ABSTRACT
The structure of petroleum has been a topic of some interest for at least five decades, ever
since the first theory of petroleum structure was published (Pfeiffer and Saal, 1940). And, the
structure of petroleum has become a much more important issue with the increased use of the
heavier crude oils. Studies of petroleum structure present indications of the interactions and
interrelationships of the constituents. In fact, the implications of petroleum structure as it
relates to recovery operations and to refinery operations has become of importance.