List of Articles Stress

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  1 - Determination of stress state and tectonic regime changes in the brittle structures of Chah Yusuf Mountain (East of Gonabad)
  فرهاد  زارعی  Ghaemi  Ghaemi
  In this study, structural elements, such as faults and fractures and their formation mechanisms and relationships with tectonic regime of Chah Yusuf Mountain in East of Gonabad city have been recognized and discussed. Their relation with regional fractures, based on dat More

  In this study, structural elements, such as faults and fractures and their formation mechanisms and relationships with tectonic regime of Chah Yusuf Mountain in East of Gonabad city have been recognized and discussed. Their relation with regional fractures, based on data’s from satellite image process and field data, is also shown. Major faults in this area were identified by using fault plain features such as striations, stretching vein and cumulative steps of minerals that helped us to determine fault mechanisms. In general, faults were oriented in three main directions: 1) Reversed faulting along N90-120˚, 2) Right lateral strike –slip faults along N140-160˚ and 3) Normal faults along N0-15˚. Based on the obtained data and using the inversion method, the orientation of the principal stress axes (σ1، σ2 and σ3) and the ratio of the principal stress differences R in the studied area were analyzed. The results showed two different tectonic regimes in the formation of regional structures: 1) Compressive tectonic regime, major stress along NNE-SSW, which generated structures of folds and reversed faults. 2) Shear tectonic regime, compressive stress along NE_SW and tensile stress line NW-SE, which generated structures such as strike-slip faults, normal faults, vein and tensile fracture. So, the major stress direction in this region is NNE-SSW, which shows its relation to the Late Cenozoic Arabia –Eurasia oblique continental collision. Manuscript profile
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  2 - Seismotectonics of the west of Golestan province, the east of south Caspian region
  Maryam Agh-Atabai Marjan Tourani
  Golestan province is located in one of the seismically active zones of Iran. The seismicity maps of Golestan province show that density of earthquakes in the west is more than the east. In this research, the parameters including b-value, recurrence time and seismic mome More

  Golestan province is located in one of the seismically active zones of Iran. The seismicity maps of Golestan province show that density of earthquakes in the west is more than the east. In this research, the parameters including b-value, recurrence time and seismic moment were studied to investigate the seismicity of the west of Golestan province. The focal mechanism of earthuqakes and field data were used to determine the stress orientations in the study area. The estimated b-value is obtained as 1.24±0.2 which is comparable with the Alborz. Since the northern and southern parts of the study area have different geomorphological and structural characteristics, some of these parameters were calculated for two subdivisions; Dasht-e-Gorgan in the north and foothill in the south. Results of this study show that the earthquakes in the Dasht-e-Gorgan compared to the foothill are smaller with shorter recurrence times. For the foothills, the calculated P-axes using the stress tensor inversion method is found to be subhorizontal with trend N-NNE. For this region, at least two trends, N and NW, is calculated using field data. This result show the change of stress directions during the structural evolution of this area. The calculated p-axes trend for the Dasht-e-Gorgan is NE. In both studied areas, the focal mechanisms of greater earthquakes are consistent with the E-W to NE-SW trend of main faults especially the Khazar fault. But, the smaller events in the Gorgan Plain show a different trend and mechanism. Comparison of these two subdivisions shows that the northern Alborz foothill is more dangerous than the plain. Manuscript profile
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  3 - Reconstruction of present-day local stress field affecting the North Tabriz Fault and surrounding areas based on earthquakes focal mechanism by using inversion method
  Ahad Noori Behnam Rahimi
  In this research, present-day tectonic stress field affecting North Tabriz Fault and surrounding areas was reconstructed by using 37 compiled earthquakes focal mechanism from various sources. Triangle diagrams were used to determine the sense of the earthquakes focal me More

  In this research, present-day tectonic stress field affecting North Tabriz Fault and surrounding areas was reconstructed by using 37 compiled earthquakes focal mechanism from various sources. Triangle diagrams were used to determine the sense of the earthquakes focal mechanism. The sense of these data varies from strike-slip to thrust regime. Stress separation process was applied on data set for separation of the various tectonics regimes from a poly-phase system to obtain reduced stress tensors. This was done because most of the data participated in them and reconstructed stress fields completely cover the stresses affecting the region. The results of inversion analysis and internal separation of the data set show three stress regimes acting in this region. Considerably, all three stress regimes have a horizontal pressure stress with NW-SE to NNW-SSE trend. The direction of maximum pressure in each first, second and third regimes is 09/329, 28/310 and 03/138, respectively. In this research, present-day tectonic stress field affecting North Tabriz Fault and surrounding areas was reconstructed by using 37 compiled earthquakes focal mechanism from various sources. Triangle diagrams were used to determine the sense of the earthquakes focal mechanism. The sense of these data varies from strike-slip to thrust regime. Stress separation process was applied on data set for separation of the various tectonics regimes from a poly-phase system to obtain reduced stress tensors. This was done because most of the data participated in them and reconstructed stress fields completely cover the stresses affecting the region. The results of inversion analysis and internal separation of the data set show three stress regimes acting in this region. Considerably, all three stress regimes have a horizontal pressure stress with NW-SE to NNW-SSE trend. The direction of maximum pressure in each first, second and third regimes is 09/329, 28/310 and 03/138, respectively. Manuscript profile
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  4 - Difference of in situ stress regime dependent on Structural position and geomechanical characteristics, Case study- Gachsaran and Asmari formations, SW Iran
  Hossein Talebi Seyd Ahmad Alavi Mohamad Reaz Ghasemi Shahram Sherkati
  Estimation of in-situ stress tensor in sedimentary basins using information obtained from exploration and development oil and gas wells during the drilling and logging process may be used for estimation of in-situ stress tensor in sedimentary basins. The in-situ stress More

  Estimation of in-situ stress tensor in sedimentary basins using information obtained from exploration and development oil and gas wells during the drilling and logging process may be used for estimation of in-situ stress tensor in sedimentary basins. The in-situ stress magnitude and orientation and the resulting stress regime around the studied wells have been several application in secondary recovery programs from hydrocarbon reservoirs as well as wellbore stability analysis. In this paper, the magnitude of in-situ stress is estimated by using abovementioned data in some oil wells located in the south west of Iran. Increasing the oil production by hydraulic fracturing design and sand control in the multi-layer reservoirs such as the Marun giant oil field with loose sand horizons and also improving drilling performance in the Gachsaran formation¬ requires knowledge about the prevailing stress conditions. This research, tries to analyze the stress regime of the Asmari and Gachsaran Formations around the selected wells in the Marun and Lali fields using constructed Mechanical Earth Models (MEM) and their differences are discussed. The calculated stress magnitudes in studied wells indicate a significant drop in magnitude of horizontal stresses from the Gachsaran to Asmari reservoirs in the Marun oil field. The magnitudes of the three principal stresses resulted that SHmax is the maximum principal stress and the Shmin is the minimum principal stress, thus a strike-slip stress regime (SHmax>Sv>Shmin) dominates in the Gachsaran sequence and the Asmari formation of the Lali oil field. however, in the Gachsaran formation of Marun giant oil field, stress regime is reverse-strike slip but normal stress regime is dominated in it's Asmari reservoir. The In-situ stress condition indicates that the structural condition and the depth difference of these structures plays an important role in the tectonic stress regime changes. Manuscript profile
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  5 - Analysis of stress regime in Shah Deniz oilfields and wellbore stability, in south Caspian Sea basin
  Parvaneh Alizadeh Saeid Mohammad Hassanpour sedghi Ali Kadkhodaie Malek Mohammad  Gity
  20.1001.1.17357128.1398.13.50.3.7
  Wellbore instability is one of the main problems during drilling of oil and gas wells. Analyzing and wellbore instability prediction is important. In-situ stress measurement and stress regime are important for stability studies. This study was carried out in one of the More

  Wellbore instability is one of the main problems during drilling of oil and gas wells. Analyzing and wellbore instability prediction is important. In-situ stress measurement and stress regime are important for stability studies. This study was carried out in one of the oilfields in the south Caspian basin in Iran. The compressional stress regime in the studied field was determined based on regional stress indicators and larg scale tectonic observations. . This study presented the effect of borehole inclination and azimuth on borehole stability under reverse fault regimes. The magnitude of stresses was determined from measured sonic velocities, density log and predicted pore pressure utilizing the Eaton method. In this study, the modified Lade model have been utilized to perform stability calculation for different inclinations and azimuths. In this study, to perform stability calculation with the use of STABview software is presented. It is shown that drilling wells parallel to maximum in-situ horizontal stress (NE-SW) causes less stability problems. The results of this study could help in the mitigation and/ or prevention of wellbore stability issues in this oilfield. Manuscript profile
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  6 - Determining paleo-stress based on the study of discontinuities and folds in Zagros Collision Zone; Case Study: Kermanshah Region
  سپیده  رضابیک عبدالله  سعیدی Mehran Aryan علی  سربی
  20.1001.1.17357128.1400.15.57.5.7
  The studied zone is in the Northern part of Zagros Suture Zone (Kermanshah). The presence of deep sea sediments, oceanic crust remnants, platform carbonates, igneous and metamorphosed rocks of active margin and carbonate sequence of passive margin that are assembled in More

  The studied zone is in the Northern part of Zagros Suture Zone (Kermanshah). The presence of deep sea sediments, oceanic crust remnants, platform carbonates, igneous and metamorphosed rocks of active margin and carbonate sequence of passive margin that are assembled in the studied area show a compressional tectonic regime from the late Cretaceous up to the present. As a result of convergent regime, a very complicated structural zone is developed. The main purpose of this study is stress characteristic analysis in Zagros Suture Zone (Kermanshah).To recognize and study the arrangement of stress axes a great amount of data were gathered from the folds axial surface and the faults which are appeared within the rocks specially the radiolaritic rocks. The data includes characteristics of fault surface geometry, fault slip and lineation slip. The stress recording patterns for data in this study is Multiple Inverse Method and comparison with stress position by using folds axial surface. By studying folds it was obtained the situation of main stress σ1, σ2 and σ3 respectively as 029, 127, 234 and by using the method Multiple Inverse Method, the situation of main stress is obtained as 059, 304, 194. Based on the investigations in the study area and measurements on Cretaceous rocks, the results show that the main stress direction since Cretaceous up to the present is northeastern with minor changes. The estimations of stress direction were the same in both folds and faults. As a result, the shortening direction has been constant, so the shortening faults all show one direction of stress. Manuscript profile