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The study area lies to the east of Kalar City within the Sulaimani Government of the Kurdistan Region, Iraq. Utilizing a 3D cube Seismic dataset covering an expanse of 75 square kilometers, the investigation sought to unveil subsurface geologic structures. These seismic data were sourced from the Pet Oil Company, authorized by the Ministry of Natural Resources (MNR) of the Kurdistan region-Iraq (KRI). The study involved the use of 40 inline sections-oriented NE-SW and 30 crosslines sections-oriented NW-SE. This approach revealed the presence of elongated NW-SE linear features, with one predominant feature extending throughout the entirety of the surveyed region. Within this framework, seven reflectors were identified and marked. To further refine subsurface geology interpretation, a synthetic seismogram was created by integrating 3D seismic data and check shot data from well CS-11. The combination of well data and seismic data facilitated the identification of distinct horizons, encompassing Fatha unit 1, Fatha unit 2, Fatha unit 3, Fatha unit 4, Jeribe, Dhiban, and Euphrates Formations. These horizons were correlated and linked to the seismic data through the application of Petrel Schlumberger 2017 software. Through the deployment of 3D Two-Way time maps, the study depicted reflections from the aforementioned horizons, along with the presence of three reverse faults: F1, F2, and F3. Notably, the seven reflectors clustered in close proximity exhibited undulation patterns corresponding to an anticline structure aligned along a NW-SE axis. Among the faults, F1, extending across the study area, shared a parallel disposition with the smaller F2 and F3 faults, which also exhibited reverse characteristics. However, F3's dip direction contrasted with that of F1 and F2. After converting time-to-depth, seven depth maps were generated. Notably, the first four maps spotlighted a prominent NW-SE anticline structure that dominated the study area over a distance of 10 kilometers. The varying tilt of these structures was observable along their length, with the northeastern limbs demonstrating a less pronounced tilt (45°) than the steeper southwestern side (50°). Within this geological context, two distinct faults emerged. F1, spanning the study area over 10 kilometers, paralleled the major anticline trend. On the other hand, F2 extended 2 kilometers, aligning parallel to F1 and potentially contributing to localized deformation patterns. The seismic depth maps underscored the intricate nature of the region's structural features, prompting a call for expanded exploration to refine subsurface geology interpretation and detect potential hydrocarbon reservoirs. Incorporating the seismic depth maps of Dhiban, Jeribe, and Euphrates, the study highlighted the presence of two observable domes, with the larger situated in the southeast and the smaller in the northwest. ii Significantly, the contour lines on the domes' northeastern sides displayed a shallower incline in contrast to the steeper dips on the southwestern side. While F1's identification within these formations was limited due to its constrained vertical and horizontal extension, F2 was consistently identified, extending 2 kilometers in the NW-SE direction. It's conceivable that F2 contributed to localized changes in the area's deformation pattern, contributing to the overall complexity of its deformation history. geological evolution can be attributed to ancient tectonic forces originating from the northeast. Seismic attribute analysis played a pivotal role in deciphering these structural complexities, spotlighting their significance in terms of hydrocarbon exploration and production. The study employed seismic attributes including variance edge, curvature, root mean square, envelope, and sweetness. These attributes unveiled a major NW-SE trending anticline, a major fault, and two parallel minor faults. Envelope and sweetness attributes highlighted bright spots within Fatha, Dhiban, Jeribe, and Euphrates Formations, suggestive of hydrocarbon presence. Using 3D seismic data interpretation, a geomodel for the Chia Surkh oil reservoir established a structural framework. The model accurately captured essential features, aiding precise property estimation. TWT grids of reflectors and the 3D seismic volume were input for constructing the static model using Petrel software. Porosity modeling, pivotal in oil and gas industry, yielded six models indicating porosity variations (0-49%) due to lithological diversity. Notably, a major NW-SE trending anticline aligned with Zagros series tectonic trend, spanning 10 km by 7.5 km. A major fault with 150m displacement, 10 km length, extending beyond study area, and two parallel minor faults (displacements 40-70m, lengths 1.25-3 km) were observed. Seismic attributes confirmed these features. Attributes like envelope and sweetness indicated bright spots across formations, implying hydrocarbon presence. Detected geological features - anticline, carbonate rocks, gypsum, anhydrite as cap rocks, and bright spots as Direct Hydrocarbon Indicators (DHI’s) - suggest oil trap reservoir presence in multiple formations. Structural features - major anticline, three parallel reverse faults - formed during Alpine Orogeny in Early Miocene. Study area’s geological structure suggests oil prospectively, with anticline as trap, evaporites as seal, limestone as reservoir. Notably, major fault intersecting anticline near crest could lead to hydrocarbon escape, though interbedded claystone may retain some hydrocarbons. Geomodel elucidates study area as anticline oil trap with geological formations as reservoir.

Abstract: The study area lies in the northern part of Iraq in the western part of Nainawa governorate. It is surrounded by Tigris River to the east, Mashuradagh anticline to the north, Sinjar anticline and Baaj area to the west and Al- Gayara region to the south, The study area locates within the foothill subzone including Mosul block consisting of secondary blocks which was suggested by a stratigraphic correlation based on deep oil exploration wells. The Bouguer gravity map covered the study area reflects a gravity high which its centre locates near Atshan anticlinal structure. The previous gravity high extends over many anticlinal structured surfaces Allan, Shaikh -Ibrahim, Sasan, Ishkaft, Gusair, Ain-Zalah, Butma, Rafan, Atshan, Nwaigit, Qlaian, Adayia and Najma. Twenty-three gravity traverses were chosen. (T1-T8) with NW-SE direction and the others (T10-T24) with NE-SW. The present study conducted simulation of gravity data with different computer techniques taken in to consideration the previous studies. The calibrated gravity field was chosen visually and upward continually avoiding both the personal bias and the pure mathematic. Mosul block reflects a huge mass of 120 Km length and 60 Km width which is divided into a southern block with Zagrosian trend and a northern Taurosian trend by a strike-slip fault might explaining why the anticlines changing their axes orientations from NW-SE to the southern one with E-W on the northern. The gavity anomally of Mosul block reflects density vaiation between basement rocks and the sedimentary cover. On the other hand, the study explained subsidiary block faults surrounding and within Mosul block which extends in role to deep depths. This conclusions leads to the large importance of the study area due to presence of hydrocarbon resources in sedimentary basins as a result of tectonic activities during the geological eras.