The Upper Triassic Kurra Chine Formation in the Sarta oil field of the Kurdistan Region of Northern Iraq has garnered limited attention, notwithstanding the keen interest of numerous international oil companies in drilling wells within this geological epoch. This study endeavors to thoroughly investigate the Formation Evaluation and petrophysical properties of the Kurra Chine Formation in the production oil field, with a specific focus on Sarta Well-2 (S-2). The research incorporates diverse methods for formation evaluation and analysis of petrophysical properties, employing conventional wireline logs such as Gamm-Ray, Neutron, Density, Sonic, Resistivity, Caliper, and Bit size. The research findings reveal that the thickness of the Kurra Chine Formation in S-2 is approximately 380 m. The pay zones of S-2 exhibit an average shale volume of 17 %. The dominant lithology in S-2 comprises Limestone, Dolomite, Anhydrite, Shale, and Sandstone. The average total porosity within the pay zones is determined to be 6 % in S-2. Furthermore, the average effective porosity in reservoir zones of the S-2 is estimated to be 5 %, while the average secondary porosity in these zones is found to be 6 % in S-2. The average permeability in the pay zones of the Sarta well is reported to be 30.6 millidarcy (mD). Additionally, the average water saturation in the pay zones is determined to be 35 % in S-2, whereas the average hydrocarbon saturation is estimated to be 45 % in S-2. This study furnishes comprehensive descriptions and analyses of the formation evaluation and petrophysical properties of the Kurra Chine Formation in Northern Iraq, shedding light on the characteristics and potential of this oil-bearing formation.

Palynofacies (PF) analysis was conducted on 34 crushed samples of the Upper Triassic Kurra Chine Formation. These samples were collected from one outcrop sample and two production wells in northern Iraq. A 10μm nylon mesh sieve was used for the concentration of palynomorphs. Four palynofacies types were found in this study. PF1 was characterized primarily by amorphous organic matter (AOM), suggesting a distal suboxic-anoxic depositional environment. PF2 comprised of AOM, along with some Phytoclasts and palynomorphs, indicating a distal dysoxic-oxic shelf depositional environment. PF3 displayed an increasing volume of palynomorphs, signifying a distal dysoxic-anoxic shelf depositional environment. PF4 predominantly consisted of palynomorphs and Phytoclasts, representing a mud-dominated oxic shelf (distal shelf) depositional environment. Kerogen types were identified as type II, which is oil-prone in three palynofacies, and type III which is gas-prone in one palynofacies.

The current research deal with evaluating the Late Triassic Kurra Chine Formation using the Rock-Eval Pyrolysis technique in selected wells in Sarta-2 and Tawke-17 Oil fields, and the Sirwan Valley outcrop, in Northern Iraq. A total of twenty-six samples were selected for this study; nineteen cuttings samples from the wells and seven outcrop samples from Sirwan Valley. The total organic carbon wt.% of the formation in Sarta oilfield samples ranges 0.43– 2.51, and in Tawke samples ranges between 0.13–1.52, and for Sirwan Valley ranges between 0.02–0.32. Based on the total organic carbon content the Kurra Chine Formation can be considered as poor to very good source rock in the Sarta Oil field and poor to good in Tawke, and poor to fair source rock in Sirwan samples. Generation Potential shows some potential to generate good source potential, moderate source potential, and poor generation potential in the Sarta well, Tawke well, and Sirwan Valley as Generation Potential ranges between 1.47– 8.55, 0.48–4.46 and 0.02-0.11, respectively. The values of S1 range between 0.57–4.13, 0.15–1.02 and 0.01–0.03 mg HC/g rock for Sarta, Tawke, and Sirwan Valley respectively. Based on the S1 values the Kurra Chine Formation is considered fair to excellent, fair to good and poor source rock in the Sarta, Tawke, and Sirwan respectively. The analyzed samples show an immature level with Tmax ranges between 292-405 and immature to early mature with Tmax between 425-439 and immature to postmature with Tmax values between 339– 597 for Sarta, Tawke, and Sirwan respectively. Tmax-HI plot shows Kerogen types (II-III, III-IV), (II to III), and (III-IV) for Sarta, Tawke, and Sirwan Valley respectively

Abstract The study of carbonate petrography is essential for understanding reservoir properties and the quality of rock formations. High-resolution cathodoluminescence spectroscopy and optical microscopy were used to determine the impact of cement on the porosity evolution of carbonate rocks of the Kurra Chine Formation at Sirwan Valley, Northern Iraq. This study represents the first-ever attempt to investigate sedimentology at this location. A total, of 183 thin-section slides, 18 X-Ray Diffraction (XRD) samples, 14 Scanning Electron Microscope (SEM) samples, and 6 Cathodoluminescence (CL) samples were analyzed from the outcrop section of the Kurra Chine Formation. Four types of dolomite textures are recognized and classified based on the crystal size distribution and crystal-boundary shape. The porosity within Kurra Chine Formation includes primary and secondary porosity, with the majority of primary porosity being occluded by cementation. Cathodoluminescence analysis revealed two phases of calcite cement in the Kurra Chine Formation. The first phase (C1), is characterized by weak-zoned blocky calcite, displaying a dull luminescence with typical homogenous red color, which fills most of the interparticle and moldic pores. The second type of calcite cement (C2) is ghost-zoned calcite exhibiting red to slight orange luminesces interfingering with dolomite cement. XRD analysis indicated a predominant of calcite and common dolomite. SEM analysis revealed the predominance of secondary porosity occurring within fractures of the dolomite.

A detailed sedimentological investigation of the Baluti Formation (Late Triassic) in the Warte section, Imbricated Zone, northeastern Kurdistan region of Iraq has been undertaken for the first time. The formation is comprised of 34 m of dolomitic limestone, marly limestone, and marly dolomitic limestone which is partially brecciated and all interbedded with shale and several beds of marl in the lower part. Based on the field observations and petrographic inspections, four different lithostratigraphic units were identified in the studied section, which are, in ascending order: marly dolomitic limestone interbedded with marl and shale unit, brecciated marly dolomitic limestone interbedded with shale unit, fractured marly dolomitic limestone unit, and marly limestone interbedded with shale unit. The petrographic study of 19 thin sections of Baluti carbonates shows that the majority are composed of carbonate mud (micrite). The skeletal grains include ostracods, calcispheres, benthonic foraminifera, gastropods, bivalves, clasts, and bioclasts. While non‐skeletal grains include peloids, intraclasts, and extraclasts. The results of X‐ray diffraction (XRD) of five samples and scanning electron microscope (SEM) of three samples of the shale and marl of the studied formation show that the main clay mineral is illite, whereas non‐clay mineral is dolomite. The carbonate rocks of the Baluti Formation were subjected to different diagenetic processes, such as micritization, dolomitization, cementation, compaction, solution, pyritization, neomorphism, and fracturing. Three main microfacies were identified in the Baluti carbonates and according to their environmental interpretation, they are grouped into one basic type of facies association—subtidal‐semi restricted lagoon. Field observation, petrographic, microfacies, and textural analysis indicate that the Baluti Formation in the Warte section was deposited in a shallow marine, subtidal (lagoon) environment with semi‐restricted conditions.