Geopersia
Volume:2 Issue: 1, Winter-Spring 2012

This study shows that ichonology can be used to refine sequence stratigraphy as well as to interpret the depositional environment of the Kalat Formation (Upper Maastrichtian) in the Central Kopeh- Dagh Basin (NE Iran), Dareh-Gaz section. Field studies and petrography of these deposits led to recognize four lithofacies and nine subfacies that formed in the tidal flat (lithofacies A), lagoon (lithofacies B), shoal (lithofacies C), and open marine (lithofacies D) within a carbonate ramp system. Trace fossils in this succession consist of Psilonichnus quietis, Thalassinoides suevicus, Diplocraterion parallelum, Rhizocorallium je‌nense and Ophiomorpha isp. that are classified in the Psilonichnus ichnofacies and Thalassinoides suevicus, Diplocraterion parallelum, Rhizocorallium je‌nense, and Ophiomorpha isp. in the Cruziana ichnofacies. Based on lithofacies and ichnofacies analyses, two depositional sequences (DS1 and DS2) were identified, that are composed of transgressive and highstand systems tracts. The maximum flooding surface (MFS) in DS1 is characterized at the top of the bed containing Rhizocorallium jenense, while this surface in DS2 is recognized by Diplocraterion parallelum grading into Ophiomorpha isp. in similar lithofacies. This study is an example where ichnology provides additional support for high-resolution sequence stratigraphy in carbonate deposits.

Detailed organic petrography analysis were conducted on drill core and cutting samples from the Nahr Umr (Middle Albian), Burgan (Lower Albian) and Ratawi (Hauterivian) formations on the Soroosh and Nowrooz fields, NW part of the Iranian sector of the Persian Gulf. The thermal maturity of the Middle Albian Nahr Umr Formation appears to have reached the top of the oil window. The underlying Burgan (Kazhdumi) Formation shows vitrinite reflectance values less than those within the Nahr Umr Formation. The Burgan organic matter is terrestrial in origin and appears to be formed in a coal measures part of the section. Lamalginite is not prominent within the Burgan samples that were examined. The vitrinite found is texturally immature. The association of low reflectance values and textural immaturity could be due to early impregnation with oil, presumably from deeper horizons within the section. The Ratawi samples are lithologically dominated by carbonate and contain abundant lamalginite macerals. Much of the lamalginite is unusual in having a diffuse form. Most of the lamalginite macerals are associated with free oil inclusions. The Ratawi Formation is within the zone of active oil generation at present.

The Kazhdumi Formation of the Bangestan Group is a well-known and important source rock in most oil-fields in the Zagros Basin. In order to examine productivity of this formation in southwestern Iran, and to correlate petrographical and palynological data with geochemical properties, one of the best outcrops of this formation, located in Tange-Maghar 45 km northwest of Behbahan city, was sampled. Fifty-two rock samples were collected from the 270 m thick section which is made up of dark shales with intercalations of marl and limestones, and treated palynologically. Three palynofacies were differentiated based on statistical studies of palynological slides and the rock samples representing these palynofacies were geochemically analyzed. Palynofacies results were then correlated against the geochemical analysis. Palynofacies I (PF-1) with 90 to 100% Amorphous Organic Matter (AOM) presents high hydrogen index (HI) and total organic carbon (TOC) values. PF-1 contains kerogen type I/II and could potentially produce oil. The second palynofacies (PF-2) contains reduced amounts of AOM, HI and TOC and the kerogen is of type II/III, potentially producing oil and gas.

This study is focused on the biostratigraphy, sedimentary environments, facies distribution, and sequence stratigraphy of the Coniacian–Santonian sediments of Tange-Bulfaris section. Five assemblage zones have been recognized by distribution of the foraminifera in the study area. Assemblage zone 1(Chara Ostracods zone) is Coniacian in age and occurs in the lower part of the succession. Assemblage zone 2 (Valvulammina – Dicyclina zone) and Assemblage zone 3 (Rotalia cf. skourensis- Algae zone) are Coniacian – Santonian in age. Dicarinella concavata interval zone suggests a Coniacian to earliest Santonian age. Dicarinella asymetrica total range zone is Santonian in age. These sediments are subdivided into eight microfacies types belonging to various sedimentary environments, ranging from continental lacustrine to very shallow and relatively deep-water (hemipelagic to pelagic) marine environments. The observed facies patterns indicate a carbonate open shelf depositional environment. The inner shelf facies is characterized by wackestone–packstone, dominated by various taxa including miliolids, Rotalia, bryozoa, mollusca, ostracods and green algae. The middle shelf is represented by wackestone-packstone with a diverse assemblage of echinoid, corallinacean and bryozoans. Basinwards is dominated by argillaceous packstone characterized by planktonic foraminifera. Based on field observations, microfacies analysis and sequence stratigraphic concept, one-third-order sequence in the study section was identified.

The simultaneous flow of oil and water in porous media is described by relative permeability curves, mainly derived from laboratory experiments. Relative permeability is of paramount importance in predicting reservoir production performance and drive mechanisms and its value depends largely on the volume fraction of fluids present in the test samples. Nowadays X-ray scanners are one of the most accurate tools for non-destructive measurement of in-situ saturation. The mail purpose of this paper is to describe two-phase immiscible fluid flow behavior of low viscosity ratio oil/water through water-wet porous media interpreted by in-situ saturation profile data. Both steady state (SS) and unsteady state (USS) relative permeability measurement methods were applied and compared. The measured in-situ saturation profiles can confirm wettability character of studied rock samples and the yielded data are in good qualitative agreement with wettability characteristics of water-wet reservoir cores. In the USS experiments the saturation profile shapes characterize mainly production of oil before breakthrough and display front position. The flooding-rate dependency of the USS experiments was observed. In the SS experiments by imbibition process, water saturation in the samples was increased significantly even with flow of a very small fraction of water at the beginning of the test

The Muteh gold deposit (NE of Golpaygan) in the central part of intrusive-metamorphic belt of Sanandaj-Sirjan zone comprises NW-SE trending gold-quartz vein occurred in metamorphic complex. Gold mineralization is associated with quartz veins that formed during regional deformation across the mylonitic zones in metamorphic rocks of predominantly meta-volcanic, gneiss and schist. The sulfidation (pyritization) and silicification hydrothermal alteration as the main alteration adjacent to ore body and the quartz-sulfide veins with sulfide content of variable from 10 to 60% is dominated by pyrite, chalcopyrite, emplectite, arsenopyrite and minor content of galena and sphalerite. Native gold in the quartz veins occurs as the inclusion in pyrite and chalcopyrite and fracture fillings within pyrite. Pyrite of the late assemblage (py2) shows a range of 0.03 to 0.31 wt.% Au and 0.00 to 0.26 wt.% As and chalcopyrite have content of Au (up to 0.30 wt.%), As (up to 0.12 wt.%), and Hg (up to 0.15 wt.%) were detected in chemical composition. Fluid inclusion (FI) shows that three types of FI include CO2-rich or carbonic FI have homogenization temperatures of CO2 (average 19.9°C), aqueous-carbonic FI (average salinities of 7.4 wt.%NaCl eq.

Allochthonous masses are common structures in Zagros fold-thrust belt. They are generally considered as collapse structures formed by the influence of gravity and in rock units with competency contrast. However, large allochthonous masses mapped in Dowgonbadan area in Dezful Embayment near the Mountain Front Fault (MFF) of Zagros show characteristics different from the belt common collapse structures. In this paper, the influences of both gravity and thrusting on development of these masses are presented. Evidences such as the volume of the masses, the greater spacing between the masses and their origin, and the occurrence of crushed zone on the base of the masses are considered as criteria to separate these masses from common collapse structures and are classified as thrust related collapse structures. Thus, thrust faults as well as gravity are proposed as the main features controling the development of these types of collapse structures in the Zagros.