APPLIED SEDIMENTOLOGY
Year:2015 | Volume:3 | Issue:5|Papers Count:7

The Garau Formation in Tang-e-Haft area of Lorestan province has a thickness of 703m. The lower boundary is with Gotnia evaporite Formation and its upper boundary is continuous with Sarvak Formation and it is mainly consist of alternation of limestone, shaly limestone, shale and marl. In this research, the shale and shaly limestone of this rock unit were sampled in a systematic method. The results of pyrolysis of the samples were drawn in geochemical diagrams and the following results were obtained: In the studied samples, the existing hydrocarbons are indigenous.60 percent of available kerogen is from type III and 40 percent type II, which are able to produce gas and oil. Amount of Total Organic Carbon (TOC) is in the range of fair to very good and S2 values are low and according to high thickness of the shale layers, it has high ability to produce significant amounts of hydrocarbons. Also, the consideration to palynological slides identified 4 palynofacies.75 percent of samples were placed within the range of palynofacies I and II (kerogen type III and probable hydrocarbon of gas) and 25 percent were placed within the range of palynofacies VI and IX (mostly type II kerogen and probable hydrocarbon of oil).

The Asmari Formation deposited in the Zagros basin during the Oligocene-Miocene. In this study, microfacies, depositional environment and sequence stratigraphy of the Asmari Formation in Kooh-Siah anticline (north of Dehdasht) 127 sampels was studied. The thickness of the Asmari Formation in this section is 214m and consists of thick, medium and thin bedded limestones interbeded with marly limestone, dolomitic limestone and marl. Based on petrography and analysis of microfacies features, 11 different microfacies types have been recognized, which can be grouped into 4 depositional environments: tidal flat, lagoon, shoal and open marine. The Asmari Formation represents sedimentation on a carbonate ramp. A HST in Chattian, three third-order depositional sequence in Aquitanian, and one third-order sequence in Burdigalian are recognized, on the basis of deepening and shallowing patterns in the microfacies.

In this study, four sand dunes, in the East of Babolsar were studied. These dunes are of lunar parabolic type. Their sediment textures are sand and sand with little gravel;.these sediments are moderately sorted, leptokurtic and have positive skewness. More than 60 percent of these deposits are composed of metamorphic and igneous rock fragments. Three sedimentary facies (i.e. A, B1 and B2) were recognized; facies A and B2 show charactertistics of coastal plains and sand dunes; facies B1 were deposited in a swash zone. The age of the middle and lower part of the studied dunes varies from 14 to 25 ka; indicating the minimum and maximum depositional rate of 0.15 and 0.2 mm/y, respectively. Four Radar Facies were recognized; their characteristics are indicative of dune foreslope, cut and trough fill and swash zone.

The Jahrum Formation with 192 m thickness at the studied area consists of carbonate sequence which overlies Pabdeh Formation sharply and underlies the Asmari Formation gradually. The aim of this paper is to describe the micro biostratigraphy, biological facies and sedimentary environment interpretation of Jahrum Formation at the section studied. Based on biostratigraphic studies 19 genera and 27 species of benthic foraminifera were identified which are located in two assemblage zones. Biozone no.1 (Nummulites-Alveolina assemblage subzone) belonging to the Middle Eocene age and biozone no.2 (Nummulites fabiani taxon range zone) belong to the Late Eocene age. According to the diagnosed biozones, the age of Jahrum Formation at the studied section is Middle Eocene - Late Eocene. Studies led to the identification of eight biofacies of lagoon, shoal and open sea. The absence of turbidite deposits and reef facies indicate sediments deposition of Jahrum Formation has occurred in a carbonate platform of hemoclinal ramp type (including inner, middle and outer ramp).

The Sarvak Formation (Albian to Turonian) is one of the carbonate units in the southwest Iran that was deposited on Neotethys margin. The purpose of this study is to analysis sequence stratigraphy and to identify Milankovitch cyclesof this formation in wells No.20 and 48 in the Kupal Oilfield. This study was done by MESA spectral analysis method, using Cyclolog software and gamma ray data. The study of 250 thin sections led to identification of 9 microfacies that were deposited in three depositional environments including lagoon, shoal and open marine. In additions two third order depositional sequences (based on facies variations and changes PEFA and INPEFA curves) were identified. Examination of Milankovitch cycles, using both interval variations between gamma ray peaks and MESA spectral analysis methods showed that most of them formed 100, 000 years cycles type. Orbital age determination with respect to counting of these cycles showed that this part of drilled formation has 11 to12 million years age.

The Pabdeh Formation was deposited during late Paleocene- early Oligocene in the Zagros Basin. Considerable parts of the formation comprise fine-grained sediments particularly variegated shale beds which were deposited in platform margin to deep sea environments. These depositional setting may promoted preservation of OM in these sediments. Hence, hydrocarbon potential and organic geochemistry of the Pabdeh Fm. were examined in a surface section located around the Sarhal-e Shirzadi village near the Gilan-e Gharb town. After sampling, a suite of 12 selected samples were analyzed by Rock-Eval. III in the geochemistry lab. of the Research Institute for Petroleum Industry (RIPI). Low average TOC content of the samples (ave.1.2 %) imply a poor source potential of the Pabdeh Fm. in this region. Furthermore, data revealed a mixture of various kerogen types including type I, II, and III as well, among which type II is more frequent. This may reflect virtual marine nature of the Pabdeh Fm. Ro of most samples varies between 0.5 to 1.35 %, which means the Pabdeh Fm. reached the oil generation window. Cross-plot of Tmax vs. HI revealed the Pabdeh Fm. experienced catagenesis (Tmax>435oC). However, according to the calculated Tmax are not reliable, so do not reflect realistic thermal maturity of the Pabdeh Fm. In other words, Tmax and PI values calculated from Rock-Eval data suggest that only one sample passed into oil window. Organic facies of the Pabdeh Fm. comprising both platform and slope facies, which were probably deposited in the platform margin.

In this research, a stratigraphic section of carbonate rocks of Qaleh-Dokhtar Formation (Middle-Late Jurassic?) with 306.3 m thickness located in north of Qayen city, Southern Khorasan Province, has been measured and studied. This sequence has been made of thin to thick and massive layers of limestone, dolomite, sandstone, shale and marl. Based on both field and laboratory studies, totally 11 carbonate microfacies and 2 clastic petrofacies were determined which have been deposited within four coastal, lagoon, barrier and open marine facies belts within a rimmed-shelf type carbonate platform. The most significant diagenetic processes which have been observed in Qaleh-Dokhtar Formation samples are cementation, compaction, formation of various types of porosity, dissolution, neomorphism and replacement. Interpretation of paragenetic sequence of the studied limestones reveals the effects of diagenetic processes in marine, meteoric, burial and uplift stages. Geochemical studies of elemental analysis show that the palaeoenvironment of formation of these deposits has had similar to the recent semi-tropical regions. Furthermore, the diagenetic environment of these carbonate rocks has had a semi-closed to closed geochemical system.