Impact of segmentation pattern of the Pan-African trending strike-slip basement fault on the spatial distribution of hydrocarbon traps in SW Iran

Abstract:

Strike-slip basement faults and their related segments are crucial for oil and gas exploration. These faults are considered favorable channels for hydrocarbon migration. The multistage activities of these faults influence the development of hydrocarbon-bearing structures. They can also produce fracture systems that enhance reservoir properties and boost oil and gas production. Understanding how strike-slip fault segments and their associated structures affect hydrocarbon accumulation is essential for geological research and exploration planning. This study aims to characterize the geometry and structural evolution of the strike-slip basement fault with Pan-African or Arabian trends, investigate the relationship between fault segments, and assess their impact on the distribution of hydrocarbon traps. This research focuses on the structural and tectono-sedimentary analyses of the Kazerun fault system based on processing and interpretation of the surface data (e.g., satellite images and aeromagnetic data) and the subsurface data (e.g., 2D and 3D seismic and well data) in the Zagros orogenic belt, SW Iran. The relationship between the segmented strike-slip fault zone and hydrocarbon reservoirs is analyzed through map view patterns and profile features. Results reveal that the Arabian-trending Kazerun fault system comprises segmented dextral strike-slip faults and is considered a transform and wrench fault. These faults display various planar configurations, including linear, en-echelon, horsetail splays, and irregular geometries in the map view. Based on the seismic data interpretation, three structural styles develop along the Kazerun strike-slip fault zone, including vertical or oblique, pull-apart (negative flower structure), and push-up (positive flower structure) segments. Releasing and restraining bends and oversteps formed at the tail end of the Kazerun strike-slip fault segments. In the study area, salt diapirism occurred along the pull-apart segment and the releasing bend. Hydrocarbon traps are developed in the push-up segment and the restraining bend. Fractures are less prominent in the vertical segments but more developed in push-up and pull-apart segments, which act as pathways for fluid migration and improving reservoir quality. The push-up segment and restraining bend exhibit a higher degree of branching fractures, making them the most significant for reservoir development. This research shows that strike-slip fault segmentation (in the form of fault overlapping or stepping) and their lateral linkage control the reservoir distribution and connectivity. Recognizing the growth and lateral connections of strike-slip fault segments is crucial for structural analysis and predicting fault-controlled reservoirs. These findings offer valuable insights into the structural characteristics of strike-slip fault zones and can enhance oil and gas exploration in the Zagros fold-and-thrust belt and other similar regions.

 

Keywords:

Strike-slip basement fault, Segmentation pattern, Oil/Gas fields, Zagros orogenic belt, SW Iran