Fracture Analysis in the Outcrops of the Qara Chauq Anticlines, Zagros Fold and Thrust Belt of Kurdistan Region in Northern Iraq

Fracture patterns and petrophysical properties of carbonates undergoing regional folding: A case study from Kurdistan, N Iraq

Analysis of natural fractures and effect of deformation intensity on fracture density in Garau formation for shale gas development within two anticlines of Zagros fold and thrust belt, Iran

The research area concentrates in a part of the main Zagros fold and thrust belt in the Kurdistan region (Northern Iraq). From study tectono-stratigraphy we constrain the story of the basin evolution of Kurdistan during Cretaceous. However we mainly investigated the evolution of the pre-Subduction and Pre-collision periods, focusing on the relationship between tectonics and sedimentation. For this purposes we developed (1) a biostratigraphic approach using nannofossil analysis, (2) a fault tectonic analysis, and (3) a stratigraphic study. The Zagros fold belt in Kurdistan exhibits many lateral and vertical environmental and facies changes, especially during the Cretaceous times. During the Jurassic period the Kurdistan is occupied by the restricted Gotnia Basin. This basin disappeared and the Kurdistan area changed to open marine of a southwest Kermanshah Basin during the Cretaceous. During the Berriasian to Barremian the Kurdistan was covered by the carbonates of the Balambo and Sarmord formations. In the east and southeast the neritic Sarmord Formation gradationally and laterally passes to the basinal facies of the Balambo Formation. In the Aptian to Cenomanian period shallow massive reefal limestone of the Qamchuqa Formation deposited. The normal faulting that initiates during the Aptian is associated with an abrupt lateral change of the reefal Qamchuqa Formation to the Aptian-Cenomanian part of the Balambo Formation. During the Cenomanian-Early Turonian periods the graben formed in the Dokan Lake in eastern Kurdistan, where developed a deeper restricted environment (Dokan and Gulneri formations) surrounded by a shallow marine platform. During the Turonian the marine pelagic micritic cherty limestones of Kometan Formation covered northeast of Kurdistan, whereas in the Safeen, Shakrok and Harir anticlines the formation was totally, or partially, weathered during the Coniacian-Early Campanian period. The deposition during the Late Cretaceous is very heterogeneous with a gap in the Coniacian-Santonian times probably related to a non-deposition. Associated with extensive tectonics a basin developed during the Campanian with the deposition of shales, marls and marly limestones of the Shiranish Formation. The first appearance is the Kurdistan of the flysch facies of the Tanjero Formation was precisely dated of the Upper Campanian in northeastern Kurdistan. The Tanjero Formation conformably overlaying the Shiranish Formation and was deposited in the foredeep basin associated with the obduction of Tethyan ophiolites onto the Arabian Platform. The Early to Late Campanian period is a time of non-deposition in Central Kurdistan (Safeen, Shakrok and Harir anticlines). During the Late Campanian the Bekhme carbonate platform in the north disappeared when the marly limestones of the Shiranish Formation transgressed over the Bekmeh Platform. In the Aqra area the Maastrichtian Tanjero Formation laterally changed to the thick reefal sequence of the Aqra Formation that unconformably overlies by the Late Paleocene-Early Eocene lagoonal carbonate of the Khurmala Formation. The Campanian sedimentation is mainly controlled by NE- oriented normal faults forming Grabens in Dokan, Spilk and Soran areas. During the Maastrichtian in the extreme northeastern Kurdistan the NE-SW and NNW-SSE normal faults developed in the foredeep basin and originated horsts and grabens.

Iraq is located in the Western Asian continent particularly in the northern Arabian promontory. Iraq approximately lies in center of Middle East. The area of investigation cover northern and northeastern parts of Iraq-Kurdistan Region. Iraq and Kurdistan region are located in the northern Arabian Platform. The study area includes the northwestern extension of the Zagros Mountain range (the Zagros Fold and Thrust belt). Through study of Tectonic analysis, Stratigraphy, Geomorphology and satellite images; we try to constrain new classification with designation of the anticlines and compression stress orientation in Zagros fold belt. The northeastern and northern Iraq contain huge anticlines and synclines. They have been formed as a result of compression stress. These forces formed by collision of Arabia and Eurasian plates during Eocene-Miocene periods. Most of the anticlines characterize by double-plunging symmetrical to semi-symmetrical fold. The shield of the anticlines in the High Folded Zone mostly compose of carbonate sequence from Cretaceous formations. The core has Jurassic-Triassic formations. In the other hand the shield of anticlines in Low Folded Zones are Cenozoic formations. The plunging and terminate anticlines was caused by Cretaceous pre-tilting extensional normal faults. These fault become barriers in front of growing the anticlines longitudinally as example in Kosrat and Shakrok anticlines. The Cretaceous lateral facies change affected on the bend of anticline axis. The northwestern of Azmar anticline and southeastern of Surdash anticline seem to be En-echelon plunging; through this study we find out they are belong to one anticline. The Surdash-Azmar fold Axis shape is Bezier line while passing through facies change between Qamchuqa and Balambo Formations. The same phenomenon can be find in Aqra-Bekhme anticlines by facies change of Aqra-Tanjero formations. In this study, we try to make two or more anticlines to be show as one large anticline. In previous studies they split anticline into two or more anticlines because of having geomorphological features such as valley and lakes. However we try to show that valleys and lake are not barriers and not affect termination of the anticline as shown in Shirin, Bradost, anticlines are one individual anticline.

Scaled analogue models of thin-skinned simultaneous shortening above adjacent viscous and frictional décollements simulate the effect of Hormuz salt on the shortening in the Zagros fold and thrust belt. The models consisted of sand layers that partly overlay a viscous layer of silicone and were shortened from one end. Spatial distribution of the viscous décollement varied along strike and dip, as occurs in part of the Zagros fold and thrust belt. In this belt, Phanerozoic sedimentary cover was shortened partly above the Hormuz salt lying on the Precambrian crystalline basement, behaving as a basal viscous décollement. Model results display how the nature of the décollement affects the evolution of an orogenic belt. Using model results, we explain the development of deflection zones, and discuss strain partitioning, formation of different topographic wedges and differential sedimentation along the Zagros fold and thrust belt. Model results suggest the formation of a gentle taper, consisting of both foreward and backward thrusts above a viscous décollement and a relatively steeper taper consisting only of forward-vergent imbricates above a frictional décollement. However, in our models, the steepest wedge with the highest topography formed where the viscous substrate had a limited extent with a transitional boundary (pinch-out) perpendicular to the shortening direction. Shortening of this boundary led to development of frontal ramps associated with significant uplift of the area behind the deformation front.

Northern Iraq represents part of the convergent plate boundary between the Arabian and Eurasian plates. The collision zone between these two plates is manifested by the Bitlis–Zagros Fold and Thrust Belt. This belt is one of the most seismically active regions among the present active belts. This study intends to improve our knowledge on the seismotectonic activities in northern Iraq and the surrounding areas. To reach this goal, we used the waveform moment tensor inversion method to determine the focal depths, moment magnitudes, fault plane solutions, and directions of the principal stress axes of 25 events with magnitudes ≥3.5. The seismic data of these events were collected from 54 broadband stations which belong to the Kandilli Observatory and Earthquake Research Institute, the Incorporated Research Institutions for Seismology, the Observatories and Research Facilities for European Seismology, and the Iraqi Seismological Network. Computer Programs in Seismology, version 3.30 (Herrmann and Ammon2004), was used for analysis. The results show that the focal depth of these events ranged from 15 to 25 km in general. The fault plane solutions show that the strike-slip mechanism is the most dominant mechanism in the study area, usually with a reverse component. The stress regime shows three major directions; north–south, northeast-southwest, and east–west. These directions are comparable with the tectonic regime in the region.

Variations in crustal thickness in the Zagros determined by joint inversion of P wave receiver func- tions (RFs) and Rayleigh wave group and phase velocity dispersion. The time domain iterative deconvolution pro- cedure was employed to compute RFs from teleseismic recordings at seven broadband stations of INSN network. Rayleigh wave phase velocity dispersion curves were estimated employing two-station method. Fundamental mode Rayleigh wave group velocities for each station is taken from a regional scale surface wave tomographic imaging. The main variations in crustal thickness that we observe are between stations located in the Zagros fold and thrust belt with those located in the Sanandaj-Sirjan zone (SSZ) and Urumieh-Dokhtar magmatic assemblage (UDMA). Our results indicate that the average crustal thickness beneath the Zagros Mountain Range varies from ∼46 km in Western and Central Zagros beneath SHGR and GHIR up to ∼50 km beneath BNDS located in easternmost of the Zagros. Toward NE, we observe an increase in Moho depth where it reaches ∼58 km beneath SNGE located in the SSZ. Average crustal thickness also varies beneath the UDMA from ∼50 km in western parts below ASAO to ∼58 in central parts below NASN. The observed variation along the SSZ and UDMA may be associated to ongoing slab steepening or break off in the NW Zagros, comparing under thrusting of the Arabian plate beneath Central Zagros. The results show that in Central Iran, the crustal thickness decrease again to ∼47 km below KRBR. There is not a significant crustal thickness difference along the Zagros fold and thrust belt. We found the same crystalline crust of ∼34 km thick beneath the different parts of the Zagros fold and thrust belt. The similarity of crustal structure suggests that the crust of the Zagros fold and thrust belt was uniform before subsidence and deposition of the sediments. Our results confirm that the shortening of the western and eastern parts of the Zagros basement is small and has only started recently.

A statistical analysis of reserves in fold and thrust belts, grouped by their geological attributes, indicates which of the world's fold and thrust belts are the most prolific hydrocarbon provinces. The Zagros Fold Belt contains 490f reserves in fold and thrust belts and has been isolated during the analysis to avoid bias. Excluding the Zagros Fold Belt, most of the reserves are in thin-skinned fold and thrust belts that have no salt detachment or salt seal, are partially buried by syn- or post-orogenic sediments, are sourced by Cretaceous source rocks and underwent their last phase of deformation during the Tertiary. A significant observation is that the six most richly endowed fold and thrust belts have no common set of geological attributes, implying that these fold belts all have different structural characteristics. The implication is that deformation style is a not critical factor for the hydrocarbon endowment of fold and thrust belts; other elements of the petroleum system must be more significant. Other fold and thrust belts may share the structural attributes but the resource-rich fold belts overwhelmingly dominate the total reserves in that group of fold belts. There is nothing intrinsic in fold and thrust belts that differentiates them from other oil- and gas-rich provinces other than the prolific development of potential hydrocarbon traps. Many of the prolific, proven fold and thrust belts still have significant remaining exploration potential as a result of politically challenging access and remote locations.

ABSTRACTThe Zagros fold and thrust belt is a seismically active orogen that has accommodated the N–S shortening between the Arabian and Eurasian plates since the Miocene. Whereas the southeast parts of the belt have been studied in detail, the northwest extent has received considerably less attention, being part of the Republic of Iraq. In this study, we investigate fold growth in the area NE of Erbil (Kurdistan, Iraq). In particular, we focus on the interaction of the transient development of drainage patterns along growing antiforms, as this directly reflects the kinematics of progressive fold growth. Detailed geomorphological studies of the Bana Bawi‐, Permam‐ and Safeen‐fold trains show that these anticlines did not develop from a single embryonic fold but by lateral linkage of several different fold segments. These segments, with length between 5 and 25 km, have been detected by mapping ancient and modern river courses; these initially cut the nose of growing folds until eventually defeated, leaving curved wind gaps behind. Depending on the alignment of the initial embryonic folds, the segments can either record a linear‐ or an en‐echelon linkage. Comparison of natural examples from the Zagros fold and thrust belt in Iraq with published numerically modelled fold growth suggests that both linear‐linkage and en‐echelon linkage are mechanically feasible and are common processes during progressive shortening and fold growth.

The Kurdistan Region of Iraq (KRI), localized in the north and northeast of Iraq, is an autonomous territory recognized in the Iraqi constitution of 2005. Its capital and most populated city, Erbil, is also one of oldest inhabited cities in the world, dated back to around 6000 BC. The KRI’s Parliament was established in Erbil in 1970. In a highly mountainous setting, the KRI hosts colorful biodiversity and a wide range of climate and fertile lands suitable for varied agriculture. Geologically, the Zagros fold and thrust belt, to the north and northeast of the Region, is the most relevant feature. Originating from the collision between the Arabic and Eurasian plates, it gives the subsurface unique structural complexity. The first exploration well in the KRI dates back to 1901, drilled in Chia Surkh in the south of the territory. The well encountered oil shows but was abandoned. Later in 1927, the discovery of Baba Gurgur near Kirkuk was what really ignited the production of oil in northern Iraq. This field, controlled by the Federal Government of Iraq and operated by the Iraq Petroleum Company at that time, was brought onto production in 1934. Over 25 years later, in 1960, the first well was drilled at the Taq Taq field, and the discovery of oil was declared in 1978 following the drilling of a second exploration well. Nonetheless, this field was not appraised until the 1990s. In 2003, the end of the Iraq War triggered the interest of international oil companies (IOCs), which started to arrive in the KRI. In 2005, DNO spudded Tawke-1 in its Tawke license, marking the commencement of the current era in the KRI’s oil industry. The Tawke field started production in 2007, while the previously appraised Taq Taq field started producing in 2008. The Khurmala Dome field, part of the Kirkuk’s complex, was taken over by KAR in 2004 with a remit to revive production and increase it to the 100,000 BOPD mark. As a result, Tawke, Taq Taq, and Khurmala Dome became the three dominant fields in the KRI’s oil production at that time. When it comes to gas, the Khor Mor field started production in newly built facilities in 2008. This initial period of exploration, appraisal, and development in the KRI, up to 2014, has been extensively covered in a work published by David Mackertich and Adnan Samarrai in April 2015. During this time, more than 20 IOCs entered the region, and about 200 wells were drilled. By the end of 2013 the average daily production was 215,000 BOPD, mostly from the three main fields previously mentioned.

The Indication of Geomorphic Evidence for Lateral Propagation of Sheikhan Anticline - Zagros Fold and Thrust Belt – Northern Iraq

This study focuses on the Upper Cretaceous system in the Zagros fold and thrust belt in the Kurdistan Region / Iraq. The impression of this study is created by the variety of formations, facies change, and age of the Cretaceous formations, as well as the different consequences of the contact situation between the formations, particularly the Qamchuqa-Bekhme and Kometan-Shiranish contacts formations. Through investigation, evaluation, and combination of results from Lithostratigraphy and Microfacies of seven sections in various locations of KRI/ Iraq, new paleogeography of the Late Cretaceous of Northern Iraq is constrained. The microfacies of entire Late Cretaceous formations in different sections outcome 16 sub-microfacies types demonstrating open marine deep shelf environment of Shiranish Formation, the entire reef (back-reef, fore-reef, reef body) environment of Bekhme Formation and pelagic open marine ramp depositional environment of Kometan Formation. The output results of stratigraphy and microfacies of Late Cretaceous depositional successions in the Kurdistan Region are paleogeography maps reconstruction. During the Turonian to Early Santonian periods, the Kurdistan Region and northern Iraq were pre-subduction basins due to the presence of open marine outer ramp carbonate of the Kometan Formation in the east (Sulaimaniyah province exceeding Hizop area) and inner shelf of Tanuma and Khasib formations in the center and west (Erbil province). Major regression and unconformities covered the West of the study region during the Middle-Late Santonian; the result of this regression degraded the entire inner shelf facies that deposited during Turonian-Early Santonian periods. During the Early-Middle Campanian, a foreland basin emerged in the extreme northeastern and the Kurdistan Region, which was covered by open marine of the Shiranish Formation and reef platform of the Bekhme Formation. The Kurdistan Region was an active foreland basin margin in the Upper Campanian-Maastrichtian, with a greatly expanded Tanjero Formation, an Aqra reef in the north, and an open marine Shiranish Formation in the center and west.

<p><strong>The Arabian Peninsula is part of a small tectonic plate that is characterized by active and appreciable deformations along its boundaries. Knowledge of the present-day in situ stress field in the Arabian plate and its variability is critical for earth science disciplines that require an understanding of geodynamic processes. In addition, it is essential for a range of practical applications that include the production of hydrocarbons and geothermal energy, mine safety, seismic hazard assessment, underground storage of CO2, and more. </strong></p><p>This project aims at modeling the stress orientation field in the Arabian Plate using advanced computational tools together with a plate velocity model. We built a three-layer 3D model of the Arabian crust using digital elevation, basement depth, and Moho depth maps. Based on these data, we built a 3D unstructured finite element mesh for the whole Arabian plate, including the offshore area, with finer resolution at critical locations. The latter is a novel approach to this work.  To capture the deformation caused by the water bodies in the Red Sea, Gulf of Aden, and the Arabian Sea areas, we set a hydrostatic boundary condition as a function of bathymetry. Along the Zagros fold and thrust belt, we pinned the plate boundary to capture continental collision. Finally, the partial differential equation of force equilibrium (a linear static analysis) is solved using plate displacements (inferred from plate velocities) as boundary conditions for several displacement conditions.</p><p><strong>The modeling results suggest NE-SW S<sub>Hmax</sub> azimuths in northeastern Saudi Arabia and Kuwait while the Dead Sea transform areas show NW-SE to NNW-SSE azimuths, and the rest of the plate is characterized by predominant N-S S<sub>Hmax</sub> azimuth. Due to pinned boundary conditions at the Zagros Mountains, S<sub>Hmax</sub> azimuth changes from N-S at the Red Sea basin to NE-SW at the Zagros fold and thrust belt.</strong><strong> </strong><strong>We also notice significant stress concentrations in the transition from the Arabian shield to the sedimentary basins in the Eastern parts of the plate. This is in response to associated changes in rock properties. Hence, the simulated stress orientations corroborate the ongoing tectonic process and deepen our understanding of regional and local in situ stress variation drivers as well as the current elastic deformation in the Arabian plate.</strong></p>

The wide range in geological complexity encountered in fractured carbonate reservoirs requires the combination of several elements to optimize their development: a favorable structural position for drilling needs to be paired with the understanding of the fluid connectivity pathways affecting its location. In addition, the well placement criteria will vary depending on the stage of maturity of the field. This work aims to summarize key observations acquired by the authors during over a decade of field development experience in faulted and fractured carbonate oil reservoirs in the Zagros Fold and Thrust Belt in the Kurdistan Region of Iraq. The methodology of this work includes the analysis of different fracture types and their context of occurrence with respect to well behaviors during drilling, production and surveillance stages. These correlations are based on the authors’ observations from a number of producing oil fields where vertical and horizontal wells in deformed sections provided insights to the wide spectrum of geological features and their hierarchical range in flow potential. Commonalities observed from these fields are presented in this paper in a generic fashion covering multi-scale data sets. The work summarizes the understanding of the diverse fracture networks and their dynamic behavior along with key remarks on optimizing well placement criteria and completion strategies according to the maturity of the field and, ultimately, to improve the field development strategy. Outcrop examples are used to introduce the array of fracture categories encountered in subsurface and to guide the discussion on the dimension of scale and their spatial relationship relative to each other as contributors to reservoir plumbing systems and observed reservoir dynamics. As a result of this analysis, the challenges related to fractured and faulted carbonate fields such as water breakthrough scenarios, cumulative rise in water production and underperforming reservoir sections are addressed. This paper therefore intends to contribute to the discussion on development strategies, definition, and selection of drilling targets and well design applied in fractured and faulted carbonate reservoirs by utilizing observations from different reservoir types in the Kurdistan Region of Iraq.

Оценка влияния трещиноватости на коллекторские свойства месторождения Саркала в складчато-надвиговом поясе Загрос – Северный Ирак