Document Type : Original Research Paper
Authors
1 Ph.D. Student, Department of Geology, Tarbiat Modares University, Tehran, Iran
2 Associate Professor, Department of Geology, Tarbiat Modares University, Tehran, Iran
3 Assistant Professor, Department of Mining Engineering, University of Tehran, Tehran, Iran
4 Ph.D., Exploration Directorate of National Iranian Oil Company, Tehran, Iran
5 Professor, Institute of Earth Sciences ‘Jaume Almera’, Barcelona, Spain
Abstract
The long-lived Fars paleo-high, located in SE Zagros Mountains is a prolific hydrocarbon province as it contains 15% of the world’s proven gas reserves. Subsurface data sets acquired during the recent hydrocarbon exploration in the region indicated fold style variation and structural complexity deep in the sedimentary cover, understanding of which is essential for petroleum system modelling and selection of new targets for gas at depth. In order to analyse the fold style in Fars paleo-high, this study presents a new regional balanced cross-section with a length of ~130 km and a depth of 12 km, across the Fars paleo-high. The section was constructed using seismic profiles, exploration wells and field data. The results show that variation of fold style happens in accordance to variation in mechanical properties of rock units across the Fars paleo-high, as well as from surface down to the depth of sedimentary cover. Detachment folding, followed by limb thrusting, which happens above 8-12 km below sea level, is the main deformation mechanism of sedimentary cover. In the middle of sedimentary cover, however, tectonically over-thickened Triassic evaporitic rocks efficiently decouple the geometry of post Triassic succession with respect to the underlying Permo-Triassic reservoir carbonates. Restoration and balancing of the regional cross-section indicated 20% of shortening across the Fars Paleo-high, accommodated by folding and thrusting. Abrupt change in the level of synclines accompanied with trends of seismicity and linear exposure of old geological units, proposes involvement of at least two main basement reverse faults in the deformation of cover sequence.
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