SHELL INTERNATIONAL MARINE LTD. proposes to restructure its European deep sea tanker operations under one company operating from London. Shell currently operates 42 tankers in four fleets based in the U.K., Netherlands, Germany, and France. Plans to reduce the number of tankers to 30 by 1997 were presented in a 1991 review of fleet operations. Most will be sold as operational vessels. Fewer than 100 shore jobs would be cut. Shell hopes to form the new company in early 1994.