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

In the Missan oilfields, the linkage among basement faults, halokinesis, and hydrocarbon accumulation, and their control on structural-trap geometry and seal effectiveness, remains insufficiently constrained, especially the timing/drivers of salt piercing and its coupling with regional folding. To address this, we integrate 3D seismic, well, and surface data to quantify these interactions across adjacent fields. Results show a clear correspondence between surface topographic highs and subsurface salt-related deformation. Buzurgan exhibits limited fault reactivation with persistent folding until the Late Miocene, whereas Fauqi and Abu Ghirab record Pliocene reactivation and intense salt deformation that generate disharmonic syncline-over-anticline geometries. The listric–conjugate faults are structurally linked to deep-seated basement faults and display clear spatial alignment with their orientations, enhancing halokinesis and accommodating differential shortening. At the same time, hydrocarbon charge pathways are primarily governed by the intensity of deep-seated faulting and the effectiveness of salt sealing. Critically, the study integrates disparate geological processes—fault reactivation, salt tectonics, and hydrocarbon migration—into a single coherent, field-validated model for the region and provides a practical method to anticipate subsurface complexity. The results show that variations in fault intensity across three adjacent fields (Buzurgan, Fauqi, Abu Ghirab) correspond to distinct reservoir outcomes: minimal faulting in Buzurgan confines charge to deeper Mishrif reservoirs; moderate faulting in Fauqi permits entrapment in Mishrif and Kirkuk; and intense faulting in Abu Ghirab facilitates vertical leakage to shallow Kirkuk. Collectively, the work moves beyond isolated case descriptions to provide a unified, exploitable framework for predicting how basement-involved faulting and salt mobility jointly control deformation style and hydrocarbon distribution in foreland basins.