The burial history chart chosen to show the three hydrocarbon events for a petroleum system should be located in the pod of active source rock where, in the judgment of the investigator, much of the oil and gas originated. Usually this location is down-dip from a major migration path to the largest fields.
Petroleum systems are seldom so simple that only one burial history chart adequately describes the same three hydrocarbon events for every location in the pod of active source rock. The investigator chooses the burial history curve that best suits the purpose. If the investigator is presenting (oral or written) a petroleum system investigation, he or she would use the burial history curve down-dip from a major migration path to the largest fields. However, if the subject is a play or prospect, the burial history curve would be down-dip on a suspected migration path to the area of the play or prospect.