5 has now exceeded Roxi's initial expectations."We remain excited by the potential of the deep horizons at the BNG Contract Area and look forward to the results of the flow test," he said.The stock was up 7.6% at 17.75p by 14:29 on Tuesday. The shares have risen nearly 370% since the first oil discovery at Well A5 at the start of July.BC