An integrated approach to study the impact of fractures distribution on the Ilam-Sarvak carbonate reservoirs: a case study from the Strait of Hormuz, the Persian Gulf

Most of the Iranian hydrocarbon reservoirs in the Persian Gulf Basin and the Zagros Fold-Thrust Belt are composed of fractured carbonate rocks. In this regard, determining the spatial distribution of fractures has been a challenging issue. In this study, an integrated approach was applied for understanding the impact of fractures spatial distribution on the Ilam-Sarvak (Cenomanian to Santonian) carbonate reservoir rocks. For this purpose, seismic interpretation techniques along with geomechanical and geostatistical modeling were employed to characterize fractures at different scales. Initially, the relationship between fractures origin and the normal faults was investigated by conducting an in-situ stress analysis. Afterwards, the velocity deviation log (VDL) and fracture intensity log (FIL) were derived as fracture attributes from the interpretation of Formation Micro Imager (FMI) and conventional well logs. A 3D model of VDL and FIL was achieved by using a sequential Gaussian simulation (SGS) method. In order to achieve a more realistic and accurate model of the factures distribution, variations of the shear-wave velocity and geomechanical properties (Young's modulus and Poisson's ratio) were estimated by applying the advanced seismic interpretation techniques in the normal faults domain. The results show that the intensity of fractures increases once they are introduced to the normal faults, especially in the central part of the study area around well#2. Such a fractured zone is verified by fracture density log derived from FMI logs of the mentioned well. Obviously, there is a close-knit relationship between the fracture system and the normal faults. Eventually, secondary porosity caused by features was determined though identification of Hydraulic Flow Units (HFUs). Based on the porosity and permeability data, seven HFUs were determined for the Ilam-Sarvak reservoirs. The very high values of Log FZI indicate the possible presence of fractures. Overall, the fractures contributed to enhance the secondary porosity of the reservoir rocks though increasing matrix permeability. To sum up, the fractures system plays a critical role in controlling reservoir properties especially in the hanging-wall of normal faults where the majority of the macro and micro fractures are distributed

miR-1: A comprehensive review of its role in normal development and diverse disorders

MicroRNA-1 (miR-1) is a conserved miRNA with high expression in the muscle tissues. In humans, two discrete genes, MIRN1-1 and MIRN1-2 residing on a genomic region on 18q11.2 produce a single mature miRNA which has 21 nucleotides. miR-1 has a regulatory role on a number of genes including heat shock protein 60 (HSP60), Kruppel-like factor 4 (KLF4) and Heart And Neural Crest Derivatives Expressed 2 (HAND2). miR-1 has critical roles in the physiological processes in the smooth and skeletal muscles as well as other tissues, thus being involved in the pathogenesis of a wide range of disorders. Moreover, dysregulation of miR-1 has been noted in diverse types of cancers including gastric, colorectal, breast, prostate and lung cancer. In the current review, we provide the summary of the data regarding the role of this miRNA in the normal development and the pathogenic processes. © 2020 The Author(s

An Investigation of Abnormal Fluid Pressure within an Evaporitic Cap Rock in the Gavbandi Area of Iran and its Impact on the Planning of Gas Exploration Wells

A synthesis of well logs was carried out and drilling mud weight data were analyzed to figure out anomalous high fluid pressure within the Triassic evaporitic cap rock (the Dashtak formation) and study its impact on the geometry of anticlinal traps in the gas rich Gavbandi province located in the southeast part of the Zagros Mountains. The results indicated that the location of anticlinal traps at the depth in which the Permian Dehram Group reservoir unit exists is horizontally displaced with respect to surficial crest of many anticlines within the Gavbandi area. This crestal shift may be induced by abnormally high fluid pressure in the ¿A evaporate¿ member of the Dashtak formation, detected in many exploration wells across the area. When fluid pressure increases due to compaction during shortening, the higher shaliness could probably cap more fluids and consequently increase the fluid pressure within the Dashtak formation. Anomalous high fluid pressure decreases internal friction and shear strength of rock units and facilitates fracturing and faulting within the Dashtak formation, which consequently causes crestal shift of anticlinal traps. This should be taken into account when planning a new exploration well in Gavbandi area in order to prevent trap drilling

Evaluation of different gravimetric methods to Moho recovery in Iran.

  The complexity of geological units in Iran because of several unique events like tectonics and orogenic activities in this region led to extensive investigations for Moho recovery by seismic methods therein. In this research, three gravimetric methods have been evaluated by some point-wise seismic data. We applied collocation method as an iterative process as well as modified forms of Sjöberg and Jeffrey’s theory of isostasy for local Moho depth recovery. The gravity data has been generated by GOCO03S model reduced by topography/bathymetry, sediment and consolidated crust effects. Although the iteration process in collocation approach only slightly changed the estimated depths, this method led to a better agreement with seismic data rather than others. Differences between collocation, Jeffrey and Sjöberg’s solutions with seismic studies are similar but Jeffrey and Sjöberg’s methods displayed a systematic bias. The standard deviations of the residuals among seismic data and gravimetric solutions are around 6 km. Overall, the evaluation of these approaches indicated that Moho from gravimetric approaches reduced only slightly the standard deviation of seismic Moho estimates. Significant discrepancies with seismic data have been detected in Makran subduction zone, Oman Sea, Persian Gulf and Caspian Sea. The explanation of such inconsistency can be partially due to the poor quality of CRUST1.0 data in these areas, as this model has been used to correct the gravity values that were input in the inversion procedures

A recovered Moho model by integrated inversion of gravity and seismic depths in Iran

This research aims to define the depth of Moho in Iran by collocation method using gravimetric data with seismic information. The definition of the Moho in the Iranian region is of considerable importance due to the geological complexity of the area also characterized by tectonic and orogenic events of particular uniqueness. We applied the collocation method to Moho recovery using the gravity data generated by GOCO03S model reduced by topography/bathymetry, sediment and consolidated crust effects from CRUST1.0. These data have been complemented with seismic Moho depth estimates. A compilation of 213-points seismic depth has been collected over Iran and used in the integrated gravimetric-seismic inversion. Among them, 140 seismic points have been selected completely random and included as data in the integrated collocation approach for Moho depth estimation. The 73 remaining seismic points have been used as checking points for validating the estimated Moho. In the first run, gravity data only have been considered to collocation Moho recovery. When comparing this gravimetric solution with the 73 seismic checking points, a standard deviation of 6.2 km was found. In case of considering the regional seismic depths into the collocation approach, the standard deviation of the residuals between our results and seismic checking Moho depths improved to 4.9 km. It must be stated that, even in the integrated inversion, a significant discrepancy between the seismic and the integrated gravimetric-seismic Moho is present in the South Caspian Basin. Low quality of CRUST1.0 could explain this inconsistency in this area

Impact of the Late Triassic Dashtak intermediate detachment horizon on anticline geometry in the Central Frontal Fars, SE Zagros fold belt, Iran

Integration of 2-D seismic lines, well data and field studies allow us to determine the geometry variations of anticlines in the highly prolific Central Frontal Fars region in the SE Zagros fold belt. These variations are directly related to changes in thickness of the principal evaporitic intermediate detachment level, located along the Late Triassic Dashtak Formation. Anticlines of short wavelength contain a significant over-thickening of the evaporitic detachment level in their crestal domain that may reach 1900m (from an original thickness of 550-800m). Folds containing thick Dashtak evaporites show decoupling across the detachment level and, thus, a shift of the anticline crest in the underlying Permo-Triassic carbonates of the Dehram Group, which form the major gas reservoir in the Central Frontal Fars. Four main parameters control the extent and distribution of the decoupled anticlines in the study area: (a) original large thickness of the Late Triassic evaporitic basin; (b) coinciding larger amounts of anhydrites with increasing total thickness of formation; (c) parallel occurrences of abnormally high fluid pressures; and (d) shortening variations across, and along, the strike of specific folds. The present work relating the different parameters of the Dashtak evaporites with the anticline geometry allows a better understanding of the fold geometry variations with depth, which is applicable to oil and gas exploration in the SE Zagros and other similar hydrocarbon provinces characterised by intermediate detachment horizonsPeer reviewe

Slip-rate estimate and past earthquakes on the Doruneh fault, eastern Iran

The Doruneh fault, with a length of ∼600 km, is one of the longest, and most prominent, faults in Iran. It performs an important role in the regional tectonics, but has no record of large earthquakes. The geomorphology of the Doruneh fault contains numerous indications of cumulative left-lateral slip over various scales. We describe three sites where Late Quaternary landforms are displaced by the fault. (a) An incised alluvial fan near the village of Uch Palang is displaced by 800-850 m. (b) The Kuh-e Teagh-Ahmad fold is composed of folded Quaternary gravels and is displaced by ∼200-400 m. (c) A sequence of three terraces of the Shesh-Taraz river are displaced left-laterally by a maximum of 25 m. Infrared stimulated luminescence (IRSL) dating of the uppermost Shesh-Taraz river terrace gives a deposition age of ∼10 ka, which correlates with changes in global climate ∼10-12 ka ago, and provides a provisional slip-rate estimate of 2.4 ± 0.3 mm yr-1. No major recent or historical earthquakes are recorded on the Doruneh fault. Relatively fresh scarps and partially infilled fractures appear to be the preserved surface ruptures from an earthquake event of unknown age. A series of small streams showing left-lateral displacements of 3 to 5.5 m (with an average slip of ∼4.7 m) record the possible magnitude of slip during this earthquake, which from scaling relationships would have had an Mw of ∼7.5, and ruptured the fault over a length of >100 km. At the estimated slip-rate of ∼2.5 mm yr-1, the average recurrence time between large-magnitude earthquakes on the Doruneh fault is ∼2000 yr. © 2006 The Authors Journal compilation © 2006 RAS

3-D Structure of permian reservoir and timing of deformation in frontal fars, Zagros Fold-thrust belt

Evolution of the Zagros-Makran Fold Belts, Darius Workshop, 2012, 14-15 May 201