ABSTRACT: Prediction of Petroleum Migration Pathways in the Jurassic Petroleum System, Iraq

A 3D petroleum migration model of the Middle to Upper Jurassic Sargelu/Naokelekan source rock system in Iraq was developed to predict paleomigration pathways for charging major hydrocarbon accumulations in Cretaceous and Tertiary strata. The system sourced 85 fields and approximately 155 unproven prospects within the region. Potential migration pathways and zones of petroleum accumulation were reconstructed through time by integrating structural restorations of source rock surfaces, regional isopach and facies maps, and thermal maturity profiles. Maturity profiles were modeled using hydrous pyrolysis kinetics based on Type II-s kerogen and a geothermal gradient of 23°C/km. Maturation data in combination with restored structural topographies show that petroleum generation and expulsion began in southern Iraq in the late Paleocene-early Eocene and reached completion throughout most of the region sometime after the middle Miocene. In the southern part of Iraq, most fields are within or adjacent to predicted petroleum migration pathways. Overall, the pathways display only minor temporal variations possibly because the area was affected by relatively mild structural deformation compared to other parts of the region. Extensive folding and faulting related to the Zagros thrust belt had a significant impact on predicted migration pathways and areas of petroleum accumulation in northern Iraq. Remigration of petroleum from older structures into younger traps can account for approximately 90% of the fields in this extensively faulted area. Modeling of secondary migration on reconstructed structure surfaces through time explains most of the current producing fields and provides a means of risking unproven prospects.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia