There are several reasons why a high concentration of reserves might be found in a particular part of the world, but without more information, it is difficult to provide a specific answer.
In general, the presence of natural resources like oil, gas, and minerals is determined by a combination of geological factors, historical processes, and human activity.
For example, some regions may have been more geologically active in the past, leading to the formation of oil or gas deposits. Other regions may have been more conducive to the formation of mineral deposits or other resources.
Human activity can also play a role, as regions with a long history of mining or oil exploration may be more likely to have reserves of those resources.
If you can provide more context about the specific part of the world you are referring to, I can try to provide a more detailed answer.