2024-03-28T14:19:50Z
https://jtethys.journals.pnu.ac.ir/?_action=export&rf=summon&issue=492
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2014
2
1
Fracture and horizontal stress analysis of Dalan Formation using FMI image log in one of southwestern Iranian oil wells
Recognition of relationship between the present day stress state and fractures is very important in fractured reservoirs. Fractures that are parallel or oblique to maximum horizontal stress have more tendencies to tensile deformation and tensile deformed fractures will be more permeable. The Dalan formation is one of the main gas reservoirs of Iran witch most of the production from this formation is related to the fractures. In this study fractures properties and maximum horizontal stress orientation was determined by using FMI image log. 20 borehole breakouts and 9 drilling induced fractures were used for stress direction determination. The total twenty recognized breakouts in the borehole are showing maximum horizontal stress toward N18.5°E. The quality ranking of the well for maximum horizontal stress determination is A by using breakouts and B by using induced fractures. For validation of calculated maximum horizontal stress from FMI, maximum horizontal stress was calculated by DSI too and two calculated maximum horizontal stress by FMI and DSI was compatible. Two sets of fractures were recognized in Dalan formation, set1 and set2, which are striking towards SE-NW and E-W respectively. Set1 and set2 fractures are parallel and oblique to the anticline axis respectively, therefore set1 fractures may be tensional fractures. Set1 fractures are perpendicular to maximum horizontal stress then this set may be closed in future and set2 fractures is oblique to maximum horizontal stress then shear deformation may causes of higher production for this set.
image log
FMI
DSI
Drilling Induced Fractures
Maximum Horizontal Stress
2014
03
01
1
8
https://jtethys.journals.pnu.ac.ir/article_2810_6b0fdc8d45fa633b2d3e9f3523ddf58e.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2014
2
1
Sedimentary and Environmental Geochemistry of metals in the surface Sediments of the North-west of Persian Gulf (Boushehr Province Area)
Sediments are generally regarded as the sink for dissolved elements carried out to the sea by rivers. In order to study the source and mechanism of metal transport in sea water, 123 surface sediment samples were taken by using grab sampler in the northwest part of the Persian Gulf in summer. Grain size analysis and geochemical analysis by ICP-OES were carried out on samples after sample preparation. The geochemical results reveal that the mean (and standard deviation) values for trace elements are as follows: V:52 (20.83), Ti:1738 (574.67), Sr:1170 (638.15), Ni:64 (27.68), Mn:366 (104.12), Mo:0.506 (0.27), Fe:21454 (7340.8), Cu:14 (6.19), Cr:80 (26.90), Cd:0.19 (0.07), As:4 (3.35), Al:31876 (11390.6) ppm. Factor analysis and other multivariate statistical methods were used for discrimination of source of the elements. Al, Fe, Cr, Cu, Mn, Ni, Ti and V show strong correlation coefficients and they could be related to a detrital origin out of the sedimentary basin. However, As and Mo are placed in another factor which could be related to agricultural and industrial sources. Ca and Sr fall also in the third component indicating a close relationship and biogenic origin. Based on grain size analysis, fine-grained fraction are also correlated with Al, Cr, Cu, Fe, Ni, Ti, V, As, Mo, Mn, Cd and again Ca and Sr show strong correlation with coarse-grained fraction, i.e. sandy sediments of biogenic origin. The element association indicates the adsorption processes for fine-grained fractions as one of main factor for enrichment of the elements.
Persian Gulf
Sediment Geochemistry
Potentially Toxic metals
source
Statistical Parameters
2014
03
01
9
19
https://jtethys.journals.pnu.ac.ir/article_2811_9a5029d2cf0e22b2af86887efb3520c3.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2014
2
1
Study of texture the Mazraeh celestite deposit from North Central Iran
The Qom Formation, which hosts the Mazraeh celestite deposit, contains dominantly limestones, marl and subordinate evaporites deposited in shallow marine environments. Petrographic evidence indicates that the celestite deposits were formed by replacement of limestone. The presence of carbonate inclusions within celestite crystals as well as the pseudomorphic habits of some crystals suggests that celestite replaced preexisting carbonate. Based on petrographic evidences and celestite mineralization occurred as a late-diagenetic process during deposition of Qom Formation. Celestite occurs mostly at lower part of members of the Qom Formation as banded, rhythmic, massive, cavity and cave fillings. The layered, rhythmic and elongated lenticular celestite crystals are positioned parallel to the general bedding of the sequence and formed at early principal diagenetic stage. Relatively high strontium ion content of the Karadj Formation suggests a high probability of ion supply to form celestite from these formations.
Rhythmic
Celestite
Oligo-Miocene
Iran
Mazraeh
Qom Formation
2014
03
01
20
28
https://jtethys.journals.pnu.ac.ir/article_2812_301e096d10db56c6cd54004a1eff2cf4.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2014
2
1
Microfacies, sedimentary environment and geochemistry of the Badamu Formation (Lower-Middle Jurassic) in Lut Block, East of Iran
The Badamu Formation (Upper Toarcian-Middle Bajocian) mainly consists of limestone and shale and has is cropped out in east of Iran. The Badamu Formation conformably overlays Shemshak Formation and is underlaid sharply by Hojedk Formation in Kerman area and is underlaid gradually by Baghamshah Formation in Tabas and Southern Khorasan areas. The aim of this work is petrographical study of rocks and recognition of various microfacies that finally result in reconstruction and presenting depositional model and determine the paleoenvironment. Therefore, Southwest Esfak section with limestone lithology in Southern Khorasan province has been studied. Petrographical study of 50 thin sections of this formation revealed totally six carbonate microfacies within four microfacies belt including shallow marine, shoal, semi-closed lagoon and tidal channel. Comparison of these facies with standard ones indicates that Badamu Formation has been deposited in a homoclinal ramp including inner ramp, middle ramp and outer ramp sub-environments. Geochemical analysis of the limestone samples revealed high calcium and low magnesium content. Also, study of major and minor elements values determined that aragonite has been the original carbonate mineral of Badamu Formation limestones and these rocks have stabilized within a meteoric-pheratic and burial diagenetic environment. In addition, variations of Sr/Ca values versus Mn suggest that diagenetic alteration has occurred in a geochemically-opened system.
Badamu Formation
Shotori Range
Lower-Middle Jurassic
Sedimentary Environment
Petrography
Geochemistry
2014
03
01
29
44
https://jtethys.journals.pnu.ac.ir/article_2813_3d2ac385f4d568d649ea400c3e621fcf.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2014
2
1
Diversity changes among calcareous nannofossil assemblages across the Paleocene – Eocene Boundary in the Zagros (Southwest Iran)
Calcareous nannofossil assemblages of the boundary Paleocene-Eocene deposits (Pabdeh formation) of the Zagros, Dezful Embayment-Mansouri oilfield have been studied in detail. It consists of shale and grey marlstone with inter layers of calcareous argillites and marly claystone. We present a study focused on changes in calcareous nannofossils of the Pabdeh formation during the Paleocene/Eocene Boundary (PEB). As a result of this study, 15 genera and 24 species of nannofossils have been identified for the first time. The abrupt increase in genus Discoaster and Tribrachiatus abundance provide distinct data for quick recognition of the Paleocene/Eocene Thermal Maximum (PETM) warming event. The evolutionary changes among the nannofossils created two distinct biostratigraphic marker zones in PEB, described as nannofloral zones NP9 and NP10. According to these zones, the age of boundary is Late Paleocene (Thanetian)-Early Eocene (Ypresian).
Calcareous nannofloras
Biostratigraphy
Late Paleocene-Early Eocene
Iran
2014
03
01
45
54
https://jtethys.journals.pnu.ac.ir/article_2814_1a802408767b56e7c961b03f0c69c0c4.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2014
2
1
Magmatic evolution recorded by phenocrysts in volcanic rocks southeast of Isfahan
Late Miocene–Pliocene calc-alkaline volcanic rocks are exposed southeast of Isfahan in the Urumieh-Dokhtar magmatic belt. Volcanic rocks consist of lava flows and domes, chiefly basaltic andesites, andesites and dacites. Minerals in the volcanic rocks exhibit degrees of disequilibrium features. Plagioclase as dominant mineral in these rocks generally displays reverse and oscillatory zoning; sieve or dusty and clear populations, cores are unusually Ca-rich. Hornblende and biotitephenocrysts have reaction rims indicating disequilibrium growth during late stage crystallization. Quartz phenocrysts are corroded and embayed and a few show augite reaction rims. Criteria such as: a) development of sieve textures in plagioclase b) reaction rims in mafic minerals c) reverse zoning and heterogeneity of plagioclase rims d) the resorbed and embayed phenocrysts; support magma mixing as an important process in the evolution of these rocks.
Volcanic Rocks
Magmatic Evolution
Mineral Chemistry
Magma Mixing
2014
03
01
55
69
https://jtethys.journals.pnu.ac.ir/article_2815_ec98b68ed378df677bdec94ee9ab5f3d.pdf
Quarterly Journal of Tethys
JTethys
2476-7190
2476-7190
2014
2
1
Morphologic and physical features of pillow basalts of the Yüksekova Complex around Elazığ (Eastern Anatolia, Turkey)
Pillow basalts, belonging to Late Cretaceous Yüksekova Complex are extensivelly exposed around Elazıg in Eastern Turkey. This unit is a part of southeastern Anatolian ophiolite belt and the Southern Branch of the Neotethys. It represents the products of intra- oceanic subduction volcanism and mainly comprises pillow lavas, dykes and associated with sedimentary rocks. Pillow lavas and feeder dykes are basaltic in composition and subdivided in two geochemically distinct groups. Almost all of them are intruded by carbonate, silica or iron oxide-filled fractures. They are generally gray, red, purple or yellowish green, dark green in color. Thickness of shell of pillow varies between a few mm to 1 cm. Average density of them is 2.69 g/cm3, and they have average porosity of 5%. Pores with oval structure which is relativelly indicative of high viscosity reach up a few mm to 1 cm. They are filled by amygdules such as silica, calcite, chlorite, zeolites that indicate alteration by sea water.The abundance and extremely coarse size of amygdules in these rocks might signify the presence of a shallow marine environment.Also, there is no clear difference in abundance and type of amygdule observed at group 1 and group 2. Flakes of chloriteform an interpillow matrix are found mostly between of pillows. In according to the frequency distributions of pillowed basalts, samples of group 1 have a more uniform rate of rounding, while samples of group 2 represent more variable rate of rounding. The long and short axis sizes of pillow basalts vary from a few centimeters to meters. Varying sizes of the pillow basalts indicate an effusion environment long-lasting or with multi-stage. The main magmas of the examined pillow basalts, belonging to Late Cretaceous Yüksekova Complex, similar to each other because of the absence of a significant difference in compositions and morphologies of both groups.
Elazığ
Turkey
Yüksekova Complex
Pillow basalt
Amygdule
porosity
Rounding
2014
03
01
70
80
https://jtethys.journals.pnu.ac.ir/article_2816_43237e988fe512024333cb9f2f0c97d3.pdf