JOURNAL OF SEDIMENT AND SEDIMENTARY ROCK
Year:2009 | Volume:2 | Issue:4|Papers Count:8

The carbonate-evaporitic beds of Dalan Formation are some of the most important gas reservoirs in Zagros basin. The main reservoir facies of Dalan Formation in Aghar Field in terms of the relationship between porosity, permeability and the factors influencing the quality of those two factors have been studied. The main reservoir facies of Dalan Formation is ooid grainstone facies and includes three microfacies. The size of grains, the type of sedimentary facies, type of lithology, sedimentary structures and diagenetic processes are influential factors on reservoir features of this important facies. Porosity and permeability in Dalan Formation is a maximum of 27 percent and 38 milidarcy. The lithology of Dalan Formation mainly consists of dolomite and limestone rock. In the studied facies the solution is very influential in producing porosity and due to the presence of isopachous rim cement the ooid grains are mainly intact. The cement of this facies is of two processes. The size of dolomite crystals in the studied samples ranges from very fine to medium grains and increases in size from tidal flat environments to ooid shoals. Dolomitization does not cause so much increase in permeability and porosity. In the sequence of the study anhydrite is produced in different forms and the influence of fracture in increasing permeability of the reservoir is very remarkable. The highest amount of porosity and permeability in Dalan Formation relates to reservoir shoal dolostones and from sedimentary structures the type of cross bedding is seen mostly in the main facies. The size and sorting of ooid grains have a great influence on the permeability of facies including these grains.

Erosion is a process during which soil particles are separated from their beds, and they are moved and deposited with the help of a conveyor factor to another place. Sedimentation and erosion are major concerns in most regions of Iran, and estimating the scale of erosion and sedimentation is very significant.Determining the amount of erosion in drainage basin is practiced in various ways among which we can point out erosion studies methods such as, PSICAC, EPM and GIS. In this research, USLE method has been applied to assess the ratio of erosion of almost unconsolidated pre-quaternary and quaternary formation to erosion in Damavand drainage basin. For this purpose, 18 samples of unconsolidated deposits of Damavand drainage basin were taken and then by applying the effective factors in Universal Soil Loss Equation, the rate of soil loss of such deposits has been measured. The results showed that the soil loss is mostly found in the lower red formation and the highest amount of erosion is discovered in Hezar-Dar’reh formation. Since Hezar-Dar’reh, lower red and upper red formations are near the main water channel, the basin’s outgo and the dam which is under construction in Malmo, an operation of sediment and drainage control should be carried out to prevent erosion and sedimentation.

Dariyan Fromation (Aptian) is one of the main oil reservoirs in the southwest of Iran. Mansuri oilfield is located in northern Dezful, sixty kilometers to the south of Ahwaz, fifty kilometers to the west of Mahshahr port and forty kilometers to the east of Ab teymur. Mansuri structure is located in a flat plain, without any outcrops. The aim of this research is a petrophysical study of Dariyan Formation including the evaluation of water saturation, effective porosity, shale volume and detection of reservoir zones in the Mansuri sub-surface section. The petrophysical evaluation of the Dariyan Formation in Mansuri well #57 (Mansuri oil field) is done with Geolog software. Based on evaluations done on the petrophysical logs in the Mansuri well (Dariyan horizon), Dariyan Formation has three reservoir zones. The mean porosity in the first, second and third zones are 8%. 8.5%, 5%, respectively; the mean water saturation is 40%, 13.5%, 40%, and the mean shale volume is 14.5%, 11%, 0%

Qom Formation (Oligo-Miocene) is the most important hydrocarbon source in central Iran. Qom Formation stands unconformably between the Lower Red and Upper Red Formations. This Formation in Vieh section in south of Saveh was studied for stratigraphic survey, facies analysis and environmental interpretation. It is 220 meters thick. In the studied area, it mainly consists of medium- to thick-layered to massive limestone, marl and sandstone. The assessment of thin sections in Vieh section led to the recognition of 4 facies groups related to coast, lagoon, barrier and open marine. Lagoonal facies consist of packstone and wackestone textures. Barrier facies can be witnessed as boundestone and bioclastic grainstone and open marine facies have turbidities and talus characteristics.

Different methods have been innovated for the estimation of sediment yield in different basins. In this research, three methods (hydrometric, hydraulic and experimental) have been used for this purpose in Firouzabad River basin. In the hydrometric method, in addition to measuring the discharge of the river, sampling of the suspended materials is performed. No hydrometric station exists at Haiqer dam-site, but there is one in Tangab dam-site, some 60 km toward the upstream, and monthly and yearly measuring of discharge and sampling have been performed there in a period of 30 years. To determine the relationship between the river discharge and the sediment concentration, the sediment discharge is measured as a function of flow discharge using coordinated equations. With regard to existing statistical information, the average of annually suspended materials in Tangab hydrometric station has been determined and, by taking some factors and parameters into consideration, has been calculated for Haiqer dam-site exit. To control flood and fix up the river, we need to know the geometry, hydraulics and flow condition of each point of the river. To simulate a river, we usually use mathematical models. In this research, among the current models, the HEC-RAS software has been used, which is one of the most common river models and can simulate sediment transition unidimensionally. Different equations have been presented for sediment total load transition, whose operations have been analyzed and their validities have been determined. Using these equations and sediment transportation methods, the total load has been calculated in HEC-RAS software. The experimental MPSIAC method has also been used for the estimation of sediment yield in the basin. In this method, the effect of nine factors in soil erosion and sediment production (surface geology, type of soil, climate, running water, topography, vegetation cover, land use methods, erosion and channel erosion) is estimated in the basin. Depending on the intensity and weakness of each factor, a mark (of distinction) is given to it and with taking into account the sum of marks, the rate of sediment yield is estimated.

In this research, Jahrum Formation (Paleocene-late Eocene age) was studied for microfacies and diagenetic sequence in the type section. Petrographic studies led to the recognition of eleven microfacies that were deposited in four facies belts: tidal flat, lagoon, shoal and open marine. The observed facies patterns indicated a homoclinal carbonate ramp depositional environment. On the basis of petrography studies, important diagenetic processes in Jahrum Formation include Dolomitization, Cementation, Dissolution, Porosity, Micritization, Compaction, Neomorphism, Geopetal Fabric, Hematitization and Phosphatization. Dolomitization comprising the biggest volume of diagenetic processes along the sequence because Jahrum Formation is effective with early and late diagenetic environment.

The purpose of this study is to survey and compare rock types of Asmari Formation in the Hendijan field (northwest of Persian Gulf) by core Petrophysical data, change in compressional waves (Vp) and Shear waves(Vs). These two waves have been evaluated by DSI tools running in one of the wells in this field. Given the cores and DSI logging and petrophysical data, Asmari & Ghar Formations have been divided into 3 and 4 rock types respectively. According to the results of acoustic logs the mean value of vp/vs calculated in this field is 1.7 for Sandstone, 1.8 for dolomite & 1.89 for Limestone. In salt saturated areas with increasing hydrocarbon the P wave velocity decreases and the S wave velocity increases.This case is alsotrue for gas saturated and light hydrocarbon areas. The ratio of vp/vs and their crossplots are the main factors for evaluating fluids based on laboratory studies on cores, the rock-types in Ghar Formation are divided into 3 groups: 1) Well sorted Sandstone; 2) mudstone - Siltstone; 3) dolomitic mudstone along with evaporites and in Asmari Formation : 1) mudstone & dolomitic Wackestone; 2) Wackestone-dolomitic Packstone ; 3) calcareous Packstone; 4) dolomitic Grainstone.

The deposits of the Ruteh Formation (Upper Permian) in the north of Shahroud (Ghatar Seresht valley) are 187.34 meters thick.It is unconformably overlain by the Doroud Formation (Lower Permian) and is unconformably underlain by the Elika Formation (Triassic) with a thick laterite horizon. In this section, the Ruteh Formation consists of limestone with shale lime interbedded in the lower part, fossiliferous limestone with marl lime in the middle part, and a period of thick layer oncoidal limestone and marl lime in the upper part. Field and microscopic studies of the Ruteh Formation led to the recognition of one facies group of full carbonate. The carbonate facies consists of 22 facies including 4 facies groups related to tidal flat, lagoon, barrier, and open marine. The carbonate facies group has been deposited in a homoclinal ramp.