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No 12
Vol. 12 No. 6
2016
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Structural geological study is one of the most important stages of an oilfield exploration and production (E&P) program, since a knowledge of existing structures can play a fundamental role in the oilfield development plan. The main purpose of this study is to create three-dimensional (3D) structural models to determine direction of tectonic stresses at Lali oilfield using subsurface geophysical data. The study area is located within the so-called Dezful Embayment (northern Khuzestan Province, Iran). Accordingly, in order to provide a 3D model of the reservoir, geostatistical tools in Petrel Software were utilized. Incorporating density log data into several coded formulations in MS Excel Software, the reservoir had its modulus of elasticity calculated. Subsequently, maximum and minimum horizontal stresses were calculated using poroelastic equations. Fault modeling results showed that, fault dip increases with increasing the depth towards the center of the field. Obtained values of stress using the poroelastic equations show that σ_H>σ_h>σ_v, confirming a regional reverse stress regime, which is consistent with previous studies in this area. Also, the formal stress ratios (Φ = (σ2-σ3) / (σ1-σ3)) obtained from poroelastic equations and inverse analysis method were found to be well-correlated across the area. Finally, average azimuth of the reverse faults on the southern limb (as calculated by Petrel) and the fractures on the limb (as obtained from FMI images and core samples) were found to be N305 and N315, respectively (average = N310). Thus, N040E was inferred to be the average direction of principal stress, i.e. principal stress is mostly directed along a NE-SW axis (perpendicular to the general trend of Zagros Orogeny); this is probably a result of the activities of youngest Zagros orogeny phase. The agreement between the obtained principal stress directions by fractures, faults, and focal mechanism of earthquakes across the World Stress Map (WSM) confirms the validity of this study.
Nasrin kianizadeh - Behzad Zamani - Rahym khadkhodayi - Hoseyn Talebi
Keywords : Fault modeling ، Prtrel, ، Orientation tension ، fracture ، Dencity log ، Lali oil field ، Poroelastic equations
In this research, biostratigraphy, microfacies, sedimentary environments and sequence stratigraphy (using by Cyclolog software) of the Asmari Formation are carried out. These studies are done on the basis of 580 samples (core and cutting) from 430 meters thickness of the formation from the well #2 of the Qaleh-Nar oilfield. Paleontological studies are led to identification of 23 genera and 28 species of the benthic and planktonic foraminifera. According to these microfossils, four assemblage zones have been recognized which confirm the age of Oligocene (Rupelian – Chattian) and Early Miocene (Aquitanian – Burdigalian) for the whole formation. Paleoenvironmental studies demonstrate 9 different microfacies that were deposited in the outer ramp (open marine) in the lower Asmari part, middle ramp (open marine to shoal) in the middle Asmari part and the inner ramp environment (tidal flat to lagoon) in the upper Asmari part. The sequence stratigraphy on the well #2 and the auxiliary well numbers 1, 3, 5, 6 and 7 of the Qaleh-Nar oilfield using by Cyclolog software reveals 7 positive breaks and 9 negative break levels alternatively. Some of the positive breaks define sequence boundaries and some of the negative breaks present the maximum flooding surfaces. In addition, a number of positive levels specify the major chronozone (stage boundaries). Comparison of the quintuple reservoir zones of the Asmari Formation in the Qaleh-Nar oilfield with the mentioned break levels suggests a fine correlation with these levels; however this correlation is invalid for other levels.
abbas Ghaderi - adel neisi - ali Ghobeishav - mohmmad Allahkarampour-Dill
Keywords : Asmari, ، Biostratigraphy ، microfacies ، Qaleh-Nar Olifield ، sequence stratigraphy ، Software Cyclolog
Studies of the electrical Rock Type a very important role in the development process plays a field.In these studies, theporo-perm Cores data and well log data used for reservoir simulations. In the present research, the flow of four flow units was determined in the reservoir using porosity and permeability data from well logging core by regional index method. In some wells, using well logging the basic model of electrical rocktype was determined with three methods of MRGC, SOM, and DYNAMIC. The determined facies by different methods were correlated with the flow unit. Finally, SOM method was selected, which has the best concordance. The initially created electrofacieswere reduced to 4 electrofacies due to the similarity of some parameters such as effective porosity and gamma logging. To ensure the accuracy of the electrical rock type by neural networks, these electrofacies were correlated with capillary pressure data. After confirming the determined electrofacies by capillary pressure, these facies were propagated in other wells in this field. This created a model, which was able to separate different parts of the reservoir. In this model, different parts of the reservoir were determined in terms of reservoir quality.
Abouzar Mohsenipour - Bahman Soleimani - Ehsan Abharakpour - Ghodratollah Nikkhah
Keywords : Electrical RockType, Flow Unit, Bangestan Reservoir, Reservoir Quality
Asphaltene is always considered as a problem in oil industry. But, asphaltenes are desirable compounds in geochemical studies specially in oil-oil correlation. Oil-oil correlation is one of the most important issues in geochemical studies that enables to classify oils genetically. Asphaltenes due to their structural similarity with kerogen and unaffected and/or little affected from secondary processes are known as valuable compounds in geochemical studies. So, in this paper the structural characteristics of asphaltenes were considered as a correlation parameter. For this study 5 oil samples were collected from the Persian Gulf eastern part oil fields. Structural characteristics of these asphaltenes were investigated by Fourier transform infrared (FTIR) spectroscopy. 2D and 3D graphs based on aliphatic and aromatic compounds (predominant compounds in asphaltenes structure) and sulfoxide and carbonyl functional groups (which are represent of sulfur and oxygen abundance in asphaltenes) were used for comparison of asphaltenes structure in different samples. According to the results of these defined graphs, the studied oil samples comprise two oil families with distinct genetic characteristics. The first oil family consists of the Salman and Reshadat oil samples, and the second oil family consists of the Resalat, Siri E and Siri D oil samples. To validation and complement the obtained results, the other common geochemical techniques such as stable carbon isotope and biomarkers parameters, were employed and these techniques completely confirmed previous results. According to biomarker parameters, the first oil family originated from marl source rock and the second oil family was sourced from carbonate source rock.
Morteza Taherinezhad - Morteza Asemani - Ahmad reza Rabbani
Keywords : Asphaltene, ، Fourier transform infrared (FTIR) spectroscopy ، Oil-oil correlation ، Persian Gulf ، Iran
Mud volcanoes are geological structures formed as a result of gas emission, mud-fluid mixing and variably sized rock fragments in onshore and offshore settings. These structures are different morphologically which considered as significant marker of modern crustal movement and neotectonic activity. Occurrence of numerous mud volcanoes on the Makran accretionary prisms in Iran and Pakistan are reported which caused by the convergence of the Arabian and the Eurasian plates. In this study, origin of discharged hydrocarbon gases from three active onshore mud volcanoes; Ain, Borborok and Sand Mirsuban in Makran coasts of Iran were examined. The released gases of all these mud volcanoes are dominantly methane with concentration between 97.24-99.18 vol. % and minor amount of ethane (0.04-1.2 vol.%), propane (0.001-0.194 vol.%), n-butane (226 ppmvol.%), iso-butane (5-363 ppmvol.%), n-pentane (37ppmvol.%), iso-pentane (1-66 ppmvol.%), hexane (1-78 ppmvol.%) and CO2 (0.07-0.4 vol.%). Carbon and hydrogen isotope ratio of methane and its heavier derivatives indicate thermogenic source for emitted gases of all investigated mud volcanoes and evidences of the absence of biodegradation. CO2 with carbon isotope ratio of -11.1 to -14.3‰ is organic in origin. Our research suggests the presence of hydrocarbon system and active source rock in Makran active tectonic area. Although the occurrence of an exploitable gas reservoir in this area has to be confirmed by geophysical measurements, geological survey and structural settings.
Mahin Farhadian Babadi - Behzad Mehrabi - Adriano Mazzini - Elena Poludetkina - Ata Shakeri
Keywords : mud volcanoes ، gas chemical composition ، carbon and hydrogen isotopes ، gases source ، Makran accretionary wedge of Iran ، Borborok ، Ain ، Sand Mirsuban

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