Fault & Fracture Development in Foreland Fold and Thrust Belts - Insight from the Lurestan Province, Zagros Mountains, Iran

Second Arabian Plate Geology Workshop Abu Dhabi, UAE, 24 - 27 January 2010The Simply Folded Belt of the Zagros Mountains, Iran, represents one of the best examples of foreland fold and thrust belt. A regional fault and fracture analysis of the Cenomanian ¿ Coniacian Ilam and Sarvak formations, exposed in southern Lurestan Province, is presented as a case study for fault and fracture development in folded belts. The area is characterised by the occurrence of gentle to tight anticlines and synclines whose NW-SE axial traces are parallel to the general trend of the belt. Fold style is intimately related to both vertical and lateral facies distribution. The two formations belong to the Bangestan Group and, in this area, they represent the oldest strata exposed in the core of most anticlines outcropping at surface. Distribution, kinematics and timing of faults and fractures have been characterised through extensive fieldwork and interpretation of orthorectified QuickBird imagery and 3-D virtual outcrop models based on LiDAR technology. Data have been collected from 10 anticlines covering an area of approximately 150 x 150 km. Key outcrops for fracture and fault kinematics interpretations are presented. Field observations and interpretation of QuickBird and 3-D photorealistic models suggest a complex fault and fracture geometry and timing relationship. Both fractures and faults record pre-folding to uplift-related deformations. Pre-folding structures are typically represented by small-scale, flat-ramp-flat geometry thrusts, systematic veins and stylolites, which are superimposed on inherited syn-sedimentary normal faults. Folding-related structures generally reactivated pre-existing fracture and fault planes. Strike-slip faulting is typically recorded as the last faulting event and is probably related to late stage of fold tightening. All structures are geometrically and kinematically consistent with the trend of the Arabian passive margin and its subsequent tectonic inversion. Uplift and stress release induced opening and propagation of through-going fractures. Faults and fracture orientations generally change accordingly with local fold trend. Symmetry between fracture and fold orientation, although commonly interpreted as evidence for folding-related fracture development, is here interpreted as evidence of syn- to post-folding local vertical axis passive rotation

Fracture characterization in sigmoidal folds: Insights from the Siah Kuh anticline, Zagros, Iran

Fieldwork and remote-sensing data from the Siah Kuh anticline, simply folded belt, Zagros, Iran indicate that specific structures and fracture systems formed during the development of its sigmoidal shape, and that conceptual fracture models developed for cylindrical folds are inadequate for the correct evaluation and development of hydrocarbon accumulations in this type of anticline. The sigmoidal shape of the Siah Kuh anticline was achieved in the Pliocene due to vertical axis rotations of an already existing anticline. These rotations promoted the development of (1) two systems of normal faults in the outer arcs of the sigmoidal shape, (2) a low-angle thrust, and (3) the north-south Danan anticline in the inner arc of its easternmost bend. The passive margin to syn-folding structures, typically observed in nearby cylindrical and periclinal anticlines, predated the development of the sigmoidal shape and were passively rotated into the segments of the anticline. The sigmoid-related structures are spatially, geometrically, and kinematically related to the bends of the anticline trend, hence they can be predicted and modeled in the subsurface. The sigmoid-related normal faults have a great potential to preserve porosity and promote localized high flow rates or early water breakthrough. However, if they cut through thin reservoir and seal units, sigmoid-related thrusts and normal faults might compromise lateral reservoir continuity and seal integrity. The results of this study can help in reducing risks and uncertainty in the evaluation and development of business opportunities in secondary sigmoidal anticlines within the Zagros or any other fold-thrust belt. Copyright © 2018. The American Association of Petroleum Geologists. All rights reserved.Peer reviewe

Geological mapping and structural interpretation using a virtual outcrop digitiser, examples from the Lurestan province of the Zagros Range (Iran)

72nd EAGE Conference & Exhibition incorporating SPE EUROPEC 2010 Barcelona, Spain, 14 - 17 June 2010The use of high resolution satellite images associated to Digital Elevation Models and managed by 3D graphics toolkits is becoming increasingly common in supporting geological investigation for a wide range of applications. In this contribution examples are given of the use of the Virtual Outcrop Digitiser (VOD) developed by Statoil for the mapping and structural analysis of a vast region of the Lurestan Province in the Zagros mountain range of Iran. In this region the scarcity of vegetation, the poor access conditions and the limited information on the geological setting made of the Virtual Outcrop Digitiser an extremely useful tool for the geological exploration

Reservoir characteristics of fault-controlled hydrothermal dolomite bodies: Ramales platform case study

Hydrothermal dolomite (HTD) bodies are known as high-quality hydrocarbon reservoirs; however few studies focus on the geometry and distribution of reservoir characteristics. Across the platform-to-basin transition of the Ramales Platform, fault-controlled HTD bodies are present. Three kinds of bodies can be distinguished based on their morphology, that is, elongated HTD corridors, a massive HTD body (Pozalagua body) and an HTD-cemented breccia body. The differences in size and shape of the HTD bodies can be attributed to differences in local structural setting. For the Pozalagua body, an additional sedimentological control is invoked to explain the difference in HTD geometry. A (geo)-statistical investigation of the reservoir characteristics in the Pozalagua body revealed that the HTD types (defined based on their texture) show spatial clustering controlled by the orientation of faults, joints and the platform edge. Porosity and permeability values are distributed in clusters of high and low values; however, they are not significantly different for the three HTD types. Two dolomitization phases (i.e. ferroan and non-ferroan) can be observed in all HTD bodies. In general, the HTDs resulting from the second non-ferroan dolomitization phase have lower porosity values. No difference in permeability is found for the ferroan and non-ferroan dolomites. © The Geological Society of London 2012.Peer Reviewe

Sub-seismic fractures in foreland fold and thrust belts: Insight from the Lurestan Province, Zagros Mountains, Iran

International audienc

Sub-seismic fractures in foreland fold and thrust belts: Insight from the Lurestan Province, Zagros Mountains, Iran

The Simply Folded Belt of the Zagros Mountains, Iran, is a spectacularly well-exposed example of a foreland fold and thrust belt. A regional analysis of the Cenomanian-Coniacian Sarvak and Ilam Formations, exposed in the southern Lurestan Province, is presented as a case study for sub-seismic fracture development in this type of compressive setting. The area is characterized by gentle to tight anticlines and synclines parallel to the NW-SE trend of the belt. In the Lurestan Province, the Cenomanian- Coniacian interval is exposed in the core of most of the outcropping anticlines. Fold style is intimately related to both vertical and lateral facies distribution. Geometry, kinematics and timing of sub-seismic fractures were characterized through extensive fieldwork, interpretation of orthorectified QuickBird imagery and interpretation of 3D photorealistic models derived from LiDAR. Data were collected from 12 anticlines covering an area of approximately 150 × 200 km. Key outcrops for understanding fracture geometry, kinematics and timing are presented. Field observations and interpretation of QuickBird and 3D photorealistic models reveal the complexity of fracture geometry and timing. Fractures record pre-, syn- and post-folding stages of deformation. Pre-folding structures include synsedimentary normal faults, and subsequent small-scale thrusts, systematic veins and stylolites. During folding, pre-existing fracture planes were re-activated and through-going fractures and reverse faults developed. Strike-slip faults typically postdate pre- and syn-folding structures and are probably related to the late stages of fold tightening. All structures are geometrically and kinematically consistent with the trend of the Arabian passive margin and its subsequent tectonic inversion. © EAGE/Geological Society of London.Peer Reviewe

Basin architecture and growth folding of the NW Zagros early foreland basin during the Late Cretaceous and early Tertiary

We present and use the chronostratigraphy of 13 field logs and detailed mapping to constrain the evolution of the early Zagros foreland basin, in NW Iran. Large foraminifera, calcareous nannofossil, palynological and 87Sr/86Sr analysis supplied ages indicating a Campanian-early Eocene age of the basin infill, which is characterizd by a diachronous, southwestward migrating, shallowing upwards, mixed clastic- carbonate succession. Growth synclines and local palaeoslope variations indicate syndepositional folding from Maastrichtian to Eocene time and suggest forelandward migration of the deformation front. We also illustrate the basin architecture with a synthetic stratigraphic transect. From internal to external areas, time lines cross the formation boundaries from continental Kashkan red beds to Taleh Zang mixed clastic-carbonate platforms, Amiran slope deposits and basinal Gurpi-Pabdeh shales and marls. The foreland basin depocentres show a progressive migration from the Campanian to Eocene (c. 83-52.7 Ma), with rates of c. 2.4 mm a-1 during the early-middle Palaeocene (c. 65.5-58.7 Ma) increasing to c. 6 mm a-1 during the late Palaeocene- earliest Eocene (c. 58.7-52.8 Ma). Coeval subsidence remained at c. 0.27 mm a-1 during the first 12.7 Ma and decreased to c. 0.16 mm a-1 during the last 4.2 Ma of basin filling. Finally, we integrate our results with published large-scale maps and discuss their implications in the context of the Zagros orogeny. © 2011 Geological Society of London.This study is a contribution of the Group of Dynamics of the Lithosphere (GDL) within the framework of a collaborative project with the Statoil Research Centre in Bergen (Norway). We thank both Statoil and the National Iranian Oil Company (NIOC) for support in the field as well as for permission to publish these results. Additional support was provided by MCI project CGL 2008-00809.Peer Reviewe

Integrated Fracture and Matrix Heterogeneity Reservoir Characterisation of the Mid Cretaceous Aged Upper Sarvak Formation, Chenareh River Gorge, Iran: A Virtual Outcrop Display

Conference: Advances in Carbonate Exploration and Reservoir Analysis, 3-5 November 2010At: London, UKThe Chenareh Anticline, within the Simply Folded Belt of the Zagros Mountains, Iran, represents a particularly well-exposed ¿type¿ section through naturally fractured Cenomanian-Turonian neritic carbonates of the Sarvak Formation. The Sarvak Formation forms a prolific reservoir in Iran and elsewhere in the Middle East (e.g. Mishrif and Natih equivalent in Iraq/UAE and Oman respectively).. Through the integration of various structural and sedimentological data, including detailed regional-scale stratigraphic forward modelling (Dionisos), extensive fieldwork observations, systematic sampling along a measured section in the Chenareh Gorge, interpretation of QuickBird satellite imagery (0.7m resolution) and high resolution 3D photorealistic models based on LiDAR technology, a 3D dual porosity and dual permeability model has been created for the Sarvak Fm. This dataset represents a new type section for Mid Cretaceous reservoirs of the Middle East

Reservoir Modelling from Interpretation of 3D Virtual Outcrops & Field Data - A Case Study from the Upper Sarvak Fm, Chenareh Gorge, Lurestan, Iran

Second Arabian Plate Geology Workshop Abu Dhabi, UAE, 24 - 27 January 2010fracture heterogeneities are generally poorly incorporated into reservoir models. Indeed, modelling of subsurface reservoirs is often exclusively based on well log and seismic data, which are not able to capture many of the heterogeneities characterizing matrix and fracture properties across the reservoir. The analysis of reservoir outcrop analogues plays a key role for the characterization and modelling of matrix and fracture heterogeneities, especially when well log and seismic data are limited or of poor quality. A case study of reservoir heterogeneity characterization and modelling based on integration of fieldwork and 3-D virtual outcrop interpretation is presented. The case study is located in the Chenareh anticline, Simply Folded Belt of the Zagros Mountains, Lurestan, Iran. Along the Chenareh Gorge, the Upper Sarvak-Ilam stratigraphic section of the Bangestan Group is spectacularly exposed. The gorge cuts entirely across the Chenareh anticline allowing continuous fracture and matrix characterisation from backlimb to forelimb. The section, Cenomanian ¿ Turonian in age, has been extensively studied both in the field and through interpretation of high resolution 3-D photorealistic models based on LiDAR technology (up to 0.05 m resolution) and QuickBird satellite imagery (0.70 m resolution). Data from extensive fieldwork along the gorge and surrounding areas permit detailed characterisation of matrix and fracture heterogeneities across the anticline. Facies, pore type and sequence stratigraphy have been characterised in the field and through the analysis of samples collected systematically along the measured section. Data on fracture and fault network geometry have been also collected systematically through the whole stratigraphic interval. Fieldwork data have been integrated with data manually and automatically extracted from 3-D photorealistic models based on LiDAR technology and QuickBird satellite imagery. The use of high-resolution 3-D photorealistic models allows quick collection of high-quality data for quantitative and qualitative analysis of matrix and fracture heterogeneities. Integration of fieldwork and 3-D virtual outcrop interpretation was fundamental for modelling matrix and fracture heterogeneities of the Chenareh Gorge fractured reservoir analogue