Role of Faulting in Salt Deformation and Hydrocarbon Trapping in the Missan Oilfields, Southeastern Iraq

We investigate the relationship between faulting, salt deformation, and hydrocarbon accumulation in the Missan oilfields, southeastern Iraq, by integrating seismic, well, and surface data. The analysis reveals a clear correlation between surface topographic highs and subsurface salt-related deformation, which aligns with broader deformation trends observed along the Zagros Fold–Thrust Belt (ZFTB). The Buzurgan field showed limited evidence of fault reactivation, with consistent folding persisting until the Late Miocene, while the Fauqi and Abu Ghirab fields experienced Pliocene reactivation and intense salt deformation, resulting in structural disharmony characterized by syncline-over-anticline geometries. Closely spaced faults enhanced salt deformation, forming complex listric and conjugate fault systems aligned with basement-related faults, confirming their mechanical linkage. Fault activity critically influenced hydrocarbon migration: intense faulting in Abu Ghirab enabled vertical leakage to shallow reservoirs (Kirkuk Formation), while minimal fault activity in Buzurgan restricted hydrocarbon accumulation to deeper layers (Mishrif Formation), and moderate fault activity in Fauqi allowed entrapment in both the Mishrif and Kirkuk reservoirs. These findings highlight the crucial role of fault–salt interactions in controlling reservoir heterogeneity and hydrocarbon distribution, offering valuable insights for exploration in structurally complex settings.