Oil is bringing big changes to Chad, some cultural, others ambitious and practical, like the way the World Bank has staked its reputation on making sure that Chad manages its new wealth prudently. For Chad, among the poorest countries on earth, is now Africa's newest petrostate. Its $3.7 billion underground pipeline, stretching about 1,080 kilometres, or 670 miles, began ferrying crude through the forests of neighbouring Cameroon and to the Atlantic coast last year. It is the largest single private investment in Africa.