Khalil Sarkarinejad

Structural mapping of 572 km ² of the Neyriz Ophiolite was conducted to deepen understanding of the internal microstructures of deep transform faults associated with oceanic ridges. We examined the microstructural, structural and kinematic characteristics of an exposed vertical paleo‐oceanic transform fault within the Neyriz Ophiolite. This analysis identified microscale deformation and kinematic mechanisms and inferred the probable controls on oceanic transform faults. The Neyriz transform fault comprises two segments. The upper segment consists of Type I and Type II serpentinite phyllite and phyllonitic mélange. In contrast, the lower segment extends northeast–southwest and consists of high‐temperature, high‐shear‐strain amphibolite mylonite formed as a right‐lateral transpressional or thinning shear zone. The transform fault has undergone significant shear strain, reaching γ = 3.70. This shear strain is decomposed into 47% pure shear and 53% simple (or sub‐simple) shear, based on the estimated kinematic vorticity number ( W _m = 0.73 ± 0.07). Amphibole porphyroclasts in the amphibolite mylonite and plagioclase are encased in a fine‐grained amphibole matrix interspersed with slender, elongated ribbons or narrow bands of plagioclase. Kinematic vorticity number measurements of the vertical, high‐shear‐strain amphibolite mylonite along the transform fault indicate pure‐shear‐dominated transpression ( W _k < 0.81), with the mylonite oriented vertically and perpendicular (θ = 93°) to the ocean‐spreading ridge. The exposed mantle along the oceanic ridge shows that the harzburgite exhibits a sub‐vertical lineation in the centre and sub‐horizontal lineations on both sides of the mantle diapiric flow.

Fracture characterization and modeling are essential for hydrocarbon exploration and enhanced production. To model the fracture network in the Asmari reservoir of the Rag-e-Sefid Oilfield (SW Iran), this research characterizes fracture intensity using well, fracture driver, and fracture controller data. First, these data are analyzed to estimate fracture intensity. Then, fracture intensity is modeled using geostatistical methods. The geostatistical outputs are compared and calibrated based on the structural setting of the study area and the fracture indicator. Finally, selected fracture intensity data are integrated into a single model using an artificial neural network, resulting in a comprehensive fracture intensity model for the Asmari reservoir of the Rag-e-Sefid Oilfield. The results show that fracture intensity increases near the Rag-e-Sefid and Nourooz-Hendijan-Izeh Faults and in the fold forelimb and crest. The highest fracture intensity in the Asmari reservoir is observed at the intersection of structures with the N-S Arabian trend and the NW-SE Zagros trend, where the fold axis has rotated. Generally, the northwestern part of the Rag-e-Sefid anticline has higher fracture intensity than the southeastern part. The high fracture intensity in the northwest part of the Rag-e-Sefid Oilfield is related to inversion tectonics, multi-stage reactivation along pre-existing basement structures, and an older deformation history in this area compared to its southeastern part. The Asmari reservoir in the NW part of the Rag-e-Sefid anticline contains a greater share of oil and gas in its hydrocarbon traps than the SE part. Moreover, the results of this study indicate that the simultaneous use of different data and the integration of geostatistical and artificial neural network methods can effectively predict fracture distribution in hydrocarbon reservoirs and be used as a suitable technique for fracture modeling in natural oil and gas fields. This research suggests that artificial intelligence and quantum computing techniques provide efficient solutions for characterizing and modeling the entire scale of geological fractures in hydrocarbon reservoirs.Keywords: Fracture modeling, Geostatistical and neural network methods, Asmari reservoir, Rag-e-Sefid Oilfield, SW Iran

Identification of inversion tectonics and inverted structures is very important in petroleum exploration and production due to the positive or negative impacts they can exert on the hydrocarbon traps. In order to characterize the occurrence of multi-phase inversion tectonics and its effect in the Rag-e-Sefid Oilfield, located in the southern Dezful Embayment (SW Iran), this research describes the structural style and deformation history through structural and tectono-sedimentary analyses. The results obtained from the interpretation of seismic profiles and the investigation of the geometry of the sedimentary layers across the growth structures indicate that the Rag-e-Sefid anticline is created from multiple fault-propagation folds. The final shape and geometry of the Rag-e-Sefid anticline are affected by the Rag-e-Sefid and Nourooz-Hendijan-Izeh Faults activity. The deformation history in the north-western part of the Rag-e-Sefid anticline is older than the south-eastern part of it. The Rag-e-Sefid Fault set in the north-western and south-eastern parts of the Rag-e-Sefid Oilfield experienced activity at least during seven and four tectonic phases, respectively. Multiple fault-propagation folding and the fold axis rotation in the north-western part of the Rag-e-Sefid anticline controlled by the presence of several décollement surfaces and the occurrence of inversion tectonics along the pre-existing basement structures. Three-phase inversion tectonics along the Nourooz-Hendijan-Izeh Fault and the Rag-e-Sefid Fault set in the north-western part of the Rag-e-Sefid Oilfield occurred at the Late Devonian-Carboniferous (positive inversion), Permian-Early Triassic (negative inversion), and Late Cenomanian-Early Turonian (positive inversion) boundaries and modified the evolutionary history of the sedimentary basin. The inversion affected hydrocarbon trap development at the Late Cretaceous and controlled their current conditions in the southern Dezful Embayment. Based on the hydrocarbon migration in these regions from the Late Miocene to the present day, the N-S trending (Pan Africa trend) north-western part of the Rag-e-Sefid anticline has a larger share of oil and gas compared to the NW-SE trending (Zagros trend) south-eastern part. The results of this study could add data to worldwide examples of the positive impact of tectonic inversion on the hydrocarbon traps development in the foreland of a collisional orogen.

Understanding the structural evolution of the South Dezful Embayment (SDE) in the Zagros Fold-and-Thrust Belt (ZFTB) is significant for hydrocarbon exploration and production. The structural evolution of this area has been controlled by the reactivation of basement structures related to the oblique convergence along the ZFTB. In this work, we study the effect of the pre-contractional interaction between the basement step and overlaid salt layer superimposed by the Zagros shortening on the structural style and evolution of the sedimentary basin in the SDE. We use multidisciplinary approaches involving surface and subsurface data and analogue models. Disharmonic folds with small wavelength formed over the Kharg-Mish Palaeo-high (KMPH) where the sedimentary cover is thinner. On the other hand, faulted detachment folds with large wavelengths developed in the adjacent depocenters. Furthermore, the KMPH affected the geometry and kinematics of the frontal part of the Zagros Belt, which is characterized by the Mountain Front Flexure (MFF) topographic step. Long-lasting active deformation of the sedimentary cover over the frontal ramp of the KMPH developed the South Izeh Promontory (SIP). Localized contraction in the SIP was accommodated temporally by trishear fault-propagation folding and resulted in > 5 km elevation difference between this promontory and two adjacent local basins. Supporting scaled analogue models show that structural evolution, folding and along-strike variations in fold style of the SDE have been controlled by thickness variations of the sedimentary cover and the geometry of the inherited pre-salt structure. Based on the results of this study, the effect of inherited structural highs on the structure and kinematics of the SDE provide important insights for hydrocarbon entrapment, migration and exploration.

The detailed characterization of faults and fractures can give valuable information about the fluid flow through petroleum reservoir and directly affect the hydrocarbon exploration and production programs. In this study, large- and small-scale fractures in the Asmari horizon of the Rag-e-Sefid oilfield were characterized using seismic attribute and well data analyses. Different spatial filters including finite median hybrid (SO-FMH), dip-steered median, dip-steered diffusion, and fault enhancement filters were used on 3D seismic data to reduce noise, enhance the seismic data quality, and create a 3D seismic steering cube. In the next step, seismic attributes such as coherency, similarity, variance, spectral decomposition, dip, and curvature were applied to identify structural features. In order to check the validity of these structural features, results from seismic attributes calibrated by the interpreted fractures from image logs in the Rag-e-Safid oilfield. Then, the ant-tracking algorithm applied on the selected seismic attributes to highlight faults and fractures. These attributes combined using neural network method to create multi-seismic attributes, view different fault- or fold-sensitive seismic attributes in a single image, and facilitate the large-scale fractures extraction process. Finally, automatic fault and fracture extraction technique used to reduce human intervention, improve accuracy and efficiency for the large-scale fracture interpretation and extraction from edge volumes in the Asmari horizon of the Rag-e-Sefid oilfield. In addition to, small- scale fractures were characterized by the obtained information from the image logs interpretation for sixteen wells. All the detected fractures from seismic and well data have been divided into eight fracture sets based on their orientation and using the statistical analysis. The obtained results show that fractures characteristics and their origin are different in the northwestern and southeastern parts of the Rag-e-Sefid oilfield. The NW Rag-e-Sefid and Nourooz Hendijan Izeh Faults reactivation during Zagros orogeny led to create the dextral shear zone and P, R, R′, T, Y- fracture sets in the northwestern part of the Rag-e-Safid oilfield. Also, activity of the SE-Rag-e-Sefid thrust fault during Zagros orogeny caused to form fault-related fractures sets in the southeastern part of the Rag-e-Sefid field. In addition to, axial, cross axial, oblique fracture sets in the Asmari horizon of the Rag-e-Sefid oilfield were created by folding phase during Zagros orogeny. The obtained results were used to fracture modeling in the Asmari horizon of the Rag-e-Sefid oilfield.