U.S. oil and gas exploration and production company Laredo Petroleum Inc. announced plans to issue $350 million of senior unsecured notes. We are assigning a 'B' issue rating and a '5' recovery rating to the proposed notes. We are raising the issue ratings to 'B' from 'B-' on the company's existing $1.05 billion of senior unsecured notes and revising the recovery rating to '5' from '6'. The upgrade reflects the higher value of the company's oil and gas assets, based on its midyear 2013 reserves. The outlook is stable. NEW YORK (Standard&Poor's) Jan. 13, 2014--Standard&Poor's Ratings Services said today it assigned its 'B' issue rating to Tulsa, Oklahoma-based Laredo Petroleum Inc.'s proposed $350 million senior unsecured