Royal Dutch/Shell Group may have to quit onshore production in Nigeria, which supplies 9 percent of the company's oil, because of escalating civil strife, according to a new report...The 93-page survey said criminal gangs sell stolen oil to buy weapons, and it said that Shell itself "feeds" the violence and may have to leave the area by 2009. [also refers to ExxonMobil, Total, ChevronTexaco]