Yemen has oil resources but I don't know I would describe them as abundant. Same with Sudan; South Sudan (separate country) has most the oil.
I beg to differ on Yemen. Yemen has oil flowing from a number of fields, and yields some dramatically lucrative economic wells. So much, a number of western companies, in spite of the horrendous problem with rampart local tribes that institute kidnapping, robbery and murder, still are there producing oil at risk. I have worked Yemen and am positive on its oil production and potential for more. We even had a drilling foreman robbed at gunpoint taking logs back from a wellsite.
South Sudan has tremendous oil potential. Fula oil field and Palogue oil field alone are almost 6 billion barrels proved.
South Sudan is one of the top investments for Chinese oil companies which control 75% of all oil expenditures in the country.
Only the fact that Sudan has been in a civil war for 4 decades has prevented realization of its resource value.
Am not confidant that the article specifically targets Sudan or whether it includes South Sudan in its assessment.
I am confidant in my assessment though, that local politics comprise the fundamental reasons there are poor peoples in these two countries that are blessed with natural resources. Recall Sudan had control until recently of those oil provinces that were allowed to secede.