By Rhodri Morgan A gigantic oil rig performing sub-sea drilling for UK supermajor BP has malfunctioned in bad weather, reports suggest. Upstream Online has said that the semi-submersible rig known as Ocean GreatWhite, “unintentionally” dropped its riser to the seabead and subsequently lost it amidst bad weather. A riser is a large-diameter pipe that helps transport mud taken from the sea bottom to above the surface. The rig’s operator Diamond Offshore Drilling told the publication that it is “too early to tell” what the financial losses could be as the rig will likely “remain on downtime for a…