APPLIED SEDIMENTOLOGY
Year:2017 | Volume:4 | Issue:8|Papers Count:7

Carbonate Dalan and Kangan formations with the late Permian-early Triassic age are considered as the main gas reservoir rocks in some fields of the Persian Gulf. Carbonate facies of these formations which are related to shoal, lagoon and tidal flats have been developed in a carbonate ramp environment under the arid climate condition. Pores system of the formations under the effect of the primary depositional texture and diagenesis, has a significant control on the reservoir properties. In this study, in order to investigate the effects of these agents on the reservoir quality, hydraulic flow units were described. Then, based on the relationship between the identified hydraulic flow units and depositional and diagenetic characteristics, pores system of the reservoir facies was classified into four classes of porosity-permeability values of high, low, intermediate and high porosity-low permeability. The results show that the diagenetic processes such as dissolution, cementation, dolomitization and to some extent fracture, on the basis of the primary depositional texture, have the important effect on pore system distribution within the reservoir facies, and their reservoir properties. As, pervasive cementation by anhydrite and calcite have been associated with a severe decrease in reservoir quality of grain supported facies. In contrast, dissolution with creation of moldic and vuggy porosity has been acted in a way to change, improve or increase the reservoir quality. Also, in some parts of the reservoir, dolomitization by creation of intercrystalline porosity, and fracture especially in mudstone facies have been improved the reservoir quality.

Salt domes are one of the most notable features of Zagros fold belt in the south of Iran. In this study the salt of Dehkoyeh, Paskhand and Karmostaj domes located in Larestan were analyzed based on salt colors. In mineralogical studies for the first time two minerals, sassolite B(OH)3 and glauberite Na2Ca (SO4)2 which are of today 's fumaroles indexes in different parts of the world, were identified in Dehkoyeh dome as well as Hormuz salt formation. Generally, compared to other existing elements iron has the greatest impact on the changes of salt color. In salts accompanying sassolite and Glauberite certain minerals with temperature range between 50oC to 60oC were identified. Sea floor fumaroles has probably played important roles in formation of Hormuz salt in infra-Cambrian era. In all probability this fumarole was the main supply of ions needed for salt formation and this fact justifies the emergence of large volumes of Hormuz salt in a relatively short time.

The Upper Triassic Nayband Formation is widely exposed in the Tabas subzone, East Central Iran. This formation is 1410 meters thick, mainly comprises sandstone, sandy limestone, marl, coalificated shale (Coal seam) and dark shale in Parvadeh area. This study tries to reconstruct the hydrocarbon production potentiality, organic geochemistry, kerogen type, thermal maturity and recognition of depositional condition of the Nayband Formation. Totally 86 samples (coal seams and dark shales) were collected. These samples were analyzed by Rock-Eval type VI. Geochemical analysis results revealed that TOC content is more than 4 Wt% in the coalificated shales and in the dark shales is less than 4 Wt%. Parameters such as S1, S2, S1+ S2 suggest poor hydrocarbon production. Other parameters such as HI suggest poor hydrocarbon production potential (coalificated shales) to gas prone source rock (dark shales). Results also revealed that the organic matter mainly contain type IV kerogen in the coalificated shales and predominately comprises kerogen types III and IV in the dark shales. Vitrinite reflectance of the coalificated shales (0.84-1.12 %) indicate that the coalificated shales are at the mature stage (enrichment of oxidized organic matter indicates poor hydrocarbon production). Organic facies of this rock unit indicates that these sediments predominately comprise organic facies types D and CD which imply highly oxic to oxic conditions during the deposition. Based on HI and TOC parameters, majority of these sediments were deposited during relative sea-level fall.

The study of electrofacies is a useful petrophysical analysis method in oil-well exploration and evaluation of reservoir characteristics, particularly when the wells lack actual geological data. In order to interpret the electrical facies of the Bangestan group in Ghalea-Nai oil field, three surface sections were chosen and studied for petrographic and petrophysical features. This resulted in the identification of seven microfacies including: wackstone-wackstone, wackstone, sponge (spongy) spicule oligosteginid, bioclast wackstone-packstone, benthic foraminifera rudist wackstone-packstone, peloidal bioclast packstone-grainstone, peloidal microbioclast packstone-wackstone, pelagic foraminifera wackstone-packstone and oligosteginid wackstone-packstone. Porosity percentages and high quality lithofacies of the Bangestan reservoir were identified by "Geolog software", using petrographic data including: neutron, sonic (sound) and resistivity logs on predominant lithology. Based on these results, and also using of lithology determinant intersecting logs, the major identified lithologies are: limestone, dolomite and limestone with minor amounts of dolomite. Based on these results the identified porosity percentages varies between well. No.3 with 18% (the highest porosity), well No.2. with about 10% and well No.4 with 6% (the lowest porosity). The sedimentary microfacies conforming to high quality reservoir were recognized based on electrical investigation and using of MRGC clustering method. This microfacies which belong to Ilam-Sarvak formations are represented by bioclast peloidal packstone-grainstone and sponge spicule oligosteginid packstone-wackstone, respectively.

The Miocene deposits are exposed in the Nourabad region of Sanandaj Sirjan Zone. In this study, one surface section (Haft cheshmeh) with a thickness of 125 m has been studied in order to determine the sedimentary environment and sequense stratigraphy. The lower boundary of Miocene deposits in the studied section is sharp with ophiolitic unit (E1v) and the upper boundary is erosional. The Miocene deposits in the studied area are mainly characterized by marl and thin to thick bedded limestone. Also based on the field observations, petrographic studies, textural and facial characteristics, as well as the abundance and distribution of foraminifera and other components, 19 carbonate microfacies have been identified. These carbonate microfacies were deposited in 5 facies belts including lower slope, upper slope, margin, platform-margin sand shoals and lagoon facies. The existence of barrier reefs, intraclasts, oncoids, aggregate grains and the abrupt facies changes, also absence of widespread intertidal flat and the re-deposited carbonates (calciturbidites) represent that this sequence deposited on a rimmed carbonate platform. Sequence stratigraphy analysis led to identification of three 3rd order depositional sequences bounded by type I and type II sequence boundaries. The sequence 1 consists of TST and HST system tracts. This sequence is characterized by open marine, margin, sand shoals and lagoon facies. The lower boundary of this sequence is a sequence boundary type 1 (SB1) with ophiolitic unit (E1v) and the upper boundary is a sequence boundary type 2 (SB2) with sequence 2.The sequence 2 consists of TST and HST system tracts and is characterized by open marine, sand shoals and lagoon facies. The lower and upper boundaries of sequence 2 are sequence boundary type 2 (SB2). The sequence 3 consists of TST and HST system tracts and is characterized by open marine, sand shoals and lagoon facies. The lower and upper boundaries of sequence 3 are sequence boundaries type 2 andtype 1, respectively.

The Zarivar Lake, located in Kurdistan Province, is considered an important fresh water reservoir in the west of Iran. Recently, there has been an increasing risk of sediment and water pollution especially with heavy metals due to extended human activities in and around the lake. In this research, source of the metals Cu, Cr, V, Ni, Ni, Ti, Co, Sc, Zr, Li, Ca, Sr and Mg, present in the Zarivar Lake bed sediments, was determined using univariate (correlation matrix) and multivariate (Principle Component Analysis (PCA) and Cluster Analysis (CA)) statistical analyses. Thirty one samples were collected using a Grab Sampler. Based on CA results, the lake was divided into two northern and southern parts. Metals in the northern part were originated from a geological source. In the southern part, the mentioned metals had also a geogenic source except for Pb. Cluster analysis and PCA revealed an anthropogenic source for Pb in the southern part of the Zarivar Lake.

Kashafrud Formation in the Navia section (59 km west of Bojnourd) with 749 meter thickness is composed of silici-clastic sediments. In this study, based on nanofossils genus Watznaueria britannica and Cyclagelosphaera margerelii that were recorded at 350 and 710 meter above the base of formation revealed that the age of this interval can be Bajocian-.Bathonian. The fragments and feldspar are the most important constituents. Three sandstone petrofacies, including subchertarenite, chertarenite, phylarenite and feldspatic chertarenite, are identified. Modal analysis of sandstones, plotted on QmFLt and QtFL diagrams, show that the sediments of Kashafrud Formation are located on the recycle orogeny. However, geochemical studies for identification of source rocks revealed these sediments may have been derived from intermediate igneous and sedimentary rocks. CIA Index (chemical weathering), high average Plagioclase index of alteration (PIA), ICV (index for determining the type of mature and immature source rocks) as well as SiO2 versus Al2O3+K2O+Na2O show a warm and semi humid climatic conditions. Using ternary diagram (Na2O+K2O), (TiO2+MgO+Fe2O3), (SiO2/20) is also proved that these sandstones may have been deposited on a passive continental margin setting.