NOAH BROWNING and RON BOUSSO ANGOLA has accumulated around $1 billion in debt to western oil companies operating its oilfields, with the bill prompting the African country's recently launched sale of stakes in its flagship offshore blocs, three industry sources told Reuters. The magnitude of the debt, built up over several years, is a sign of deepening financial woes at state oil giant Sonangol, one of Africa's largest companies, due to underinvestment in declining offshore fields which worsened during the COVID-19 pandemic. It comes as global companies rethink their presence in high-cost ventures worldwide in order to meet their climate…