تنش

Open Access Article

1 - Paleostress analysis of Mansour-Abad area (southeast Rafsanjan - Kerman Province) using Multiple Inversion Method
لیلا عبادی Alavi Ghassemi

This study uses multiple inversion method to analyze slip data on shear planes and faults containing slickenlines in different rock units, and evaluates paleostress field in Mansour-Abad area. It was gathered the required kinematic data in 18 stations according to the s More

This study uses multiple inversion method to analyze slip data on shear planes and faults containing slickenlines in different rock units, and evaluates paleostress field in Mansour-Abad area. It was gathered the required kinematic data in 18 stations according to the stratigraphic age of the rock units. It was used the most important shear sense indicators, including mineral steps, Riedel shears and tension fractures. According to the multiple inversion method, which calculates stress tensor from the inhomogeneous fault data (data without any knowledge of stress field orientation or fault classification), four parameters of stress ellipsoid shape and axes were analyzed. It was found 3 different phases of compression, extension-shear and shear- compression using the phase separation in this method. The maximum principal stress orientation in different locations changes from N24˚ to N162˚ between Cretaceous and Neogene, while the minimum principal stress orientation changes from N79˚ to N116˚. The NW-SE strike of the reverse faults indicates that these faults developed during the activity of compressional phase. During the extensional-shear phase of the activity, local sedimentation occurred in the area. Late shear deformation of area, and change in stress field orientation, resulted in a block rotation between the fractures. Further increase in the rotation caused the fractures to increase in size, and provide space for intrusion of the magma. Manuscript profile

Open Access Article

2 - Paleostress analysis in Bozqush Mountains, northwest Iran
احد نوری Parisa Amini Sharifi Moayyed

Knowledge of the local stress field in a region is important in the structural and affecting factors on structural kinematics studies. Therefore, in this paper after describing the basic theoretical principles of stress inversion method from slickensides, it was used More

Knowledge of the local stress field in a region is important in the structural and affecting factors on structural kinematics studies. Therefore, in this paper after describing the basic theoretical principles of stress inversion method from slickensides, it was used field measured heterogeneous fault –slips as raw data to determine the average state of the principal stress axes in order to analyze the regional geodynamic situation of this area. The results of the reduced stress tensor from fault-slip measured data, show 21/156، 64/012 and 14/251 states for σ1، σ2 and σ3 axes respectively. The results of analysis of these data show substantial agreement between the determined principal stress axes and recent tectonic research in this region. Manuscript profile

Open Access Article

3 - 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

Open Access Article

4 - 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

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

Open Access Article

5 - Wellbore Stability Analysis During Drilling Using Geomechanical Model and FLAC3D Software in Asmari Reservoir, Ahwaz Oil Field
Mohammad میرانی

Abstract Oil reservoirs are one of the important sources of energy due to which is caused by specific rock mechanical properties, the ability to maintain hydrocarbon fluids. One of the major problems that are occurred during drilling a well is instability of the well More

Abstract Oil reservoirs are one of the important sources of energy due to which is caused by specific rock mechanical properties, the ability to maintain hydrocarbon fluids. One of the major problems that are occurred during drilling a well is instability of the wellbore. In order to prevent this difficulty its need to predict stability of the rocks by using geomechanical properties and in-situ stresses. A lack of accurate wellbore stability analysis brings many problems such as borehole washout, breakout, collapse, stuck pipes and drill bits. In the present research work the stability of an oil well located in Asmari reservoir of Ahwaz oil field was stimulated by using numerical software FLAC3D and information obtained from well log curves were evaluated and analyzed in two parts and the results were presented. Mud pressure and mud weight in outset of wellbore plastic flow and also outset of shear failure in wellbore were obtained for 7.5 meter of formation which mainly consists of limestone, marl. Well stability analysis was performed in vertical direction, minimum horizontal stress and maximum horizontal stress. Due to plastic movement and shear failure in wellbore, in first stage the mud pressure occurred is 33 and 26.4 Mpa and the second stage it reaches to 45 and 30 Mpa, respectively.It indicates that tensile failure is in direction of maximum horizontal stress and shear failure in direction of minimum horizontal stress. Subsequently, the result shows that the analysis due to the low mechanical properties of the sandstone layer indicates the maximum amount of displacement and loss. The safe mud window is small in this layer. Manuscript profile

Open Access Article

6 - Determination of In-situ stress in the Marun oilfield’s failure wells
میثم فارسی مدان مرتضی احمدی کاوه آهنگری جاسم دشت بزرگی

Abstract Determination of In-situ stress domain in oilfields is so important for drilling, well completion and petroleum geomechanics. Simply, determination of magnitude and direction of In-situ stress around wellbore is the first step of geomechanical studies and we More

Abstract Determination of In-situ stress domain in oilfields is so important for drilling, well completion and petroleum geomechanics. Simply, determination of magnitude and direction of In-situ stress around wellbore is the first step of geomechanical studies and wellbore stability particularly. Preliminarily, because of importance of casing collapse problem in the Marun oilfield, the magnitude of in-situ stress is determined. The magnitude of vertical stress (Sv) was in range of 85 to 90 MPa. The minimum horizontal stress (Shmin) determined by some analytical methods. For estimating of maximum horizontal stress (SHmax) domain we used Anderson’s faulting theory and stress polygon. So the magnitude of SHmax was so close to Sv and the faulting regime shows normal/strike slip. Within Gachsaran Formation in depth of collapses because of salty lithology and high pore pressure, magnitude of In-situ stress is so close and it can be assume hydrostatic stress state. Manuscript profile

Open Access Article

7 - A review of methods for determining contact stress in polymer base gears
Rasool Molhsenzadeh

Basically, gears are an evolved form of friction wheels that have teeth added to them to prevent slippage and ensure relative motion uniformity. The use of polymer gears is increasing due to advantages such as corrosion resistance, injection molding capability, operatio More

Basically, gears are an evolved form of friction wheels that have teeth added to them to prevent slippage and ensure relative motion uniformity. The use of polymer gears is increasing due to advantages such as corrosion resistance, injection molding capability, operation without lubricants and low noise. However, the mechanical strength, thermal resistance and durability of polymer gears are lower than metal gears. The locking mechanism in metal gears is different from polymer gears. Among the important damages that lead to failure of polymer gears is thermal deformation, which does not exist in metal gears. In polymer gears, due to the viscoelastic and plastic nature of polymers, a lot of heat is generated during gear engagement and the temperature increases. An increase in temperature causes the ribs to soften and, as a result, change their shape. Pitting, fatigue and wear are other factors that lead to failure of polymer gears. The contact stress resulting from the torque applied to the gear plays the most important role in the intensity of each of the mentioned delays. Investigating the contact stress in polymer gears, including the challenges of industrialists and researchers, will provide a better understanding for the better design of these types of gears, as well as life expectancy. This research is a review of various methods for determining and checking contact stress, including Hertz numerical model, standard method and finite element method. Manuscript profile

Open Access Article

8 - A review of polymer bonded explosive rheology
Mahmoud Heydari

Polymer-bonded explosives are widely used in defense and commercial industries. In this type of explosive, very high amounts of explosive crystals (about 90% by weight) are surrounded by a polymeric binder (about 10%), which leads to a decrease in sensitivity and a sign More

Polymer-bonded explosives are widely used in defense and commercial industries. In this type of explosive, very high amounts of explosive crystals (about 90% by weight) are surrounded by a polymeric binder (about 10%), which leads to a decrease in sensitivity and a significant increase in safety during application and storage. These mixtures are molded in different ways, such as pressing, casting, extrusion, and injection. Studying the rheology of these mixtures with a high percentage of solid loading leads to finding the appropriate quality control method at different production stages. The first step was to review studies on alternatives to simulating explosive rheological behavior, such as dechlorane, calcium carbonate, sugar, etc. The general behavior of simulated mixtures, such as yield stress, shear rate dependence, time dependence, etc., is compared with original explosive. The results showed that despite the similarity in some rheological behaviors, it is impossible to predict and study all the rheological behaviors of polymer-bonded explosives using simulating materials. This paper discusses factors affecting the rheology of polymer-bonded explosives, such as particle size distribution, modification of explosive crystal surfaces, and plasticizer. A review of scientific sources showed that using a wide distribution of explosive crystal particles compared to a narrow distribution led to a significant reduction in viscosity and dependence on shear rate and time. The absence of strong interactions between crystal particles and polymer binder leads to no observation of quasi-solid behavior even in 85% by weight of explosive crystals such as octogen in hydroxyl-terminated polybutadiene Manuscript profile

Open Access Article

9 - A new look at the rotation of Central Iran: A case study of the Anar fault, east block of the Yazd
Hamidreza AfkhamiArdakani farzin ghaemi Fariba Kargaran Bafghi Ahad Nouri

The Anar fault in the east of Yazd city, with a north-northwest-south-southeast strike, is a basement fault that separates the Yazd block from the Posht Badam block, and its current activity is a dextral strike-slip with a reverse component. The paleostress analysis was More

The Anar fault in the east of Yazd city, with a north-northwest-south-southeast strike, is a basement fault that separates the Yazd block from the Posht Badam block, and its current activity is a dextral strike-slip with a reverse component. The paleostress analysis was done on this fault in order to obtain the tectonic history of central Iran in the period from Devonian to Cretaceous. After analyzing 110 fault data in 13 stations of 2 tectonic phases, it was determined that the maximum stress obtained is between the azimuths of 90 to 110 and 190 to 220 and the angle of stress direction changes in the period from Devonian to Cretaceous is 130 degrees. Based on the studies on the barite veins and the dextral displacements that were seen on them, the separation of the stress phases was done, which indicates that the NNE stress direction is older. Further, according to the previous studies of sedimentology and tectonics in central Iran, it was concluded that the cause of this change in tension was the movement towards the northeast along with the 130 degree counter-clockwise rotation of central Iran. Manuscript profile

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