Harsh conditions, including sea ice during the winter, temperature variation from −35 to 40 °C (−31 to 104 °F), extremely shallow water and high levels of hydrogen sulfide, together with mismanagement and disputes, make it one of the most challenging oil megaprojects.[4][5] Commercial production began in September 2013.[3] It has been designated as the main source of supply for the Kazakhstan-China oil pipeline.[6] CNN Money estimates that development of the field had cost US$116 billion as of 2012, which made it the most expensive energy project in the world,[7][8] while other sources report the cost at up to $50 billion.[4][5]