Oil: OPEC+ Can't Meet Their Quota Targets?

If the global economy continues to open up, will oil supply become an issue? Per Reuters (Sep 27), OPEC+ can't meet their quotas. This specific article discusses Nigeria and Angola, but it mentions that only 5 OPEC countries are able to hit their quotas: Saudi Arabia, United Arab Emirates, Kuwait, Iraq and Azerbaijan. There are 13 members so that implies the following are unable to meet their quotas:

Algeria (2020 production at 1.3 mb/d) 

Angola (2020 production 1.3 mb/d) 

Congo (limited) 

Equatorial Guinea (2020 production 0.1 mb/d) 

Gabon (2020 production at 0.2 mb/d) 

Iran (2020 production at 2.0 mb/d) 

Libya (civil war in 2020, but currently is around 1.2 mb/d) 

Nigeria (2020 production at 1.8 mb/d) 

Venezuela (2020 production at 0.4 mb/d)

Though the above countries are no where near Saudi Arabia's 2020 production of 11.0 mb/d, the total of the above countries is over 8 mb/d.

So what exactly is causing Nigeria and Angola to come in below their quota levels?

Top African oil exporters Nigeria and Angola will struggle to boost output to their OPEC quota levels until at least next year as underinvestment and nagging maintenance problems continue to hobble output, sources at their respective oil firms warn.

How much underproduction is going on?

However, Nigeria and Angola have underproduced by an average of 276,000 bpd so far this year out of their combined average OPEC quota of 2.83 million bpd according to Refinitiv data.

Chief executive of Nigerian producer Shoreline Natural Resources, Kola Karim, believes the maintenance problems will be resolved by early 2022 so we're talking maybe six months.

Angola meanwhile states it will take years to meet its targets.

Based on the article, Angola is making that statement based on under-investment. The Nigeria statement seems to be an issue of resolving maintenance, but avoids the question about how under-investment could hinder longer term production.

Also, OPEC + is raising oil production by 0.4 mb/d every month. That seems to be more of a target versus reality based.