Reuters - A unit in Colombia of Toronto-based oil firm Pacific Rubiales launched a tender to sell two 1-million-barrel cargoes of heavy Castilla crude for delivery in April, according to an invitation seen by Reuters on Monday. Pacific sold to Norway's Statoil one 500,000-barrel cargo of Colombian Vasconia medium crude earlier this month and offered on the open market a cargo of Castilla crude that will be delivered at the end of March. The first Castilla cargo being offered this time will be loaded at Covenas port between April 1 and April 15 and the second one will be delivered in the second half of the month. Bidders should submit offers indexed to WTI or Brent front month prices until March 4, the company said.