Tectonics
mehdi yousefi; Sayyed Morteza Moussavi; Mohammad Mehdi Khatib; Mohammad yazdani
Abstract
Image logs of 14 wells in Rag sefid anticline are showing 6 main fracture sets treanding N45, EW, N35, N100, N150 and N162 respectively. Development of fractures in the eastern part of the Rag sefid anticline, especially in the frontal edge, are in effect of the propagation fault related folding so that ...
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Image logs of 14 wells in Rag sefid anticline are showing 6 main fracture sets treanding N45, EW, N35, N100, N150 and N162 respectively. Development of fractures in the eastern part of the Rag sefid anticline, especially in the frontal edge, are in effect of the propagation fault related folding so that the most open longitudinal and cross axial fractures show N100 and N10 trends. Due to fold axis rotation 30 degrees to the north In the western part of the anticline the orientation of the fractures have changed and major fractures are longitudinal type and have N160 trend. In the middle and curved part of anticline NE-SW trend fracture sets are more developed by reactivation of hendijan basement fault. Convergence of stress axises as a result of the fault triple interaction In effect of Rag sefid thrust dipping to the north east and dextral shears dut to reactivation of hendijan and southern part of Izef basement faults caused the Restraining bend and dextral shear zone In the western part of the Rag sefid anticline. Creation of this shear zone caused clockwise rotation of anticline axis, rising more in northen west culmination on asmari top formation than southern east culmination, change in fractures orientation and also development and increase the density of fractures in the curved part of Rag sefid anticline.
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 ...
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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.
Y Jalili; M.M Khatib; A Yassaghi
Abstract
Fracture intensity-controlling factors, which include folding mechanism, lithology and thickness of layers, have been investigated in the Asmari Formation of the Kuh-e- Asmari using field studies and satellite images. Parameters such as structural position, spacing and vertical extension of the fractures ...
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Fracture intensity-controlling factors, which include folding mechanism, lithology and thickness of layers, have been investigated in the Asmari Formation of the Kuh-e- Asmari using field studies and satellite images. Parameters such as structural position, spacing and vertical extension of the fractures in the limestone and argillaceous limestone units of different thicknesses in the Asmari Formation sequence in Kuh-e Asmari anticline were studied. The existence of large amounts of low-strength and high-porous clay minerals in the argillaceous limestone has resulted in the overall low strength of the rock, which eventually led to lower intensity of fractures in argillaceous limestone than of that in limestone. Variations in the fracture intensitiesin these two rock types showed that the thickness of the units does not much affect the fracture intensity. Hinge-parallel and hinge-perpendicular fractures resulted from flexural-slip folding and outer-arc extension in the hinge area of the fold exhibit the largest development, and exert the highest effect on wellbore instabilities. Results show that the maximum fracture intensity is in the hinge area of the fold, and that folding mechanism is the most important factor in controlling the intensity of the fractures.
M Javid; H Memarian; S.M Mazhari; R Zorofi; B Tokhmechi; F Khoshbakht
Abstract
In the oilreservoirsof the ZagrosBasin, fractures play a major role in hydrocarbon migration and production. Borehole image log is a powerful tool to study and identify fractures around the wells. These logs provide critical information about orientation, depth and type of natural fractures. Since thereis ...
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In the oilreservoirsof the ZagrosBasin, fractures play a major role in hydrocarbon migration and production. Borehole image log is a powerful tool to study and identify fractures around the wells. These logs provide critical information about orientation, depth and type of natural fractures. Since thereis noaccuratealgorithmfor automaticidentification of fracture parametersonimage logs of the carbonatereservoirsin Iran, interpretation of theselogsisoftendone manually. This process may become erroneous if the interpreter is not sufficiently experienced. Aimed at automatic detecting of fractures in image logs, this paper presents a new implemented method, which is based upon image processingandoptimization techniques,as well as Artificial Bee Colony Algorithm. According to this approach, points related to fractures arefirst extracted from images using classification methods. Then, the Artificial Bee Colony Algorithmis used to determine the number, depth, dip and dip directionof fractureson extracted points. The proposed method is performed on FMS image log ofonewell located in an oilfield in southernIran. Results areshownindensity log, rose diagramandstereogramfor the identified fractures, and the obtained resultsshow efficiency of the proposedmethod.
B Soleimani; G Saedi; A Charchi; E Salarvand
Abstract
Natural fractures analysis as a main controlling factor in fluid currents is very important in the reservoir characterization. This matter was studied using thin sections, cores, and FMI and velocity deviation logs in one of the fields in the southwestern of Iran. FMI initial data, which were input to ...
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Natural fractures analysis as a main controlling factor in fluid currents is very important in the reservoir characterization. This matter was studied using thin sections, cores, and FMI and velocity deviation logs in one of the fields in the southwestern of Iran. FMI initial data, which were input to Geoframe software, processed and interpreted. Velocity deviation logs and secondary porosity were also measured and compared. The results indicated that stylolites, pores, open and filled microfractures in the reservoir are present. The relative density of open fractures decreased to depth while filled fractures increased. The fractures are mainly longitudinal and latitudinal types with high angles to bedding surface. The main porosity system of the reservoir is inter particle and fractures types. According to the presence of oil staining in thin sections, it is revealed that the fractures are suitable conduits to transferring the fluid.
A. Keynezhad; M. Pourkermani; M. Arian; A. Saeedi; M. Lotfi
Abstract
Detailed geological and structural analysis of north of Torud-Moalleman area (Central Iran), between Anjilu fault in north and Torud fault in the south, led to tectonic elements of this limit such as fractures and relative of their mechanism with left lateral sheared zone of two main faults. This study ...
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Detailed geological and structural analysis of north of Torud-Moalleman area (Central Iran), between Anjilu fault in north and Torud fault in the south, led to tectonic elements of this limit such as fractures and relative of their mechanism with left lateral sheared zone of two main faults. This study provides a movement system of Chalu, Gandi and Hafez faults in this shear zone. On the basis of kinematics findings and using general methods of fault slip analysis (orientation of slip plane, slip vector, shape of stress ellipsoid and angle of internal friction) region stress field were calculated after determining the angle of internal friction for each one of fault limits. Then, the main stress orientation determinates for combination data that values of ،وwere 195/10, 339/78 and 104/07 respectively. The shape of stress ellipsoid was defined on the basis of shape factor, [R= (-) / (-)], (Angelier, 1975). The R-value for whole studied regions was about 0.5 and deformation type was mainly left lateral transpressional with reverse component. Such results are evident from N-NE (N195) trending in the region and northward movement of the lithosphere. These finding are in line with field research results of fractures, faults and mechanism in this general shear zone.
Mehran Arian; R. Mohammadian
Abstract
Marun oil field is situated on the eastern part of Dezful Embayment zone (Zagros).Aghajari Formation is cropping out on the surface. Asmari formation, Bangestan and Khami Groups are the Main reservoirs in this field. Asmari formation with six reservoirs layers is the most important reservoir. Dolomitic ...
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Marun oil field is situated on the eastern part of Dezful Embayment zone (Zagros).Aghajari Formation is cropping out on the surface. Asmari formation, Bangestan and Khami Groups are the Main reservoirs in this field. Asmari formation with six reservoirs layers is the most important reservoir. Dolomitic carbonates are dominant lithology in the 1,2,3layers and so, fracture density is high, especially in the first layer(90% Dolomite).Increasing of shale and Marle Layers in the 4,5,6 layers caused to decreasing of brittle property and fracture density is low. According to this research, Marun Anticline is a fault (thrust) related fold with faulted Detachment Fold mechanism. Two major fractures system in the Marun oil field could be recognized which are regional fractures (with east-west trending) and local fractures (fold and bending related fractures). The main fractured sectors, Marun Anticline are being seen in the southern limb and the eastern part of northern limb by curvature investigation (by Differential and Graphical methods).The results of Isopermeability, RFT, PI maps are consistable with the results of fracture study in order to identification of fractured sectors in the Marun Anticline
H. Hajialibeigi; S. A. Alavi; J. Eftekharnezhad; M. Mokhtari; M. H. Adabi
Abstract
The Chenareh Anticline is located between Lurestan Zone (in north) and Dezful Embayment (in south) in the Zagros Folded-Thrust Belt. This anticline is documented and interpreted to constrain the kinematic evolution of a fold. The development of fractures is confined to the Asmari Formation. In the study ...
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The Chenareh Anticline is located between Lurestan Zone (in north) and Dezful Embayment (in south) in the Zagros Folded-Thrust Belt. This anticline is documented and interpreted to constrain the kinematic evolution of a fold. The development of fractures is confined to the Asmari Formation. In the study area, the fracture pattern is interpreted to identify six main fracture sets (from A to F). The first fracture set (A) striking 68◦, oblique to the further fold trend, is interpreted as a regional fracture set that predates compression phase. The second set (B) striking 110◦, parallel to the fold trend, are found in both limbs and interpreted as extensional fractures. Two other fractures set, (D, E) striking 10◦-70◦ and 80◦-140◦ are conjugate fractures existing in both limbs. The youngest fracture set (E) had formed during the folding process especially at the late stage of fold growth. Later on the first fracture group (A) are reactivated and called as (F) fracture set. Due to geometric characteristics of the Chenareh Anticline, it is categorized as a fault -propagation fold which is affected by the blind Balarud fault zone. The Z-shaped hinge zone of present anticline is attributed to the linkage of the two early individual anticlines.
