Woodside Petroleum has sealed a deal to buy 20 years of liquefied natural gas from a $US11.5 billion terminal to be built in Texas, but with no softening in the pricing despite the plunge in global crude oil prices since a preliminary agreement was struck in mid-2014. The step forward for Woodside's emerging LNG trading business came after US LNG export pioneer Cheniere Energy sealed a $US8.4 billion debt deal on Wednesday to help finance the Corpus Christi project, which will be built by private firm Bechtel.