Nelson complexity index

[1] The index provides an easy metric for quantifying and ranking the complexity of various refineries and units.

[3] It was developed by Wilbur L. Nelson in a series of articles that appeared in the Oil & Gas Journal[4] from 1960 to 1961 (Mar.

The NCI indicates not only the investment intensity or cost index of the refinery but also its potential value addition.

In the second edition of the book Petroleum Refinery Process Economics (2000), author Robert Maples notes that U.S. refineries rank highest in complexity index, averaging 9.5, compared with Europe's at 6.5.

[6] The Oil and Gas Journal annually calculates and publishes a list of refineries with their associated Nelson complexity index scores.