FIVE YEARS AGO, the World Bank lent money and credibility to a risky experiment. Despite the depressing record of oil projects in poor countries — they tend to fuel corruption rather than boost development — the bank provided $190 million to kick-start the oil industry in one of the world’s most impoverished dictatorships, the landlocked African state of Chad. As a condition of its lending, the bank insisted that oil revenue be used for poverty reduction, and at first it mostly was. But now Chad’s government wants to relax the restrictions on how it spends its petrodollars. Unless Chad backs down, it will become harder for the World Bank to justify future oil projects in poor countries.