L-R: General Manager External Relations, The Shell Petroleum Development Company of Nigeria Limited (SPDC), Igo Weli; Business Relations Manager, Steve Okwuosah; Group General Manager, National Petroleum Investment Services, Musa Lawan; and Head, Sales and Marketing, OES Energy Service Limited, Rosy Edward-Awoloja, at the public launch of a book, Top Tier: The Leading Upstream Companies in Nigeria held in Lagos… on Tuesday.