A government official in Kazakhstan said that ConocoPhillips (COP), the No. 3 oil company, plans to leave that country's oil development consortium. The Kashagan oilfield, believed to be the biggest find since the 1960s, is being developed by a group that includes the nation's state oil company, along with Exxon Mobil (XOM), Royal Dutch Shell (RDS-A) and companies from Italy, France and Japan. Conoco, which has an 8.4% stake in the consortium, had no immediate comment. Conoco shares fell 0.1% to 57.37.