Refinery Complexity

Refinery complexity refers to the ability to process feedstocks, such as heavier and higher sulfur content crude oils, into value-added products.

The configuration of complex oil refineries is typically oriented towards the production of gasoline (fluid catalytic cracking), whereas the configuration of less complex refineries is oriented towards the production of middle distillates (thermal conversion and/or hydrocracking).

Complexity is commonly measured by the Nelson Complexity Index which assigns a value, or complexity factor, to each major piece of refinery equipment based on its capability. This factor is compared to crude distillation, which is assigned a complexity factor of 1.0. Adding up the complexity values assigned to each piece of equipment, including crude distillation, determines a refinery’s total complexity value. A refinery with a complexity of 10 on the Nelson Complexity Index is considered ten times more complex than crude distillation for the same amount of throughput. The average Nelson Complexity Index rating for refineries in Western Europe is approximately 6. The average Nelson Complexity Index for Petroplus refineries is approximately 8.3.