E. Kosari; A. Bahroudi; M. Talebian; A. Chehrazi
Abstract
One of the essential studies in exploration, exploitation and development of hydrocarbon fields is to evaluate the fault and fracture systems and the role that they can play in reservoir quality and geometry. If the hydrocarbon reservoir is a fractured carbonate reservoir, assessing the mentioned properties ...
Read More
One of the essential studies in exploration, exploitation and development of hydrocarbon fields is to evaluate the fault and fracture systems and the role that they can play in reservoir quality and geometry. If the hydrocarbon reservoir is a fractured carbonate reservoir, assessing the mentioned properties is of great importance. Assessment of the structures should be done simultaneously because of their close relations, and the their probable genesis connection should be revealed. In this research, subsurface data including 2D seismic profiles, underground contour maps and FMI log and eventually analogue modeling have been used for evaluation of probable scenarios explaining formation of faults and fractures. The studied area is located at the front of Zagros deformation belt and the Zagros stresses have apparently not affected it. Two sets of faults of different geometry and role have been detected; the first reverse set (N-S trending) was apparently controller of the reservoir geometry in the structure; the second normal set (NW-SE trending) are most likely causative of the main fractures in the field. It is likely that positive inversion tectonic of the basin led to the development of this field in form of a pop-up structure. Based on the interpretations, the internal normal faults have been formed probably by the rise of Hormuz salt or by local stretching due to left-lateral component of the boundary reverse faults. Using interpretation of drilling-induced fractures and break-outs derived from FMI, trends of the Shmax and Shmin are determined. Also it was revealed that the natural fractures and the main set 2 of faults are sub-parallel with the fractures induced by drilling. Therefore, the compatibility between trends of the natural fractures, breakouts and local normal faults can suggest a tectonic origin for the natural fractures.
A Malaekeh; M.R Ghasemi; S Hakimi; A Bahroudi
Abstract
The Vijehnan anticline is located to the south of the Gilan-e-Gharb, in the simply folded belt of the Zagros. For analyzing the geometry and kinematics of the anticline, we first produced a geological map using a variety of satellite imagery, published geological maps and field studies. Four structural ...
Read More
The Vijehnan anticline is located to the south of the Gilan-e-Gharb, in the simply folded belt of the Zagros. For analyzing the geometry and kinematics of the anticline, we first produced a geological map using a variety of satellite imagery, published geological maps and field studies. Four structural cross sections (A1-A2, B1-B2, C1-C2, D1-D2) perpendicular to the fold axes are produced in AutoCAD software. To analyze the geometry and kinematics of this fold, the horizontal shortening has been calculated for two cross sections. The average shortening of these cross sections is 11 percent. Kinematics analysis of the Vijehnan anticline based on the Publet & McClay model (1996) indicated that the geometry of the anticline is of detachment fold type. This result is also confirmed by the scheme which was introduced by Jameson (1987). To ensure the accuracy of the results, aspect ratio of the fold have been used which is presented by Sattarzadeh et al. (2000). The calculation of this factor indicates that the Vijenan anticline classified as detachment fold.
M Najafi; A Yassaghi; A Bahroudi; SH Sherkati; J Vergés
Abstract
The long-lived Fars paleo-high, located in SE Zagros Mountains is a prolific hydrocarbon province as it contains 15% of the world’s proven gas reserves. Subsurface data sets acquired during the recent hydrocarbon exploration in the region indicated fold style variation and structural complexity ...
Read More
The long-lived Fars paleo-high, located in SE Zagros Mountains is a prolific hydrocarbon province as it contains 15% of the world’s proven gas reserves. Subsurface data sets acquired during the recent hydrocarbon exploration in the region indicated fold style variation and structural complexity deep in the sedimentary cover, understanding of which is essential for petroleum system modelling and selection of new targets for gas at depth. In order to analyse the fold style in Fars paleo-high, this study presents a new regional balanced cross-section with a length of ~130 km and a depth of 12 km, across the Fars paleo-high. The section was constructed using seismic profiles, exploration wells and field data. The results show that variation of fold style happens in accordance to variation in mechanical properties of rock units across the Fars paleo-high, as well as from surface down to the depth of sedimentary cover. Detachment folding, followed by limb thrusting, which happens above 8-12 km below sea level, is the main deformation mechanism of sedimentary cover. In the middle of sedimentary cover, however, tectonically over-thickened Triassic evaporitic rocks efficiently decouple the geometry of post Triassic succession with respect to the underlying Permo-Triassic reservoir carbonates. Restoration and balancing of the regional cross-section indicated 20% of shortening across the Fars Paleo-high, accommodated by folding and thrusting. Abrupt change in the level of synclines accompanied with trends of seismicity and linear exposure of old geological units, proposes involvement of at least two main basement reverse faults in the deformation of cover sequence.
H Nikoogoftar; A Bahroodi; B Tokhmchi; G.H Norouzi; B Mehrgini
Abstract
Identifying and interpreting subsurface heterogeneities, especially Litofacies, plays definitely an important role in assessing and managing hydrocarbon resources. Variety of methods have been developed in order to model discrete features of hydrocarbon reservoirs, as Litofacies, which the majority of ...
Read More
Identifying and interpreting subsurface heterogeneities, especially Litofacies, plays definitely an important role in assessing and managing hydrocarbon resources. Variety of methods have been developed in order to model discrete features of hydrocarbon reservoirs, as Litofacies, which the majority of them have focused on intra-well modeling, and are not applicable for 2D or 3D modeling between oil wells. Furthermore, developing a novel methodology to bring a more factual reservoir facies has always been a matter of attraction, and is effective in lowering risk of decision making in different exploratory stages. These days, Markov Chains is used as a powerful tool for facies modeling. This method is based on conditional probabilistic and providing transitional matrix of states. This study is carried out on an oil field, South-West Iran; where the Asmari Formation is its main reservoir. Here, interval of the Asmari Formation and its cap rock in a 12 kilometers long section, 110 meters width, is classified into three main parts, by the means of Markov Chains modeling. The best result of modeling was obtained with nine wells and four seismic horizons that brought 87% accuracy in average.
S Kianpouryan; M Farahmandian; M Karimi; A Bahroudi
Abstract
Considering the existence of many copper deposits in Iran and the importance of their exploration, mineral potential mapping with high accuracy is an important tool. The process of mineral potential mapping is a cumbersome process which can be performed using different methods. The Hybrid Neuro-Fuzzy ...
Read More
Considering the existence of many copper deposits in Iran and the importance of their exploration, mineral potential mapping with high accuracy is an important tool. The process of mineral potential mapping is a cumbersome process which can be performed using different methods. The Hybrid Neuro-Fuzzy approach is one of the powerful ones for mineral potential mapping in which both conceptual and empirical components of earth science information are employed, so using both components simultaneously increase the confidence interval. In this paper we were used Adaptive Neuro-Fuzzy Inference System (ANFIS) for mineral potential mapping in Chahar-Gonbad area 1:100000 sheet, Kerman province. The database consists of geology, geochemistry, airborne radiometric, regional faults, ETM+ data, and 22 deposit and occurrence locations. At first, the factor maps were provided in GIS environment in which each cell in the grid data represents a 100 m square on the ground, and then the outputs of this layer were used for training the network. As this technique requires some data for training the network, the occurrence locations were used for training and checking points. Since, the training points were not enough for this procedure, we assigned buffer from 100 to 1000 m for occurrence locations. The results showed that when the buffer is 500 m, the best classification which ANFIS identify about 80% of the known deposits and occurrence locations in high favorability zones.
M Najafi; A Yassaghi; A Bahroudi
Abstract
Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels ...
Read More
Mechanical characterizations of sedimentary cover, especially presence of ductile rock units is a major controlling parameter on deformation style within fold and thrust belts. Interpretation of seismic profiles as well as scaled analogue modeling allows us to determine the influence of ductile levels on structural style in the Central Zagros folded belt. Seismic interpretation indicates that the Miocene Gachsaran Formation forms a major median detachment level decoupling fold geometry in surface structures from Pre-Miocene units below it. In addition, the Infra-Cambrian Hormoz salt or equivalents decouple the folded sedimentary cover from basement. To evaluate the significance of multiple detachment levels, a scaled analogue model was set. Two layers of silicon putty, with thicknesses equal to 15% of total cover thickness, were placed at the base and in the middle of sedimentary cover. The rest of the sedimentary cover was simulated using dry loose sand. The result of modeling supports seismic interpretation of the Central Zagros proposing that thick middle detachment layer totally decouples structural style at surface from depth. However, the open synclines with long wavelength and low angle thrusting are developed at surficial levels, and duplex thrust systems are formed between two detachment levels. Therefore, the role of ductile detachment levels should be obtained before exploring deep hydrocarbon targets in the Zagros fold belt.
M Royatvand; A Bahroudi; M. Qoreshi; M. R. Ghasemi; S. A. Aghahosseini
Abstract
The Oligocene salt in the Garmsar and Eyvankey plateau, south–central Alborz, has extruded on the quaternary sediments and formed a salt glacier. This open-toe salt glacier is about 24×17 km that is unique continental salt glacier in the world, dimensionally. Also, this ductile substrate ...
Read More
The Oligocene salt in the Garmsar and Eyvankey plateau, south–central Alborz, has extruded on the quaternary sediments and formed a salt glacier. This open-toe salt glacier is about 24×17 km that is unique continental salt glacier in the world, dimensionally. Also, this ductile substrate has affected on structural styles of this region. However, little systematic work has done on it. To investigate the structural styles of the region that affected by a ductile substrate and adjacent region with a frictional decollement, and also the structures of the salt glacier,series of models were done which were scaled sandbox models. These sandbox models simulated the propagation of deformation of thin-skinned simultaneous shortening above adjacent ductile and frictional of two end member of decollement. Model results illustrate that above a ductile substrate, deformation propagates further and more rapidly than above a frictional substrate as we can see in the nature that the region with a ductile substrate is so broader than the adjacent region with a frictional decollement. Like the models, toward the north in the nature where the Decollement is frictional, from North Tehran Fault as a frontal fault to Mosha and Kandovan Faults in the core of Alborz Mountain, the dip of the faults are increased and only forward-vergent imbricate faults, whereas above the ductile substrate the dip of faults has not a definite pattern of dip and also, both foreland and hinterland imbricate faults develop.
